LTIiRITE3
TRACi E£AAT STUDIS IA
OF "u Z0RITES
AND THL OtIGI
by
INSU4 , JR.
WILIAM HAWT
dT
LT
TECI
A.B., Emory University
1948
Emory University
M.S.,
1949
SUBMITTED IN PA RTIA L FUISILLENT OF TME
B4UIRi;IITS FOR TE
DEOREE OF
DOCTOR OF PHbO2OPHY
at the
MASSACHUS&TTS INSTITUTE OF TECHNOLOGY
1951
Signature
of
Author.
.......
.........
Department of Geology
November 27,
Certified
by
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1951
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*
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Thesis Supervisor
Chairman, Departmental Committee on Graduate Studente
.
ACkXOSLDGMN TS
I am especially grateful to the following individuals
and organizations, without whose aid this investigation
would not have been possible:
Dr. i. H. Ahrens, who taught me the quantitative use
of the optical spectrograph in the investigation of geological problems, and who has pointed out to me many of the
most fruitful lines of research in this investigation.
Dr.
Ahrens suggested, for example, that we could prove by analysis that the K/Rb ratio in meteorites and common rocks was
nearly constant, and that this fact would have important
geochemical and petrological implications.
The entire staff of the Geology Department at the
Massachasetts Institute of Technology.
Dr. H. i. Fairbairn, under whose guidance I acquired
a large part of my knowledge of petrology.
Dr. Harlow Shapley and the entire staff of Harvard
College Observatory,
who made it
possible for me to acquire
sufficient astronomical knowledge to write on the "origin
of meteorites".
Dr. C. L. Frondel of Harvard, who kindly supplied the
meteorites for analysis from the Harvard MAuseum.
Dr. H. Hess and Dr. G. L. Davis of the Carnegie Geophysical Laboratory, who supplied a collection of well-known
altramafic rooks for analysis.
Miss Geraldine Sallivan, who did several flame photometer analyses of meteorites for this investigation.
The entire staff of the Geology Department at the
gassachusette Institute of fechnology.
My wife, Mary Pinson, who typed this thesis and helped
in the proof-reading.
Finanoial assistance for much of the work was given by
the Division of Industrial Cooperation of the Institute.
My thanks a given to all of the above.
iii
ABSTRACT
This investigation was andertaken because there is a
well-rOognized need for more abundant and more accurate
knowledge of the trace element content of meteorites.
Pre-
vious investigators nave analyzed but few individual meteorites for trace elements, and for several of the trace
elements, e.g., Rb, our knowledge of their abundances rests
entirely on a single analysis of a composite sample.
thermore,
Fur-
trace element analyses by different investigators
are generaliq so widely divergent that it was suspected
tnat many abandance values were in error.
For the above reasons the spectrograms of twenty-one
ohondrites (which comprise over 90% of silicate meteorites)
were analyzed for 4, Rb, Ba, Sr, So, and Zr,
All of these
elements,with the possible exception of a small proportion
of Zr, are confined to the silicate phase in meteorites.
The speetra of all ohondrites investigated were remarkably
similar.
The trace elements determined were all constant
in abundance within a factor of approximately 2, with two
minor exceptions oat of a total of 125 analyses of chondrites.
On the basis of the constancy of the trace elements in these
randomly selected specimens, new abundance values are derived for several trace elements in chondrites, and argaments presented for their acceptance on the basis of the improved analytical techniques employed.
The argument is presented that from the constancy of
trace elements in meteorites we may infer that they all had
a similar origin, in further support of the shattered planet
hypothesis for the origin of meteorites.
Approximately 400 analyses of trace elements in meteorites and rocks were made and the coomoohemical and geoohemical signifiance of the results are discussed.
Three ele-
ments, Rb, Sc, and Zr which had not been previoasly determined,
were determined in a suite of rocks from the Skaergaard intrasive and shown to show enrichment or impoverishment according to accepted geochemical laws.
At the saggestion of Dr. L. H. Ahrens, the
% K/Rb ratio
was determined in a large number of meteorites and rocks.
These values plotted on a graph show the characteristic enrichment from basic to acidic rooks.
is the proof that the ratio
Of great importance
%K/Rb is nearly constant in
meteorites and common igneous rock types.
This fact supports
the belief that meteorites originated by processes of magmatio dirrerentiation known in terrestrial rocks.
The graph de-
picting the linear relationship or the ,bK/Rb ratio includes
the analyses of both Ahrens and
inson.
Two chapters are devoted to the mineralogy and structure
of meteorites.
Those features which are significant in the
study of origin are discussed.
The final chapter, The Shattered Planet Hypothesis, is
V
an attempt to present in logical order the wealth of geological and astronomical facts which support this hypothesis.
Inooneistenoies are few, and the lack of adeqante explanation
of the oause of shattering does not detract from the hypoe
thesis,
Almost all evidence converges to the conclasion
that meteorites originated within a planet, comparable to
Earth or Mars in size.
vi
TK8]E OF GONTEWTS
CRAPTR I.
Introduction
CRADTER II.
Preparation, Spectrographic Techniques,
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lreparation of samples
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and Experiments
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flame photometer chooks of K content
. . .. . .. . .. .
of meteorites
Teehniqass for analysis of involatiles .
Standards
*
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*
*
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8
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8
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0
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0
9
Zr standards for chondritic
meteorites
.
*
.*
Ba, Sr, So in meteorites
.
.
Ba, Sr, Se, Zr in Skaergaard suite
and ultramafios . .
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0
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9
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9
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Separation of the silicate phase
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Photometric measurements . .0
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12
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14
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.5
14
0
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16
K, Rb in meteorites
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K, Rb in Ontario diabaues.
K, Rb in altramfices
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.
.
*
K, Rb in Skaergaard suite.
K, Rb (and other alkalies) I
tektites.
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*
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.
occentration for analysis o
f
CHAPTER III.
Us
.
*
K and Rb in Meteorites and Roaks
Historical Oatline
*
. .
. .
Geohemistry of K and Rb .
0
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*
0
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,
00
Constancy of the ratio.,% K/Rb.
*
0
17
vii
Page
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21
...........
25
.
meteorites .
X and Rb in
K and R in diabasee
.
.
X and Rb in Skaergaard rooks.
.
. .g
.....
25
.
28
. . .
29
.
. .
30
.
46
Rb in altramsfios. .*.*.
.
.
*
The primitive K/Rb ratio
Tetites
OHAPTER IV.
.
. .
,
.
Ba and Sr in Meteorites and Rocks
Historioal review
..
. .
46
,.........
Geoohemistry of ba and Sr.
Sr and ba in meteorites
CHAPTER V.
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.
. . ,.
. .
. . . . . . .
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49
. . .
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. . . . .
50
Sr and Ba in Skaergaard saite.
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53
Sr and Ba in ultramafio rooks. . . .
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58
So and Zr in Meteorites and Rocks. . . . .
69
Historioal review.
. . . ..
.*.
*
Geochemistry of scandim
So in
meteorites.
. . .
.
.
.
So in
Skaergaard rooks. .
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.
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.
So in altramafio rooks.
Geochemistry
Zr
in
of
hr.
.
. . . .
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70
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. ..
71
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. ..
72
........
74
..
. . . . . . . . . . ..
hr in Skaergaard rooks .
Zr in altramafic rocks
. . .
. . .
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0
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76
76
. . . .
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75
75
..
.....
*
meteorites..
69
85
QHAPE VI.
Mineralogy
.
*
C0APt iR VII.
Struottres and Textures of Meteorites.
.
106
. . . . .
106
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.--
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Nature of ohondri (ohoadriAles)
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viii
Page
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*110
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112
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ft
115
Gooling of the parent planet . . .
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119
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.t
123
Origin of chondri. . .
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.*
Faults, fractures, and sliokensidee.
asteorites.
Veins in
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,
QEATER VIII. The Shattered Planet Hypothesis.
Astronomical
Astronomical facts and theories.
*
,
ft
32$
Geological facts and theories.
..
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.t
124
.
.t
124
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ft
127
Association of meteors with omets
and meteorites with asteroids
Roohe's limit; a oause of shattering
.
Fragmental shapes. *
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129
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4
ft
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130
Geological
The meteoritio seqence..
Geochemical and jetrologioal evidence.--
132
Natare of pallasites . *
ft
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.t
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.t
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137
Geochemical eqwilibria
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.t
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.t
.t
139
Widmaastatten figures
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.t
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.t
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144
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ft
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.t
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ft
ft
.t
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9
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ft
ft
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153
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Ages of meteorites
Olastio struatares
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GOAlER I.4
Conclustons.
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.*.
C0APT1R X.
Suggested Research .
Biographical
Bibliography
Appendix
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Data
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164
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162
im
LIST OF TABS
ago
TAB.E I.
K and ib in Meteori tes and Rocks
TABA II,
ha and Sr in Meteorites and hooks.
.
. . .
TAB±4 III,
So and Zr in Meteorites and Hooks.
.
.
. . *.
.
. .
40
60
8
45W0? IGuRSs
Figure 1. l X/b in Common Rooks and
steoritee . . . .
K/Rhb in Skaergaard Intrusive Rooks
24
..
.
19
26
.
3.
Variations of K and Rb In Skaergaard Rooks.
4.
*
27
.
4O in Metal-free Homestead Meteorite by
Addition Method
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.
. .
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34
.
35
....
.#
MeteoriteS.
Metal-free
5.$KOO in
.
Working CMroe
6. # Rb 0 in Metal-free Homestead Meteorite by
Method.
Ad ition
7.
%3b2 0
.
10.
% K in Diabases
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36
...
*
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,
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. *. .
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. *
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.4 , * .
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37
38
.
39
.
Variations of Ba and Sr in Skaergaard
* .
Intrasive 0 .
11a.
.
in Metal-free Meteorites, Working Carve.
8. % Eb in Diabase.
9.
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55
.# .
%ba in Metal-free Homestead Meteorite by
.
*
61
a *.
..
62
..
63
14.
% sr in staergaard fooks and Ultramafios . . ..
64
lb.
Variations of So and Zr in Skaergaard
Addition Method, . .
12,
Method
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Intrasive
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.,
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f So in Metal-free Homestead Meteorite by
Addition Method. .
17.,
*
% Ba and Sr in Metal-free Meteorites, Working
Carves..
16.
.
..
% Sr in Metal-free aomestead Meteorite by
Addition
13.
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.
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*
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7?
.
So in tetal-free Meteorites, wiorking
Curve.
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.
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78
..
18.
5 So in Skaergaard Gabbros, Working Carve
.
79
19.
% So In Skaergaard Granophyres and Tektites . .
so
.
.
GHAPTER I
INTRODUTION
The purpose of this investigation has been threefold:
1.
To establish more accurate abundanoe values for the
elements K, Rb, ba, Sr, Sc, and Zr in ohondritio meteorites.
*
To relate and compare these abandanoes with terres-
trial basic and altrabasic rocks.
3.
To review the geological and astronomical litera-
ture on meteorites and to present in logical order an argumont for the origin of meteorites.
A review of the literature led to the conclusion that the
abundance values for traoe elements in meteorites rest indeed
on scant analytical evidence.
For example, the abundance
value for meteoritic Rb is due entirely to its determination
by the Noddaoks in a gomposite sample.
Ba, Sr, Zr, and So
have been determined in but a very few meteorites, and results nave been so erratio that averages would seem likely
to be in error.
Recent analyses for K in ahondritio meteorites
indicate tnat many of the older analyses by wet chemical
methods were in large error, as demonstrated reoently by W.
danl.
The same criticism could be applied for all bat a very
few traos elements.
Harrison brown recently found the aban-
dance value for Re as determined by the Noddacks to be in error by a factor of b.
No reflection is intended on the works
of earlier analysts, for their analyses were necessarily of a
reconnaissance nature.
They have been extremely useful,
and in most cases the order of magnitude was correct. However, new improved methods of mioro-chemioal analysis make
new determinations of certain elements feasible.
The need
for more accurate determinations to place cosmic abundance
values on a better statistical basis, and especially the need
of a knowledge of the cosmic ratios of the elementsis wellrecognized by physicists and cosmologists.
The most striking observation to the writer is the near
constancy of composition in trace elements of chondritic
meteorites, as shown by their~spotra.
Finally, the writer has attempted to present in logical
order an argument for the "shattered planet hypothesis" as
the origin of meteorites.
that meteorites originated in a
planet -of Mrth-sre (or smaller), which was subsequently
shattered afttn cooling, is suggested by a wealth of geologloal an'P astronomical observations.
of this theory seem few.
The inconsistencies
0. Bauer of Harvard College Ob-
servatory (1949) has written one such excellent argament.
It is noped that the writer, as a geologist, has added some
strength to this nypothesis.
CHAPTER II
PBARATION SPEOTROGRAPUIO
ISD ZXPSM.ISTS
TE
Preparation of
aMLes
]Every effort shoald be made to
prevent contamination in a trace element analysis.
in mind,
With this
the writer made wide use of the life-long experience
of H. S. Washington, as recorded in his book on silioate analysis, and followed Washington's advice on the principles of
preparation of silicate samples for analysis.
The rook samples were each selected on the basis of
their homogeneity of mineral content; that is, sufficiently
large samples were selected wherever possible to ensure
that a representative portion was msed for aroing.
Five to
ten pound specimens were used for the Ontario diabases.
Bach
was first broken in a screw vice and the fragments granalated
in a jaw craher. This portion was coned and quartered,
followed by further pulverization in a diamond mortar, and
suocessively quartered until a twelve-gram sample was obtained.
This portion was finely palverized in a mechanical
agate mortar and pestle, and a 3 gram sample separated by
ooning and quartering.
This portion was used in the spectro-
grapado analyses, and is considered highly representative
of tne composition of the original rook.
Similar procedures were followed for the altramafic
rocs, except that the jaw-crasher stage was omitted, for
only smaller samples (approximately
available.
t
to * pound) were
However, because all the specimens were homogen-
eous in mineral oontent, as shown by thin section or hand
lens stady, these speoimens were considered adequate in
size.
The seven specimens from the Skaergaard saite of rooks
averaged only 10-20 grams each.
For this reason, if the
analytical results of this investigation vary from those of
L. R. Wager and R. L. Mitchell (1943), it is probably because of the small samples employed, for Wager and Mitchell
However, for the
used larger, more representative samples.
purpose of tais investigation, the samples show the trend of
enrichment for the elemants K, Rb, l5a, and Zr from base to
top of tao intrusive, a similar deerease in So content, and
a oonstanoy of the ratio K/Rb.
Also, analytical agreement
with Wager and Mitohell is in most cases close.
The magnetic separation of the metallic phase from
chondritic meteorites is extremely tedious.
The meteorite
samples, weighing from b to 100 grams each, were pulverized
in a new diamond mortar.
The fine portion was sifted through
a fine-meshed silk bolting cloth, a fresh cloth being used
for each meteorite.
The coarse metal grains were extracted
by magnet and hand-picking, while the remaining coarse fragments were again pulverized and sifted.
This process was re-
peated until the meteorites were reduced to coarse metallic
grains and a finely palverized separate portion of silicates
and salfides (the non-magnetic portion) was obtained.
However, considerable metal remained in the palverized
portion.
Previous investigators have removed the metal with
a magne tic comb.
meteorite,
All workers report spending hous
on each
The tenacity with waich metallic particles remain
in the mixture is remarkable,
The writer employed a variation
in tAis procedure -- bat also spent hoars in each separation.
The palverized mixture was plaseA in a glass sample jar,
waich was rotated by hand while a powerful hand magnet was
held against the glass.
A piece of paper was placed between
magnet and glass, so that when the metallio particles were
drawn out the mouth of the sample bottle they would not adhere to the magnet,
Unfortunately,
some olivine is uagneti-
cally inoladed, probably due to inclmsion of Ni-Fe particles,
even in finely pulverized grains.
However, these silicate
particles are less strongly attracted than the metallic partie
ales, so taat separation may be made by spreading the attracted portion on a sheet of paper, rolling the particles
about with the fingers through a paper sheet to separate them,
and then passing the magnet over at a sufficient distance
above the particles to attract only the more
ta
metal particles.
agnetic ones --
If this detailed description seems
lengthy, it is inserted here only in the hope that it will be
of use to futare workers with meteorites in this tedious
process.
Finally, great oars was taken throaghout the investigation to prevent contamination with radioactive materials,
for these meteorite samples are to be analysed for radioactive content.
of meteorites;
flame photometer cheeks of X content
n
'""M
-
-_
-
1.00a
M0
60
'"W1
Miss Geraldine Sallivan, Research Assistant at M.I.T.,
made
flame photometer analyses of three meteorites for content of
K, and, incidantally, Aa.
The meteorites were prepared for
analysis by the writer by dissolving one gram samples in
HF (plus 5% 12 304 ), evaporating to dryness and repeating.
Description of the technique is given by L. H. Ahrens (1951).
The residue (Si removed as SiUt) was dissolved in 250 ml,
aliquots of 2% 101.
The flame photometer analyses were made
by Miss Sallivan.
Resalts in all cases, as shown in a table of Chapter II,
agree excellently with spectrographic analyses and serve to
ennance the validity of both analytical procedares.
techniques for analysi
of involatiles:
The elements
Sr, Da, So, and Zr present a special problem in spectrographic
analysis in that these elements, especially So and Zr, are
among the most involatile.
In order to enhance the sensiti-
vity or these elements, the rooks and meteorites were mixed
with equal portions of pare electrode carbon powder. This
powder was checked qalitatively and found free of impurities
of the elements sought.
Palladium, as palladium chloride, was added as internal standard.
However, the intensity of the sensitive Pd
line sought did not seem to be of sufficient constancy to
warrant its ase.
Equally precise, and more trustworthy re-
salts were obtained without use of an internal standard for
the four elements soaght.
However, in future investigations,
teonniques using internal standard will be developed for meteorites.
Analysis was fade with the Wadsworth grating spectrograph, whieh has been adequately described in other publicstions (Denen, 1949).
Seven steps, each in the intensity
ratio of 2.0, were recorded, tsing a rotating stop sector.
Pare carbon electrodes, of dimensions 3/16", 1/8", 1/4"
were employed.
The cylindrical cavity in eaoh electrode
was loaded with from sixty to seventy ug, of material.
Anode
excitation was used, and arcing time averaged 3'10" for the
meteorites, and slightly less than 3 minutes for the less
refractory rook samples.
All arcing was to completion, for
So and Zr are among the last materials to be volatalized.
The plate holder was centered at 3800 A, and loaded with
3 plates (Eastman 103-0).
The ninety plates of this inspection for involatile elements were developed in batohes of fifteen, tas comprising
six developings.
All plates were saved for developing until
all arcing was complete, so that constancy of developing
ditions would be better assured,
This is,
of course, of sa-
preme importance in qaantative spectrographio work.
veloper (D-19,
Qon-
The de-
Eastman) was sufficiently freshened for each
lot of plates developed to insure uniformity.
was 4.b minutes, at 2000.
Developing time
The plates were immersed at 1900,
and being somewhat warmer than the developing solution, the
temperature rose to nearly 210C at toe end of 4.5 minutes.
Standards: Several different standards were necessary,
because of the diversity of materials arced.
Zr standards for ehondritic meteorites:
The addition
method described by L. H. Ahrens (1950) was employed.
This
mtnod htes tao advantage of using the material analyzed as
base (matrix material), an important consideration in analysis of meteorites, beoause of the difficulty of producing a
syatinetic base that would simulate stony meteorites in arcing
characteristics.
The Homestead meteorite, with tatal magnet-
ioally extracted and FeS onverted to Fe20% by heating, was
used as base to which successive quantities of the Standard
Granite G-1 were added, in the ratio of 9/1, 4/1, 2/1, 1/1
of meteorite to granite.
Intensity of the line Zr 5391.975
was plotted against tAe percentage zirconium added, as G-I.
Analyses were in triplicate for each point.
beoaaae of the
spread of the points a considerable leeway in fixing the line
slope and its point of intersection with the percentage axis
* Fairoairn, H. W.,
U.S.G.S.
Special Bull.,
1951.
was encountered.
However, after the best line possible was
drawn, this value ror percentage zirconium in the Romestead
meteorite was compared with the value obtained by comparing
it with the known zirconium content of the standard granite
G-1,
for wnioh a single working curve was construoted.
The
two values than obtained, being very nearly equal, were averaged to give the value Zr in the samples of Homestead analyzed.
Ba,
an
r,aand So in Meteorites:
For the elements Sr, Ba,
So the addition method was employed, as above.
W-1 was
added in the ratio 99/1, 49/1, 19/1, 9/1, and the results were
compared with single point working curves of W-1, and results
averaged.
Thas the Homestead meteorite was found to contain
0.0012% Sr, 0.0011% Ba, and 0.00124 So.
(V. M. Goldsohmidt
found 0.001* So in Homestead).
", sr, so,
Zt iA gegaard ,Suite and Ultramsfica;
The
values -for, the be four elements were obtained from single point
working carves of W-1 and G-1.
4 Rb in Meteorites, The addition method was employed,
in which K and Rb were added as G-1, the ratio of Homestead
to
-1 being 99/1, 49/1, 19/1, 9/1 for sucoessive arcing:.
K, Rb in Ontario diabases:
Values for the thirty dia-
bases analyzed were obtained from two point working curves,
employing G-A and W-l.
K, Rb in Ultramafios:
Analysis values were obtained from
single point working curves of W-1.
K, Rb in Skaergaard Saite: Comparison was made with two
point working curves of W-1 and G-1.
KRb In Tektites:
All spectra were compared with spec-
tra of G-1.
Note:
All analyses for K and Rb were made with the 111-
ger prism spectrograph in the Cabot Spectrographic Laboratory.
Eastman I-L plates were used; developing in D-19 at 2000 for
4.b minates.
All meteorites were sintered before arcing to
convert iron sulfides to oxides.
Sintering was necessary to
insure smooth burning and prevent loss of sample by spattering.
Seven steps of a rotating step sector were used.
Slit
height was 10.5 mm.; allt width, 0.06 mm.
Experiments
Concentration, toR analysis of Oeeaat Considerable effort was made to concentrate Cs from stony meteorites.
Cs
was not found in tne six specimens concentrated (3 of Homestead; 5 of Hayes Center).
It is concluded that the aban-
danse of Go In stony meteorites is less than 0.00001%.
The concentration method (Ahrens,
solution of the meteorite (1
-
1951) employed was
2 grams) In hydrofluorio and
perchlorie acid; prolonged heating at 45000 in furnace,
in
which all elements bat alkalies are converted to oxides; solation of alkali chlorides in various organic agents in which
they exhibit different solubilities; arcing the portion enriohed in K, Rb, Cs.
This method is fully described by F. B.
-
*~
an
~b~n
11
Whiting (1951).
However,
L. H. Ahrens (personal communiaic.
tion) has sugg3ested a method of further enriching Rb and Ga.
Worn is now in progress on this suggestion.
saration of the silicate phase of ohondritio meteorites;
Mach work has been done by the writer and previous workers
(Prior, 1919) on this problem.
Chondritio meteorites are com-
posed of a mixture of three phases, metallio, sulfide, and
silioate.
So intimate is this mixture that it defies methan-
ical separation techniques.
in which Hgal
3 (JH3)2
Prior (1919) suggested a technique
was used as a dissolving agent for the
retal and sulfide phases (stronger agents are not suitable,
for they dissolve olivine).
This method was attempted.
The reagent reacted with
the pulverized meteorite for 96 hours in an inert, nitrogen
atmosphere.
At the end of this period, however, considerable
metal was still andissolved, as shown under a microscope.
Also, it appeared that the olivine had been attacked.
The
experiment was repeated three times, asing HgOl 2 on one ocaseion with similar unsatisfactory results.
This technique worked
for synthetic mixtures of iron filings and pulverized diabase,
but not for ohondritio meteorites.
The resulting material
could not be used for pure silicate phase analysis for trace
elements.
For future trace element analyses of the silicate phase.
of meteorites and the analysis of individual meteoritic miner-
12
al.s, the writer suggests that mauch effort would be saved
utilizing materials from actondritic stony meteorites, in
many of which mechanical separation techniques can be *aploLy.
However,
detailed traoe element studies in meteorite
minerals is greatly needed, and further investigations should
be made.
.4Wahl (1901) has suggested methods used by metal-
largists in separating silicates from cast iron for analysie whioh will be tested on meteorites by the writer.
This
reference did not come to the writer's attention in time
tor tWie investigation.
The various working earves for the different elements
are incladed in subsequent chapters which are pertinent to
the particular element.
Photometric measurements:
Photometric determinations
of the elements K, Rb, Ba, Sr, and So were made with a
Hilger microdensitometer.
bThe
responses of a photoelectric
cell and galvanometer were converted into intensities by
means of a calibration ourve.
All analyses were in triplicate except those for the
Skaergaard suite of rocks, which were in quadraplicate.
Zir-
coniam was determined visually.
The analysis lines of the elements sought were selected
on the basis of their intensities and lack of interference of
background and interfering lines.
Great care was taken throughout this investigation to
13
prevent contamination.
The carbon eleotrodes used were arced
as blanka and found to be free of impurities of the elements
sought.
no chemical agents or adulteranto were added to the
standards or unknowns.
CHAPTER III
X AND Rb IN MTWEORITS AND ROCKS
!istorical outline:
Potassium has almost always been
determined in the analyses of siliente meteorites.
Until
quite recently K was determined by wet chemical methods.
At present it seems that K,'as well as Na, can most easily
and accarately be determined by either flame photometer or
spectrographic methods.
Farringtoa (1911) oompiled a catalog in which are
listed selected analyses of stony meteorites.
The norma-
tive mineralogic oompositioas for all the meteorites were
calcalated and the meteorites classified.
Most of the me-
teorites analysed for trace elements by the present writer
are included in Farrington's catalog.
Detailed descriptions
will not be repeated here, for this catalog may be easily referred to by anyone interested in the major element analyses
of these meteorites.
In the appendix of this thesis is in-
cluaed a brief mineralogic description of the meteorites analysed in this thesis, based both on Farrington's catalog and
the writer's stady of thin sections of his specimens.
W. Wahl (1950) has recently proved that in a number of
old analyses K and Na were wrongly determined by a large
factor.
He concluded that any analysis showing abnormally
high K or Na percentages should be regarded with suspiolon,
and that these meteorites should be reanalyzed before being
incladed in meteoriti* or cosmic abandancet compilations of
the elemnts.
The restlts of the writer in the analyses of twenty-one
ohondrites oos&ra this conolasion of 4ahl.
Even casual
visaal inspection of the spectra of these meteorites reveals
most strikindl
their near identity, both in composition and
abundance of the elements.
Although twenty-one specimens
are admittedly a small nAmber o" which to base final oonelusions, it is most remarkable that these randomly selected
spooimens should be so alike in composition.
The abundaao
valaes for & in the current literature
are based on the compilations of G. P. Merrill (1950) and
the Noddaeks (1930).
Recalolations were made by V. M.
Goldsohmidt (1938) and by H. Brown and 0. Patterson (1949)
of seleoted analyes.
Rankama and Sahama (19bo),
viewing tae literature, derive the valuae 0.20
silicate phase of meteorites.
Ib
after re-
% K for the
Assuming an average value of
tree-metal phase, hankama and Sahame's valae soald be
cfia. 0.17% for silicate meteorites.
Assuming that I0A of
silicate meteoritee are aohondritic, and very low in K
ountent, as the writer's investigation has indioated, the
value would be redaoed to cir. 0.lb% in silicate meteorites.
the abundance of K and Rb in terrestrial rooks and
minerals has been reviewed exhaustit#l7 by Rankama and
Saname (l90)* Solar and stellar abundanoes of D. g. Hans.el , K. 0. Wright, and A Unsold have been tabulated by
H. G. UrOy (1951).
Rabidiam has been detected in the San t s
atmosphere.
The abundance data for Rb in meteorites is Indeed scanty,
and are based almost entirely on the analyses of the Noddaoks
(19130).
These analyses were made by optioal spectrographic
methods, and the abundance value of 0.00045% Rb in the silk.
atse phase of meteorites is based on the analysis of a composite sample, composed of forty-two separate meteorites.
The ned for individual analyses for Rb in meteorites is
obvious.
To the writer's knowledge, these twentywone ana-
lyses represent the first individual analyses for Rb.
This investigation on twenty-one ohondrites indicates
that both K and Rb are constant within a factor of approximately 2.
G11heoft
X and Rb:
Rankama and Sahama have ex-
cellently reviewed the literature and diseassed the geohemistry of the alkali elements.
Here only a brief review, ger-
mane to this thesis, will be given for K and Rb.
The elements K and Rb are known to sabstitute for one
another in the crystal lattices of minerals.
This eabstitmoo
tion is possible because of the close similarity in chemical
properties of these elements, dae to their identity of charge
and their similarity of sizes. The ionio radii are given below.
K+
r45 A
Rb+
1#49 A
17
The bulk of K and Rb in the igneous rocks is found in
the potash feldapars, and to a lesser extent in the potash
micas.
minor amounts of K and Rb are contained in the Teld-
spathoids, alkali pyroxenes, and alkali amphiboles.
Both potash feldspars and micas are late crystallates
during magmatic differentiation. For this reason these elements are concentrated in rocks of late crystallization, e.g.,
However, potash micas, especially
syonites and granites.
biotite, are common constituents of certain altrabasio,
basic, and acidic rocks.
Some ultramafic rocks, such as
kimberlite and mica peridotites, contain large percentages
of K and Rb, comparable to granite.
For this reason, as
pointed out to the writer in conversation by Professor G.
Kennedy of Harvard University, abundance valaes of the elements (e.g., K and Rb) in altrabasic rooks will depend largely on our knowledge of the actual percentages of mica-bearing altramafic rooks in the Earth's crust.
However, except in abnormally mioa-rich rooks of a
class, the K and Rb oontent increases markedly from basic to
acidio roccs, and, as shown in this investigation, the ratio
K/Rb is remarkably constant, as demonstrated in Figure 1.
GOnstancy of fth
Rao
fK/Rg
On a basis of geochem-
ical theory, it was saggested to the writer by Dr. L. H.
Ahrens that X and Rb should be found in nearly constant
ratio in all common rocks and meteorites that formed by
magmatic proOesses.
Dr. Ahrens had already detcrmined L
and Rb in over two hundred granites, diabases, and basalts,
and found the ratio to be remarkably constant and to aver.
age approximately 80.
At Als suggestion, the writer deter-
mined X andi Rb in twenty-one chondritic meteorites and sevoral aisoellaneous types, and in several gabbros, twentynine diabases, and some altranafics,
The results of these analyses are plotted in Figure 1,
as
£X against
% Rb.
Almost all of the points fall near a
straignt line, and this line closely approximates 450 in
slope.
The points include the analyses of the writer and
those of Dr. Ahrens a4 his assistants at M.IIT.
It should
be pointed oat that numerous other analyses for 9 and Rb
have beetn made by Dr. Ahrens which have not been plotted on
tais graph (for the sake of clarity in drafting), but these
values invariably lie close to the inoluded points.
If ins
oluded they would statistically improve the relationship.
Any anomalous results (such as the one point which is isolated) have been included.
rare, and all analyses
,
Anomalous results were indeed
fall close to the value100 for the
/rb ratio,
This straight line relationship is significant in that
it demonstrates that K and Rb readily substitute for one
anotner in common igneous rooks and meteorites. Furthermore,
tne enrichment in X and Rb from basic to acidic rocks is
Fi~are 1.
'1,f'
'H'
1:
If
74
I
1
-
It
if
K217+
It:,
g
1441
T,
I
~p~:: ~4It+4~~ li
I..J~i'{
jr
4
41.
4i
It
7.
tg -- T
11J
=
.U:
4,
14
;1
TR4*tIM
-
ttl
rH~v
1:
*1±
~~
±i17±tii Itititi-LiJI
r
t
j-Tp-
fl~-
:17
.. L
71 -ii]lifITftJiHllltiW-UAI
rTr
:a4uH41glimja m
rT
"-H-+-i
1 TZORIT'S
ljpffffm iill 11111111
H-H-H-;441i v:HH 111#4+4W444+4 H t44+4i.444M4
I'M
mm
tr
VI,~
demonstrated.
A straight line drawn through the points in Figure 1
will be slightly lose than 400.
This would indicate a
slight enrichment of fib over K from basic to aoidio rooks,
i.e., from meteorites to granites,
However, the deviation of the line from 450 is but
slight, and could possibly be due to small analytical error,
as for example the use of several different standards in
determining K and Rb in the different rook types,
For this
reason, only casual mention is made of this possible relationship.
However, on theoretical grounds Rbt should be slightly
enrifal
over K in more acidic rooks.
At the higher temper-
attres at waich meteorites and basie rooks orystallised, the
Rb+ ions would possess higher thermal energies than the X+
ions, and are less likely to be captured in existing crystal
lattices, with resultant slight enrichment in the residual
magmatic liquid,
The larger Qs+ ion is known to be greatly
enr Lofted :akSen
rooks and even to rorm cesium minerals.
Rb is not taown to form rubidium minerals.
Also, numerous
analyses of K and Rb in late small volame residual rooks by
Dr. Ahrens have shown that Rb is significantly enriched over
K. These rooks are not included in the graph booause they
are not common rook types.
ohondrites are incladed.
For a similar reason, only the
21
The resalts of this investigation seem to the writer to
be particularly significant.
The K/Rb ratio in chondrites is
essentially the same as in terrestrial igneous rocks.
Were
this ratio different in meteorites, it.would be reasonable to
assert that ohoadrites formed by some other process than
cooling of a silicate melt.
As previously pointed out, the sole determination of Rb
in silicate meteorites is based on the analysis of a composits sample by the Noddaoks, and is given as 0.00045%.
The
currently accepted valaes for K in silicate meteorites is
approximately 0.2.
Thus the ratio is indicated to be great-
er than 400, larger by a factor of 4 than the ratio in common
terrestrial igneous rooks.
The analyses of the writer have saggested that the 4Rb
ratio in chondrites (and silicate meteorites in general) is
approximatelyD00, in agreement with terrestrial rooks.
Al-
tnough systematic error may exist in the writer's analyses
for the aotaal percentages of K and Rb in meteorites, there
is good reason to believe that the ratios of these elements
is correct, for the intensities of the Rb and K lines measured
in the ohondrites are nearly constant.
is approximately 3, as it
The ratio
0 0
is in common igneous rooks.
X end Rb in Meteorites:
The alkali metals, inclading K
and Rb, are unknown in the metal-salfide phases of meteorites.
As defined by V. M. Goldschmidt, they are specifically
22
lithophile elements.
Potassiam and rubidium were determined in twenty-one
cnondrites, two carbonaceous meteorit-es, olivine from a pallasite, one oladnite (composed almost entirely of bronsite)
and in three tektites.
The determinations were in tripli-
cate.
Becaase of their common occurrence, investigations in
this thesis are confined chiefly to the chondrites.
For a
similar reazoa, deter4nations of I and Rb are confined to
the most common rock types, which are representative of the
balk of material in the Earth's crust.
The alkali elements Li, Na, and X all may be deteoted
in meteoritic olivine and pyroxene.
It is easpected that
Rb and possibly Gs are likewise present as minute traces.
The elements Li, Na, and X were deteoted in all the dunites,
serpentisttes, and pyroxenites analysed, as traces.
However,
in all these specimens it is suspeeted that Na and K are present in mineral structures other than olivine or pyroxene perhaps in mioas.
In meteoritio olivine, beeause of the ani-
versal occurrence etinlausions of other mineral grains and
glass within the crystal, it is not known whether these elements are incorporated in the olivtine.orystal lattice.
suspected that they are not.
There is a tendeacy for Li
to proxy for Xg
It is
and Fe
becaase of similarity of ionic sites, but prozying ooaurs
significantly only in sI0essively lower temperature minerals, rather than in Aidh temperature olivine and pyroxenes.
Olivia, from a pallasite specimea (locality unknown) was
analyzed.
The olivine fragments were knooked loose with a
ammer ad te aaterial ortbshed,and freelof aetattic particles
by a magnet.
Ties analysis demonstrates tnat K and hb do not
readily abstitute.
Likewise, the Johnstown, Golorado, chladnite was analyzed to demonstrate that the alkali elements do not readily
enter the crystal structures of the meteoritic enatatitehypersthene series,
Aikali feldspars are unknown In silicate meteorites,
except by norm analyses.
S
The elements Ua,
, Al, Si, and 0
are all present, bat thin section studies fail to reveal alkali feldspar minerals.
Meteoritic olivine and pyroxenes do not contain K, nor
is it in the metallic or salfide phass.
It is conoladed
that K is contained in the interstitial glass, which is a
common and usually abundant constitaent of anondritio meteorites.
Micas and amphiboles are unknown in meteorites, due to
the complete absence of water, or the hydroxyl ion, which is
essential to tna
ionic structares of these minerals.
Either
Cl" or F- can proxy for 05" in these mineral stractures.
fluorine has never been detected in meteorites, although it
24
has been caref4ly searched for, as will be Later reviewed
in the oaapter on mineralogj.
Chlorine is present in large
quantities in metallic meteorites, and has been reported
for stones.
keoaase of its greater affinity for iron, it
occurs as tAe rerroas chloride mineral, lawrenaite.
The average 4 content of the twenty-one chondrites anas
lyzed was found to be 0.084%.
An average of 0.00085% Eb
was found for the ohondrites.
The aaalytical results for
& were
oecked by the flame photometer (G. Sallivan and W.
Pinson, analysts) and are given in the following table. -A
was determined incidentally.
The writer's results are smal-
ler by a zactor of approximately 2 than analgsea cartently
appsaring in the literature by good analytical chemists; for
example,
those of t. Weahl.
The writer does not wish to cast
any aspersion on each analysea in any way.
The present re-
sults are acepted here as tentatively oorrect, because of the
good agreement of flame photometer results with spectrograph-
Ic resalts. Nonetheless, regardless of whether or not the
actual percentages are correct, the relative intensities of
tne i and Rb lines measared do not seem to be in error, and
are in the ratio of intensities of approximately 3:1.
wise, the
Like-
£/Rb is elose to 100 on the average, and would
not seem to be in error.
The table comparing flame photometer results with spectrographic results appears on the following page.
dKV
%iK
Na
Sample
ae&
Sairide
Flm Photo-meer
iate & loatf
SulieSlfide
lT
TIi"Thoto
tro
lie~ir
&
' Spec
Gah
Homestead
0.79
0.01
0.11
Haye's Center
0.68
0.096
0.07
Aernoive
0.72
0.103
0.11
K and Rb La Diabases; Twenty-nine diabases from the
fippiesing and Matachewan areas of Ontario were analyzed for
K and Rb.
These rooks and numerous others are currently
being investigated in the geology department of M.I.T. by
L. H. Ahrens, H. W. Fairbairn, and assistants, for other
trace elenmats.
The average K content was found by the
writer to be 0.94*: the Rb oontent is 0.014% Rb.
ratio % K/Rb is approximately 70:1.
Thas the
Plots of these analyses
are recorded in Figure 1. Indiviaal analyses for K and Rb
are given in Table I, and were determined spectroscopically
by the writer.
and Rb in te Sje5ard Rocks:
Seven specimens rep-
resentative of the Skaergaard intrasive from base to top were
analyzed for K and Rb.
The petrology and mineralogy, with
especial reference to trace element distributions, are described in several publications by L. R. vager and W. A. Deer
(1939), and L. R. Wager and H. L. Mitchell (1943, 1951).
Rubidiam had not been previously determined in six of the
specimens.
The writer's determinations of X were in reason-
Figure 2.
.--..
I
.
........
--.
X
W
leP
~
~g~a/1
.
.~
F
'-4
- -
lt[/r~
I
~1-
F
%7.
in
II
8
9
SkaeraaWr,' iorek 9it/e
46
6
7
8
9
10
0-OV
Fi~re 4~
11
I
It
I
Id
M
~- 4 v~4
/A'7Tdc?4~5/
a-24% k
MitIevae/
& AliI
4-4
Ao6 7
1 4 rot
/go?'
/S05
8"9
sore
I
able agreement with those of Wager and Mitchell.
Figure 2
is a plot of the writer's determination of K and Rb showing
variation in composition from base to top of the intntsive.
The analyses of Wager and Mitchell are plotted for comparison.
The sympathetic increase in both K and Rb from base to
top of the intrasive are illustrated.
Figure 3 is a plot of
%K against % Rb in the Skaer-
gaard intrasive and demonstrates the straight line relations
ship of K and Rb oontent from basic to acidio rooks: again,
it is not known whether the deviation from 450 slope reproseats an enrichment of Rb over K, or is due to analytic
error.
In these analyses W-1, the standard diabase, was used
in analysing the gabbros, while G-A, the standard granite,
was used for acidic rooks.
K nd Rb in, 3ltramafo Rooks
Potassimm and rabidium
are impoverished in most altramafic rooks, except those that
are rich in miea,
Of the twelve altramafics analysed, only
the diamond-bearing Arkansas peridotite and kimberlite *ontained significant K and Rb.
All the danites, serpentines,
peridotites, and pyroxenites showed negligible quantities of
K ( 0.05%), while Rb was not detected.
The K and Rb in the Arkansas peridotite and kimberlite
are present almost entirely in biotite.
The ratio % K/Rb
is smaller in these two specimens than in common potash
29
feldspar-rich rocks, demonstrating that Rb is enriched over
K in the biotite stractare,
as compared to feldspar strao.
tares.
A specimen of anorthosite contained 0.05% K and 0.0005%
Rb, with the sonsequent ratio.% K/Rb of 100:1.
To the
writer's knowledge, this is the ffrst determination of the
K/Rb ratio in anorthosite.
Both K and Rb possess radioactive isotopes, viz. K40
and RbOT.
Oalaulations based on the half-lives of these two
isotopes and their present relative abundanoes dtow that the
change in ratio of K/Rb throughout geologic time has been
negligible.
Data for making these calcalations is based on the
constants used by Sawyer and Wiedenbeck (1950) and Ahrene
and Gorfinkle (1950).
The caloalations are as follows for K40,
Half life of 0 =
1.27 x 109 years
Decay oonstant, k, = 5.47 x
Relative abundance K
9:
00o(years)r
K0 iel = 93.8: 0.012: 6.61
KeS= Present abundanes of K 0
60
= Initial
abundance of X40, aseaming geologic time,
t, to be 3 x 10P years.
40
40 -kt
40
5.17
30
Similarly for Rb8 7 ;
Half life of Rb87
= 5.9 x 1010
Decay constant, k = 1.18 x 10'11
Relative abunda~oe,
RbSZ
-
= 7.28: 27.2
b8 5 ; Rb8 7
1.036
Thus it is readily seen that- the primitive ratio K/Rb
was almost identical with the present ratio.
Assuming
geologio time (or cosmio time) to be twice or three times
as great as 3 x 109 years would make no significant differenoes in present and initial ratios.
The constanoy of the
K/Rb abundance ratio is due to the very small isotopio abundance of t0 , making the changes in abundanoe of
40 insigni-
ficant with respect to the other potassium isotopes, and to
the long ha lf-life of Rb8 7 , making the changes in abundance
of Rba8
insignificant in geologic
time.
Incidental to this observation is the heat production by
radioactive disintegration throughout geologic and cosmic
time due to K40 and Rb87 . Three billion years ago the heat
prodaction from K4 0 , beoaase of its greater abandance, was
approximately five times that at present.
Because of the long
half-life of Rb8 7 , heat production from this isotope was almost exactly the same as at present (greater by a factor of
1.036).
Teztites: The origin of tektites is unknown.
Beoaase of
31
their peculiar occurrence and geographical concentration in
certain areas and their peculiar compositions they have been
classed as meteorites by most investigators.
The purpose of
this investigation is not to establish either the meteoritio
or terrestrial origin of tektites.
However, trace element
studies indicate that their compositions are extremely unlike
terrestrial rocks and more nearly resemble meteorites in
trace element composition.
The anomalies are briefly listed
below, based on visual comparison of the spectra of tektites
with those of common Earth rooks, eg.,
standard granite and
standard diabase, and on the literature.
1.
Average 8i02 content Is 77%, being more acidio than
any granites and comparable only to some alaminoas shale in
gross composition.
2.
Al content (approximately 11%) is higher in tektites
than in most granites and shales or other common terrestrial
rooks.
5,.
Na( % X, opposite to the relationship of these two
elements in terrestrial igneous rooks, but similar to average
granite in ratio,
4*.
% S comparable to that of meteorites, diatases, and
altramafio rooks, and distinctly higher than for terrestrial
siliceous roocs, such as granites and shales.
5.%
Zr comparable to that of granite.
6. % Sr> % Ba, in contradistinction to the relationship
32
of Ba to Sr in acidic terrestrial rooks, in which Ba is always greatly enriched.
Ratio & Ba/Sr found to be 42 for aver-
age Of three tektites.
Ratio
% Ba/Sr > 8 in granites.
7. Ni content markedly higher than in highly siliceoas
terrestrial rooks, such as granites and shales.
8. The content of iS, Rb, and o is comparable to that
of granites, as shown in the following table, based on the
analyses of three tektites.
Tektites
Analyis of Linok
S0yI
Tektites
Pinson
Nap0
3.b8
1.79
0.45
K2 0
Li2 0
5.42
0.00045
2.71
2.48
Rb2 O
0*061
0.02
----
0.00025
0.00025
e---
.a0
0.0005
a
On the basis of the dissimilarities between the chemical
compositions of tektites and terrestrial rooks, it is diffioult to support the theory that they were derived (by lightning striking and fasing rooks, or otherwise) from terrestrial
roeks,
They do not resemble even remotely any known volcanic
glasses or other terrestrial rooks.
The origin of tektites will probably never be established
as meteoritic uAntil one is seen to fall as a meteorite, but we
*Link, Gottlob, Aufban des £rdballs, Rede gehalten sur Feier
des akademisohen 2i4ThVerTTelr*inMgam 21. June, 1924, Jena.
33
may conolade that they are dissimilar to all terrestrial
rooks in so many ways that their terrestrial origin seems
doubtfal.
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39
Figure 9.
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ld
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35
(Ontdrio)
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7 89
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40
TABtL1
I
K AND Rb IN IETSORITES AD ROOKS
AARb L
lihates
a~lEffde
Homestead
CHONDRITESS
a
#&Olates
Va r
Uorr.
oorr.
0.11
0.0013
0.0012
85
Ranoome
0.18
0.13
0.00019
0.0014
95
Hayes Center
0408
0.07
0.0007
0.0006
115
Waconda
0.10
0.09
0.0011
0.0010
90
Assn
0.11
0410
0.0012
0.0011
90
Holbrook
0.09
0.08
0.0009
0.0008
100
Bj3rbole
0.11
0.10
0.0009
0.0009
90
Paltask
0408
0.06
0.0006
0.0005
120
Forest City
0.06
0.05
0.0008
040006
85
Hessle
0.310
0408
0.0008
0.0006
130
Kernoave
0.11
0909
0.0009
040007
130
Barratta
0413
0412
0.0014
0.0013
90
Moos
0.12
0411
0.0011
0.0010
110
Tennasilon
0.11
0410
0.00009
040008
125
Muaroe
0.09
0.07
0.0009
000007
100
Long Island
0.06
0406
0.0011
0.0010
Beaver Creek
0.10
0408
0.0008
0.0006
Analyst, W. H. Pinson
Triplicate averages
***
Chondrites average 6)SSai,"i
phase
60
130
41
eftates
eta
Laumpkin
0.07
cangas
0.10
EStacado
Warrentown
r~Erro's u'ar
0.0008
0.0007
85
0.08
0.0010
0.0008
100
0.09
0.07
0.0008
0.0006
115
0.06
0.06
0.0006
0.0006
100
K AD
MaG
EANU
b
N
E1 TT8 AND
e
"T0 S i
11ets
rn=
RIT-
aates
pallasite
olivine
(0.001
Ohladnite
Johnstown
Carbonaeosos
ohondrite,
Orgueil
awr
0.001
MO
fl-a
-
<0.0001
an---a
-o
x677.no-
(0.0001
---
0.019
90
.o..-
----
son
Carbonaoooas
nodle, He ase
Thktito
Annam, Indo
1.74
o---
China
Tektite, N'
0.018
1.74
Cambodia,
Indo China
Tektite,2.I*
-......
1.83
go
n
0.018
100
42
AND RB
Sample
IN 3ABASES
e ao tioa
R1140
Diabase
0.631
0.0097
68
11147
Graaophyrio diabase
1.61
0.0356
48
111148
Oliviae diabase
1.33
0.0fl6
115
Gabbro
0.79
0.0100
79
Graaophjria diabase
0.86
0.0120
71
1.34
0.0180
7b
0.97
0.0180
54
0.96
0.0150
64
0.60
0.0100
50
R1323
0.52
0.0079
66
R1324
2.30
0.0320
72
0.60
0.0130
46
1.64
0.0230
71
1.01
0.0130
78
68
R1314
"t
"
R1518
R13220
R14b0
R1468
Altered diabase
0.46
0.0068
R1470
Graaophyrio diabase
0.75
0.0074i
101
R147b
Altered diabase
1014
0.0180
64
11480
Diabase
0.74
0.0071
104
R1489
4ltered diabase
0.25
0.0023
109
R7f08 Is a Dalath gabbro specimea. Specimens R1147, H1322,
R1324 and R1328 are fron Ontario, Mataohewan area. Balme are
from Ripiesiag area of Ontario.
43
Description
%K
'flIioate
Averages
R149
Altered diabase
0,54
0.0087
62
R1497
Sheared diabaso
0.66
0.0150
44
Olivine diabase
0.93
0.0074
126
0.65
0.0050
130
0.32
0.0037
87
Altred diabase
0.37
0.00?
100
Granophyric diabase
1910
0.0150
73
1934
0.0230
be
0.89
0.0100
87
0.0180
68
0.0290
b7
Rl016
R1506
flbZV
R1627
R161
ElbZG
Riba1
Rib39
Rib50
"
"
1.66
44
s&
sal
e
-
a
a
saaan
iption
g.
%K/JIb
% Ka
E 69
Acid granophyre
3.06
0.024
128
Melanooratlo told
granophre
2.60
0.022
118
Basic hedenbergito
granophyro
1.01
0.007
144
Faalte forro-
0.72
0.006
120
1907'
Hortonolite terrogabbro
0.27
0.0015
180
Z661
Gabbro withoat
olivine
0.0
0.0016
188
4067
Olivino gabbro
0.24
30b8
4142
,gabbro
141
MISELAKK0US ULRAMAFICS
I
K
Rb
%K/Rb
gAsiwi
Dauapton
3,44
Aaorthosito,
Split Rook, Minn.
0.05
0.0005
S-49
Mica aqgitb 9efIdotlt*, Aarfroeboro,
Ars.
.4.6.
0.11
42
------
Kimberlite, 3. Afr.
1.7
0.028
61
50-10
Lhorsolite,
Baltimore, Ad.
0.015
<0.0002
--m
S-b7
2irozenite,
Wbter, 3. 0.
0.,001
<0.0002
Saxonite, Riddle, Ore.0.004
(0.0002
-
an-
100
--
45
U90"MAMAFIA$
QE uI $S AltO
Sample
MPANlS
%K/ab
Devaription
xge!
P140
Danite, Balsam
Gap,
2141
L
~0.001
(060002
--
Me-
G.
Serpentine,
~'0.0005
e--
-O
<0.0002
--
---
Serpentine, Bele-~.0Q35
<0.0002
---
Ser pentenised dan- ~0.003
its, ig,'s Mine,
<0.0002
o-e---n
~O.011
<0.0002
en
---
.C.~'0.004
<0.0002
--
Geiger's Quarry, 4
Wa sh.
Daite, Twin Sistere Mt., Whateen,
0.0004
P18
ders Mt., Vt.
P3x0O
Wt*;;.
P369
Websterite,
231
Daite, Addle,
--
4.
Webster, N. C.
--
-e
This Sale of roots was analysed for radioaotive content
and stadied petrographioally by 0. L. Davis and i. H. Hess,
1949.
CHAPTER IV
BARIUM AND S
U
Historg-al ReLgws
$N MEfITES
ND
X
The determinat ion of Aa in silicate
meteorites is due almost entirely to the work of Ida and W.
Ioddack (1930),
and to the work of Wolf von Engelhardt (1936).
Goldschntdt (1937) reeloulated the abundance values.
DeSerminations of Sr in meteorites are based on the work
of the Noddaoks, W. Boll (1934), and G. v.
Wudrstlin (1934).
evesy and K.
Largely on the basis of these values H.
Brown and 0. Patterson (190) have calcalated oosmic abundance
valaes for the elenents Sr and a. Hevoesy (1932) has oompiled abundance values for Sr and Ba in stony meteorites from
nis sad *irstlin's analysea and the analyses of the ioddaoks.
Rantama and Sahama (1950),
in a review of the literature, also
derived abundaace values for lr-and Ba.
Abandant analyses have been made for Sr and Ba in terrestrial roax
Sanama .
and the literature is reviewed by Rankama and
loll (1934), Bevesy and Wilretlin (1934), and von
Engelhardt determined Ba and Sr in various rook types.
Other
worters include F. Wioakan (1948) for the cosmic abundanoe of
Sr, Sahama (1945a, 1945b) ror Ba in rooks of Fennosoandia, and
Ba in Swedish rocka by P. H. zandegardh (1946).
In the following table are given the resalts of various
workers, inolading those of the writer.
4(/
Anal
rt
r
%Ba in silicate
1 a in sp11oatt
meteoriete
ewer
teor ites
**
,,*
*
Hevesy & Waretlin
0.03, 0.1-0.5
0.00
Noddaaks
O.072
0.0020
Goldpchmidt
0.0026
Rantama and Sahas
0.0026
0.0009
v. Engelhardt
a-----
0.0001-0.0048
Pinson
0.0007
0.0008
a
i
0.0009
IndividQal analyses of the meteori tes by v. Engelhardt
are listed below, showing comparison with the writer's.
Name
BaO
4"em"MIMP.
Ua
gelhardt
Nakrite, Stannern,0seohoslovakia
* Javinas, Franee
--
0.0048
0.001-0*003
Chondrite, L'Aigle, France
0.0003-0.001
Silicate phase, Holbrook, Ariz.
0.0003-0.001
asa~.An
jLIuMuulj, bw
neA:1000
be
-----0.00I
T
Silicate phase, Ungarn ahoadrite
0.0001-0.0003
Chondrite, Erxleben, Sazony
0.0001-OO0003
eas e awes
"I
*
" Chantonnag, France
0.0001-0.0003
" Barbotan, Frane
0.0001-0*0003
" Aviles, Mexico
0.0001
, bjub'le, Finland
0.0001
0*0008
"* Pltat, Poland
a--
a sea
0.0007
Reyesy, 1932.
** Heyesy and Wairstlin, 1934.
w-----
0
Simarly, a table for Sr is presented.
Namae 0
S
sOmy
44
o
Wurstlin
y _&
Waconda, Kansas
es. 0.01
Ouanta, Spain
"
0.01
Paltash, Poland
"
0.02
0.0007
0.02
------
Vigarano,
Tabory,
Piave, Italy
0.0009
0.03
Russia
Karoonda,
'
South Australia
"
?
------
0.05
------
Revesy and Warstlin used x-ray spectrographic techniqies.
Thus it is seen that the work of v. Engelhardt on Ba is
in reasonable agreement with the analyses of the writer.
employed the optical sp*etrograph.
Both
The writer used new im-
proved quantitative techniques for determining trace elements
-
tno addition method, wherein a typical ohondrite was used as
the matrix material rather than a synthetia standard.
Ba and
Sr were added as W-1 and G-1, which have been independently
analysed by several other workers and are based on mean values.
The analyses of Hevesy and Warstlin, based on x-ray spectrographic sechAiqes,
seem to the writer to be in error by a
factor of at least 10 for Sr, and it is sugested that these
valaes be no longer used in computing oosmio abundance valaes.
Recalcalations of the results of the Moddaoks and Hevesy and
Wuratlin by Goldschmidt (1958) led to the conalusion that Sr
* Fairbairn, H. W., U.,..S. Special Ball.,
1951.
41
was more abundant in silicate meteorites than Ba.
The re-
salts of the writer's investigations indicate that Ba and Sr
are almost equally abundant in meteorites.
On the basis of the present analyses of the writer it is
suggested that the abundance values in chondrites be revised
to jir. 0.0WS% for Ba and cir. 0w%
for St, and that these
two elements are present in a ratio of approximately 1 in
chondrites.
Chondrites comprise over 95% of silicate meteor-
Beoaase of the low concentrations of these elements
ites.
and spectral background error possibilities, the values, n-.
pecially that for Ba, ay be slightly high, possibly as much
as 20%.
Gooshemistry of Ba anA Sri Stroatiam and barium are
widely distributed in the rooks of the Earth's orast, and are
among the most abundant of the traco elements.
However, the
quantity of Ba and Sr concentrated in minerals of these elements, e.g., barite and celestite, is relatively small.
Fur-
tnermore, the barium and strontiam minerals are chiefly products of sedimentary and hydrothermal or pegmatitic-hydrothermal origin and are not believed to be mineral products of
magmatic differentiation.
When contained within a cooling
magma strontium and bariam substitute and are captured within
the other minerals.
Following are listed the ionic radii for the four elements
which commonly freely substitute for one another, specifically
50
Ba2t for X and Sr2t for Ca2+
Oa2 +
- -
2+
-
Sr
Ba
K
+
-
. 0.99A
-
-
-
-C
-
o
-
1.12A
0
1.34A
a
1.33A
From these ionic sites it would be expeoted that Sr 2 +
and Ga Z+ would readily sabstitate for one another, while Bat2
would follow Kt
This generalisation has been found to be
true by observation.
The mineral distribation of Sr and Ba
has been tally discassed by Rankama and Sahaa (1950).
Ob-
servations in this thesis will be confined to the meteorites
and rooks investigated.
Sr and Ba in Meteorites:
On the basis of twenty-one ohon-
dritic analyses, the average Ba and 3r content are given below,
and are compared to values derived by v. Engelhardt, Hevesy and
Wurstlin, the Noddacks, and Goldschmidt.
The working curves
used in determining Sr and Ba in meteorites and rooks are oontained in this chapter.
The spread of points in these curves
serve to demonstrate the degree of reproducibility possible
by these spectrographio teohniques.
The following table com-
pares the writer's results with carrently accepted values for
Sr and Ba in silicate meteorites.
%Ba
Sr
4*
Pinson
.Bnejn
flhjl
0.0006
0.0007
0.0009
0,0026
Ahrea, L. H., New Ionic Rettn4In
Atoa).
*~Rankama and Sahama, 1950.
j
1aestilgators,
sor
press, Geocheimica
Table II gives the analytical results for Ba and Sr of
the writer's investigations for individual meteorites and rocks.
It is seen that the weight percentage values for Ba agree
well, but taat of Sr is smaller by a factor of 3.7.
Two of
the stones analyzed showed anomalous Ba content; the Rancome's
Bridge, B. C. stone containing 0.0032% Ba and the Long Island
stone containing 0.0110% Ba.
The analysis of the Long Island
stone was not included in the averaging for Ba content for
two reasons.
The specimen analysed was badly weathered and
has conoeivably been contaminated with Ba.
Secondly, the near
constancy of the other meteorites in Ba content suggests the
Ba content for the Long Island stone not to be representative
of chondritic meteorites.
In all other specimens the spectra
of chondrites were remarkably similar.
The danger of error
in relying on composite samples is demonstrated by the anomal.
ously high Ba content of the Long Island meteorites.
This
specimen (weathered, however) contains 14 times the average
Ba content or the other meteorites analyed.
zeoluding the Long Island and Rancome's Bridge meteoritem, the Ba content of the other 19 chondrites is remarkably
oonstant, with a maximum variation of only 6 parts per mile
lion.
In all twenty-one obondrita analyses the content of Sr
is remarkably constant, with a maxiamm variation of only 7
parts per million.
1t flObb,
rbasonable to believe that Sr and Ba are present
in almost constant quantity in silicate meteorites, on the
basis of these twenty-one analyses.
The variation in content
is approximately within the factor 2. This factor may, in
fact, be smaller, beoause its magnitude is partly due to experimental error.
Probably it is not larger.
It was hoped
that this investigation possibly would prove that the qantity of those trace elements which are restricted to the silicate phase (Sr,
Sa, Sc, alkali elements, eto.) would show
that their quantity depended on the amount of free metal
phase present.
This relationship has been demonstrated by
Vrior and others in the ease of Mg and FeO, and is fully disCassed in this thesis in the chapter on mineralogy.
However, it
is concluded that the results of this investi-
gation are not sufficiently acourate to warrant such Oonolmsions for Sr and Ba.
The relationship may exist that these
elements are very nearly constant in the silicate phase, and
the total qaantities in the ohondrites are leseeod proportionately to the amount of free metal present, but more accurate
analyses are needed to prove it.
Spectrographic analysis
with use of an internal standard should be able to establish
or disprove this hypothesis, and fatare work of the writer
will be along this line.
RanXama and Sahama (1950) conclude that BaZ# cannot substitate for Mg
sizes.
because of the great difference in ionic
However, in the case of Fe-rich olivine from a palla-
site of this investigation, it is seen that Ba in present as
0.0007% oomparable to that of the ohondrites.
Srt ion is,
The smaller
on the other hand, definitely impoverished.
The sam relationship holds for the bronsite analysed from
the Johnstown, Colorado, chladnite.
Ba2
Since neither Sr2 nor
would be expected to fit into the olivine or bronsite
lattioes,
it is reasonable to believe that these ions were
entrapped --
that orystallisation was too rapid for their es-
*ape (differentiation),
These large ions shoald distort the
bronaite and olivine lattices, and measarement of the lattice
constants by x-ray diffraction methods may enlighten this
relationship.
Srz+ seems to have been largely exeladed from meteoritic clivine and bronsite, and thz
it is auggested that in the
chondrites Sr2+ is a oonatitUeat of either the rare cnloio
plagioolases, or more probably the abwdaant interstitial
glassy material.
Chilling in the former planet's interior
may have proceeded too rapidly to allow normal sabstitution
of these two elements into crystal lattices.
Sr ana Ba in the Skaergaard suite: The analysis of these
rooks for Sr and Ba has already been done by L. R. Wager and
R. L. Mitchell.
Although the Skaergaard rooks represent a
wide range in composition they are believed to be the resalt
of the difrerentiation of a single intruded magmatic body (Wager and Deer, 1939).
Although the elements Ba and Sr have already been analysed for by Wager and Mitchell (1943), these elements were
again analyzed for by the writer because Sr appeared to be reported as unasaally abundant for these types of basic rocks.
Wager and Deer reported 0.2% SrO (or 0.17% Sr) present in the
original Skaergaard magma, as represented by the marginal
olivine gabbro, and state "SrO, as has already been noted, was
particularly abundant in the original magma."
It is suggested
on the basis of the writer's analyses that this conclusion is
erroneoas and das to analytical error,
The value 0.2% is
ten times larger than the amount in Noll's
*
**
and Daly's
average gabbros, and is almost equal to the potash content -indeed an anomaly.
Petrologists would indeed like to believe that the
original Staergaard magma was in no way abnormal, for this is
probably the most thoroughly stadied example of the fractional crystallization process daring magmatio differentiation.
The variations- for Ba and Sr from bottom to top of the
Skaergaard intrasive are shown in FigareZ.
AThe results of
Wager and Deer are plotted for comparison.
The trends of the
two "oarves" are sympathetio, and the analytical agreement for
Ba is reasonably good. However, Wager and Deer's values for
* W. Noll in 1934 prepared a composite sample from 14 gabbrolike rooks for analysis, and 14 gabbros for analytical oomjarison.
* R. Daly in 1937 likewise compilated from the literature
the composition of an average gabbro and an average granite.
Fi jure 1.
0-0201%
Sr
*.007%8
-. 0,1 '%*
VARIAT/ON OF Ba & Sr
IN
V7
S/'A ERGAA RD IN
r US/VE
Analyst, Pinsoo
AnMa/ysts,
C
I,.
qoET6
366/
/S 07 -
a
4.
1- 42
Wager & Mthefl
'Jib
/00oar
0a
L%
56
Sr are approximately 7 times those found in the present inYestigation.
The spectrographio plates were rechecked and
the values found in the present analyses seem to be correct.
It is Qoncluded that the anomalously high Sr content found
by Wager and Deer in the original magma (marginal gabbro) and
the suacessive gabbros were due to an analytical error, and
that the Skaergaard rooks contain a reasonable and expected
amount of Sr.
SrZ+ is shown to vary sympathetically with Ca2+
ions are of like charge, and although Ca
These
is somewhat smal-
ler than Sr 2 + (0.99A and 1.12A) the difference is less than
tae 20% of the empirical geoohemical rule stating that solid
sabstitution to a significant extent can oooar only if the
replacing ion is within 20% of the size of the ion to be replaced.
Sr and fa both decrease abraptly in the acid granophyre
phase.
In another paper Wager and Deer (19Z9) have discussed the
olivines of the Skaergaard rooks.
Although this remarkably
complete olivine series crystallized in a lime-rich environment, the olivine minerals have remained nearly pare members
of the FoS104 - MS2 Si0 4 series, and are practically free of
Gaz2i0 4 .
However,
the experimentally observed series GaO -
FoG - S10 2 suggests that these olivines should contain from
six to seven percent 0a2 3i0 4.
Baritam and potassium have likewise been plotted in Figare l anl the resalts of Wager and Deer compared with those
of the writer.
The agreement is reasonably good.
Although
the ionic sizes of K+(l.33A) and Bag+(1.34A) are very similar, the Ionic charges are different. However, the
saboti-
tation of BaS+for K + is not believetto take place as readily
as that of Sr2+ for
a2+(Rankama and Sahama, p.471, 1950).
W. Noll (1934) oonoludes that Ba in relation to Sr is
enriched in potash feldspar rooks, doe to the smaller radios
of sr2+ which is entrapped in the crystal stractares of the
early formed caloic plagioolaeas and caloic pyroxenes, sub..
stitating for Ca +.
study of ti
Thas, observation is confirmed in the
Skaergaard intrusion, where the Ba Is enormously
enriched. in the final differentiate, potash &aid granophyre.
However, in the case of shoandritic meteorites, this investigation has shown Sr and Ba to be present in almost eqaal
and constant quantities, in amoants lesser by a factor of at
least 20 less than is normally found in diabasic rooks and
granites, but on the other hand enriched by a factor of 10 or
more over altramafio Mg-Fe rooks.
This observation suggests
that the silicate magma from which chondritic meteorites
formed cooled too rapidly to permit differentiation of Sr and
Ba, and that these elements were entrapped.
It is suggestive
that a value of approximately 0.0008% for both Sr and Ba may
represent the true abundance ratio in the silicate magma which
58
formerly existed in the planet from which meteorites may
have been derived.
Ultramafic rooks:
Thirteen tltramatios, inoluding seven
specimens which have been analyzed for radioactive content by
Hess and Davis (1948) have been analyzed speotrographically
for Sr and Ba, as well as for K, Rb, So, and Zr.
Noll (1934) reported Sr absent in danite.
Hevesy and
Warstlin (1934) reported 0.0020% Sr in peridotites, eologites,
and danites, while von E;ngelhardt found cir. 0.0003% Ba in
ultrabasio rocks.
Sahama (1945a) found air. 0.0009% Sr and
air. 0.0018% Ba in Lapland altramafies.
An anorthonite from Split hook, Minnesota, which is a
-alciam-rich root composed almost entirely of bytuwnite,
showed 0.008% Ba and 0.029% Sr.
This rook contains a large
percentage of Ga (in calen plagioolase), bat is almost free
of K (0.05). This is the first analysis of an anorthosite
for Sr and Ba known to the writer.
The enrichment of Sr over
Ba is as woald be expected, although the Ba content seems a
bit too large for a rook so low in K oontent.
fouad a oontent of 0.01
W. Noll (1934)
Sr and 0.035 in two specimens of
plagioolase analysed.
A specimen of kimberlite from Soath Africa contained
0.07%Ba and 0.028% Sr.
A thin eetion study could not made
of this rook, beoaase the specimen was received in a palverized form.
However, its most abundant mineral oonstituents are
olivine and biotite, which probably accounts for the enrichment of BS2a
by substitution for K+.
But Sr2 4 is also great-
ly enriched, as in Ca-bearing altramaficas.
A review of the
literature (Johannsen, 1938) shows typical kimberlite to contain tremolite, a caleio mineral.
Also, a visual inspection
of the spectra of this specimen showed Ca to be present in
significant quantities.
Biotite was shown by von Engelhardt
to be greatly enriched in Ba, while W. Noll showed approximately 0.0008% Sr in the biotites, which contained on the
average 1.89% 0aO.
F. Whiting (1951) found approximately
A similar valae was found by S. R.
O.5* Ca in biotites.
Noctolds and R. L. Mitchell (1948).
Both values are onsid-
erably smaller than those found by won Engelhardt.
A specimen of the Arkansas diamond-bearing peridotite
was analysed for Ba and Sr.
Sr content was 0.013.
Barium content was 0.1%, while
Thin section study of this specimen
revealet it to be composed of phenochrysts of olivine set in
a fine groud mesh of augite and biotite Orystals.
Augite
contains abundant Ca2+, while biotite is rich in Kt *
Also,
analyses showed 4.6% K, while a visual estimate of Ca showed
it to be present in large qantity.
Ba2+ and Sr t +for K+ and 0a
Thus the substitution of
is again found as expected.
A specimen of Lherzolite from near Baltimore, Maryland,
was analysed.
This rock is composed of olivine and ortho-
rhombic pyroxenes.
Inspection of its spectra showed both Ga
and K to be present in minor amounts (0.0154) as were Ba
(0.0006%)
and Sr (0.0014*).
In all danites, serpentines, and non-calole pyrozenites
analyzed the content of Ba was found to be lower than 0.0013o.
This value is in close agreement with that of chondritic
meteorites.
The average for 10 Mg-Fe rooks of these types
was 0.00040% Ba, in olose agreement with the average value
of Ba in chondritio meteorites.
Strontium in these rooks
averaged 0.0001% Sr or slightly less.
All were exceedingly
low in K and Ca, as shown by examination of the spectra.
Those specimens that showed appreciable quantities of Ba
all contained traces of X, which thin section studies indieated probably to be present in minor constituents of mica.
G. L. Davis and H. H. Hess (1949) give excellent petrographIc descriptions of the suite of seven altramafios analyzed
by the writer.
Saxonite, a terrestrial rock which most often is cited
as closely resembling stony meteorites in mineral composition,
was found to contain only a traes of Ba,
0.0005% Sr.
0.0001% and
Thas both Sr and particularly Ba are lower than
in meteorites.
This observation again demonstrates the im-
propriety of comparing this rook with meteorites, particularly on a basis of mode of origin.
Figure 11.
Vt~II-
- - -
- -
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r --
61
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62
Figure 12.
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66
i
4Bates
4
!"toro
oates
Gor 1
e
/Sr
u37r-
Lumpkin
0.0007
0.0006 9.0007
0.0006
1.0
Cangas
0.0007
0.0005 0.0008
0.0007
0.8
Estacado
0.0008
0.0006 0.0008
0.0006
1.0
Warrentown
0.00005
0.0006 0.0006
0.0005
0.9
gLa
ASA.
I
ITE3SD
MiIELA fioUS METEOLIL*AS
rwrr
-3.
C.
pallasite
Olivin*
0.0007
0.0007 0.0001
0.0001
6.7
Culadnite,
Johnstown
0.0006
0.0005 0.0002
0.0002
2.3
Garbonaq.
0.0003
esous ohonaritto
----
0.0004
0.8
Caz bonaqe OLas------
0.*0008
----
0.9
TeXtite,
Indo China
0.*000
- - ---
0.0075
4.0
0.*032
---
0.0087
3.7
0.0085
4.9
Orgueil
nodale, Heable
----
?.kt i toI
Tektite,
Palo
0*042
6w
Ba
AND own"
Sr
IN
SKAERGAARD ROOKS
mab
a
NOa
sample
Desgriptiona
I
gSo
fliariges
3068
Ba/Sr
Acid granophyre
0.081
0.0081
Nelanocratic acid
granophyre
0.07S
0.010
1905
Basia hedenbergite
granophyre
o.O6
0.035
442
Payalite ferro-abbro 0.013
0.008
1.6
1907
Sortoalite ferrogabbro
0.006
0.018
0.35
$661
Gabbro withoat
olivins
0.010
4067
Olivine gabbro
0.007
10.0
7.5
10.3
1.8
0.020
3.6
ISCZ2 ANECEIS ULTRAMAFICS
%Ba/Sr
SaMp loleription
teragesS-44
S-49
a---
------
as
0
V1g,
Anorthosito,
Split Rock, Minn.
0.0008
0.029
0*28
Miea augite peridotite, Murfreesboro,
Ark.
0.1
0.013
0.77
Kimberlite, S. Afr.
0.07
0.028
0.25
Laerzolite,
Baltimore, Nd.
0.006
0.0014
Pyroenite,
Webeter, . C.
0.0013
0.00016
8.1
Traes
(0.0005
-- a
-Saxoite,Riddle,Ore. ?,Praoe
66
ULTRAMTAFIS OF HESS AND DAVIS
sane
Description
3r
Averages
&0.00014
P140
Danite, Balsam
Gap, N. 0.
0.00067
P141
Serpentine,
0.00081 A 0.00005
16
0.09070
(0.00005
My
Geigerr's Qarry,
Wash.
P145
Dunite, Twin Sis-
tere Mt.,Ahatoon,
P318
Serpentine, Belvedore Mt., Vt.
0.00050
A. deteted
PS20
SerpentInised dsanite, Zlng's Mine
The t
,Pf.4.
0.00049
(0.00005
2369
Webe terf to,
Webster, E..
0.00004
~0SJ002
27
P391
Danite, Addie, 5.0.
0.00055
~.-P0
2.7
08o
--
CHAPTER V
MTEORImhS AZI RociS
S0 AD hINER
Utetorical Revie; Rankama and Sahama (1950) have reviewed the literature on the abundanoes of So and hr in meteorites and rocks.
The Noddacke (1934) found 0.011% So in
a composite sample of silicate meteorites and 0.0006% So in
terrestrial rociks,
V.
. Goldeshmidt and CX. Peters (1931)
analyzed a large number of minerals and rooks and twenty-six meteorites, including roarteea ohondrites, olivine from
a pallasite, and a onlaAnite.
Goldsohmidt and Peters found
0.0000 - 0.001% So in silicate meteorites.
(193U)
W. van Tongeren
compiled abundance values for rare elements, includR. Brown
ing So, in the rooks of the Datoh East Indies.
(1949)
compiled cosmic abundance values for both So and hZr.
Zironium was determined as 0.010%in the silicate phase
of StOy ateorites by the Nodttaks (193Q# from a composite
sample, and In the metal phase as Q.u00% hr.
Warstlin (1934) determined So as
Hevesy and
0.010% So in silicate
meteorites, by the analysis of a composite sample composed
og 40 meteorites representing £0 separate falle.
Hevesy and
wuaretlia employed x-ray spectrographic techniques (1932),
while the other investigators used the optical speotrosraph.
Revesy and Wurstlin also determined hr in numerous minerals
and rocks and in several individual meteorites.
zr was do-
70
termined in some igneous rooks by van Tongeren (1938).
The Nottacks determined Ht as well as Zr in silicate
meteorites,
presamably by chemical conentration and spea-
trognphio methods.
Goldschmidt and Peters were unable to
detect Y in metorites, and reported
0.0001%Y.
The
present writer was likewise unable to detect Y or Uf- in
meteorites, nor any of the rare earths.
Cerium, La, and
Y were sought but not found.
ScandiAu
G0oaemistry of Soadiu m:
Soandiam, Z = 21, is of ten
incladed in the grotp of rare eairth metals (Z = 57 for La
and Z = 71 for La),
because So in closely similar to the
rare earths in chemical properties and in geohemic distribation.
Yttrium, Z = 39, is often included for the same
reason.
These similarities of So, Y, and the rare earth
elements (or lanthanides) are due to the lanthanide contraction, whereby, starting with La, additional electrons in
sacoseeding elements are added to the inner N shell, and all
the elements of this group remain trivalent.
Beoauise of the
increasing nuclear charge-and the electrons being added to
an inner shell closer to the nuoleus, there is a compensating
contraction of the ionic sizea, with the result that all of
the rare earths are or very nearly equal ionic sizes.
The
population of the outermost eleotron shell remains constant.
Scandiam, however, is of smaller size than the rare earths,
71
which accounts for the fact that its geochemical behavior is
somewhat different from that of the rare earths.
So in ateorites:
Scandium was detected in all twenty-
one ohondritos of this investigation.
ly constant amounts.
It is present in near-
In the silicate phase it varies from a
minimum of 0.0006 in the Warrentown, Missouri, specimen to
0.0013 in the Homestead, Iowa, specimen.
Analytical results
for So in rocks and meteorites are given in Table III.
So
was not detected in olivine from a pallasite, which seems anusaal in the light that Soc+ is usually thought to substitute
freely for Mg2+ and Fe2+ of similar ionic size in early magmatic orystallates.
The average abundance value of Sc in the ohondrites analyzed is 0.0006%; that of the silicate phase of chondrites is
0.0007% So, as determined in the present investigation.
These
valaes are in close agreement with those of the Noddacks, who
analyzed a composite sample, and with the values quoted by
Rankama and Sahama (1950).
Goldschmidt found O.0O1
So in the
Rosestead meteorite.
One obladnite, Johnstown, Colorado, an achondritio meteorite composed of approximately 98% bronaite, 1.bf free
metal, and 0,5% YeS, was fouand to contain 0.0014
analyses of ultrabasio rooks by Qoldsohmidt (1934,
So.
Many
1937) and
Sahama (194b) have established the fact that pyrozenites contain the highest percentages of So.
Thus it is not surprising
to find a meteorite oomposed almost entirely of bronaite, as
is the Johnstown okladnite, to contain a greater abundaaoe of
So than any of the other meteorites analyzed.
Soandium was first believed to be one of the rarest of
elemants terrestrially, due to the fact that 6oncentrations
of this element are rare (thortvsitite, 3023107 is rare, and
is believed to be the only So mineral known).
With the dis-
oovery that So was camoaflaged by substitution in the crystal
lattices of many common minerals, the known abundanoe of So
was greatly increased.
Thas, So in igneous rocks is as abun-
dant as arsenic and 1000 times as abundant as gold or platinam.
On the basis of a cotve, plotting the cosmic abundanoe
value of the elements against their respective atomio numbers by R. Brown (1949),
it was suspected that previous ara.
lyses on which the value for So was compiled we
too low.
However, results of this investigation, as well as of the investigations of L. H. Ahrens on oommon rook types, have
failea to raise signirioantly the apparentLy low abundance
value for Sa.
So in the gaargaard rooks:
This element has not been
previoaly determined in these rooks.
Analyses by the writer
showed an expected enrichment by a factor of approximately
lb from base to top of the intrasive.
The variation diagram
for So in the Skaergaard intrusive is shown
tA graph accom-
Fi~u.r~ ib.
IArTOIv /,IV~
t
t
Zr
&
SAM 7$4 T4 ARD
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panying this section.
So in altranafic rooks:
Goldschmidt (1939)
reported a
maximum value of 0.016% So in pyroxenite, and found that So
is enriched in augite (separated from eruptive rocks) and in
garnet (separated from eoclogite).
Garnet from eologites is
enriched from 2 to 10 times over pyroxene in specimens of
sologite.
In the present investigation So was found in all specimens analysed to be present in qantities of the same orders
of magnitude as in the silicate meteorites.
our in the metallio or sulfide phases.
danite averaged 0.0008% So.
So does not oc-
Three specimens of
Goldschmidt and Peters (1931)
found from 0.0005% to 0.001% So in seven dunites analyzed.
Goldschmidt reported 0.0005% in kimberlite, while the analysis of the writer is 0.0017.
Thus it is seen that the
present investigation agrees closely with the work of Goldschmidt and keters.
Scandium was detected only as the barest
trace in a specimen of anorthosite from Split Rook, Minnesota.
Goldsohmidt and Peters likewise found So either absent
or present as barely detectable traces in plagioolase foldspars, and it
is concluded that So is excluded from plagio-
clase crystal lattices.
In eruptive rooks it is confined
chiefly to ferromagnesiam types.
I. Oftedal (1943) observed that nearly all the So in
igneous rocks is contained in biotite, pyroxenes, and amphi-
boles, and found a maximum of 0.0150
So in pyroxenes from
basic igneous rocks and 0.0300' So in hornblende from a
hornblende gabbro.
In biotite and muscovite from granite
pegmatites he found as high as 0.1% Sc.
Oftedal contended
that Sc aould be used as a geologic thermometer if other
ferromagnesium minerals were not present in the rock, for
he believes that biotite is always saturated with So for
given temperatures.
Higher temperatures are believed by
Oftedal to exclude So progressively from the biotite straoture.
The writer saggests that this So thermometer may poa-
sibly be used as a eriterion of granitization.
Zirconiam
Gooohemistry ofZr:
Zirconium, boause of its large
size and high charge is believed to concentrate progressively in magmatic residual liquids. Zirconam content is low in
early magmatic crystallates, for Er oano -readily substitute
in the crystal lattioes of early formd minerals.
Zr in meteorites-
All analyses for Zr were made by
visual inspection of the line Zr 3591 and comparison with
W-1 and G-1.
Analyses for meteorites and rocks are tabu-
lated in Table III.
The Zr content of silicate meteorites
was found to be remarkably constant, with a minimum of 0.002%
Zr and a maximam of 0.008% Zr (LampkinQeorgia, chondrite) in
chondrites.
The average for twenty-one ohondrites is 0.005%
± 0.001% Zr, a value approximately half the ourrently aocepted
valas (Rankama and Sahama, 19b0).
The Noddacks (19Z0) reported 0.0008% Zr in the metal
phase of meteorites.
However, on the spectrograms of the
writer, with dispersion of 2.53 A/mm, interfering Fe lines
prevented analysis of the two most sensitive Zr lines in the
metal phase of silicate meteorites and in one specimen of
Canyon Diablo iron meteorite analysed.
2& in
Sastgaard rooks:
4he
Zirconiam had not been
previoasly determined in the Skaergaard rooks (Wager and
Mitchell, 194Z).
The characteristic enrichment from base
to top of the intrasive in Zr is shown in a variation diagram in this chapter,
£r UJ utramfialrok:
Zr has been determined visual-
ly in several altramsfic rooks by the writer.
All speci-
mens, except kimberlite, which is rich in btotite (and X),
are low in Zr content, ranging from the barest traos
( (0,0005)
to 0.004% Zr.
A specimen of mioa augite peri-
dotite, which contains approximately one-third as mach biotite (and K) as the kimberlite specimen, contains 0.Q00
Zr.
Saxonite from Riddle, Oregon, which reseables chondrit-
ic meteorites in gross silicate mineral composition (olivine
and monoolinic pyroxenes) contained only a bare trace of Zr,
and is impoverished compared to chondrites it Zr by a factor
of at least 10.
77
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81
TAbis III
$4 AAj ZI
MESTORITES AIi
So
zri
ate$
W-sa
ROCKS
CEONDRITES
0
care-
a~ees
tE
4esr
Homestead
0.0013
0.0012
0.000
0.0045
Ranome
0.0006
0.0004
0.003
0.0022
Hayes Center
0.0007
0.0006
0.005
0.0046
Wacoada
0.0008
0.0007
0.003
0.0028
Assan
0.0008
0.0007
0.003
0.0027
Holbrook
0.0010
0.0009
0.003
0.0028
Bjarbole
0.0006
0.0006
0.00b
0.0047
ultusk
0.0007
0.0006
0,004
0.0032
Forest City
0.0010
0.0008
0.005
0.0039
Resale
0.0012
0.0009
0.003
0.0024
Kernouve
0.0009
0.0007
0.003
0.0024
Barratta
0.0006
0.0005
0.003
0.0028
Moos
0.0006
0.0006
0.003
0.0029
Tennasilon
0.0008
0.0007
0.003
0.0026
Manroe
0.0006
0.0005
0.005
0*0037
iLong Island
0.0006
0.0006
0.003
0.0028
beaver Creek 0.0006
0.0006
0.003
0.0023
.Laumptin
0.0006
0.009
0.0076
0.0007
* Analyst, W. H. ilnson
** Triplicate averages
**
Chondrites average 6$ sulfide phase
82
.zr
#&oates
SET'sf
Iicate
Or.
%zr
a
Ia
cangas
0.0008
0.0006
0.003
0.0024
Estacado
0.0007
0.0006
0.003
0.0025
WarroatowA
0.0006
0.0000
0.003
0.0028
8.6
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Lamle
rns
a
TE
US
IETIES "D
MEORIES
lCftr
a-
aad
aOMW
Rallaaite
olivine
n. detnatC4
n.deteted
0.005
Uhladnite,
Johnstown
0.0014
0.0014
0.00
0.003
(0.001
----W
Carbonaceoas 0.0005
4
g
ohondri te,
Orgaeil
Carbonaceous
nodalo,
Hessle
TeWti te,
Annaa,
Indo China
Teotite,
North Cambodia, Indo
China
Tetiteo, 2.-----
------
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e
a
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0.0004
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0.0004
a
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0.020
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0.020
So
Sample.
Z
Z
A SKARAARD ROQKS
Descriltion
tSo
Averages
r
f *vragee
308
Acid granophyre
0.0002
0.015
359
uelanocratic acid granoptre
0.0002
0.050
1905
Basie hodenbergite
granophyre
0 * 0015
0.024
414Z
Feyalite ferro-gabbro
0.0010
0.006
1907
Rortonolite ferro-
0.0015
0.004
gabbro
3661
Gabbro without olivine
0.0023
0.008
4067
Olivine gabbro
0.0036
0.004
MISO)U4ANoUS
Sample
AMAWICS
Deeeription
r
se
rAe,
Averages
S-44
Anorthosite, Split Rook,
Minn.
Trage
nadeteated
S-49
Mica augite peridotite,
Murfreseboro, Ark.
0*0009
0*040
Kimberlito, S. Arrica
0.0017
0.010
So-10
Lhersolito, Baltimore,
Md.
0.0022
0.005
S-87
Pyroxenite, Webster,E.C.
0.0014
0.003
Satonite, RiddleOre.
0.0014
Trace
----
am
<0.0000
>0.0001
*0*
*TDPY
. *4Tna
T6Ct
200*0
9000*0
100*0
0o00*0 *0*N'aistq#, 's$aieqrns
6963
900*0
1100*0
M.,e&
'JgPAIRet
petc,$es *u
1000*0
£00.0
0100 0
900*0
0100*0
900*0
9000*0
se'*
SW~"O*
?40AOtQ
*WTW9SJOC
A **IP
OUR RflUTIT
gtit?
*eZ*Tg '*uTrudaes
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SIAVCr (19swzI Jo so5aYMIM
tICJ
Qtflt
CHAPTER VI
MIm;RALOGY
It is most interesting to inquire Just how olosely the
rooks from space which we call meteorites resemble the rooks
on Earth.
Since we are led in every approach to the belief
that meteorites are fragments of a shattered planet, we are
not surprised to find that meteorites are distinctly unlike
the common rocks of the Earth's earface.
for we believe that
the outer craet of any planetary body, be it of gaseous, molten, or planetesimal origin, would have aiergone differentiation, and would be different from the deep-lying rocks of the
planet's interior.
Further, we may safely assume, and we are
backed by a wealth of geologic (geophysical, geochemical,
petrologic, and structural) data, that a planet's crast is
thin, and that its total volume is extremely small compared
to the total volume of the planet.
' hus from a shattered
planet, relatively few of its Aragments would be from the
crust, and we would be fortunate indeed to find on Earth
such a meteorite.
te have not yet been so fortunate.
Howevor, the meteorites we know possess just those
properties and characteristics we expect from geological
investigation to exist in Earth's interior.
geochemical facts and theory, stuaies of
Seismic data,
arth's magnetio
86
properties, studies of Larth'8 ellipticity of shape, and a
score of other approaches point up the belief that iarth possesses a dense core surrounded by successive shells.
;%l-
though it may be difficult to discover two geophysicist who
agree on the nature of iEarth's interior, or to find one who
knows with certainty its nature, it is safe to say that all
geophysicists agree that iEarth possesses discontinaous shells
--
that the barth is layered.
Farther, we know the approxi-
mate depths and thicknesses of these shells.
So perhaps we may agree with Shand, who states (1949),
"It is quite immaterial what view one holds
regarding the origin of meteorites
....
So
whether one regards meteorites as shattered
stars or shattered planets, nebular knots or
condensed comets, as bolts from the Sun or as
bombs from terrestrial volcanoes, the important fact for as is that meteorites blgj to
in Me*ON
our notice a tyoo of rook ~~ a
that
Wom
I
a d47fIf
W6TaF"T*17iTe W
;and
Jane;
r
orS
tRI ihel T' r
itT a th7
a
ne0 "taer
T0ilise
pD6o sition
ofo comlo
tEI flaTrtT E "fl"E
that petrology, geophysics and astronomy combine to indicate as likely to be found in the
interior of the Larth."
In general, the minerals of meteorites are similar and
in most oases identical with ,*arth minerals.
The minerals
that are known to be exclusively meteoritic are becoming
fewer and fewer (eaerburg, 1949).
Of the several minerals
that are uknown in tarth rooks, it is believed that we can
explain their absence on accepted chemical laws.
have been made artificially.
Several
87
7nere are Listed in the following table the relative
order of abundanae of Earth rooks and meteorites.
Average Gristal Rock
Feldopars
Average Meteorite
59.5
Pyroxene and hornbleande 16.8
12.0
Olivine
) 25
Pyrozene
) 20
Mica
Z8
Fe-Ni(Kamaoite &
Tuenite)
Troilite
Others
7.9
Plagioclasee
%AartE
15
~
S
< I
Others
The abawdance order for meteoritic minerals is the
writer's own compilation and is at variance with the orders
of mineral abandances usaal4 quoted.
H. S. Washington
(1939) lists the order of abuidanoes as nickel-iron, olivine
rhombic pyroxene (eastatite, broazite, hyperathene), plagioolase (anorthite, labradorite, oligoolase) and maskelynite,
based on compilations of Washington, G. 2. Merrill (1916),
0. C. Farrington (191b), and t. W. Cohen (1894).
In all
cases the mineral abandances have been based on the weight
and/or numbers of meteorites in collections, rather than
the proportion in which stony and iron meteorites strike
Earth.
* Clarke, F. ii., and washington, 14. 5., U.S.G.S. Prof.
Peper 127.
isrhaps the most strikind differences in meteoritic and
terrestrial mineral abundanoes is the paucity of the feldspars, which comprise approximately 3/b of Larth rocks and
are comparatively rare in meteorites.
Furthermore, due to
the Low amounts of 4 and Na in meteorites the potash and
soda feldspare, orthoclase and microoline, are unknown in
meteorites, except as traces by norm calculation.
These
minerals are unknown in modal analyses of meteorites, but
are large in the bulk of Earth rooks.
Of the plagioolasee,
only the caloic ones are abundant in meteorites, and the
sodic varieties are rarities.
Another striking difference is the complete absence of
the mioas and amphiboles in meteorites.
This is due to the
fact that water is entirely unknown in meteorites, and water
is essential to the struotares of these minerals.
Similarly, the common terrestrial mineral quartz is
extremely rare and perhaps unknown in meteorites.
In a few
cases it has been reported in the superficial portions of a
few iron meteorites, bat it
ic mineral.
ay not be an original meteorit-
There have been a few reports of tridynite in
stony meteorites.
quarta would not be expected to ocour in
material of the chemical composition of meteorites,
for
these rocks contain sauch a deficiency of silica that it all
is used to form olivine and pyroxenes when the magma is cooling.
F.
G. Watson (1939)
has made an exhaustive study of the
falls of meteorites; that is, meteorites that have aotually
been observed to strike the Larth and then collected,
watson
oonoluded that the ratio of stony meteorite falls to iron
falls is about ten to one,
However, assuming that stony
meteorites are more likely to be shattered and lost by
scattering in small pieces, he made a further study of the
relative weights of irons and stones from falls.
Than 39E
stones yielded 7,705 kilograms, while 21 iron falls yielded
730 kilograms.
The conclusion was that while the total
material from stony falls is approximately ten times that
from iron falls, the average iron yields nearly twice as
much material as the average stone (Watson, 1945).
Watson finally concluded that because there were so
many uncertainties it was impossible to make an exact statement of the trae proportion of falling stone to iron, bat
that the stj
material is from foar to nine times as abuge
ant as the metallic. It was on the basis of this conclasion
that the preceeding table was compiled, in order to compare
meteoritic mineral abundances with terrestrial abundances,
with the assumption that stony material is from four to nine
times as ubuadant as metallic.
Meteoritic Minerals:
0. G. Farrington (1915) has al-
ready adequately discussed the minerals of meteorites and
their properties.
The descriptions will not be repeated
90
here, a4d only those properties that are dermne to this
deo8astson will be repeated.
The followings Is the liet of aeteoritlo minerale Listed
by ?arriagton.
iJleme ate
Orthoai Lioatee
imetasliiates
ineral
CompositIca
Olivi a (chrsolito )
inotatia forsterite
stati to
(Mg,Y. F Z4) 04
9g3104
MgS10 3
brenate
(Mgtre 13W3g
t6 M,Fe) (Si03)2
H persethone
t4ltaeastatito
CLinohyperatheam
9g 13103
(Mgo)(3103)2.
(Mg,
(SiO105
Aadite
edonbergIte
foltepare
laeiooblses
Maakte att
(Oligooae
Oxides
LxS Cal
glass)
yiouJl2
;Quarts (tentative only)
Tridpnistotentative oay,
MfenO U to
Fe304
Chroeite
Salti dos,
Ehosaphids a
Cabtesn
Trollito
FOS
Oldhtmito
CasY
t4aabnelbU to
Og
t
FeSr23
i
Johriobersite
Elements
Other
(Fenico)zP
Uoheni to
FogC
On Oornite
Oxysulfide of
Ca and Ti
Moissanite
sic
Sictel--iron
Xamaoite
Taenite
2tesgite
FeNi
Diamond
Graphite(Cliftonite)
2hosphors (tentative)
C
C
Weinbergerite (one
ocoarreneoo)
MAISLG &
3FeS8i03~
Rydrocarbone
n(OxHyOz)
Apatite
Ca(F C1),Ca4
PONI
Brewanerite (tentative)
Lawrencite
(Mg,Fe)C03
FecI 2
Minerals exclusively meteoritic:
G. J. Neuerburg (1946,
1349), in a series of two papers has listed the minerals that
are exol&sively meteoritic, and has discussed their occurrence
and compiled an excellent bibliography.
LNeuerburg lists the following minerals as exclusively
meteoritics daubreelite, kosmochlor, merrillite, oldhamite,
osbornite, schreibersite, weinbergerite, Oliaoeaatatite, and
clinohypersthene.
Reasons for including or excluding miner-
als from the list are exhaustively documented by Neuerburg.
Mineral descriptions:
Kamacite,
taenite, and plessite
92
are alloys with variable Fe-hi content.
5-6i nickel, cooasionally less.
Laatcite contains
Taenite contains 48% nickel.
Plessite is not a mineral species at all, but is an intergrowth of kamacite and tasnite.
Althouh terreutrial nickel.
iron does not show identical crystal structares with meteoritic iron, it is now reognized that the crystal structure is
a fanction of the mode of crystallization,
rather Ahan a re-
salt of composition (kohl and &erge, 1938).
Clinoenstatite and clinohypersthene:
A. N. Winchell
(198) reports olinoenstatite in terrestrial rocks.
hyperethene has been reported by E. Service (193)
J. Verhoogen (1937).
Clinoand by
Enetatite and hyperathene ordinarily
found in rocks are orthorhombic.
S. 4. Shand (194
states
that at high temperatures (114000 for U6=i05, below 9550C
for varieties rich in FeSi%) they transotr
varieties.
into monoolinic
Ferrosilite, FeSio%, is apperetitly unknown in the
crystalline state.
both olinoenstatite and clinohyperethene
have been made synthetically (Allen, 4right, and Clement, 1906).
by rapid cooling of a molten mass of pure magnesium silicate
intergrowths of clinoentatite, similar to those foand in the
Bishopville meteorite were formed.
It was concaluded that the
presence of such intergrowths in meteorites indicated rapid
oooling.
They further discovered that clinoenstatite trans-
forms to the orthorhombio form at
j3650Q,
bat that this or-
thorhombio form was "quite distinct from enstatite and uan-
93
known in nature".
N. F. U. Henry, however, concluded that there was,
with the exception of clinoferrosilite, no unquestionable
ocaorrence of clino Mg-Fe pyroxenes.
Neuerbarg,.in reviewing the papers of Winchell,
Service, Henry, and Verhoogen concluded that with the possible exception of olinohyperethene cited by Verhooeen the
terrestrial occurrence of clino Mg-re pyroxenes hns not
been definitely established.
Troilite:
Though closely resembling each other, troll-.
its and pyrrhbtite are now recognized as distinct mineral
species.
froilite more nearly approaches the composition
FeS, while pyrrhotite approaches the composition Fe
11 S12 *
Troilite is non-magnetic.
A. 3. .akle (1922) describes an
occurrence of troilite associated with magnetite in a
sheured serpentine.
The mode of origin he attributes to
the hydrothermal alteration of magnetite.
Certainly this
mode of origin is different from that of meteoritio troilite.
Neuerbarg suggests that the great abanidaace of free iron in
meteorites may accoant for the formation of troilite.
However, as pointed oat by Allen (1912), troilite
probably should not be considered a separate mineral speoies, bat rather the "end point" of a solid solution series.
O. C. Farrington (l916) states that "pyrrhotite (troilite)j, like impurities in artificial irons, tends to be
most abundant sowards the periphery of a meteoritio individlal".
This statement bears further verification, and,
if true, would be most difficalt to explain on the basis
of ta0 shattered planet hypothesis.
ther study and verification tan
However, without fur-
writer is Uaable to comment
on its significanco.
oissanitez
his exclusiveij meteoritic mineral, with
the composition SiC, is,
of course, eoommoonly known as the
artifioial prodact carborwidam.
L.
. Chresohall and
C.Milton (1931) reported finding moissanite in six examples
of sedimnxtary rocks from the
rooks.
rdovician period to
ecent
Identification of the mineral by x.ray spectrography
was unmistkable,
These invstigators, after a critical
examiation for sourSs of
ountamination (pulverized samples
and not thin sootions were used) conalwded that moissanite
in sedimentary rooks either represeated meteoritic dust or
was the indestruotable residue from fossil meteoriteo.
ever,
How-
eaerbarg suggests that the "moissanite" reported was
most likely a contamination dae to carborundam paste used in
oleaning water taps, introduced when wasing the heavy mineral residues.
Oldhamite:
This mineral of the composition CaS would
hardly be expected to ocoar in terrestrial rocks.
but a strongq redaLuin
oxidized to the sulfate.
In any
environment this salfide wouLd be
However, the mineral
gSalaband-
9b
ite, occurs terrestrially but is unknown in meteorites.
Laar (1897)
reported CaS terrestrially, but Neuerburg be-
lieves his evidence inconoluaive.
Qebornite:
This oompound (Tii) has been reported from
blast £turnace saIas (Banaioter, 1941, find Stcry-Maakelyne,
1870).
4o0moehlor or Kosmohromit (A16 Fe4 Cri0
8 );
F. Las-
peyree (1897) deseribtd this mineral from the Toluca iron.
Subsequent mention was mnLade by Groth, Cohen, and Heintze
(Neaerburg;, 1946).
Lawreneite (Fe,ii)Cl
: E. P. Henderson, in a person-
al commnioation to feuerburg, reported lawrenoite doubtftlly in terrestrial irons from Greenland.
Ferrous chloride,
lacking, however, a nickel oontent, has been reported from
Vesuvias (Yarrington, 1915).
Although chlorine Is a common
constitaent of lawrenoite in meteoritee (partioularly irons)
flaorine has never been detected, althoah G. 2. Merrill
made a careful
eaarch for this element (1918).
Cohenite (?eUi,0o30):
as
This minertl has been reported
ucaurring in the terrestrial irons of Greenland (1944).
It is identical with the artificial iron carbide cementite
ocouring in steel.
Uerrillite (Caaa22O9):
G. J. Ueuerburg (1946)
cites an extensive bibliography on the ocurrence of merrillite.
Neuerbarg sugests that merrillite may not be a
96
a distinct mineral species,
but rather mahy be a member of
the complex apatite isomorphous series.
Critical x-ray analy-
sin is necesuary to establish its existence.
Maskelynite:
Tochermak (1872) first deseribed this min-
eral from the Shergotty stone.
It is believed to be a con-
stituent of nearly all stony meteorites.
In the Shergotty
stone, which consisted of Wet maskelynite,
the mineral ocour-
red in feldspar-like laths, but lacked foldepathic cleavage.
The composition was
Si02
A12 03
G0
!a2O
K20
56.3
25.7
11.6
5.1
1.3
100
Techermak regerded this mineral as a fused feldspar.
However, Winchell (1897) found the mineral in the Fither mteorite amidst an isotopia material, portions of which resembled plagioolase.
Winchell conoladed that the isotopio ater-
ial was glsa from which the plagioolase had crystallized.
The reverse view, however, is equally tenable: that the anisotropic plagiooleee is a devitrifioation prodact of an original
glass that formed through too rapid cooling.
The existence of
maske4nite was also confirmed by A. ta Croix (1923) and G. k.
Merrill (1918j.
kerrill reported that the large proportion of
stony meteorites contain a colorless, interstitial MAterial,
which may be either isotropic or slightly doubly refracting,
possessing a rather low index of refraotion which he designated
as maskelynite.
He noted that in all bat the Shergotty stone
the glassy particles are of microscopic dimensions, defying
separate ohemical analysis.
In a study of the Holbrook stone
(1912), Merrill 4etermined the refraction index to be 1.5,
which, according to Larsen's tables, is that of oligoolase
glass. Further stadies led Merrill to the conclusion that
maselyAite may range in composition from oligoolaee to anorthite.
Merrill attribates its glassy state to fusion since
the original crystllization, "followed by a cooling which
was too rapid to allow it
to regain its normal properties".
fraces of plagioolase twinning are occasionaliy present.
This fact is interpreted by ferril to prove maskelynite a "refused feldspar, rather than a residual and original feldspathiO glass", confirming the inVestigations of Tahermak.
It
is
farther pointed out that "an elevation in temperature sufficleat to fuse feldspar, without at least partial destraction
of the olivine, would be impossible but in an atmosphere completely devoid of all oxidizing gases".
However, the writer
has observed in many thin sections of chodritic meteorites
that ohondri are often composed largely of olivine and/or pyroxene glass, evincing destruction of olivine along with feldspar.
In the case of the metallic salfides we may be sure that
the atmosphere was reducing and under high pressure when and if
the plagioclases and olivine were re-fased, for troilite diesociates at approximately 1150 0,
fusion point of oligoolase,
a temperature less than the
98
Farrington (I1lb) states that massieinite may be either
an alteration proacut or way be of primary origiA.
atzt
Merrill's observations ox twinninj laeL.Le strongly suggeets
the former, viz., by re-fusion.
This fact mAust be taken
strongly into account in theories of the uooling history of
the shattered planet.
Feldspar;
21aeioolaiss
are Comon
1oatitaents of stony
meteorites (they occuar also in Toluua iron in silicate inclasions), bat oomprise minor mineral peruentages in all bat
the eakrites and howaritea.
mon.
northite is by far most o om-
PLagioolaao rich meteorites exhibit ophitio flruoture,
interpreted in terrestrial rooks as cryatallization o
spur before pyroxene from a ailicate melt and
ive of the maSmatic differentiation,
Ohondritio plagioolaaso
feld-
ighly sagest-
n. Michel (1914) foaud
to be chiefly audio (oli600laae)
while ekrites and howardites contain chiefly anorthite.
arrington (l9lb) found feldspar as abundant in white ohondrites and nearly absent ln bluok ohondritea.
The brecciated
waoada stone, oonsisting of distinct light and dark fragments, shows this variation of plagloolaae content, as if the
fragments were separate meteorites.
iyroxnnos;
stony meteorites.
The pyroxenes are second only to olivine in
Choadritia Stones, which comprise the balk
of stony meteorites, have slight excessea of olivine over
pyroxenes.
Acnondritio eknkites and howardites,
which most
losely resemble certain terrestrial rooks, contain but
little olivine and consist of ophitic intergrowths of anortiite and pyroxene and generally are aar4y metal and suafide free.
$oMs achondrites, Etch as 4ishopville, consist
almost untirely
cf
pyroxene.
Bishopville consists of re-
markably pare onstatite, with little free metal or ealflde.
The orthorhombic pyroxenes are more abundant,
bat an-
like terrestrial rocks, munoolinio olinometatite-olinohypersthene is fairly common in meteorites.
pyroxetnes, such as diopside, audlte,
he Oa-Al-rich
uedenbergite
and pigs-
onite are common meteoritic minerals, bat are chiefly restricted to the caloim-rich achondritee (containing anorthitoj, which are rare meteorite typea.
A remarkable characteristic of the meteoritic enstatite-bronzite-hperethene series is
that bronsite (14 - 15
F7O) is a rarity, whereas bronsite is common in the terrestrial series.
In meteorites the change is abript from on-
statite to hyperathene.
or iron rich.
These pyrozones are tither Mg-rich
Intermediate brouite is rare.
of this phenomenon is wanting.
Prendel (189V)
hxplanation
found in the
Grosaliebeathal stone enstatite and bronsite to characterize the chondri, while the groatSmass contained hypersthene.
The Moore County, N. U. meteorite has recently been
studied by E. P. Henderson and H. Tc. Davis (1936) and H. H.
Hess and Henderson (1949).
In bulk composition this meteor-
-
100
it* resembles a Sudanry norite.
These investigators dedaood
that the variety of six pyroxene Phases present were probably
derived from a single initial phase, tigeonite.
Temperatur'
of its original 4nVironmeUt was approximately 11360;, and
Wthe uieeorite left this enviroament with tatastrophio saud-
dsnness".
The fabric is interpreted as sugestiag a primary
layered developsent by orystal acoamaLation on the floor of
a magma chamber - a crystal differentiation that ouotrrod in
the original environment.
xvi4enos for thia is that the py-
roxene c axes and the plagioclase b &ad a axes tie in one
Plana.
Hess and Henderson point out that while pigeonite is rostricted in terrestrial 2oaks to rapidly cooled lavas or
small hypabasal intrasions sad considered a metastable phase
originating from rapid cooling, pigeonite
alo oooars in
rooks evincing intratellaric eystallisation, as at Mall,
Sootland(Haflemond. 191).
It is also a comon oonatituent of platonic rooks, but
hero has altered on slow sooling to ortho-byperathene, containing !xMolt
001
aqgite plates in the planes parallel to
of pigeonito
Identical exsolation phenomaena of augito
troa pigeonite ocar in the Moore County mteorite.
This me--
teorite contains only about 10% hyperotheno, and susgests t o
loe
and )iendrsoa that cooling in the original environment
4id not prooeed to the extent for tho inversion pigeonito-
I
101
hypersthene to occur.
They attribute the 10% hyperathene
present to inversion after it became ai meteorite.
The most striking features c!f the plagioolase (bytowna
it.) in the Moore County meteorite is the complete absence
of zoning, indicating slow crystallization, and pronounoed
linear orientation of its c-axes.
Lack of cleavage in the
plagioclase indicates a high-pressaure original environment.
However, the pyroxenes have well-developed cleavage, which
probably resulted from decrease of pressure when the planet
was shattered.
R. A. Daly (1938) believes that pyrozene
cleavage could not exist at depths within the £arth greater
than 40 kilometers because of escessive pressure.
Ross and Henderson believe the temperature of the
original environment to have been above 106500, the inversion temperature of pyroxene.
Pressure could have inon aeed
this temperature to 120000.
These investigators,
in this most interesting petrolo-
gic study of a meteorite, conclude that it was derived from
an Earth-sized planet, for the gravity field must have been
sufficiently great to produce crystal settling, a condition
a small planetoid-sized body could not fulfill.
Becaus of
more rapid cooling, a planet of smaller diameter than the
"arth would not have sufficient time to differentiate a
basaltic (nor granitio) crust.
Thus, such meteorites may not
exist. Anywati#-*#have found none.
These observations sub-
102
stantiate the argumeats based on phase equilibria by Brown
and Satterson,
The rare meteorite mineral tridgmite ocoaz..r
County meteorite.
in the ak&
The fact trat it did not invert to quartz
(nor did the balk of the pigeoaite invert to orthorhombia
forms) indicates sudden ohilling, an interraption we mnay possibly attribute to the shattering of the original planet into small fragments which would chill rapidly.
Oliviae
ate mineral.
Olivine is the most abundant meteoritic siliOne meteorite, Chaeeigny, is composed almost
entirely of olivine and is unique.
Rammelsburg (1879) in a
stuiy of cnondrites found the ratio of olivine to pyroxene
to be V:8.
Meteoritic olivine usually Ia Mg-rich, contain-
ing from 10 - 15% fayalite molecule, and should be called
onrysolite, according to the classifiaation of Wager and
Deer (1939).
Weinbergerite (3aAl04*3FeS0P: -.
Berwerth (1906)
desoribed the single ocarrence of this mineral, and from
his analysis the proceeding chemical formula is taken. Berworth stated its orystal aystem to be orthorhombic.
However,
additional information is oertainly needed to establish the
existence of taie unique mineral.
Phosphoru:
A single occurrence or native phosphorous
has been desoribed by ?arrington (19@5).
3acrieberoite (Fei,Co)3P);
Few, if any, minerals
103
found in meteorites nave -attracted as much attention as
schriebersite.
Great interest in this mineral was inspired
by tne fact that a phosphide mineral of such oomposition
would not *e expected as likely to occur in Earth orastal
rooks, beoaase it would probably be oxidised to the phosphate.
This fact is of particular interest in interpreting the
origin of meteorites, for it suggests a strongly reducing
environment.
The calcium sulfide mineral, oldhamite, is in
the same category of interest.
Tornebohm (date unknown) re-
ported sctriebersite from the Ovifak terrestrial Iron of
Greenland, bat 0. C. Farrington considered his method of dotr44ation inoonclusive.
3ohreibersite has been prepared
synthetioally.
Diamond;
The discovery of diamonds in the Canyon Dia-
blo and Magara irons and in the Carcote and Nowo-Urei chondrites was of especial interest, leading koisan (1890, 1894)
to his famoas successful experiments on prodacing artificial
diamonds. Moissan'a method was to compress sugar charcoal
in an iron cylinder sealed by an iron plug.
this cylinder
was then placed in a cruoible which oontained 200 grams of
molten iron and placed in an electric furnace for further
melting.
On withdrawing, the crucible was rapidly cooled by
immersion in molten lead (water was unsatisfactory, since it
formed a badly conduoting layer of steam).
Thus crystale of
diamonds up to 0.5 mm were reported producea, which were re-
104
oovered by diasolvingj the iron in jala
Moissan's experinento
g
suggeot a rapid cooling for me-
teoric irons containing diunmoads.
Eovver, the eperimente of
Derge, IMehl, Bradley, and Baddhae suggont that Widmanstatten
figureu require slow equilibrium conditions of cooling for
tnis formation, indicating slow rather than rapid cooling
for meteoritic iron.
The Magura iron has an octahedral
etcning figure, and the presence of this struactare with diamouds may perhaps appear inconsistent with Moissan's theory
for rapid cooling.
However, it
is Cenerally .condeded by
geologists that large diamonds require long periods of time
for thir
growth.
Graphite:
Graphite has been found in several irons,
inoluding Magura (1.7
and
graphite), Tolaea, Chulafinae,
Maaapil (Farriagton, 191).
Graphite is tsaally associated
with troilite, either as intergrowths or inalasions.
Far-
rington quotes the origin atggested by J. Lawrence Smith
that meteoritio graphite formed by action of 0 3z on inoandescent iron, and is in no way analogous to terrestrial
graphite in origin.
G. Ansdell and J. Dewar (1886) conolUted
after oomparing many meteoritio and terrestrial graphites that
they were similar in origin, and were formed by action of water and gases *a metal carbides.
seems antenable,
However, this view certainly
The great balk of terrestrial graphite did
not form in this manner, but occurs rather in crystalline
105
schists, contact metamorphic rooks, limestones, slates, and
other rooks of sedimentary origin -- rooks in which we sure-
l7 do not expect to find metallic earbides.
Graphite in
metamorphio aooks is believed to be derived from carbonaceous
(organic) material originally deposited with the sediments.
When graphite does occur in igneous rooks it is related to
the pegmatites and hydrothermally altered rooas.
However,
it is sae to say that there is at present no evidence saggeating an organia origin for meteoritic carbon.
Daubrei1te (YeCr 2i 4 );
Dabrelite is exclasively me-
teoritic.
It is an 4ncommon mineral usually associated with
traflite.
It is exluive to iron meteorites and is not
known in the stones,
Manier produced this mineral epithet-
ically by heating an iron-ohromium alloy in an atmosphere of
hydrogen sulfide.
CHAPTER VII
STRUCTURS
AlD TEXTURSS OZ MToRITES
kiatare of Chondrules;
Among the most prominent physical
featares of stony meteorites are small, rounded silicate
grains kuowa as chondri or chondrales (diminutive), from the
Greek word Xo vPog , or grain.
Chondri occur in the complex metal, silicate sulfide
matrix of silicate meteorites.
They vary in thickness from
approximately three centimeters to minute size.
Their form
is generally spherical, bat they may be oval or flattened, as
if by deformation, or they may be most irregular in shape, as
demonstrated in thin-section studies of this investigation.
Like a common distingaishing feature between sandstones and
qaartzites, chondritic meteorites may sometimes be broken
around the chondri and sometimes through them.
Thin section
study reveals the chondri to be composed of a wide variety of
minerals.
Olivine and pyroxenes are most common, but augite
chondri sometimes occur, and even plagioclase chondri have
been reported by Lachermak in the stone of Dharmala.
Glass is a common and probably universal constituent of
chondritic meteorites.
It occurs in a great variety of ways,
such as matrix or groundmass material, substance of the chondri, and portions of mineral grains, as inclusions and intergrowths.
Ieteoritic glass is usually brown, but may range
from colorless to opaque-black.
107
The occarrence of glass is the result of rapid cooling
of a silicate melt (or with remelting of crystals), and the
analogy with glassy terrestrial rocks is extremely suggestive that cooling was too rapid to allow complete crystallization.
Few, if any, ohondri are entirely crystalline.
Glass is
uasally conspioous, and forms a major portion of their
substance.
In gross structure ohondri resemble spheralites found in
terrestrial voleanio rooks.
However, thin section study re-
veals invariably an ecentric radiating crystalline structure
for chondri, whereas epheralites generally possess conoSn-
trio radiating stractures.
Explanation for this difference
is still lacking.
The crystalline minerals of chondri occur most commonly
as radiating or porphyritic structures in a ground mass of
glass.
Frequently chondri possess a crystalline nucleas,
which is surrounded by glass.
observed.
Network structures also are
Chondri are most often light-colored, but may
occasionally contain so many included grains of metal and
troilite as to be black and nearly opaque in thin section.
Chondri of a radiating structure are asaally composed of pyroxene (enstatite or hyperethene, rarely bronzite), while in
those of porphyritio texture the insets are asaally olivine.
Vorphrytio ohondri are usually predominantly glassy, while
radiating structures approach more complete crystallization.
108
However, completely crystalline pyroxene chondri are anknown (Farrington, 1915).
At common form of ohoadti is
composed of both olivine and pyroxene.
one
Olivine uually
ococars as insets in a groundmass of slaos and fibrous pyrox'Zither mineral
ene.
ay be in excess.
The fibroas pyroxene-
glass matrix indicates a later crystallization than the
olivine insets, and is in keeping with the observations of
Bowen and others on the order of orystallization of silicate
Melts.
We may safety assume that ohondri represent molten
droplets that underwent rapid cooling.
The ohondri may have
solidified completely as glass and then have undergone slow
reoryetallization in the solid state -- a process similar to
the devitrifioation of glasses.
However, chondri composed
entirely of glass are known, in which no crystalline material
is present.
Such glassy ohondri indicate that devitrifica-
tion, solid Qrystallization, was not the major process in the
formation of ohondri.
There is little reason to auppose that
some ahondri ehoald have remained unchanged and completely
glassy, while others devitrified almost completely to crystalline forms.
A more likely explanation is that the molten,
highly viscoua droplets underwent different rates of cooling,
dependent apon their location in the planet's interior.
Those
near the surface cooled more rapidly and are more glassy, while
the more crystalline forms represent slow cooling, deep-lying
109
material.
Several other comoucnly £baerved feaWtres of chondri doserve mention, and us&y eveatually be of Use in solving the
problem of the origin of' chodritic teztures.
Chondri of a
wide varioty of rlneralogio compositions and physical straotures are Common4 Closely associated in any chondritio me-
teorite.
within the same thin section =,y be observed rounded
ohondri, possessing both radtttiat and porphyritic texture,
fibroas and network text4ree,
Olivine onondri ocoar intimate-
ly associated with those of pyroxene chondri, mixed mineral
ohondri, or glassy ohondri.
Tschermak has described from the Daarmsala stone a large
porphritic chondras completely enolosing a smaller ohondras.
A photograph of this phenomenon is shown in Farriugton's
Meteorites, on page 106.
Chondri which have
een feagmented sometimes oacur, as
in the Mezo Madaras stone described by Tschermak.
The sepa-
rate fragments of a single chondras may rarely be aisoovered
in Jzxtaposition.
dhatever prodaced the fragmentation sepa-
rated the fragments,
This could be oauased either by explos-
ive activity or by violent movement in a viscoas, partly
crystalline matrix.
chondri.
Specimnas frequently
ocur with whole
The fragmentation process mast not have been too
violent.
If
we coald but understand the origin of the ohondri we
110
would no doubt be well along in our understanding of conditions within the former planet.
However, immense inconsist-
enoes confront us in oar investigation. That stony meteorites are fragmental in nature is strongly suggested by the
The fragmental nature of such meteorites as the
ahondrites.
Camberland Falls stone (U.S. National Museum) is hardly contestable.
This stone has a marked brecoiated and fragmental
structure, being composed of large angular black fragments
imbedded in a white matrix,
We mast know not only how chondti formed, bat how they
have come to occupy their present positions.
Certainly they
underwent fragmentation after solidification, as a thin sotion study of the Mezo
adaras stone (see picture in Farring-
ton's Meteorites, pg. 190) and many others will attest.
Various oridin theories have been proposed, of which
several will be reviewed.
G. 2. Merrill (1920) regards
ahondri as "rook fragments reduaed to their present form
through mechanical attrition".
Farther, Merrill states, "In
brief, their present structural pecularities,
both external
and internal, are entirely inconsistent with any conceivable
theory of origin bat that of detrital particles from solidified magmas."
However, the occurrence of ohondri completely
enclosed within chondri, as in the aforementioned-Sharmsala
stone, seemingly makes this explanation untenable.
Attrition,
the abrasion by rubbing together of fragments, cannot account
111
for the inolasion of one choandras within another.
F. G. Watson (1943) notes the strikingly fragmental
nature of the Sharps Meteorite and asserts that the ohondri
and fragments are "so distributed about the larger ones as
to afford
nmistakable evidence of mechanical attrition."
It seems to the present writer that, though evidence
of mechanical attrition is unmistakable in stony meteorites,
this process cannot account for the formation of chondri.
After formation the ohondri were undoubtedly modified in
shape by attrition and often fractured.
The breociated character of a large portion of stony
meteorites is unmistakable and must be taken into account in
any theory of origin.
Their resemblance to agglomeritio,
tuffaceous volcanio rooks is striking.
Several investigators
have suggested that ehondrules represent molten droplets
blown explosively from the surface of the former planet.
In
falling, these drops cooled and assumed spherical shapes.
If
this hypothesis is true we are forced to admit that originally
the chondri solidified wholly as glasses and that the crystaltine structures we now observe are the result of devitrification.
Where is, however, a strong argament against this origin
for the ohondrales,
This mode of origin suggests that the
chondri should be confined to a thin surface shell of relatively small volume, bat we know that fully 90% of the stony
112
meteorites are chondrites.
They possess ahondri.
Chondrites,
therefore, must represent the major portion of the total
volume of the shattered planet.
salt of surface explosions,
Thas, they are not the re-
Solely as a working hypothesis
the writer presents the following.
Fissares connecting with
the deep interior of the planet could conduct molten material
explosively to the surface, where it would be ejected and
rained back to the surface as fragments, ashes, and chondri.
If this process were continuing, each new surface would be
saccessively baried under new explosive material, becoming
more and more deeply buried.
It is barely conceivable that
ultimately the whole silicate shell of the planet could be
reworked from deep interior to surface.
In such a manner
the chondri could be distributed throughout the silicate
shells surrounding the core.
Evidence of mechanical movement within the solidified
meteoritic material is abundant, e.g., the frequent brecciated structure of stony meteorites, and the occurrences of
faults, slickensides and polished surfaces.
S. Meunier made
an interesting study (1873) of the mineralogical and stractaral similarities of meteorites and terrestrial rocks.
He
classified rocks and their meteoritio analogs as 1) Normal;
Z) Brocciated; 3) Metamorphio; 4) Eraptive; 5) rooks traversed
with veins (filonniennes concrstionnees); and 6) Volcanic.
Veinas in both rocks and meteorites he regarded as fracture
113
fillings. He pointed oat that Just as faults in terrestrial
rooks may be detected by the amount of throw of the rooks constituting their two sides, so can the faults of meteorites.
Many Otony meteorites exhibit apparently true faults, with
demonstrable throws and polished surfaces.
For example,
the
stone of Aamieres, described by Meunier, exhibits a fault out
by another, with a downthrow of several centimeters.
This
remarkable stone (and many others) exhibits the property of
turning black when heated.
The material adjacent to the
fault surfaces in this meteorite has been altered from grey
to black, presumably by heat of friction due to fault movements.
When the throw is greatest, the blackening has ex-
tended the farthest from the fault surface.
Thus we have an
effective and sensitive thermometer, with which we can conceivably measure the dynamic energy that accompanied this
cosmological faulting and illuminate oar knowledge of the
conditions in the former planet's interior.
G. Tschermak (1878) in a study of the Groenja stone, as
well as others, made matny interesting observations on the
nature of chondri.
He noted the occurrence of a crust fre~
quently surrounding chondri, especially over those composed
of bronzite which possess fibrous structure,
The crust is
likewise fibrous and is optically orientated like the enclosed
silicate.
Tschermak suggests that this crust has been "pro-
ducoed by some agent acting from without, perhaps heat in con-
114
Junction with a reducing gas" (quoted from -. Flight, 1887).
This agent has not caused fusion, bat only a textural modification of the surface mterial.
The present writer finds it
difficult to picture the role of a "reducing gas".
The second
important observation of Tachermak is the distribution into
zones of "magnetic pyrite"(troilite?) in many of the granular
inclosed masses,
Refloted light studies of chondri in thin
section revealed sometimes a metallic sulfide crust to the
ohondri, and sometimes the metallic sulfide occupied the center of the ohondrus.
In all asses, the metallic sulfide in-
clusions apparently occupy the interstices, as if
had "impregnated the rocky mass".
the sulfide
The metallic sulfide is
always absent from the crystalline insets, and Tuchermak belicves the impregnation to have ocourred after the insets
took their present shapes, i.e., after their orystallization
within the glassy matrix, and to have occurred when the whole
taffaeouw mass was strongly heated.
Tschermak assumes that
the fractured crystalline and glasay material of the ohondri
drew the molten metallic sulfides into fractures and cavities,
The writer suggests that the metallic sulfide arose as an
immiscible phase.
It probably was already present.
As the
temperature fell in the silicate mix, globales of immiscible
metal and sulfide phases separated.
The melt cooled rapidly,
permitting only a partial crystallization of silicate minerals
in a glassy matrix.
Cooling oaused contraction of the glass
115
and the crystals and produoed fractures which were intimately
filled by the metallio and sulfide phases present.
High pres-
sareuat be assumed and is certainly expected, in order that
the sulfide phase would not dissociate, for troilite completely disaooiates at approximately 115000 under atmospheric conditions.
Tochermak concladed his study with the hypothesis that
there were two distinct stages in the formation of chondri.
First the olivinous taff was produced by fracturing and at.
trition, whereby the tougher particles were rolled and rubbed together until they had rounded or spherical forms.
Second, the material was strongly reheated (though not to
the melting point of silicates, bat only to the melting point
of salfides) and the surfaces of the ohondri were modified by
the "redacing action of gases and vapors".
That the iron inclusions in chondri could have been derived directly from the siliceos
melt as an immiscible pro-
dact receives direct support from the work of N. L. 13owen
and J. F. 3ohairer (1932), who have shown this system to
melt incongruously, with separation of iron.
In a study of the Rangala meteorite J. A. Dunn (1939)
made interesting observations on the dissooiation of troilite
as observed in the crusts of meteorites.
7e assumed (correct-
ly) that the velocity of a meteorite would decrease due to
air resistane as it
fell to Larth, and that as a consequence
116
the surface temperature generated by friction would be
progressively diminished.
He observed that the first
change in troilite occurred at the base of the cruet, with
lose of sulfur, accompanied by the appearance of "exeolation
droplets of iron".
surface,
Under great heat, that is, nearer the
the molten sulfide streamed out through fractures,
and remained as veinlets of troilite and iron.
He further
disassed the matter of development of iron from the troilite
as to whether it resulted from simple dissociation or whether the sulfur was burnt off as 30,
oxygen.
due to atmospheric
Hematite (?) was developed in the "slag selvage",
suggesting the possibility that SOg was formed, but he farther pointed oat that it is difficult to conceive how oxygen
ooald have been absorbed down to the inner zone of the crust
against the opposing stream of outwardly dissipating S and
Fe vapor.
Dunn concluded from his study of crustal veins and veins
within the body of the meteorite that the latter veins were
already present when the meteorite entered Earth's atmosphere.
There is no parallel between the arrangement of troilite,
kamaoite and taenite in the crastal veins and in the interior
veins.
The metallic constituents of the interior veins were
solid and in place when the meteorite entered the E'arth's atmosphere.
Veins in meteorites differ in aenoral from veins in ter-
117
restrial rooks in that the vein material of meteorites is
essentially of the same material as the material of which the
Farrington concludes that thejmaterial
meteorite is composed.
has not beer injected, but has been altered in place and
states that some of the broader veins show a distinct flow
structure,
He concludes that veins are oaased by "penetra-
tion of heat into the fissares of the meteorite during its
passage through the atmosphere", and discards the theory that
the veins are of preterrestrial origin.
However, there seem to be both inconsistency and error
in Farrington's conclusion here,
are known to be cold.
The interiors of meteorites
Heat cannot be conducted to the me-
teorite's interior as fast as it is generated and stripped
away from the surface.
Thus the flow structure in veins
could not have been produced during the meteorite's flight
through Earth's atmosphere, bat more likely was produced by
the heat of friction caused by movement along the fault
plane.
Expersiental evidence is abundant, and almost incon-
testable, that blackening of the chondritio material may be
caused by heating alone.
In the writer's preparation of ohondritic meteorites for
spectrographic arcing the material was first heated in a
blast flame in order to dissociate the sulfides present and
to convert them to oxides, so that they woulc not explode
from the eleotrod~e crater ou arcing.
In a reducing flame the
118
material would blacken, whereas tnder oxidizinc conditions
the sulfides would be converted to iron oxides with characteristic reddish color.
It is con laded that cholcritic tacttor-
ites may be blackened by heat alone.
Ir conclasion, it
may be said that the faulted veins of
meteorites, their brecciated condition, and the almost invariable ocoarrence of fragmented ehondri and other mineral grains
indicate that forces have operated that are entirely inconsietent with forces that could occur in a small body.
mast have been of planetary size.
The body
Baer (1949) interprets the
elastic struatare as the reeult of "the breaking up of incipient crystallization by convection currente duringz. eolidification of a parent-sized planet".
Olivine is the most abundant silicate mineral in chondritio meteorites.
However, pyrozene is present asally in almost
equal amoants.
It is of significance that meteoritic olivine
is aeally mnagnesium rich, containing from 10-1b% of the fayalite molecule.
Aoording to the equilibrium diagram of Bowen
and Schairer (195), olivine of this composition would have
crystallized from a melt at temperatures ranging from 1650 0
to 1760 0C.
C
a iron-enriched silicate residae would remain.
If cooling had proceeded out of equilibrium, this ironenriched residue would solidify as a
laus.
In thin section
almost all olivine grains are observed to be surrounded by,
imbedded in, or interspersed with dark brown silicate glass.
119
However, we are always faced with the posadbility that all
the silicate may have solidified as glass, and that the Orystale present represent a devitrification product; i.e., arza-
tallization from the solid, amorphoas state.
2xperimental
work on the devitrification process in mineral glasses is
needed to solve this problem.
It is here suggoeted that according to the chemical law
of LeChatelier devitrifioation under hig
resre
generally be favored for silicate mineral glasses.
would
In the
following table are aaown the specifUic gravities of several
silicate minerals which occur in meteorites and the corrnsponding valaes for their glasses.
Cooling in an tarth-sized planetary body would initialls be rapid.
The rate of cooling would increase with de-
creasing planet size.
life would be short.
fell.
If a molten crust should exist, its
Cooling would slow as the temperature
Small planets (spheres)
cool more rapidly than large
planets, due to the greater surface area compared to their
masU.
Initial cooling is rapid in a molten planetary body
due to convection currents in the high4 fluid interior conveying heat to the surface, where it is radiated into space.
Rapid initial cooling would favor vitrification of silicates.
The slower cooling that followed would allow time in which
the ions of the silicate glass could rearrange in crystal
structures.
Assuming a temperature of 1000'-- 15000C,
a
120
Mineral
Olivia
Anorthite
Sp. G.
Glass
0.381
2.831
16.3
3.175
4.743
13. 6
2. 765
2.700
2.4
R. A. Daly,
p.
$ decrease
Sp. G.
ry a tal
Cry s ta l
Sp. 0.
Gla ss
Igneoums Rooks and the Deptaof the Earth,
50, McGraw-Hill,
1933.
121
temperatu~re at which the refractory silicates could exist in
the solid state, thia high temperaturo would greatly favor
the ionic migrations noceeary to form crystal structures.
Because in the planet's interior there would exist hifh
preasures, the silicate chemical system would tend (by Le
Chatela's lawj towards a state of minimum volume.
This
state, in the case of silicates, is the cryatalline state.
Since none of the meteorites we possess are extraordinarily porous, this adjustment to lesser volume mast
result in a decrease in the planet's diameter.
This decrease
in volume would partly be accomplished by solid flow of the
glasses and crystals present, then violent movement, of the
natare of fracturing, faulting, and breociation would occur.
The almost aivereal brecciated strcture of meteorites,
their fraotures and faults, attest that such movements ocarred.
The inward, contracting forces of the silicate shells
woald be opposed by an outward force of the expanding nickeliron core, for this alloy, like water, expands on solidification.
uhether or not the total planet increased or decreased
in volume would depend, of coarse, on the relative sizes of
cores and shells, of which there is at present no sure knowledge.
ie can only conjecture that interior adjtstmente in
volume would be expressed on the planetts crust in auch
phenomena as mountain-building, faultinc, possibly valcanism,
I-,
122
and other pheaomena,
Bat whatever the surface resflte, or the total change in
volume, we may safe4y assume that the solid mater14l of the
planet's interior would flow, and be fratured, faULte&, and
brecaiated.
If
such forces are at present operating in the interior
of the Earth, here is a possible eowroe for the forces which
build mountains.
CHAPTER VIII
SAT
EDPATH
?OTHSIS
A wide number of independent approcches have almost invariably led to and confirmed the belief that meteorites are
,the remaants of one or more shattered planets,
C. A. Bauer
(1949) has made an admirable argument for this theory.
Also,
F. G. Wateon (1938) has contributed many argaments in its
favor.
The argamoats presented by baaer ani fatson are in-
oorporated in this chapter.
Their astronomical arguments
are given in full or in part, withoat major discussion here.
It is hoped that the geological ideas of the writer will enhance the theory and add some bit to our knowledge of the
meteorites, Earth's interior, and the origin of the Solar
System.
Perhaps the final solation to the problem of the
origin of the Solar System may best be reached through this
analytical approach.
Following ic presented a list of facts and observations
which all point to the plausibility of the shattered planet
hypothesis.
It is hoped that this presentation will raise
the hypottesis to the statme of taeory.
Astronomieal
1.
Association of meteorites with planetoids (aster-
oids) (and non-association with oomets).
2.
Roohe's limit -- a case for shattering.
124
Geological
l.
The meteoritic sequenoe.
2. GeocahemiCal and petrological evidence.
6.
Struoture oZ pallasites.
4.
Geochemical equilibria.
b.
The widmanstatten figares, suggesting a slowly
cooling planetary oore --
6.
solid on disruption.
Structures: brecciation, chondrales, fractures
cnd.
faults.
Astronomical Evidence
AasoMiation or meteors with comets:
A great stride
forward had been made in our understanding of meteorites
when it was recognised that meteors and meteorites are separate phenomena.
The distinction was difficult to make,
for
botn manifest similar appearance as they streak through
Earta's atSosphore.
The distinction was made chiefly through discovery of
the facts that no meteorite ?ws ever been associated with a
meteor snower radiant, and that the meteor showers are assoe
eiated with -- are, in tact, derived from oomets.
Shower me-
tecrb are tiny particles, too small to sarvive their journey
throug Iatth's atmosphere.
Meteoritea are larger fragments,
pro'bably elfleding three kilograms when they enter Earth's
atmos phere.
Astronomers have long argaed the existence of interstel-
125
Opinion has nwaag widely for and against such
lar meteorites.
visitors.
H. A. Newton
(4.)
conoluded from a study of 116
falls on which data was then available that 109 had orbits
witain the Solar System, had direct motion, and nad orbits of
Opi
low inclination.
(1933),
in studies of orbits of me-
teors concluded that a high peroentage had hyperbolio orbits
and thas were visitors from interstellar apace.
However, the writer was told by Professor F. L. whipple,
of Harvard Observatory,
that in the early 1930's many as-
tronomers strongly believed in meteors with hyperbolia orbits, bat that photographic meteor research has steadily
ahaten this view, and now an upper limit of 2 or 3% may be
set on possible nyperbolic meteors; furthermore, that the
chances of this apper limit being too small are becoming inIt is safe to say that the grest majority
oreasingly less.
of mateork Are members of the Solar System, and until evidenSe to she contrary is presented, meteorites may likewise
be so considered.
The observational data of known falls
strongly suggests that meteorites are in orbits about the
Sun, and that their orbital elements closely resemble those
of a large number of asteroids that olosely approach Earth
(Baaer, 1949).
The majority appear to have direct motion
about the San.
Planetoids lie in a breed belt about the SuAn, in orbits
aeaally confined between the orbit of Jupiter and that of Mars.
126
Kepler had suggested the existence of eUh a planet.
The
Titius-Bode law may be expressed mathematically as
rn= a+b*2Z,
where r is the distance of the nth
planet from the Sun, and a and b are constants.
This law
prediated the distances of the planets from the Suan.
To the
early 18th century astronomers, its otherwise near infallibility strontlg
suggested that a small planet existed between
the orbits of aars and Jupiter.
They were led to a dtligsnt
search of the heaven& which resulted in the discovery in 1801
of the asteroid Cores by 2iazzi.
Discovery of these small
planetary bodies hue continued until at present more than
1500 are known.
All are small in size.
Vesta, the largest,
is less than 400 kilometers (air. 240 miles) in diameter (or
greatest thickness,
;Aeverrier, in a study of the motion of the line of apsides of the orbit of Mare, coaladed that the total aggregate
mass of the planetoids could not exceed one-fourth that of
Earth,
Assuming a mean density of that of Mars for the plan-
etoids, their total volume would equal that of a planet approximately 8000 kilometers in diameter.
Photometric studies of the planetoids have revealed that most
are variable.
This phenomenon can be interpreted either as
du# to materials of different retleoting power on different
parts of a planetoid, or as dae tofdd shapes.
As there is
no reason to suppose that planetoids are composed of differ-
127
Oet materials on their opposite sides, the second hypothesis
is more tenable.
For, if the planotoids were fragmental in
shape, the areas of their reflooting surfaces presented to
Earth would vary (if
they rotated or if
not).
This variabil-
ity in the light from planetoids stronly suggests that they
are fragments and not spherioal bodies.
We know from the odd
shapes of meteorites (Farrington, 1915) that they were fragmental too before their entry into $arth't atmosphere.
R,0oe
limit: The fragmental shape of both planetoids
and meteorites suggests explosive shattering or collision as
a mode of origin, and strongly negates any ideas as to oondensatory or aceretionary origin for either.
An argument is here presented that the planetoids did
not result from explosion.
An explosion from within a planet,
if violent enough to erapt a planet 8000 kilometers in diameter, would probably produce a large quantity of finely
pulverized material.
A series of fragmental sizes, contin-
uouas down to minute particles or dust should be prodaoed.
It is well known that saceossive division of any mass
incresses its total surface area.
Calculations will show
that fine dust from a palverised planet of such size would
have sufficient surface area to be visible from Earth as a
glow, similar to the Zodiacal light and Gegenschein (which
arise from reflection from particles between Earth and Suan).
Such a glow is not observed in the planetoid belt.
Perhaps
we ean safely assue that the planetoids do not diminish in
size beyond a certain limit.
This limit ia set by the miner-
al grains and glassy entities of which the planetoids (meo
teorites?) are composed.
It is aujgested that tidal disruption would be zuoh
loen violent than an internal explosion.
hoohe proved (18f1)
that if two homogeneous liquid spheres of planetary (or
stellar) size approachod within 2.46 radiI of the
argor,
primary body, the smaller sphere would be dierupted b- tiaal foraes.
G. H, Darwin elaborated thia theory.
Although Roooe's limit theory applied to homogonoois,
liquid spheres (atellites),
non-homogeneous,
we ay with safety apply it
solid spheres.
to
The same tidal forces would
exist, but undoubtedly the limit at which disruption would
occur would be greater.
ither a liquid or a solid sphere
'would be distorted (as Earth is by tides) into an ellipsoidal shape.
When the cohesive forces between the solid (min-
eral) grains of the smaller sphere were exceeded, tidal disraption would ocar.
This tidal disruption would be less violent than disruption from internal explosion.
Violent ezploeion would
ejeot fragments randomly with no preferred orbital orientation about the Sun,
On the other hand, the less violent fli
dal disruption would tend to leave the fragments in the original orbit the smaller planet was pursuing before its die-
129
raption,
That this mode of shattering is bat theoretical is admitted, bat we may point, for example, to the rings and satelittes of Saturn.
The rings, which
lork Maxwell in 1859
proved to be composed of small fragments,
lie just within
Roche's limit, while the first satellite lies jast withoat.
The first moon of Uranas lies just outside Roche's limit,
and some astronomers predict that in the future it will spiral inward until it reaches the point of disruption.
Then,
like Saturn, Uranas will possoes a ringL
Fragmentaa
ea ea:
That meteorites are fragmental and
most irregalar in shape as they enter Barth's atmosphere
from space is attested by their fragmental shapes when collooted.
0. G. Farrington (1915) has given an excellent
classification of meteorite shapes and the extent to which
burning in the atmosphere altered their original shapes.
The facts and argumente need not be repeated hero.
it
SUffice
to say that their present shapes attest the fact of their
pro-atmospheric fragmental shapes, and that few, if any, were
spherical.
The fragmental shape of meteorites is in line
with the above cited evidence that the planetoids are irregalar in shape and are likewise fragments.
Efforts have been made by astronomers to determine the
sabstance or which the planetoids are made by the nature of
their reflooted light.
F. G. Watson (1939) concludes that
130
from reflected light alone we cannot tell the nature of the
planetoids, even to the extent of whether they have metallic
or stony surfaces.
feolocal
MEtiO
*A
qenOO:
vidence
0. G. Farrington discovered
the relationship in iron meteorites that with the decrease of
iron content (increase of Ni) the width of kaoscite lammellao decreased; thas the iron meteorites coald be arranged in
sequenoe.
In the light of our knowledge of ex-solution
phenomena in cooling of alloys, this discovery suggests
that the continuoas variation in width of the kamasoite lamellae is a result of progressive cooling rates.
This observ-
ation may be interpreted that the metallic meteorites originated in the core of a planet.
As the planet cooled,
center of the core would be the last to solidify
--
the
the near-
er to the surface, the faster would be the cooling rate, thus
producing the variation in widths of kamaoite lamellae.
0. A. Baaer (1949) extended this knowledge by comparison wita our seismic knowledge of Earth's interior. It is
pointed out that a mrked discontinaity exists in tarth at a
distance 0.b5 of its radias from center.
Likewise the meteor-
itic seqaene from irons to pallasites is rather abrapt.
Iron
meteorites average about 7.5 in specific gravity, while pallasites average about 4.2 and intermediate varieties are unknown.
Thus it is indicated that in the shattered planet there
131
existed a discontinuity analogous to that in Earth.
Because
we do not know the true relative abundances of stones to
irons we can not know the size of the planet's core.
Watson concluded that the ratio of atones to irons by
weight was within the limits of four to nine stones to one
iron, and was unable to fix a more precise ratio.
Bauer (1949)
However,
obtained a value of 0.45 of the radiom as the
planet core size, on the assumption that Watson's studies
were correot.
Bat Watson did not fix the ratio of stones
to irons except as a lower limit of 4:1 and an apper of 9:1.
Thus Bauer's value is not acceptable on the assamption made.
Using *atson's ratios of stones to irons of 4:1 and
9:1, and assuming a specific gravity of 7.5 for the core
and 4 for the silicate shell, a minimum value of 0.36 of the
planet's radian is obtained and a maximum of 0.62, the mean
value of which is 0.48, about 0.45, which is saser's value,
However, we have only observational data (Watson's compilation) allowing us to set an upper and lower limit, and we
are still left not knowing whether the core of the shattered
planet was larger or smaller than £arth's core (0.55 of radias), except that the mean from our observational data indicates a lesser site.
Jeffreys (1924) concludes that the smaller a planet is
the smaller its core.
His studies were based on the ellip-
tioity of the shapes of Earth and Mars, for ellipticity is a
132
function of mean density, rotation period, and the increase
in density towards center.
Unfortunately the elliptioity of
Venus and Mercury is not known, to extend this hypothesis,
but we may suppose from their known volumes and masses that
their cores are relatively smaller than that of Earth.
Geochemical and pe trological evidence;
A. F. Badding.
ton (1943) has made a number of interesting dedactions on
the
arth model from meteorite data.
He found that as oli-
vine increases in quantity the olivine is richer in fayalite,
Variation is from Fogo to 7063, and he observed that this
variation is the opposite to that found in terrestrial stratiform sheets.
Furthermore, the near oonstancy (air. 5%) of troilite
in ohondritic meteorites indicates to baddington and Chirvineky that this mineral was not differentiated by fractional crys.tallization and settling of crystals.
A feasible ex-
planation is that convection currents prevented settling of
the heavier components, although the gravity field intensity
was sufficient to have caused it.
A final observation was that the pyroxenes became more
magnesium-riah the greater the amount of pyroxene,
This
trend is in harmony with fractional crystallization in terrestrial stratiform sheets.
The constancy of troilite and the variation of olivine
composition make the hypothesis of simple crystal fractiona-
133
tion in the former planet untenable.
However, it
should
here be pointed out that simple crystal fractionation has
apparently rarely occurred in 2karth stratiform sheets, as
the numerous inconsistencies in applying this process alone
attest.
Hess and Henderson, as noted in Chapter VI, have
shown that in at least one shell of the planet, that from
which the Moore County stone came, crystal fractionation
may nave occarred to give the observed preferred orientation
to the feldspar and pyroxene crystals.
A. E. Nordenekiold (1878) and W. wahl (1910)
showed
that for several ohondritic meteorites the atomic composition is very uimilar, and conoluded that the difference between the enstatite-rich Daniel's Kial (Hvittis) stone and
other (more FeO-rich) ohondrites 4#gaonong
an
Q
W. Flight
amount
of jggen t
stones contain.
the dif-
(1881-82) showed that if the ohondrites are arranged in order of increasing free metal phase content, then the Ni content of the free metal decreases.
G. T. Prior (1916),
after making a systematic study of
chondrites, stated that "the lees
the amount of Ni-Fe in
ahondrites, the richer the metal phase is in Ni and the
richer in Fe are the Mg silicates".
He farther pointed out
that the total ratio of Fe atoms to Mg atoms varies but
little; 1.0 for Daniel's Kial (25
Soka Banja (4% free metal).
free metal) and 1.8 for
Thus for all chondritio meteor-
134
ites the percentage of MgO varies only within narrow limits.
The meteoritic sequence is remarkably continuoas for stony
meteorites, with nearly all proportions from metal free to
metal rich specimens in our collection.
This remarkable relationship *rw be observed most
strikingly in the spectra of meteorites, as in the twenty-
one chondritic spectra of this investigation.
In fact, the
most striking feature of analytioal studies of these spectra
is their almost identical appearanos, any one spectra being
unidentifiable from any other, and the trace elements being
present in almost constant amounts.
The saggestion is
strong that all chondrites had a similar origin, possibly
within a planet-sised body.
Wahl and Prior both attributed these remarkable relationships of Ni, Fe, Ig0, and FeO to the results of oxidation.
Prior oonluAed that
"all meteorites have had a common origin
from a single magma, which is most nearly representad by that which gave rise to the Bastes
and Daniel's Kial (Rittis) types of meteoritic
stones, and that from this magma all other types
have been prodtsed by progressive oxidation of
the nickelferoas iron."
Prior states that in the Daniel's Kial magma only outficient oxygen was present to react with Si, Mg, Al, and Na
(and to a slight extent with Ca and Or), but that scarcely
any reacted with Fe, because there was not enough oxygen
present.
135
In other environments, presamably in other shelle of the
planet, when the magmas enoountered more oxidizing agents
(&ore oxygen) the iron would be progressively oxidized; part
of the Mg-llioate (enstatite) would be reduced to ferriferous olivine and part to bronsite.
In all of these re-
actions 1i took no part, bat remained and became enriched
in the free metal phase.
'W.Wahl (1910) explained the non-
reactivity of i as duo to the lower heat of production of
NiO as compared with that of 7.0.
Wahl suggested that
ohondritic stones were produced unAer surface conditions
like volcanic tuffs, and stated "that it may be that the oxidation of
bronaite
i-4e with resultant prodaction of olivine and
was of sach violent nature that drops were thrown
out (tae ohondri) in a hot and ratified atmosphere (as sug-
gested by L. H. borgetrom, Da motiorit von S.
Michl, Ball.
Comm. Geol. Fialande, No. 34, 38, 1912) and oonsolidated suftioiently slowly to form the crystalline chondrules".
The
ditficulty of this argamsnt for the surface origin of ohondri,
on the basis of the predominance of chondritic material (at
least 76% of the total volae of meteorites) has been diecussed in the chapter on the mineralogy of meteorites, this
thesis, and a theory proposed to explain the great paradox
--
that tUe great volume of meteorites resemble volcanio agglomNote: "Hyperstheae" would be more correct here than "bronsite", for bronaite of intermediate Fe content, compared to
enstatite and hyperathene, is remarkably rare in meteorites.
*
136
critic material and appear to result from sarface phenomena.
H. Brown and G. Sattersoan (1947) extended the work of
previous investigators and made several important further
observations listed below:
l. The average Bi content of the metal phase of stony
meteorites is greater than the average Ni content of iron
meteorites.
2.
The average Co content of the metal phase of stony
meteorites is greater than the average Go content of iron
meteorites.
3. Graphical spreads of the Fe, AL, Co is greater in
the metal pase of stony meteorites than in iron meteorites.
Prior postulated that the achondrites represented a
higher stage of oxidization than the chondrites, and average
much higher in AlgO 3 and CaO, bat are poorer in sulfides and
free metal.
Badaington (1943) oonsiders Prior's theory of
progressive oxidization adequate for the ohondrites but not
for the achondrites.
baddington points oat that there is a
striking contrast in the mode of variation of the composition
between the chondritio and aehondritic meteorites.
The Ohon-
drites may fit the theory of progressive oxidization of a
primary magma, but the achondrites are better explained on the
basis of fractional crystallization.
In conclusion, our present state of knowledge indicates
137
that in the planetary body in which the meteorites originated
several processes of magmatic differentiation operated.
In
te shell of the planet, wherein the ohondrites were formed,
the progressive oxidation of a primary magma seems to be the
most plausible hypothesis.
However,
the ahondritic strao-
tare of these meteorites has get to be explLAned.
Evidenoe
points to the belief that within the aohondritic shell
fractional orystallization was the dominant differentiating
process.
Natare of pallasites:
The problem of the origin of the
pallasites (meteorites composed of a continuous mesh of
i-
Fe phase inclosing olivine) has interested many investigatore.
It
can be concluded at once that the environment in
which pallasites orytallized was deficient in oxygen and
that a limited amount of silicon was present.
The shapes
of the olivine crystals mast be explained in a theory of
origin, for they are rounded or fragmented, as if produced
or modified by attrition.
R. a. 'Dalg (1945) argad that all of the meteorites
originated from the fragmentation of a single planet, and
that the pallasites were the result of gravitational settling within this planet,
The meteorite Itsawisis has unfratured olivine crystale enclosing metallic particles, demonstrating that metal
was present before crystallization of the olivine.
138
Merrill (1930) concluded that the metal phase of meteorites (and pallasites) wra derived from ferrous chloride,
which was originally introduced at a temperature lower than
the melting point of the silicates,
and was then redaced,
He interpreted the small amounts of laiwrencite found in mete
allio meteorites as unreduced residue.
Lord Rayleigh (1942,1944) attempted, with quite good
success, to reprodaos the struActares of chondrites.
He ae-
samed that pallasites originated by olivine weathering out
of rocks, which became immersed in molten iron and were
He prodaed artificial pallasite
rounded by attrition.
structares by pouring molten solder over fragments of stoatits and thas produced the shapes of olivine orystals in pallasitee.
He concluded that pallasites did not originate
from free metal separating out of a silicate malt.
However,
the olivine crystals of the Itsawisis meteorite, and the
e-
periments of Bowen and Shairer, both evince that metal would
separate from a Fe, Mg, Ni-silioate melt, containing a saperabundance of Fe and
i.
H. J. Sel (1949) has contributed mouch to our knowledge
of pallasites and their origin.
Nel ooncluded that variations
in meteorite types are the result of "magmatic differentiation processes similar to those that operated in the Earth's
crast".
Nel, like the writer and many other geologists,
finds it difficult to concelve of the meteorites having formed
139
as individual entities.
ge believes, rather, that they
must fave resulted from cooling in space within a large
planetary body.
Bel produced variation diagrams showing differentiation of the Bashveld stratiform sheet from peridotite to
anortaosite, and compared this diagram with a variation
diagram of meteorites.
He concluded that gravitational
differentiation separated the original molten material
(taie is assaming immiscibility) into silicate and metal
phases, bat that separation was not complete.
Nel ob-
served that the metallic portion of pallasites is "to a
certain extent inversely proportional to the amount of
iron present in the essentially Mg-silicate", and that
pallasites are the most
afic in the series of aerolites
and are the transitional stage during magmatic differentiation between siderolites and aerolites.
In a stady of the
Bashveld complex van der Walt (1941) discovered that the
formation of chromite and orthopyroxene exerts a reciprocal
effect on their respective chemical compositions, which is
shown in their rAg ratios (mg
MgO mol/agO mol
FeO mol).
Nel concludes that the same sort of chemical equilibriam an
differentiation controlled formation of the pallasites, except that oxygen was very deficient.
Geoahemial
juilibria:
H. brown (1948) has made among
the most significant contributions to our knowledge of the
140
origin of meteorites and has made an admirable attempt to
place the theory that meteorites originated within an Earthsized planetary body on a thermodynamic basis.
brown plotteA variation of percentages of the several
major elements in meteorites against the percentage by
weight of free metal.
On these graphs he thci plotted the
variations of the major elements in average igneous terrestrial rocks and plateaa basalts,
percentage free metal.
These were plotted at zero
by extrapolation he showed that
terrestrial rooks were natural extensions of the variation
curves of meteorites.
Alaminam was the only exception founA.
Brown also noted that the major element composition of meteorites is strikingly different from the major element
composition of terrestrial rooks, and pointedly suggested
that ortain low abuadanoe elements are present in the
harth's crastal rooks only by"statistioal flactuations".
The presenoe of certain ilemeats, e.g. the platinum group,
which is strongly siderophile and enormoasly enriched in
the metallic phase of meteorites, is due to inoomplete differentiation of Earth's arust.
equilibriam conditions it
Had cooling been under ideal
seems reasonable to believe that
certain elements might have been oompletely exoladed from
Larth's orust.
Brown farther showed that certain achondrit-
to meteorites are almost identical to certain terrestrial
rocks (e.g., Hess and Henderson showed the bulk composition
141
or the Moore County meteorite to be almost identical with
norite), and conclades that it is most difficult to explain
their origin other than by differentiation processes within
a planet-sized body.
Brown and Patterson (1948) made the fundamental assumption that the observed distributions of the elements between
the various phases in meteorites represent equilibrium conditions.
They assume that equilibrium must have been es-
tabliened at temperatures of approximately 300000 and
presearee of 105
-
106 atmospheres.
These investigators noted the surprieingly smooth de-
pendence of the distribution coefficients between the metal
and silicate phases upon the affinities of the various elements for oxygen.
They found the distribation coefficient
dependent on As , the heat of formation, and suggested that
the elements distribated themselves between the various
phases (metal, silicate, sulfide) under near equilibrium
conditions.
An example of this, whioh has already been ade.
quately disassed in the chapter on mineralogy, is the
strong dependence of the distribution ooefticient of Ni on
the free metal phase content of a meteorite.
Brown and
Patterson particularly investigated this observation, for
i is the only element for which adequate experimental evidence exists.
Zur Strassen had previously measured the equilibrium
142
Ni + f8Si03
U13±03 + Fe at 18400K and one atmosphere
N
and tound the equilibrium constant to be 7.25 x 103.
The equilibrium constant is defined as
Iel a xii .s
a
[jzilm(Felei
0- 3
18400y7.
BO%
Atm.
where "m" and "ai" refer reupectively to the iietal aad sili-
cate phases.
Lar Strassen found GM± = 7.25 % 10-3, which is approximately 40 times smaller than the value 0.24 observed in
gross meteoritic material.
Thas there is an enormous dis-
orepanoy btween the experimentally determined value of
The question of
OGb and the OGi observed in meteorites.
how this major difference, at the temperatures e:xpected in
the interiors of planets, could be explained arose.
Brown
and Patterson assamd that the temperature at the center of
Earth was nearer to 400000 than 3000 0 C.
This assumption
was based on a lower limit of temperature at which Ug-rich
silicates could remain molten and an apper limit net by
astronomioal and geophysioal theories (s.g.,
that of ter
Harr).
by toe Chatelier's principle, either a pressare or
temperature increase would increase the value of Ci (i.e.,
suitt the reaction to the right).
On the assumption that
temperatures within an Earth-sised body would be of the
same order of magnitade (air. 2000 0 K) as ased by sur
I.
-
-
~.J.
143
Strassen in his determination of ai.
Brown and Patterson
concluded that the discrepancy could only be explained by an
enormous increase in pressure, of the order 105 atmospheres.
This pressure is of the same order of magnitude that astron.omers believe to exist within a planet approximately the
size of Mars.
Brown and Patterson found an even greater discrepancy
in the case of
%jifor
the reaction
Mi + FeS
S * Fe
or, CNi i[ia2 s
(i] m(Fe] a
phase.
,
where "a" denotes the sulfide
0ji for this reaction determined in the laboratory
at 12000K and one atmosphere equals approximately 1. For
gross meteoritic material the value is approximately 0.02.
In this reaction, increase of temperature shifts the
reaction to the left (doreases O31), while pressare increase shifts it to the right)
The temperature at whieh
meteoritic silicates are molten exlAes the possibility of
a lower temperature.
BrowA and Patterson concluded that the
discrepancy mast be due to increased pressure -- again of
the order of 105 to 16 atmospheres.
Such pressures would
be quite impossible within a body of the size of meteorites
that strike the Earth, or even in bodies hundreds or even
thoasands of times more massive.
The conclusion is almost
inescapable tht ateorites originated within a planet oomFor a vigorous adverse criticism of the work of brown and
Patterson read I. m. Klotz, Science, 109, Z48-2bl, 1949.
a
I
-
144
parable in size to Earth.
a further conlasion, equally
inescapable, is that this planet was in some way shattered,
for meteorites reach Earth as small fragments.*
"a
tatten fiures
These figures, which are oba
tained by etching the polished surfaces of meteoritic Ni-Fe
have long intrigued metallurgists and investigators interested in the origin of meteorites.
Until very recently, metallargists were unable to produce these
igros. Widmanstatten figures are due to ex-
solution phenomena, wherein the two alloys kamaoite and taenit. crystallize in lamellae along octahedral crystal faces.
N. A. Owens (1938) ooncladed that saitable heat treatment would lead to the prodation of a two phase structure in
certain alloys.
Owens discarded the theory that the figures
formed by heating in Earth's atmosphere,
for the interior of
meteorites are not heated in this manner.
Furthermore, rapid
heating Is known to destroy the figures.
Owens, as well as S. -g.J. Smith and J. Young (1939),
attributed the figures and the kamaoite-taenite lamellae to
the T- O(lattice mechanical transformation.
They concluded
that meteorites (metal phase of stony meteorites possesses
Widmanstatten figures) formed during slow cooling inside some
massive heavenly body
--
in which the lattice transformation
took place so slowly that almost perfect equilibrium prevailed.
Smith and Young produced a similar lattice transform-
145
ation in a 10% Ni-F. alloy by slow ooling.
Owens and
Williams likewise studied the cooling of a Ni-Fe alloy and
produced the lattice transformation, and concluded that the
structure may form in the range 3500-58000 and requires
several months to break down when the temperature drops below 35000.
Breakdown will occur only when the temperature
drops approximately one degree per day, and not for more rapid rates.
Their experiments produced only submicroscopic orystals.
Subsequent investigators concluded that only extreme-
ly slow cooling could produac the gross Widmanstatten figares observed in meteorites.
R.
. Mehl and G. S. Barrett (1931) pointed out the
fall significance of Widanstatten figures, and these structares are now universally recognised by metallurgists and
crystallographers as solid-metal reaotions which operate by
crystallographic mechanisms.
Mehl and G. Derge (1937) found
that "these mechanisas may be described and specified by relations which exist between the parent matrix-lattice and
the product or preipitate lattice",
the mechanism is two-
fold; transformation of the face-eentered cubic lattice of
r -iron
to the body-oentered cubic lattice of X -iron.
Mehl and Derge have sceeded by prolonged slow cooling
of Ni-Fe alloy in produoing Widmanast'tten figures of macroscopic size.
Also, J. D. Buddhas (1949) suooeeded in pro-
146
dacing significantly large figures by slow oooling of a 27%
Mi-Ye alloy,
The conolasion is strongly supported that Widanstatten
figures could develop only within a large body
--
probably of
planetary size -- for a smaller body of the present size of
meteorites known to us would cool with great rapidity in specs.
!t.esa
The Barth is generally conceded
of Meteorites;
by geologists to be at least B x 109 years old.
Investiga-
tors have long sought to establish the ages of meteorites.
If a similar age could be round for meteorites and Earth,
this would strongly eaggest that both originated at the same
time and may have had similar modes of origin.
F. A. Paneth has determined the "ages" of many iron meteorites and at least one stony meteorite (1928).
C. A.
Baaer (1949) gives a complete bibliography of Paneth's works.
Paneth derives ages ranging from 30 million to 8.6 billion years for meteorites.
There is no olastering of ages
and the meteorites appear to be entirely randomly distributed
as to date of origin.
This spread of ages is most disconcert-
ing to a theory proposing a common origin for meteorites.
However, Baaer has proposed a logical explanation for
the ages determined by Paneth.
Baaer observed from Paneth's
measurement of He in meteorites that the content of He was direotly related to the masses of the meteorites measured (1949).
The meteorites of small mass contained the most He, while
147
those of large mass contained the least, with a consequent
great age for small meteorites and a small age for large
meteorites.
Bauer proposed the explanation that He was produced in
meteorites by cosaio ray bombardment oausing nuclear disraptions.
The cosmic rays could not penetrate deeply into
ssnes.
large
Consequently, large masses contained the
least He.
Bauer concluded that all the He present in meteorites
could have been produced in 60 million years, and set this
as the apper limit for the time of disruption of the parent
planet.
In fairness, it should be stated that Bauer's work is
statistical and theoretical and is not yet completely proved
by experimental evidence.
Nonetheless, it
is the only ex-
planation which has been advanced to explain the great divereity in ages shown in meteorites by He measurements.
All
other evidence points to the belief that meteorites had a
contemporaneous origin.
Recently, S. K. Gerling and
. G. Pavlova (1951) have
determined the ages of two ckondritic meteorites by the
argon/potassium ratio (s0
disintegrates by (3-doay to A4 0 ),
They found for the Zhotnevy Khator meteorite an age of
3.03 x 10
years, and for the Saratov meteorite the age
3.00 x 10
years.
These two ages are in close agreement
a
a--
a
148
with the earrently accepted valmes for the age of Earth,
and saest
a common date of origin.
Glastie struotares of meteorites:
Meteorites ezhibit
in most cases strikingly elastic struotares, each as fraotares, faults, sliokensides and brecoia.
These features
have all been di seassed in the aapter on mineralogy.
is sufficient to point oat here that it
It
seems quite impos-
sible that these elastie struatures could have developed
in small bodies.
They are featares that geologists common-
ly associate with massive movements within the Earth.
Con-
sequently, the olastic structares of meteorites most probably developed wi thin a assive body -- a body possessing a
strong gravitational field; in short, a planetary body, oomparable to Earth in size.
CO CLUSIONS
The remarkable constancy of the traes elements K, Rb,
Ba, Sr, Sc, and Zr in chondritic meteorites as evineed by
their spectra strongly saggests that thee elements are present in nearly constant quantity in the chondritic meteorites,
and rarely vary by a factor greater than 2.
The results of those analyses indicate that the followi4
AW abandanco values should be aeaepted.
0.080
0.0008%
0.0008%
0.000%
0.000%
000$P
x
Rb
Ba
Sr
So
Zr
A review of the literature indicates that the abundance
values for namorous traos elements rests on very scant anain many oases almost entirely on the ana-
lytical evidence
lysis of a composite sample.
Obviously, current trace ele-
ment abundanoes in meteorites may be in rather large error.
A study of the ratio
%K/Rb in meteorites and common ig-
neous roots proved that the ratio is nearly oonstant, approximately 100:1.
This project was suggested by Dr. L. H. Ahrens,
Analysis of the Skaergaard rooks for Sr indioates that
this element was present in a sImal amount in the original
Skaergaard magma.
Wager and Mitohell had previously found Sr
abnormally high -- comparable to percentage of K present.
The
160
writer oonoludes that this result was due to analytical error.
Zirconium, So, and Rb were determined for the first time
in the Skaergaard suite of rooks.
Both Rb and Zr show char-
aeteristio enrichment from base to top of the intrasive,
while So content decreases. The behavior of these three elements is farther evidence that the Skaergaard intrusive uandorweat fractional crystallisation in cooling.
A review of the astronomical and geological literature
led to the conolasion that there is a wetlth of evidence sapporting the shattered planet hypothesis for the origin of
meteorites.
Negative evidence, and inconsistencies, are few.
SUGGESTED RESEARCH
In view of the fact that the abndanoe valaes for several trace elements in meteorites were fouA
in error daring
this investigation, it is sagested that all the other trace
elements not analysed for in this thesis be determined by new
improved methods.
For example,
os could not be detected in
this investigation, but may be present.
It may possibly be
detected and determined by saitable chemical concentration.
It is suggested that internal standards for silicate
meteorite analysis be investigated and applied in fature analyses,
The need for large numbers of analyses of meteorites
is obvious, if the cosmic abundanoes of the elements from
meteorites is to be put on as son
a statistical basis as
are averages of terrestrial rooks.
A possibility exists that the age of meteorites (at least
7 method
an apper limit) might be determined by the Sr8 7 -- 3bR
Even an upper limit value would
by careful analytical work.
be extremely interesting.
The only previous determinations of
ages of silicate meteorites have been by the helium method and
a recent determination by the
404:A 40 method.
The helium
metnod is not considered valid when applied to meteorites, in
the opinion of the writer.
Age measurements by an indepen-
dent method would be very aeful.
152
It is suggested that an extensive researeh be made on
tracs element abundanoes in altramafic rooks -- similar to
the program on granites, diabases, and basalts in programs
now in progress in the
.I.T. geology department.
BIOGRAPHICAL DATA
The writer was born in Atlanta, Georgia, on September
6, 1919.
He completed one year's work at the Georgia Insti-
tate of Teohnology, 1937-38.
After five and a half years
military servics he entered Emory University, Atlanta, in
1946. He graduated as Bachelor of Arts in the Sohool of
Arts and SOienOes in 1948, and received the degree of Master of Science from Emory University in 1949: master's
thesis on "The Geology of Polk County, Georgia". Farther
post-graduate work was started at the Massachasetta Institute of Technology in 1949.
The writer married Mary Latta in 1942, and has two
children, Mary and Naomi.
His professional experience includes two years as
laboratory instructor at imory University and one summer's
field work with the Geological Survey of Georgia.
He was
for one year editor of the monthly pablication, Atlanta
Astronomers'
Report.
He is at present employed as Research Fellow, Department of Geophysics, and as Instractor, Department of Astronomy, Harvard University.
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