Manuscript - unpublished
CONCENTRATIONS OF 17 ELEMENTS IN 36
CHONDRULES FROM ALLENDE
C. MENNINGA1
1
Geology, Geography, and Environmental Science, Calvin College, 1740 Knollcrest Circle,
Grand Rapids, MI 49546-4403, USA
Abstract
Thirty-six chondrules and four matrix samples from fragments of the meteorite Allende
were analyzed by non-destructive instrumental neutron activation for Al, Au, Ca, Co, Cr, Eu, Fe,
Ir, Mg, Mn, Na, Ni, Sc, Si, Ti, V, and Zn. Statistical evaluation of data provides information on
correlation relationships among those elements.
Introduction
Meteorites have long been of interest as sources of information about the early history of
the solar system since they are the only samples available to us that present evidence from which
the processes of that early formation may be inferred with some confidence [1, 2]. While many
meteorites exhibit evidence of metamorphic processes in their histories, the C3 chondrites appear
to be among the least affected by such metamorphism [3]. Consequently, the C3 chondrite
Allende, with the large amount of material recovered from that fall, has received a lot of
attention.
Many compositional analyses of whole meteorites have been published [4-10]. Some
studies have also been done on chemical and mineralogical characteristics of individual
chondrules [11-13]. Since many puzzles regarding the early history of the solar system remain
unsolved, additional observational data are always welcomed. This paper reports the
concentrations of 17 elements in 36 chondrules from the meteorite Allende by non-destructive
instrumental neutron activation.
Macrozoom photos of a few of the chondrules at various magnifications are shown in
Fig. 1. Photos of chondrules #2-#35 can be found at
www.calvin.edu/academic/geology/menninga/allendechondrules.
Fig. 1 Three chondrules in reflected light (Graduations on the scale are 0.01 in.)
Note: The irradiations and measurements for the elemental analyses reported in this paper
were done during the span of years 1969-1975, and the results lay on the shelf until now,
with publication delayed largely for personal reasons.
Experimental
A. Sample preparation
The chondrules in this study were obtained from fragments of the Allende
meteorite that were supplied by the Smithsonian Institution. Most of the chondrules were
taken from a single fragment that had been picked up in Field No. 22, and had been
purchased by the Smithsonian in Santa Ana; the others were obtained from uncataloged
fragments.
Chondrules were picked from a freshly broken surface of the meteorite with the
tip of a scalpel in a laminar-flow clean hood, and handled with Teflon-coated tweezers.
Samples were weighed on a Mettler Microgram balance and numbered in order of
increasing weight. Matrix samples were scraped from the region surrounding each of four
of the chondrules, weighed, and sealed in polyethylene containers for analysis. Great care
was exercised to avoid contamination with any of the materials in the environment in
which the analyses were performed. (Chondrules #1-35 remain in the possession of the
author.)
B. Irradiations and counting procedures
Samples were irradiated in the Hanford K-East plutonium production reactor in
1969 for two short irradiations (1-6 minutes) to measure the concentrations of Al, Mg,
Mn, Na, Ti, and V. Counting was done promptly with a Ge(Li) detector system with 3%
relative efficiency. After some elapsed time, samples were also counted in a lowbackground anticoincidence-shielded multi-parameter gamma-ray spectrometer at
Battelle Pacific Northwest Laboratories [14, 15] to verify the measurement of Mn and
Na.
Samples were exposed in a longer irradiation in the Hanford K-East plutonium
production reactor in 1970 to a time-integrated flux (fluence) of about 1018 neutrons/cm2
for the measurement of Au, Ca, Co, Cr, Eu, Fe, Ir, Na, Sc, and Zn. After some elapsed
time for the decay of short-lived isotopes, samples were counted with a Ge(Li) detector
system with 3% relative efficiency, and with a low-background anticoincidence-shielded
gamma-ray spectrometer. [16] Samples were counted again in 1971 (one year after
irradiation) with the low-background anticoincidence spectrometer for measuring Eu and
Zn.
Silicon and nickel content were measured in 1974 by irradiation with 14-MeV
neutrons from a Kaman Nuclear Model A-711 fast neutron generator with an output of 4
x 1010 neutrons/sec. Samples were counted with a Ge(Li) detector with 26% efficiency.
Additional irradiations of several samples were carried out at the Washington
State University Nuclear Radiation Center in 1974 to double-check earlier results. Nickel
content was measured by fast neutron activation in a Cd-shielded facility in the 1-MW
Triga reactor at WSU-NRC. Samples were counted with an anticoincidence-shielded
gamma ray spectrometer incorporating a 14% Ge(Li) detector surrounded by NaI(Tl). A
24-hour irradiation with thermal neutrons was also carried out to double-check results for
some isotopes, with counting done by instruments at Battelle Pacific Northwest
laboratories. No significant differences from earlier results were found.
The output from all counting systems was processed by 2048-channel analyzer
calibrated so that the channel number equals the gamma ray energy in keV, and printed
on paper strip. Sums of events under each gamma-ray peak of interest were taken
manually with the help of a multi-function electronic calculator. All calculations were
also performed manually with the help of a multi-function electronic calculator.
Nuclear data for all nuclides used in this study are presented in Table 1.
Table 1. Nuclear Data for isotopes used in this study
_____________________________________________
Element Target
Abundance(%) Reaction Activated
Half-life
Gamma(s) (keV)
____________________________________________________________________________
Al
Al-27
100
n,γ
Al-28
2.2414 m
1778.969
Au
Au-197
100
n,γ
Au-198
2.69517 d
411.80205
1
Ca
Ca-46
0.0035
n,γ
Ca-47
4.536 d
Sc-47
3.3492 d
159.377
Co
Co-59
100
n,γ
Co-60
5.2714 y
1173.237
Cr
Cr-50
4.35
n,γ
Cr-51
27.7025 d
320.0824
2
Eu
Eu-151
47.8
n,γ
Eu-152
13.537y
121.7817
Eu-153
52.1
n,γ
Eu-154
8.593 y
123.071
Fe
Fe-58
0.3
n,γ
Fe-59
44.503 d
1099.251
Ir
Ir-191
37.3
n,γ
Ir-192
73.831 d
468.07152
Mg
Mg-26
11.01
n,γ
Mg-27
9.458 m
1014.42
Mn
Mn-55
100
n,γ
Mn-56
2.5785 h
1810.772
Na
Na-23
100
n,γ
Na-24
14.9590 h
1368.633
Ni
Ni-62
3.6
*n,α
Fe-59
44.503 d
1099.251
Sc
Sc-45
100
n,γ
Sc-46
83.79 d
889.277
Si
Si-28
92.23
*n,p
Al-28
2.2414 m
1778.969
Ti
Ti-50
5.2
n,γ
Ti-51
5.76 m
320.0824
V
V-51
99.76
n,γ
V-52
3.743 m
1434.068
3
Zn
Zn-64
48.6
n,γ
Zn-65
244.26 d
1115.546
______________________________________________________________________________
* 14-MeV neutrons; all others thermal neutrons
1
Ca concentrations determined through Sc-47, the radioactive daughter of Ca-47
2
Counts in composite peak consist of 95% Eu-152 and 5% Eu-154, effective t½ = 12.9y
3
Zn corrected for partial overlap with Sc-46 @ 1120.505 keV by excluding the count in the
channel in the valley between peaks from the Zn count, and using the valley count as the
background for the adjacent channel on the shoulder of the Zn peak
Blanks consisting of the packaging materials for all samples and standards were
run along with the samples and standards in all of the irradiations and counting
procedures in order to insure that the packaging materials did not contain any impurities
that would affect the results attributed to the chondrules.
Copper discs or high-purity iron wires were used to measure relative timeintegrated neutron flux with all sample irradiations. Corrections for decay during
irradiation and counting were made by the method of Hoffman [17].
C. Standards and data handling
The composition of samples was determined by comparison with known
standards. Standards in the form of the high-purity element were used for measuring
concentrations of Al, Fe, Mg, Ni, Si, and Ti. Standard solutions were prepared from
reagent grade compounds in ionized water for measuring concentrations of Ca, Co, Cr,
Eu, Ir, Na, Sc, and Zn. Aliquots of standard solutions were absorbed in filter paper and
dried in a desiccator at room temperature; the impregnated papers were then folded
compactly and sealed in envelopes of polyethylene foil and heat sealed at all edges.
U.S.G.S. rock sample W-1 was used as a standard for V [18], and the Au concentration
was determined by the published production cross-section and decay characteristics
relative to those of Co, Fe, and Sc.
The possibility of interference from reactions other than neutron capture
producing the nuclide of interest was investigated by irradiation of samples of Al and Mg
and determination of the amount of Na-24 produced by fast neutron reactions Al-27 (n,α)
Na-24 and Mg-24 (n,p) Na-24. The results were applied to the analysis of chondrule #2
(high Al), and found that the interference from fast neutrons amounted to 7 counts of Na24 in 100,000 total counts of Na-24 following a 2-minute irradiation, and to chondrule
#23 (low Na), and found that the interference amounted to 25 counts of Na-24 in 10,000
total counts of Na-24 following a long irradiation of 24 hours. These results confirm the
assurance that this author received from workers at Battelle National Laboratory that fast
neutron reactions need not be considered from irradiations in the Hanford K-East reactor
facility in this study.
Samples of U.S.G.S. rock standards G-1, W-1, BCR-1, and DTS-1 and a sample
of whole rock Allende reference material were irradiated and counted along with the
chondrules. The results show a few cases where the spread of values for multiple samples
of the same reference material was greater than would be expected, but the overall pattern
was acceptably close to the published composition of those standard materials. Those
results are available in tabular format at
www.calvin.edu/academic/geology/menninga/allendechondrules.
Results and discussion
A. Results
The measured concentrations of 17 elements in 36 chondrules and 4 matrix samples are
presented in Table 2. Uncertainties listed are due to counting statistics only.
Table 2. Elemental composition of Allende chondrules
_____________________________________________________________________________
chon.
mass
(mg)
Si (%)
Mg (%)
Fe (%)
Al (%)
Ca (%)
Na (%)
____________________________________________________________________________________________________________
1
0.075
15.8
± 2.4
23.9
± 1.9
9.7
± 0.3
3.66
± 0.18
1.5
± 0.4
0.091
± 0.005
2
0.250
12.6
± 1.4
12.3
± 1.0
5.5
± 0.2
21.7
± 1.1
7.27
± 0.15
1.55
± 0.08
3
0.300
16.1
± 1.3
22.3
± 1.8
17.0
± 0.5
1.78
± 0.09
1.70
± 0.20
0.320
± 0.016
4
0.385
16.9
± 1.6
22.0
± 1.8
14.0
± 0.4
1.49
± 0.07
1.58
± 0.16
0.426
± 0.021
5
0.405
18.1
± 1.4
17.8
± 1.4
14.4
± 0.4
3.66
± 0.18
2.03
± 0.13
0.82
± 0.04
6
0.430
14.8
± 1.2
23.3
± 1.9
13.0
± 0.4
0.76
± 0.04
1.72
± 0.28
0.179
± 0.009
7
0.430
16.7
± 1.1
21.2
± 1.7
5.6
± 0.2
2.63
± 0.13
2.70
± 0.35
0.78
± 0.04
8
0.445
19.3
± 1.4
20.6
± 1.6
9.3
± 0.3
2.00
± 0.10
2.45
± 0.09
0.250
± 0.013
9
0.575
17.2
± 1.0
24.7
± 2.0
10.5
± 0.3
1.11
± 0.06
1.48
± 0.37
0.302
± 0.015
10
0.660
16.3
± 1.3
21.1
± 1.7
11.7
± 0.4
2.92
± 0.15
2.06
± 0.33
1.14
± 0.06
11
0.710
18.6
± 2.3
23.3
± 1.9
4.6
± 0.1
3.30
± 0.17
2.68
± 0.21
0.86
± 0.04
12
0.715
21.0
± 3.2
20.3
± 2.6
10.6
± 0.3
1.83
± 0.09
1.31
± 0.38
0.434
± 0.022
13
0.765
21.8
± 2.8
26.7
± 2.6
17.9
± 0.5
2.12
± 0.11
2.31
± 0.37
0.465
± 0.023
14
0.790
16.1
± 1.7
13.2
± 1.1
19.7
± 0.6
2.84
± 0.14
3.16
± 0.35
0.83
± 0.04
15
0.960
15.6
± 1.8
21.5
± 1.7
14.1
±0.4
1.76
± 0.09
2.15
± 0.26
0.338
± 0.017
16
1.410
24.9
± 2.2
21.6
± 1.7
9.2
± 0.3
2.01
± 0.10
1.77
± 0.21
0.69
± 0.03
17
1.470
21.2
± 2.8
29.6
± 2.4
6.2
± 0.2
3.41
± 0.17
3.76
± 0.20
0.63
± 0.03
18
2.040
18.8
± 1.6
23.9
± 1.9
5.3
± 0.2
3.02
± 0.15
3.35
± 0.16
0.51
± 0.03
19
2.190
17.1
± 1.2
12.7
± 1.0
9.7
± 0.3
8.71
± 0.44
3.25
± 0.24
2.21
± 0.11
20
2.365
18.0
± 2.1
20.7
± 1.7
15.8
± 0.5
1.38
± 0.07
1.45
± 0.20
0.384
± 0.019
21
2.380
16.1
± 2.0
27.2
± 2.2
3.8
± 0.1
0.95
± 0.05
1.00
± 0.15
0.344
± 0.017
22
2.400
22.3
± 3.1
21.1
± 1.7
12.1
± 0.4
2.35
± 0.12
2.45
± 0.20
0.60
± 0.03
23
2.645
15.2
± 2.6
21.9
± 1.8
11.9
± 0.4
0.74
± 0.04
1.10
± 0.20
0.190
± 0.010
24
3.635
20.8
± 2.7
18.1
± 1.4
10.8
± 0.3
1.67
± 0.08
1.70
± 0.20
0.68
± 0.03
25
4.535
17.2
± 1.3
18.8
± 1.5
7.5
± 0.2
3.14
± 0.16
3.10
± 0.20
0.96
± 0.05
26
4.635
13.9
± 1.1
19.0
± 1.5
14.5
± 0.4
1.45
± 0.07
1.70
± 0.17
0.385
± 0.019
27
5.150
19.3
± 2.0
23.3
± 1.9
8.4
± 0.3
1.99
± 0.10
1.25
± 0.12
0.820
± 0.04
28
5.225
16.8
± 1.4
22.4
± 1.8
9.4
±0.3
2.18
± 0.11
2.40
± 0.15
0.292
± 0.015
29
7.045
21.4
± 1.7
18.7
± 1.5
7.7
± 0.2
3.57
± 0.18
2.60
±0.13
1.70
± 0.09
30
8.780
19.5
± 1.4
22.2
± 1.8
8.0
± 0.2
1.76
± 0.09
1.33
±0.13
0.79
± 0.04
31
9.035
17.6
± 1.2
21.8
± 1.7
6.0
± 0.2
3.16
± 0.16
3.20
± 0.18
0.376
± 0.019
32
10.220
20.5
± 2.7
19.9
± 2.0
7.4
± 0.2
3.86
± 0.19
2.96
± 0.15
1.80
± 0.09
33
11.660
21.9
± 1.0
18.1
± 1.4
9.0
± 0.3
2.68
± 0.13
2.78
± 0.14
0.88
±0.04
34
18.980
21.9
± 1.6
23.9
± 1.9
6.8
± 0.2
2.42
± 0.12
2.07
± 0.10
1.02
± 0.05
35
20.900
19.6
± 1.2
20.8
± 1.7
6.1
± 0.2
2.29
± 0.11
2.28
± 0.11
0.77
± 0.04
36
82.140
14.5
± 1.2
5.6
± 0.2
1.61
± 0.08
3.00
± 0.9
0.78
± 0.04
Matrix
10X
12.11
18.4
± 2.4
13.8
±1.1
23.3
± 0.7
1.36
± 0.07
2.45
± 0.25
0.306
± 0.015
17X
1.63
17.9
± 2.9
15.5
± 1.5
26.2
± 0.8
1.77
± 0.09
1.50
± 0.25
0.199
± 0.010
27X
5.78
17.2
± 2.5
14.4
± 1.2
25.6
± 0.8
1.50
± 0.07
1.70
± 0.15
0.262
± 0.013
34X
16.00
18.0
± 2.4
16.5
± 1.3
22.7
± 0.7
2.10
± 0.11
2.60
± 0.20
0.407
± 0.020
Table 2. (continued)
____________________
mass
chon. (mg)
Ni (%)
Ti (%)
Cr (%)
Mn (%)
Sc
(mg/kg)
V
(mg/kg)
_______________________________________________________________________________________
1
0.075
0.36
± 0.04
TLD
0.274
± 0.014
0.071
± 0.004
7.9
± 0.4
212
± 17
2
0.250
0.020
± 0.006
0.47
3
0.300
1.44
± 0.10
0.11
± 0.09
0.081
± 0.004
0.053
± 0.004
32.6
± 1.6
977
± 78
± 0.02
0.481
± 0.024
0.127
± 0.006
11.6
± 0.6
128
± 10
4
0.385
0.41
± 0.04
5
0.405
0.84
± 0.06
0.13
± 0.03
0.369
± 0.018
0.126
± 0.006
12.0
± 0.6
91
±7
0.17
± 0.03
0.404
± 0.020
0.071
± 0.004
12.1
± 0.6
102
±8
6
0.430
1.15
± 0.07
0.07
± 0.02
0.493
± 0.025
0.069
±0.003
11.0
± 0.6
95
±8
7
0.430
8
0.445
0.28
± 0.03
0.23
± 0.04
0.284
± 0.014
0.069
± 0.003
17.8
± 0.9
54
±8
0.72
± 0.06
0.11
± 0.03
0.368
± 0.018
0.091
± 0.005
12.2
± 0.6
82
±7
9
0.575
0.64
± 0.05
0.08
± 0.02
0.394
± 0.020
0.071
± 0.004
7.8
± 0.4
119
± 10
10
0.660
0.28
± 0.03
0.17
± 0.03
0.336
± 0.017
0.091
± 0.005
17.0
± 0.9
86
±7
11
0.710
0.85
± 0.09
0.21
± 0.03
0.233
± 0.012
0.083
± 0.004
24.3
± 1.2
100
±8
12
0.715
0.64
± 0.05
TLD
0.563
± 0.028
0.148
± 0.009
13.0
± 0.7
106
± 15
13
0.765
1.25
± 0.08
0.29
± 0.11
0.466
± 0.023
0.108
± 0.007
16.8
± 0.8
113
± 15
14
0.790
1.16
± 0.05
0.18
± 0.03
0.383
± 0.019
0.139
± 0.007
21.6
± 1.1
107
±9
15
0.960
1.78
± 0.14
0.15
± 0.06
0.383
± 0.019
0.063
± 0.005
14.9
± 0.7
156
± 12
16
1.410
0.36
± 0.03
0.13
± 0.02
0.298
± 0.015
0.074
± 0.004
14.5
± 0.7
84
±7
17
1.470
0.49
± 0.04
TLD
0.239
± 0.012
0.048
± 0.004
23.8
± 1.2
87
± 12
18
2.040
0.051
± 0.006
0.20
± 0.03
0.351
± 0.018
0.046
± 0.002
21.3
± 1.1
132
± 11
19
2.190
0.62
± 0.04
0.50
± 0.03
0.412
± 0.021
0.073
± 0.004
64.2
± 3.2
97
±8
20
2.365
1.20
± 0.05
0.09
± 0.02
0.375
± 0.019
0.115
± 0.006
12.1
± 0.6
87
±7
21
2.380
0.146
± 0.008
0.09
± 0.02
0.161
± 0.008
0.031
± 0.002
17.8
± 0.9
189
± 15
22
2.400
1.06
± 0.05
0.13
± 0.02
0.384
± 0.019
0.091
± 0.005
16.1
± 0.8
95
±8
23
2.645
0.82
± 0.04
0.08
± 0.02
0.409
± 0.020
0.058
± 0.003
8.0
± 0.4
81
±6
24
3.635
0.91
± 0.04
0.24
± 0.05
0.562
± 0.028
0.295
± 0.015
13.5
± 0.7
89
±7
25
4.535
0.59
± 0.03
0.23
± 0.03
0.315
± 0.016
0.086
± 0.004
16.8
± 0.8
130
± 10
26
4.635
1.52
± 0.06
0.10
± 0.02
0.411
± 0.021
0.059
± 0.003
11.9
± 0.6
103
±8
27
5.150
0.85
± 0.03
0.16
± 0.04
0.307
± 0.015
0.053
± 0.003
16.5
± 0.8
118
±9
28
5.225
0.93
± 0.04
0.12
± 0.03
0.263
± 0.013
0.046
± 0.002
15.0
± 0.8
122
± 10
29
7.045
0.44
± 0.02
0.15
± 0.05
0.339
± 0.017
0.113
± 0.006
24.5
± 1.2
131
± 10
30
8.780
0.26
±0.01
0.13
± 0.03
0.460
± 0.023
0.074
± 0.004
14.3
± 0.7
103
±8
31
9.035
0.144
± 0.009
0.15
± 0.03
0.439
± 0.022
0.052
± 0.003
24.2
± 1.2
112
±9
32
10.220
0.55
± 0.03
TLD
0.395
± 0.020
0.074
± 0.004
20.4
± 1.0
184
± 15
33
11.660
0.60
± 0.01
0.17
0.435
± 0.022
0.113
± 0.006
20.3
± 1.0
115
±9
34
18.980
0.66
± 0.02
TLD
0.336
± 0.017
0.087
± 0.004
9.8
± 0.5
138
± 11
35
20.900
0.28
± 0.01
0.15
± 0.04
0.449
± 0.022
0.092
± 0.005
18.6
± 0.9
112
±9
36
82.140
0.10
± 0.04
0.514
± 0.026
0.389
± 0.019
11.7
± 0.6
73
±6
± 0.03
0.332
± 0.017
0.145
± 0.007
8.1
± 0.4
64
±5
0.341
± 0.017
0.140
± 0.007
8.0
± 0.4
85
±9
0.415
± 0.021
0.121
± 0.006
12.6
± 0.6
72
±6
0.365
± 0.018
0.121
± 0.006
9.9
± 0.5
59
±8
± 0.03
Matrix
10X
12.11
1.28
± 0.08
0.12
17X
1.63
1.42
± 0.04
TLD
27X
5.78
2.12
± 0.08
TLD
34X
16.00
1.59
± 0.06
0.27
± 0.06
TLD = too low to be determined accurately
Table 2. (continued)
chon.
mass
(mg)
Co (mg/kg)
Zn
(mg/kg)
Eu (mg/kg)
Ir (mg/kg)
Au (mg/kg)
___________________________________________________________________________________
1
0.075
202
±6
37
±7
0.058
± 0.007
0.441
± 0.015
0.287
± 0.007
2
3
0.250
42
±1
533
± 43
0.533
± 0.003
0.080
± 0.008
0.009
± 0.002
0.300
724
± 22
62
±6
0.086
± 0.011
0.602
± 0.001
0.051
± 0.004
4
0.385
294
±9
42
±5
0.094
± 0.006
0.191
± 0.006
0.045
± 0.004
5
0.405
454
± 14
70
±6
0.124
± 0.007
0.525
± 0.008
0.071
± 0.006
6
0.430
706
± 21
54
±4
0.049
± 0.009
0.825
± 0.017
0.530
± 0.027
7
0.430
118
±4
19
±2
0.176
± 0.004
0.058
± 0.005
0.044
± 0.010
8
0.445
342
± 10
38
±3
0.135
± 0.007
0.358
± 0.014
0.172
± 0.002
9
0.575
314
±9
38
±3
0.072
± 0.005
0.442
± 0.006
0.170
± 0.009
10
0.660
198
±6
33
±3
0.151
± 0.004
0.63
± 0.05
0.048
± 0.008
11
0.710
55
±2
22
±2
0.181
± 0.003
0.032
± 0.010
0.116
± 0.006
12
0.715
339
± 10
54
±4
0.140
± 0.005
0.470
± 0.012
0.195
± 0.010
13
0.765
685
± 21
87
±7
0.171
± 0.011
0.56
± 0.05
0.070
± 0.010
14
0.790
522
± 16
104
±8
0.187
± 0.006
1.26
± 0.02
0.118
± 0.010
15
0.960
791
± 24
80
±6
0.129
± 0.010
0.87
± 0.05
0.100
± 0.005
16
1.410
167
±5
43
±5
0.119
± 0.005
0.096
± 0.010
0.044
± 0.003
17
1.470
203
±6
20
±2
0.210
± 0.006
1.26
± 0.02
0.087
± 0.007
18
2.040
39
±1
39
±3
0.256
± 0.002
0.038
± 0.008
0.007
± 0.002
19
2.190
282
±8
117
±9
0.294
± 0.006
3.63
± 0.02
0.097
± 0.004
20
2.365
507
± 15
66
±6
0.093
± 0.007
0.496
± 0.010
0.076
± 0.003
21
2.380
77
±2
24
±3
0.053
± 0.002
0.033
± 0.008
0.038
± 0.003
22
2.400
464
± 14
69
±6
0.163
± 0.006
0.228
± 0.010
0.047
± 0.003
23
2.645
467
± 14
39
±5
0.055
± 0.005
0.456
± 0.010
0.139
± 0.005
24
3.635
408
± 12
39
±4
0.127
± 0.004
0.447
± 0.008
0.076
± 0.003
25
4.535
244
±7
43
±4
0.200
± 0.004
0.387
± 0.007
0.039
± 0.004
26
4.635
657
±20
67
±5
0.126
± 0.005
0.596
± 0.008
0.104
± 0.004
27
5.150
355
± 11
43
±4
0.139
± 0.004
0.708
± 0.007
0.243
± 0.005
28
5.225
432
± 13
36
±4
0.137
± 0.004
0.735
± 0.007
0.096
± 0.003
29
7.045
231
±7
50
±4
0.245
± 0.003
0.305
± 0.006
0.042
± 0.003
30
8.780
116
±3
34
±3
0.130
± 0.002
0.410
± 0.007
0.091
± 0.004
31
9.035
74
±2
28
±2
0.226
± 0.002
0.119
± 0.005
0.007
± 0.003
32
10.220
305
±9
35
±4
0.190
± 0.004
0.234
± 0.007
0.094
± 0.004
33
11.660
278
±8
41
±3
0.177
± 0.003
0.503
± 0.005
0.035
± 0.004
34
18.980
279
±8
48
±4
0.147
± 0.002
0.369
± 0.004
0.062
± 0.003
35
20.900
135
±4
34
±3
0.160
± 0.003
0.810
± 0.006
0.123
± 0.003
36
82.140
58
±2
22
±2
0.102
± 0.005
0.020
± 0.005
0.010
± 0.002
10X
12.11
629
± 19
75
±6
0.114
± 0.007
0.384
± 0.005
0.205
± 0.005
17X
1.63
583
± 17
125
± 10
0.070
± 0.004
0.624
± 0.014
27X
5.78
838
± 25
98
±8
0.074
± 0.006
0.758
± 0.008
34X
16.00
676
± 20
115
±9
0.127
± 0.004
0.602
± 0.007
Matrix
Note: The high Al and Ca in sample 2 and the high Al in sample 19 might lead one to suspect
that they are CAI’s in whole or in part, except for the fact that the external appearance of those
samples is not different from that of most of the other samples.
The ranges of the concentrations of these elements relative to CI (C1) chondrites
are presented in Fig. 2. (CI concentrations of Ir and Au from Lodders [19], others from
Barrat [20]).
Fig. 2 Concentrations of 17 elements in Allende chondrules relative to CI chondrites
A casual review of the results finds some values for several of the elements
involved in this study that appear to be “outliers.” The data for each element were
evaluated by iterative Grubb’s test, and were also checked by the “ROUT” test that is
included in the Graphpad Prism 6 software that was used for statistical calculations in this
study; the two tests yielded the same list of values identified as outliers.
Therefore, all statistical analyses in this study were performed on the full set of
data, as well as on sets of data from which one or more identified outliers have been
excluded. Differences among these analyses will be the subject of some later discussion.
B. Correlation Coefficients
Statistical analysis calculations were performed with Graphpad Prism 6.04
software for Windows from Graphpad Software, LaJolla, California,
www.graphpad.com.
Possible correlations among the elements in this study were sought by correlation
coefficient calculations. The analyses included chondrules only; matrix samples were not
included since they represent a different population.
The correlation coefficients for the full set of data, as well as for sets of data from
which one or more outliers were excluded, are available at
www.calvin.edu/academic/geology/menninga/allendechondrules.
There are two main clusters of positively correlated elements that merit attention:
1. The cluster that includes iron, nickel, and cobalt, shown in Table 3.
Table 3. Correlations among siderophile elements
________________________________________________
Mn
Co
Zn
Ir
Au
Ni
Cr
____________________________________________________________________________
Fe
0.74
0.42
0.09
0.85
0.01
0.25
0.20
x-2
0.73
0.38
0.07
0.84
0.72
0.23
0.17
x-2,19
0.73
0.39
0.07
0.84
0.86
0.50
0.17
x-2,19,24,36
0.52
Ni
x-2
x-2,19
x-2,19,24,36
0.39
0.31
0.31
0.23
0.20
0.20
0.22
0.93
0.93
0.92
-0.11
0.60
0.73
0.22
0.20
0.47
0.27
0.23
0.23
Cr
0.54
0.56
0.57
0.51
0.42
0.36
0.37
-0.40
0.30
0.31
0.15
0.11
0.10
0.19
0.14
0.14
-0.01
-0.04
-0.04
0.25
-0.11
-0.04
0.00
0.48
-0.10
-0.12
-0.13
0.14
-0.15
-0.17
-0.17
Co
x-2
x-2,19
-0.05
0.64
0.78
0.26
0.24
0.54
0.37
0.34
0.34
Zn
x-2
x-2,19
0.05
0.65
0.46
-0.13
0.08
0.09
Ir
x-2
x-2,19
0.20
0.18
0.37
x-2
x-2,19
x-2,19,24,36
Mn
x-2
x-2,19
x-2,19,24,36
Zinc, though not classified as siderophile by Goldschmidt [21], is strongly correlated with
Fe, Ni, and Co if the Zn outlier in sample #2 is excluded. Manganese shows barely
significant correlation with iron only if the Mn outliers in samples #24 and #36 are
excluded. Chromium shows positive correlation of low significance with manganese, but
no correlation of significance with other elements in the iron cluster. Iridium shows
barely significant correlation with Fe, Ni and Co only if the Ir outlier in sample #19 is
excluded, and with Zn if the outlier in Zn is also excluded.
1. The cluster that includes aluminum, calcium, sodium, scandium, and
europium, shown in Table 4.
Table 4. Correlations among lithophile elements
________________________________________________
Al
Ca
Na
Ti
Sc
V
Eu
Zn ??
_______________________________________________________________________________
Mg
-0.50
-0.45
-0.55
-0.54
-0.42
-0.33
-0.47
-0.49
x-2
-0.39
-0.26
-0.49
-0.42
-0.36
0.26
-0.28
-0.45
x-2,19
-0.11
-0.18
-0.34
-0.17
0.01
0.25
-0.12
-0.30
Al
x-2
x-2,19
0.85
0.59
0.66
0.55
0.75
0.59
0.76
0.75
0.40
0.57
0.86
0.60
0.91
0.10
0.26
0.88
0.74
0.71
0.92
0.36
-0.09
Ca
x-2
x-2,19
0.51
0.45
0.39
0.64
0.40
0.34
0.55
0.55
0.69
0.72
-0.12
-0.10
0.91
0.80
0.79
0.74
0.05
-0.09
Na
x-2
x-2,19
0.64
0.60
0.32
0.73
0.71
0.52
0.29
0.01
0.07
0.65
0.67
0.58
0.35
0.23
-0.10
Ti
x-2
x-2,19
0.79
0.80
0.45
0.52
-0.14
-0.12
0.78
0.66
0.56
0.65
0.48
0.16
Sc
x-2
x-2,19
0.25
-0.06
0.03
0.68
0.75
0.83
0.36
0.39
-0.14
V
x-2
x-2,19
0.71
-0.09
-0.06
0.94
0.00
0.05
Eu
x-2
x-2,19
0.75
0.21
-0.02
Titanium, vanadium and zinc appear to be strongly correlated with aluminum when all
data are included; the correlation of those elements with aluminum is very weak when the
outliers in each of those elements and those in aluminum are excluded.
Only a few anti-correlations in this study have coefficients of greater significance
than -0.50, and none of greater significance than -0.57. Therefore, those relationships
have not received any detailed consideration in this study.
These correlation results are significantly different from those reported by Osborn
[11]. The differences are most notable when the correlation coefficients have been
calculated with sets of data from which outliers have been excluded, but some differences
remain even when the full set of data is used in the calculations. The differences when the
full set of data is used are likely due, at least in part, to the variability of elemental
composition from one chondrule to another, considering that each collection of randomly
selected chondrules examined was necessarily different from other collections, and no
collection encompasses all of the population.
C. Regression Analysis
Regression analysis was performed with the procedures of weighted Deming
regression in Graphpad Prism 6, providing data on slope and intercepts of the regression
lines, and graphs of these data. Regression analysis was performed for all pairs of
elements that showed any significant correlation, both with outlier data points included,
and also with one or more outlier data points excluded. The summary statistical data are
available at www.calvin.edu/academic/geology/menninga/allendechondrules.
The graphical representations for those results are instructive for the consideration
of the appropriate treatment of outliers in this study. A few examples are presented to
demonstrate some undue influence of one or more outliers on the correlation coefficients
and the regression lines. (Note differences in scale among the graphs presented.)
1. In some cases an outlier has such a strong influence that the regression line is
far from the trend that is obvious in the remaining 35 or 34 samples, and the
correlation coefficient with the full set of data is near zero. Excluding the
outlier(s) results in a regression line that follows the remaining trend, and
reveals a strong positive correlation. An example is provided by Fe vs. Zn in
Fig. 3.
Fig. 3 Regression graphs of Fe vs Zn
Similar patterns are found in Ni vs Zn and Co vs Zn. Also, similar patterns are
found in Fe vs Ir, Ni vs Ir, and Co vs Ir in comparing the correlation coefficients and
trend in the graph for the full set of data with the remaining set after excluding the Ir
outlier in sample #19.
2. In some cases one or two outliers lie far from a cluster of the remaining 35 or
34 points, controlling the regression line and indicating a strong correlation of
the two elements involved. Excluding the outlier(s) leaves widely scattered
points with very low correlation coefficient. The plot of Al vs V shown in Fig.
4 provides an example.
Fig. 4 Regression graphs of Al vs V
Similar patterns are shown by Al vs Zn, Sc vs Ir, V vs Zn, Zn vs Eu, Ca vs Zn, Ca
vs V, and V vs Eu.
3. In some cases there are two outlier points on the graph, quite far apart,
strongly influencing the regression line to be drawn roughly midway between
them, and the remainder of the samples in a cluster quite separated from the
two outlier data points. Exclusion of one of the outlier points may or may not
alter the correlation coefficient, but exclusion of both outlier points leaves the
remaining points widely scattered, and the correlation coefficient near zero.
The example of Al vs Ir is shown in Fig. 5.
Fig. 5 Regression graphs of Al vs Ir
Similar patterns are found in Ti vs Zn and Ti vs Ir. Very similar patterns are also
found in Fe vs Mn and in Cr vs Mn by comparing the results for all data with the results
when the Mn outliers in samples #24 and #36 are excluded.
The regression line graphs of all pairs of elements with significant correlation
coefficients can be found at
www.calvin.edu/academic/geology/menninga/allendechondrules.
So, what are we to make of the influence of the outliers on the regression lines
and correlation coefficients? Which set of data is most meaningful with regard to the
correlation of the elements under consideration in the environment of the early solar
system in which the chondrules were being formed?
To this author it would seem contrary to good sense to base conclusions regarding
the formation history of chondrules on an apparently strong correlation (or anticorrelation) that is heavily influenced by one or two outlier data points when the
remaining 35 or 34 data points do not support that apparent correlation, or to ignore an
obvious correlation shown by 35 or 34 data points that is masked by the influence of one
or two outlier data points.
D. Effect of volatility on elemental composition of chondrules
Studies have been done on the effects of volatility of elements under early solar
system nebula conditions on the elemental composition of bulk chondrites of various
classes [22]. In this study the arithmetic mean of the elemental composition of Allende
chondrules, with outliers excluded, relative to CI chondrites and Mg has been plotted vs.
50% condensation temperatures [23] under likely early nebular conditions, shown in Fig.
6.
Fig. 6 Elemental composition of Allende chondrules vs. nebular condensation
temperature
The more refractory elements are indeed enriched in these samples, relative to CI
chondrites and Mg, with the glaring exception of iridium. The data for the more volatile
elements, however, are widely scattered and do not present a smooth pattern of variation
with condensation temperature, such as was reported by Davis [22] for CV chondrites.
Surely, factors other than volatility/condensation were predominant in producing
the wide variation in elemental composition of the nebular materials from which these
chondrules were formed.
Conclusions
The formation history of chondrules receives a lot of attention in attempts to gain
understanding of early solar system history. Postulates regarding the processes of their formation
include 1) direct condensation from the solar nebula [24, 25], 2) impact melting on the surfaces
of large bodies [26-28], 3) impact melting by collisions of small bodies [29, 30] or dust grains
[31], and 4) melting of condensed material by lightning-type discharges [32]. At the present time
there is considerable consensus that chondrules were formed by an unexplained brief heating
event that melted existing matter, probably aggregates of dust particles in that region of the
nascent solar nebula, followed by rapid cooling [1, 33].
That consensus leaves many puzzles unsolved, of course. In Meteorites and their Parent
Bodies, McSween [1] wrote (p. 56), “thus far no consensus has emerged” and “Chondrules are as
much a puzzle to us now as they were to Sorby [34].”
The results reported here are an addition to the data to be accounted for in searching for solutions
to those puzzles, and will hopefully aid in finding those solutions.
Acknowledgements
I am grateful to the U.S. Nuclear Regulatory Commission and to Washington State University
Nuclear Research Center for providing access to neutron irradiation sources. I appreciate the
generosity of the Radiochemistry Division of the Pacific Northwest National Laboratory
(formerly the Battelle Pacific Northwest Laboratories) for providing access to their facilities and
radioactivity counting equipment for carrying out the neutron activation analyses. I am grateful
to the Smithsonian Institution for providing sample material. I am grateful for the support
provided by the Northwest Colleges and Universities for Science and by a sabbatical leave from
Calvin College. I thank Ned Wogman of Battelle Northwest for encouragement and smoothing
my path to performing this research, and I am especially grateful to Louis Rancitelli for his
invaluable help in obtaining the sample material and in gaining access to neutron irradiation
facilities at the Hanford Works, and to the radioactivity counting equipment at the Battelle
Laboratories.
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