Supporting Online Materials for:
XANES and Mg Isotopic Analyses of Spinels in Ca-Al-rich Inclusions: Evidence for Formation
under Oxidizing Conditions
J. M. Paque, S. R. Sutton, S. B. Simon, J. R. Beckett, D.S. Burnett, L. Grossman, H. Yurimoto,
S. Itoh, H.C. Connolly, Jr.
Appendix A: Bulk compositions of experimental samples.
Appendix B: Ti valence profiles for TS34 spinel inclusions in anorthite.
Appendix C: Theoretical modeling of Ti and Ca intensity profiles.
Appendix D: Aluminum, magnesium and oxygen isotopic results.
1
Appendix A
Bulk Compositions of Experimental Samples
Table A1. Bulk compositions used for experimental samples; all values are in wt %.
HC1
1316
SiO2
30.9-32.2
34.02
TiO2
1.1-1.2
1.15
Al2O3
26.4-27.6
24.24
MgO
9.0-9.9
8.0
CaO
28.5-31.2
30.51
Total
97.2-98.7
97.92
References
Beckett et al. (1990);
per. comm. M.
Connolly and Burnett (2003) Johnson
1
Analyses of bulk composition are from Beckett et al. (1990); they also included trace elements
in the starting composition. Connolly and Burnett (2003) doped the starting material with 0.25 wt
% each of Co, Mn, V, and Cr. Samples used in this study were from Connolly and Burnett
(2003).
CAI
31.1
1.12
28.3
10.1
29.2
99.82
Stolper (1982)
2
Appendix B
Ti valence profiles for TS34 spinel inclusions in anorthite
Spinel sp7 in TS21. The irregular morphology of TS21 sp7 (Figure B1) suggests that it is not a
single crystal but instead part of a sutured chain of 10-20 micron crystals. The measured Ti
valence profile is approximately down the axis of the chain and shows a constant Ti valence of
around 3.75 (Figure B2). The Ti concentration along the axis of sp7 is relatively constant but
shows highly significant (about 12.5%) quasi-periodic variations (Figure B3). This may just
reflect small Ti concentration variations in the presutured grains or it may be due to partial reequilibration of larger variations in presutured Ti concentrations. The relatively high Ca counting
rate (Figure B3) at the beginning of the profile (0, 10, 20 micron points) indicates some sampling
of adjacent melilite/alteration but as the Ti valence is the same in these points as in the deep
interior, either the apparent melilite/alteration valence is 3.8, or more likely, essentially all of the
measured Ti comes from spinel. Depending on details of subsurface geometry, the high Ca
points should have sampled a Ti+3 rich spinel rim, but this appears to be absent. However, more
study of TS21 would be required before any definitive conclusions are possible.
Figure B1. TS21 sp7. A series of sutured spinels inclusions in mantle melilite/alteration. Blue arrow
indicates direction of XANES profile with x=0 at the beginning of the arrow.
4.0
3.8
Ti Valence
3.6
3.4
3.2
3.0
0
50
100
Distance (microns)
150
Figure B2. Ti valence profile for TS21 sp7 for the scan indicated in Figure B1.
3
50
Ti counts (/1000)
1400
Ti counts
Ca counts
1200
1000
40
800
30
600
20
400
10
Ca counts (/1000)
60
200
0
0
0
50
100
Distance (microns)
150
Figure B3. XANES Ti and Ca counting rates for TS21 sp7 for the scan shown in Figure B1.
Spinel F2 (Figure B4). The Ti valence (Figure B5), Ti counting rate (Figure B6), and Ca
counting rate (Figure B7) for F2 are similar to those for spinel B4 (text Figure 5c; Appendix C).
Counting statistics errors (2σ) on the counting rates are smaller than the size of the points. On
both the entrance and exit portions of the profile, there is an indication of an edge enrichment of
Ti+3 (Figure B5). However, unlike B2 there are significant boundary clinopyroxenes around F2,
as shown in Figure B4.
melilite
witness marks
cpx
spinel
70 µm
Figure B4. Spinel F2, backscatter electron image.
4
Ti valence
4.20
4.10
4.00
3.90
3.80
3.70
3.60
3.50
3.40
3.30
0
20
40
60
microns
Figure B5. Spinel F2, Ti valence, 7 micron steps.
The small increase in Ti counting rate with the drop in Ti valence for the 0 and 7 micron
points is suggestive of clinopyroxene interference. The case for an edge enrichment in Ti+3 thus
rests on the 49 and 56 micron analyses.
The correlated Ti counting rate decreases and Ca counting rate increases (Figures B3 and
B4) are expected as the primary photon beam on the exiting part of the profile passes through
progressively thinner amounts of spinel and increasing amounts of anorthite (see Appendix C,
Figure C2). A measurement of the Ca counting rate on pure anorthite is not available, but the
maximum Ca counting rates on Figure B4 are much less than those expected for pure anorthite
(on the order of 105 cps). Thus, a significant amount of spinel is being sampled even at 56
microns. However, the drop in the Ti counting rate between 49 and 56 microns is smaller than
expected based on the decrease between 42 and 49 microns. This could be the signature of
sufficient clinopyroxene interference to cause the Ti valence to be low and not due to a Ti +3
enrichment in spinel.
6000
5000
cps Ti
4000
3000
2000
1000
0
0
10
20
30
40
50
60
microns
Figure B6. Spinel F2, counts per second Ti, 7 micron steps.
5
25000
cps Ca
20000
15000
10000
5000
0
0
20
microns
40
60
Figure B7. Spinel F2, counts per second Ca, 7 micron steps.
Spinel F3. Analogous to Figures B5 to B8 for F2, figures B9-B12 show an SEM image as well as
profiles for Ti valence, Ti counting rate and Ca counting rate for spinel F3, an inclusion in
anorthite. Unlike spinel F2, a two dimensional electron probe map of F3 shows only a small
clinopyroxene grain near one corner far from the start of the XANES profile.
There are fewer points in the F3 profile but overall, it is similar to those of spinel B4 (text
Figure 5c) or spinel F2 (above). The overall shapes of the profiles are exactly what is expected
given the analytical geometry (see Appendix C). The decreases in Ti valence in the 30 and 40
micron points are quite significant, and that for the 0 micron analysis is about 2 sigma lower than
that of the 10 micron point. There is a strong suggestion of an edge Ti+3 enrichment for spinel
F3.
Witness
marks from
microprobe
XANES
traverse
Figure B9. Spinel F3, secondary electron image.
6
4.00
3.90
valence
3.80
3.70
3.60
3.50
3.40
3.30
0
10
20
30
40
50
40
50
microns
Figure B10. Spinel F3, Ti valence, 10 micron steps.
4500
4000
3500
cps Ti
3000
2500
2000
1500
1000
500
0
0
10
20
30
microns
Figure B11. Spinel F3, counts per second Ti, 10 micron steps.
Dis
cuss
ion
Bot
h
the
7
F2
and
F3
prof
30000
25000
cps Ca
20000
15000
10000
5000
0
0
10
20
30
microns
40
50
Figure B12. Spinel F3, counts per second Ca, 10 micron steps.
Discussion. Both the spinel F2 and F3 profiles are consistent with an edge Ti+3 enrichment
(decreasing Ti valence) in spinel; however, F2 contains large amounts of boundary
clinopyroxene, and has suggestive features in the profiles that clinopyroxene interference effects
might be important. Although there are fewer points, the F3 profiles have none of the
complications of F2. This, and the dearth of observed boundary clinopyroxene around F3, makes
it a good candidate for documenting a real spinel edge enrichment in Ti+3. Detailed modeling, as
was done for B4 (see Appendix C) would be required to be sure, but the anhedral shape of F3
(Figure B5) offers no clues as to the nature of the sub-surface geometry.
8
Appendix C
Theoretical Modeling of Ti and Ca Intensity Profiles
Taken at face value, the XANES profiles indicate that there are Ti+3–rich rims on TS34
spinel grains. (Figure 6 in the main paper; Appendix B). The analyzing photon beam is quite
small (approx 2 microns); however, the relatively large attenuation mean free paths of the
incoming (4970 eV) photon and fluoresced X-rays (23 microns for Ti K in spinel) complicate
the interpretation of the profiles.
The 45 degree angle of the incoming photon beam and the outgoing fluoresced X-rays
has both advantages and disadvantages. Considering both incoming and outgoing attenuation, the
effective depth resolution is considerably enhanced. However, when analyzing the edge of a
grain, the 45 degree inclined path of the incident photon beam makes it highly likely that X-rays
from the adjacent phase will be detected, but this is not always bad, as it enables preferential
sampling of the crystal rims if there is negligible interference from the host phase.
As discussed in the text, contributions from adjacent phases seriously complicate the
analysis of zoning profiles for spinel inclusions in clinopyroxene because clinopyroxene Ti
concentrations are 10-20 times higher than in spinel. Analyses of Ti zoning for spinel inclusions
in Ti-poor melilite, alteration, or anorthite are much more favorable as spinel Ti concentrations
are 20-30 times higher than these other phases. However, the presence of ubiquitous Ti-rich
spinel boundary clinopyroxenes (Paque et al. 2009) is a problem. Even though the locations of
profiles were chosen to avoid visible boundary clinopyroxenes, these are clearly present in the
profiles for TS34 A9 (spinel inclusion in mantle melilite; Figure 7 in the main paper) and B2
(spinel inclusion in core melilite, Figure 8 in the main paper).
A favorable case for studying Ti valence state profiles is TS34 grain B4. The B4 spinel is
an inclusion primarily in core alteration, but no interpretations are affected if we assume that (1)
the alteration was melilite at the time the Ti zoning profile was established and (2) there are no
Ti rich phases in the alteration. A two-dimensional electron probe Ti map of B4 and the adjacent
alteration shows no observable boundary clinopyroxenes or Ti-rich phases in the alteration,
supporting assumption (2). However, a fraction of a micron of boundary clinopyroxene can
account for the rim Ti+3 enhancements.
One test for the presence of boundary clinopyroxene is to model the observed Ti and Ca
counting rate profiles for B4 assuming only fluorescent X-rays from spinel and alteration
(adopting an average alteration composition to be that of Åk40 melilite). If an adequate
description of the Ca and Ti profiles is obtained, this is evidence for the absence of boundary
clinopyroxene contributions to the Ti counting rate.
Table D1. TS34 spinel B4 analytical data.
µm from edge Ti valence error
0
3.80
0.06
6
3.86
0.06
12
3.90
0.06
18
3.91
0.06
24
3.84
0.06
30
3.88
0.06
36
3.79
0.06
42
3.81
0.06
cps Ti
cps Ca
2942
3550
3592
3584
3514
3422
3198
2719
12121
5501
4283
3923
3891
4374
5491
10051
Corr cps Ca
8304
1684
466
106
74
557
1674
6234
9
48
54
60
3.59
3.43
3.43
0.06
0.07
0.08
1838
1301
909
28053
33798
38710
24236
29981
34893
The analytical data for the B4 profile are given in Table C1. Allowing for the 45 degree
incidence angle of the incident photon beam, the starting point of the XANES analytical profile
(0 microns) was selected such that the path of the incoming photon beam entered the spinel.
Consequently, at the end of the profile (here 60 microns) the incoming photon beam path will
exit the spinel into the surrounding alteration (see figure C1). Because of the large number of
spectra summed during the XANES analyses, the counting rate data are quite precise. The
relatively slow drop-off of cps Ti and the anticorrelated, relatively slow, rise of cps Ca at
positions greater than 30 microns (Table C1) are quite significant. Qualitatively, this trend is best
interpreted as the incoming photon beam passing through the edge of the spinel (producing most
of the cps Ti) and then into alteration producing most of the cps Ca. (Figure C1). The goal is to
quantitatively model these trends with reasonable assumptions about the subsurface shape of B4.
A
X
X=0
Melilite/
alteration
B
Spinel
Figure C1. XANES irradiation geometry for section plane perpendicular to symmetry axis of
octahedral spinel truncated by thin section thickness. This is the same as Figure 6 in the main
paper.
The flat cps Ti profile from 6 to 30 microns means that essentially all fluorescent Ti Xray production is from spinel of uniform thickness or from thicknesses significantly larger than
the incoming photon absorption mean free path (23 microns in spinel). The slightly lower cps Ti
for the 0 micron point indicates that a thinner layer of spinel is traversed relative to the more
central points. In practice this probably means that the 0 micron beam was, as planned, right on
the spinel boundary. The relatively soft Ca profile from 0 to 12 microns is a problem as
discussed below.
Our profile modeling requires measured Ti and Ca counting rates for pure phases. Our
adopted values are given in Table C2. As these have to be inferred from the B4 data, the adopted
values can vary slightly with model assumptions, as discussed below.
10
Table C2. Adopted pure phase counting rates for B4.
Model
Normal Octahedron
cps Ti spinel
3590
cps Ti alteration
183
cps Ca spinel
108
cps Ca alteration
46600
Tilted Octahedron
3590
183
108
47300
The infinitely thick spinel cps Ti is based on an average of the 12 and 18 micron
analyses. The cps Ti in alteration was based on the ratio of the measured average electron
microprobe concentrations of TiO2 in the alteration surrounding B4 (0.019 %, a typical value for
TS34 melilite) and the center of the B4 spinel (0.225%). Then:
CpsTi alteration = (cpsTi sp) [TiO2alt / TiO2sp] [(isp + sp )/(ialt + alt) ]
where (cpsTi) refers to XANES analytical conditions, i is the incoming photon (4970 eV)
absorption coefficient in the indicated phase and  is the absorption coefficient of the outgoing
Ti K X-ray. Absorption coefficients were calculated from values for line X-rays and elemental
absorbers given by Mayer and Rimini (1977) and interpolated to 4970 eV. Absorption
coefficients for alteration assumed a composition of Åk40 melilite.
The cps Ti for the 60 micron point is significantly higher than expected for pure
alteration, indicating that a small amount of spinel was penetrated by the primary photon beam
before entering alteration. The attenuation of the incoming photons in the thin spinel means that
the measured cps Ca for the 60 micron point will be less than that for pure alteration.
Connolly et al. (2003) measured a wide range in CaO for TS34 spinel but higher values
for smaller grains are seriously affected by continuum secondary fluorescence. For larger grains
like B4, a reasonable range is from 0.08 to 0.12% CaO. We adopt 0.10. The errors in this choice
are insignificant. By the same procedure used for Ti in alteration, a very low 108 cps Ca for
spinel is estimated.
Thus, the measured Ca counting rates in the center of B4 (Table C1) are far higher than
expected. Moreover, there is an apparent edge enrichment in the Ca counting rates. The final
column in Table C1, in which a constant counting rate background has been subtracted, clearly
illustrates the apparent edge enrichment.
Grain Shape Models. Any element profile can be fit if the B4 subsurface shape is
unconstrained. However, text Figure 5a shows that the shape of B4 in the plane of the section is
an almost perfect square of about 60 microns in size. This is not strangely fortuitous, as B4 was
selected from hundreds of other spinel grains because of its large size and euhedral shape. Thus,
a reasonable assumption is that the plane of the section is normal to the symmetry axis of the
presectioning B4 octahedral crystal.
For TS34, spinel inclusions in melilite are zoned with higher core Ti (Burnett et al. 2004).
The highest measured amounts of core to rim zoning are 30%. For B4 the core to rim excess is
only 10%, thus we infer that the plane of the section through B4 is above or below the central
symmetry plane of an originally octahedral crystal. For a 60 micron square cross section, the
bottom of the thin section is expected to truncate the sub-surface shape of B4 at the thickness of
the thin section (assumed to be 30 microns, although variations in this thickness are not
important). This leaves the three alternative subsurface shapes for B4 shown in Fig. C2.
11
Figure C2. Possible subsurface shapes for spinel B4.
Qualitatively, we estimated that shapes with a cross section decreasing with depth would
better describe the observed profiles, so modeling focused on case (b): a 60 micron equilateral
triangular cross section truncated either by a natural crystal face or by the thickness of the thin
section.
As already noted, if the thickness of B4 is determined by the thin section thickness of the
order of 30 microns, the Ca counting rates in the center of B4 should be much lower than
observed. One possibility is that B4 is a relatively thin spinel with sufficient Ca x-ray production
from alteration/melilite underlying the spinel.
The observed minimum Ca counting rate of 3891 cps measured for the 24 micron point
would indicate a spinel thickness of around 12 microns. Considering B4 alone, this geometry
cannot be totally ruled out; however, three other large (50-100 µm) spinel inclusions in low Ti
hosts, analyzed in the same run as B4, show similar high Ca counting rates in the centers of the
grains. It is highly unlikely that all four large grains would have thicknesses much less than the
thickness of the thin section, so we need an alternative explanation of the high Ca counting rates
in the centers of the large spinel grains.
Normal Octahedron Model (Figure C2b). The origin of the high Ca counting rates in the
centers of the large spinel grains is unknown, but we assume that it is some form of background,
possibly from a non-Gaussian tail in the focused synchrotron radiation beam. As a minimum
correction, we subtract a constant cps counting background, calculated to leave only the 108 cps
estimated for Ca in spinel at 24 microns, the position with the lowest measured cps Ca. Thus,
modeling here is based on the “corr cps Ca” data in Table C1. An accurate background
correction would describe the observed increase in the Ca counting rate towards the rim of the
spinel, thus a constant correction is almost certainly an undercorrection, and the calculated Ca
counting rates are expected to be below the measured values.
For each analysis position, the paths of the incoming photons and fluoresced x-rays were
determined. For each point along the incoming photon path, the phase causing x-ray production,
the attenuation of the incoming beam and the thickness of the absorbing phases were calculated.
The emergent x-ray fluxes were then calculated by integrating over the incoming photon path
relative to that for a pure phase of infinite size.
The initial (0 micron) and final (60 micron) points require special consideration. As noted
above, the Ti counting rate for the 60 micron analysis is too high for the beam to have sampled
only alteration. Thus, a small edge of spinel was clipped with most of the path in alteration. If the
analyzed spot is assumed to be 2.8 microns on the spinel side of the spinel-alteration boundary,
the observed cps Ti is accounted for. Correcting for the amount of attenuation of the incoming
photon beam in the spinel edge, the pure phase alteration Ca counting rate is calculated to be
46600 cps compared to the measured 39000 cps. The measured and model counting rates are
effectively normalized at 60 microns.
The relatively high Ca counting rate for 0 microns cannot be explained if the beam first
enters spinel, but, as shown in Table C3, if the beam is assumed to pass through Xm = 1.0 to 1.1
12
micron of alteration before entering spinel, the small increase in cps Ca can be accounted for.
The calculated cps Ca is very sensitive to Xm, as shown. However, for this alteration thickness, a
much larger decrease in cps Ti relative to the grain interior analyses would be expected.
Alternatively, as shown in Table C3, if an alteration thickness of only 0.1 micron is assumed, the
relatively small amount of attenuation of cps Ti relative to the grain center points measured cps
Ti is reproduced, but 0.1 microns does not produce nearly enough cps Ca compared to what is
measured. The discrepancy also indicates a source of Ca background not adequately
compensated for the by the constant background correction discussed above. Giving more weight
to Ti, we adopt Xm=0.1 micron, effectively normalizing the cps Ti profile at 0 microns. This
normalization affects no other points except 0 microns. In any case, the 0 micron beam location
is essentially right on the spinel-alteration boundary.
Table C3. Modeling the 0 micron analysis*.
Xm, micron alteration
Calc. cps Ti
0.10
2927
1.0
2383
1.1
2327
Measured
* Normal octahedron model.
2942
Calc cps Ca
1373
8072
8671
8338
Given the required special treatments of the 0 and 60 micron points, the model and data are
effectively normalized at the 60 micron point for Ca and 0 and 60 microns for Ti. In addition, the
center of the profile was adopted as the pure spinel Ti counting rate. Beyond these adjustments,
the model can predict the remaining Ti and Ca counting rates.
Calculations show that contributions to cps Ca from the glass slide (assumed to be soda-lime
glass with 10.2% CaO) beneath the thin section are negligible given the high amounts of
attenuation of the incoming photon and outgoing fluoresced x-ray beams as long as the section
thickness is the nominal 30 microns or greater. If the section thickness were less than about 20
microns, glass contributions would be significant.
13
4000
model
3500
meas
3000
cps Ti
2500
2000
1500
1000
500
0
0
10
20
30
40
50
60
70
microns
Figure C3. Predicted and measured B4 Ti profile for normal octahedral model. Data effectively
normalized at 0, (12, 16), and 60 microns.
The predicted and measured Ti and Ca counting rate profiles for B4 for the normal
octahedral model are shown in Figures C3 and C4a and C4b.
The drop-off in the calculated Ti counting rate beyond 42 microns (Figure C3)
corresponds to the path of the incoming photons passing through the side of the spinel rather than
the bottom (e.g., Figure C1), accompanied by decreasing path lengths in spinel. The measured
profile drops off more rapidly, as if the path lengths in spinel were longer than in the model. In
the central region (Fig. C3), the model and measured Ti counting rates are flat as expected. The
drop at 0 microns is due to the attenuation of the primary photon beam in a small amount of
alteration before entering spinel as discussed above.
Although agreement is not perfect, the model reproduces the essential features of the
measured profile. If the measured Ti counting rate had been much higher than the model,
contributions from boundary clinopyroxene might have been indicated, but this is not the case.
Complementary to the behavior of the Ti profile, the Ca counting rate rises beyond 30
microns (Figure C4a) as the primary photon path passes through the edge of the spinel into
progressively increasing thicknesses of the surrounding alteration (Figure C1).
14
40000
model
meas
35000
30000
cps Ca
25000
20000
15000
10000
5000
0
0
10
20
30
40
50
60
70
microns
Figure C4a. Predicted and measured B4 Ca profile for normal octahedron model.
100000
model
meas
cps Ca
10000
1000
100
10
0
10
20
30
40
50
60
70
microns
Figure C4b. Log scale of Figure C4a to show central region comparisons.
As more clearly illustrated in a log plot (Figure C4b), the model tends to underestimate
the measured Ca counting rate except for the 24 and 30 micron points. Most of this discrepancy
can be understood by the inadequacies of the Ca background correction as discussed above, and
until this background is better understood, it is sufficient to have the model counting rates below
the measured values.
Tilted Octahedron Model. Inspection of the results of the truncated octahedron model
suggested that a counter-clockwise tilted octahedron relative to Figure C1 would provide a better
match to the measured profiles by providing a thinner edge at the beginning (0 and 6 microns)
and a less steeply-dipping subsurface boundary at the end of the profile. Cross-sectional images
of tilted octahedrons produced by the SHAPE software (Dowty, per. comm.) show that tilts as
15
large as 40 degrees would still produce an approximately square cross section for the grain in the
plane of the section. A counter-clockwise tilt of 22.5 degrees was modeled.
The calculation proceeds exactly as for the normal octahedron model, although the
derived x-ray production and attenuation equations differ. The bottom of the tilted octahedron
was assumed to be set by the thin section thickness (30 microns). The adjustment parameters for
the 0 and 60 degree points were slightly different from the normal octahedron model as shown in
Table C4. Other pure phase counting rates are the same as the truncated octahedron case in Table
C2.
Table C4. Model adjustment parameters.
Model
Distance of 0 micron analysis from spinelalteration boundary, microns
Distance to boundary from 60 micron analysis,
microns
Ca counting rate of alteration, cps.
Normal
octahedron
22.5 degree tilted
octahedron
0.1
3.1
2.8
46,600
6.4
47,300
Figures C5, C6a and C6b show the results of the 22.5 degree tilted octahedral model
analogous to Figures C3, C4a and C4b for the normal octahedron model.
4000
3500
3000
cps Ti
2500
2000
1500
"22.5 tilt"
1000
500
0
0
10
20
30microns40
50
60
70
Figure C5. Grain B4 Ti profile for 22.5 deg counter-clockwise tilted octahedron model.
16
45000
40000
"22.5 tilt"
35000
cps Ca
30000
25000
20000
15000
10000
5000
0
0
10
20
30microns40
50
60
70
Figure C6a. Grain B4 Ca profile for 22.5 deg counter-clockwise tilted octahedron model. Linear
scale.
100000
"22.5 tilt"
cps Ca
10000
1000
100
10
0
10
20
30microns40
50
60
70
Figure C6b. Log scale plot of grain B4 Ca profile for 22.5 deg counter-clockwise tilted
octahedron model.
Comparison of Figures C5, C6a and C6b with C3, C4a and C4b shows a somewhat better
match between the model and measured profiles. In particular, the model prediction for Ca is
now always less than the measured counting rate, which is the expected result since the Ca
background correction is almost certainly too small, as discussed above.
17
Summary and Conclusions
Table C1 and text Figure 5c shows that there are decreases in the Ti valence from about
3.9 observed in the 6-24 micron analyses to lower values as the edges of the spinel grain are
approached. Lower valence spots include alteration from beyond the edge of B4 the Ti counting
rates are lower and the Ca counting rates higher for these points, i.e., part of the primary photon
beam path is in alteration. In the model, Ti counts come from both spinel and alteration, but there
are specific predictions of the fractions of the observed Ti from spinel and from alteration, as
shown in Table C4.
Table C5. Calculated percentages of Ti counts from spinel.
Analysis point, micron
Normal Octahedron
0
99.8
36
99.6
42
99.2
48
98.2
54
95.7
60
86.0
22.5 Degree Tilted Octahedron
98.5
99.7
99.4
98.7
96.4
86.1
With the possible exception of the 60 micron analysis, the measured Ti X-rays are almost
entirely from spinel, and the measured valence can be ascribed to spinel. We do not know the
effective valence of Ti in the alteration, and if it were entirely Ti+3, then the valence measured in
the 60 micron analysis could be slightly too low for spinel. However, because the primary
photon beam for the 60 micron analysis passed only through the edge of B4, it would be
expected to show the lowest valence, as observed, if B4 had an edge enrichment in Ti +3. The
modeling involves many assumptions, but, although clearly not perfect, the results provide a
good argument that B4 has an edge enrichment in Ti+3. The modeling could be improved if the
source of the Ca background were better understood. We can never rule out completely that the
model cps Ti profile is erroneously high and that there are unrecognized boundary clinopyroxene
contributions to the measured edge data for cps Ti, but our best estimate is that such
contributions are absent for B4.
B4 is the best case for a Ti+3 edge enrichment, but it is likely that the apparent edge Ti+3
enrichments in other large TS34 spinels are also real, as opposed to being due to interferences
from spinel boundary clinopyroxene.
18
Appendix D
Aluminum, Magnesium, and Oxygen Isotopic Results
Figure D1. Oxygen isotope data for Allende TS34 spinels.
19
20
21
22
Figure D2. Magnesium isotopic data for Allende TS34 spinels.
23
References
Beckett J.R., Spivack A.J., Hutcheon I.D., Wasserburg G.J., and Stolper E. 1990. Crystal
chemical effects on the partitioning of trace elements between mineral and melt: An
experimental study of melilite with applications to refractory inclusions from carbonaceous
chondrites. Geochimica et Cosmochimica Acta 54:1755-1774.
Burnett D. S., Paque J. M., and Beckett J. R. 2004. Zoning patterns in spinel from type B Ca-Alrich inclusions: Constraints on sub-solidus thermal history (abstract #1253). 35th Lunar and
Planetary Science Conference. CD-ROM.
Connolly H.C. Jr. and Burnett D.S. 2003. On type B CAI formation: experimental constraints on
oxygen fugacity variations in spinel minor element partitioning and re-equilibration effects.
Geochimica et Cosmochimica Acta 67:4429-4434.
Mayer J. M. and Rimini E. 1977. Ion Beam Handbook for Material Analysis. New York:
Academic Press.
Paque J. M., Beckett J. R., Ishii H. A., Aléon-Toppani A., Burnett D. S., Teslich N., Dai Z. R.,
and Bradley J. P. 2009. The formation of boundary clinopyroxenes and associated glass
veins in type B1 CAIs. Meteoritics & Planetary Science 44:665-687.
Stolper E. 1982. Crystallization sequences of Ca-Al-rich inclusions from Allende - An
experimental study. Geochimica et Cosmochimica Acta 46:2159-2180.
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