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ELEMENTAL ABUNDANCES in METEORITIC CHONDRULES Abstract Approved: Redacted for Privacy Roman A AN ABSTRACT OF THE THESIS OF THOMAS WARD OSBORN III for the Doctor of Philosophy . (Name) (Degree) in Chemistry presented on September 28, 1971 (Major) (Date) Title: ELEMENTAL ABUNDANCES IN METEORITIC CHONDRULES Abstract approved: Redacted for Privacy Roman A. Schmitt High-precision instrumental neutron activation analysis has been used to determine Al, Na, Mn, Sc, Cr, Fe, Co, and Ni in a suite of more than 500 chondrules from 26 distinct meteorites. These meteorite specimens represent the H, L, LL and C chemical classes and most of the petrologic types. In addition radiochemical activation analysis has been used to determine K, Rb and Cs in a suite of chon- drules from the LL chemical class. To a limited extent trace element data on individual chondrules were correlated with petrographic obser- vations on the same chondrules. I. In general it was found that the siderophilic elements Fe, Co, Ni and Ir are depleted in chondrules compared to the whole chon- drite. The lithophilic elements Na, Mn, Sc, Cr and Al are generally enriched in chondrules compared to the whole chondrite. In contrast to the other lithophilic elements, Rb and Cs are generally depleted in the chondrules. Both major and trace elements may exhibit multi- modal population distributions for the chondrules sets. II. Petrographic observations of the same chondrules for which trace element contents were determined by INAA suggest that the trace element distribution may be consistent with the mineral assemblages except for a positive Ir-Al and Al-Sc correlations which occur in many chondrule sets. Correlations between chondrule mass and Al, Na, Sc, Co, Lr and Cu contents were observed for certain chondrule sets. III. Chondrules from the H and LL groups appear to exhibit consistent compositional variations in going from low petrographic grades to high petrographic grades. The variations are observed most readily for an increasing Al-Na correlation coefficients and decreasing Mn-Na correlation coefficients with increasing petrologic types. A decrease in the dispersion of Mn and Na was also observed with in- creasing petrologic types. Na contents in the chondrules increase as a function of petrologic type. These observations are interpreted as indications of increasing equilibration of the chondrules with their matrices. IV. It appears that there are slight chemical differences between the Vigarano and Ornans subgroups as defined by Van Schmus (1969). This work supports the conclusions of Van Schmus and Wood (1967) and Van Schmus (1969) that the C2 and C3 groups are not generally related to one another by thermal equilibration processes while Karoonda may be a product of thermal equilibration of material similar to the Ornans subgroup. V. The Ni/Co ratio was found to be variable within chondrules from the same meteorite; for example, the range in Ochansk chon- drules is from 10 to 60. VI. Theories concerning the origin of chondrules are discussed in the context of the elemental abundances and correlations observed in this study. a. Some chondrules may be produced by volcanism or impact on a homogeneous magma but they are not believed to be the main mechanism of production due to the chondrule inhomogeneity and the Al-Sc and Al-Ir correlations. b. The constrained equilibrium theory appears to be inconsistent with the positive Al-Ir and Al-Sc correlations and with the mass ele- ment correlations observed for Cu, Al, Sc and Ir. c. Some chondrules may have been produced by impact onto solid rock but this mechanism does not appear to be able to produce the necessary chemical fractionation observed in some chondrules. d. The chemical data is consistent with the remelting of pre- existing dust in the solar nebula. The remelting appears to have occurred during terminal stages of the metal silicate fractionation or by a preferential melting of silicate material. The chondrules pro- duced in any one event were apparently mixed with chondrules from other events and finally incorporated into the parent body. Additional chondrules may have been produced by impact during the terminal stages of accretion. The chemical evidence then suggests that some of the chondrules equilibrated with the matrix material of their parent body. 01971 THOMAS WARD OSBORN III ALL RIGHTS RESERVED Elemental Abundances in Meteoritic Chondrules by Thomas Ward Osborn III A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1972 APPROVED: Redacted for Privacy Professor of Chemistry in charge of major Redacted for Privacy Chairman of the Department of Chemistry Redacted for Privacy Dean of Date thesis is presented September 28, 1971 Typed by Opal Grossnicklaus for Thomas Ward Osborn III ACKNOWLEDGEMENTS This research was supervised by Dr. R. A. Schmitt who pro- vided continuing guidance and a stimulating environment; without his patience and concern this work would not have been completed. Dr. G. G. Go les made many suggestions throughout the course of this work and stimulated my thinking by his penetrating questions. Important suggestions for improving the manuscript and con- tributions through discussions were made by Dr. W. D. Loveland and by D. B. Curtis. M. Dudas provided great assistance with helpful suggestions concerning the petrographic thin sections. Dr. H. Wakita provided helpful suggestions concerning the experimental procedures and data reduction. The cooperation and assistance of A. G. Johnson and the OSU Health Physics staff is appreciated. The assistance of T. V. Anderson, reactor supervisor of the OSU TRIGA REACTOR and his staff, was vital to the success of the work. High flux irradiations at the K reactor in Hanford, Washington could not have been completed without help of Mr. J. Steward; Mr. J. Schlapper and the reactor crew at the University of Missouri are acknowledged for their help with high flux irradiations. Additional help was provided by T. D. Cooper, D. G. Coles, V. N. Smith, J. B. Corliss and the late R. H. Smith, and many of my fellow graduate students both in chemistry and nuclear engineering who by thoughtful suggestions aided in the data reduction and data analysis procedures. My parents and friends are also thanked for their moral support during this work. This study was supported by grant NAS9-8097 of the National Aeronautics and Space Administration to Dr. R. A. Schmitt. TABLE OF CONTENTS I. INTRODUCTION 1 II. EXPERIMENTAL 4 Selection of Chondrules 4 Instrumental Analysis 5 Silicon 8 Aluminum 9 Sodium and Manganese 11 Calcium and Vanadium 13 Iron, Scandium, Chromium, Cobalt, Irridium, and Nickel 13 Radiochemical Procedure 18 III. SUMMARY OF ANALYTICAL DATA 21 Statistical Considerations 21 Chondrules from the H Chondrites 25 Chondrules for H3 Chondrites 26 Chondrules from H4 Chondrites 30 Chondrules from H5 Chondrites 36 The H Group Chondrules 46 The Chondrules from LL Chondrites 47 LL3 Chondrules 47 LL4 Chondrules 57 LL5 Chondrules 62 LL6 Chondrules 67 The Alkali Elements in LL Chondrules 78 The LL Group Chondrules: A Summary 80 The L Chondrules 81 Chondrules from the C Chondrites 86 Chondrules from the C2 Chondrites 86 Chondrules from the C Chondrites 98 C4 Chondrules 111 The C Group Chondrules: A Summary 117 IV. HOMOGENEITY OF INDIVIDUAL CHONDRULES 118 V. MINERALOGY AND ELEMENTAL CORRELATION COEFFICIENTS 120 VI. VARIATION BETWEEN PETROGRAPHIC GRADES 135 Comparison between H and LL Chondrules 135 Comparisons between the LL Chondrules 138 Comparisons between the C Chondrules 144 VII. THE ORIGIN OF CHONDRULES 151 Introduction 151 Volcanism and Impact into a Magma Pool 155 Impact onto Solid Rock 157 Chondrule Formation Prior to Accretion 168 Chondrules as Direct Condensates 170 Chondrules by Remelting Pre-existing Dust 173 VIII. SUMMARY AND CONCLUSIONS 179 BIBLIOGRAPHY 183 APPENDICES 193 LIST OF FIGURES Page. Figure 6 1. Flow diagram of analytical procedure. 2. Logarithmic gamma ray spectrum of chondrule 3 months after high flux irradiation using a 30 cc Ge(Li) detector. 16 42 3a. Na-Al covariance diagram for Allegan chondrules. 43 3b. Na-Al covariance diagram for Richardton chondrules. 54 4. Al-Na covariance diagram for Chainpur chondrules. 55 5. Al-V covariance diagram for Chainpur chondrules. 56 6. Ca-Al covariance diagram for Chainpur chondrules. 68 7. Al-Na covariance diagram for Olivenza chondrules. 8. Al-Na covariance diagram for Cherokee Springs chondrules. 74 9. Al-V covariance graph for Cherokee Springs chon- drules (LL6). 75 10. Al-Ca covariance graph for Cherokee Springs chondrules. 76 11. Na-Ca covariance graph for Cherokee Springs chondrules. 77 12. Cluster analysis for LA chondrules at the 95% significance level. 85 13. Al-Na covariance graph for Mighei chondrules. 95 96 14. Si-Al covariance graph for Mighei chondrules. 15. Cluster analysis for C2 chondrules at the 95% significance level. 116 Figure Page 128 16. Photomicrograph of Chainpur #8. 129 17. Photomicrograph of Chainpur #9. 130 18. Photomicrograph of Cherokee Springs #2. 131 19. Photomicrograph of Cherokee Springs #6. 132 20. Photomicrograph of Kaba #10. 133 21. Photomicrograph of Kaba #16. 134 22. Photomicrograph of Ochansk #9. 137 23. Cluster analysis of petrographic grades for H chondrules at the 95% significance level. 24. Cluster analysis for LL chondrules at the 95% significance level. 143 25. Cluster analysis for C group chondrules at the 99% significance level. 148 26. Chemical fractionation trends for vaporization of tektite glass. 159 164 27. Q-mode factor analysis Apollo 11 glass spheres. LIST OF TABLES Table Page 1. Summary of instrumental neutron activation analysis. 2. Typical results for Si determination. 9 3. Typical results of multiple Al analyses. 11 4. Summary of radiochemistry. 19 5. Summary of H3 chondrule abundances (24 chondrules). 27 6. Correlations at the 90% significance level for H3 chondrules (error weighted means were used). 29 7. Summary of H4 chondrule abundances (32 chondrules). 31 8. Correlations at the 90% significance level for H4 chondrules (error weighted).
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