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University Microfilms International 300 North Zeeb Road Ann Arbor, Michigan 48106 USA St INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You w ill find ja good image o f the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large dieet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding o f the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NOTE: Some pages may have indistinct print. Filmed as racpivnd. University Microfilms international 300 North Zeeb Road Ann Arbor, Michigan 48106 USA St. John's Road, Tyler's Green High Wycombe, Bucks, England HP10 8HR 77-21,370 DONOFRIO, Richard R., 1942- THE MAGNETIC ENVIRONMENT OF TEKTITES. The University of Oklahoma, Ph.D., 1977 Geology XsrOX UniVBrSity Microfilnis,Ann Arbor, Michigan 48106 THE UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE THE MAGNETIC ENVIRONMENT OF TEKTITES A DISSERTATION SUBMITTED TO THE GR/iDUATE FACULTY in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY by RICHARD R. DONOFRIO Norman, Oklahoma 1977 PHE MAGNETIC ENVIRONMENT OF TEKTITES APPROVED BY f h'éyUé^ \ / < y yC ' / f DISSERTATION COmiTTEE THE MAGNETIC ENVIRONMENT OF TEKTITES TO DAD The last thing you said to me was to go back and finish up. This is for you. ill THE MAGNETIC ENVIRONMENT OF TEKTITES ABSTRACT Magnetic properties of tektites from the four strewn fields along with certain impact glasses were analyzed through paleomagnetic techniques and measured with highly sensitive superconducting magnetometers. The results revealed that tektites have a stable natural remanent magnetization arising from a thermo- remanent magnetism which was acquired at the time the glasses cooled through the blocking temperature of the ferromagnetic phase. Scanning electron microprobe studies in conjunction with thermal and alternating field demagnetization indicated that the magnetic carrier of the natural remanent magnetiza­ tion is magnetite on the sub-microscopic level. Based on the accumulated magnetic data, it was concluded that the natural remanent magnetization of tektites was reliable and could be used for ancient magnetic field estim­ ations. Paleointensity determinations on interior cores of IV ablated tektites, as well as other forms, demonstrated that tektites cooled in a field similar in amplitude to that of the earth. This data refutes the lunar hypothesis. In addition, on the basis of particular magnetic properties, the preliminary findings suggest that there may be a genetic relationship between certain strewn fields and large impact sites. ACKNOWLEDGMENTS This research was conducted at the paleomagnetic laboratories of the University of Oklahoma, the University of California at Santa Barbara, and the University of Texas at Dallas. The facilities of Superconducting Technology Inc., at Mountain View, California were also employed. I am grateful to these institutions for permitting me to use their equipment for the studies on tektites presented in this paper. Without the training I have received over the years from my advisor. Dr. Robert Dubois, this paper would not have been possible. He along with Dr. Virgil E. Barnes made this re­ search enjoyable and well worth the effort. I thank Dr. Robert Fowler of the OU physics department for his consideration and time in constructing the electrical discharge unit used in this research. Assistance was also rendered by Dr. Michael Fuller and Dr. Charles Helsey along with their respective paleomagnetic staffs. Appreciation is also extended to Dr. Dean Chapman, Mr. Leroy Scheiber, and Mr. Frank Centolanzi at Ames Research Center. I also express gratitude to Dr. Aurellio deGasparis for his comments. In addition to Dr. Dubois and Dr. Helsey, I thank the other members of the reading committee. Dr. Charles Harper, VI Dr. George Huffman, and Dr. Edward Stoever. Part of this research was made possible through National Aeronautics and Space Administration grant # NGR- 39 - Oil - 156. Vll CONTENTS Page DEDICATION .......................................... iii ABSTRACT ............................................ iv ACKNOWLEDGEMENTS.................................... vi CONTENTS ............................................. viii TABLES .............................................. xi FIGURES .............................................. xii PLATES .............................................. XV FOREWORD ............................................. xvii INTRODUCTION ........................................ 1 Purpose of Research .......................... 1 PREVIOUS MAGNETIC RESEARCH .......................... 3 LABORATORY PREPARATION .............................. 5 Source of Specimens .......................... 6 Contamination and Selection .................. Related Glasses .............................. 9 Sample Identification ........................ 10 INSTRUMENTATION ...................................... H The Superconducting Magnetometer .............. 11 O v e n s ........................................ 18 M a g n e t s ...................................... 18 Demagnetization Equipment .................... 20 Other Equipment .............................. 20 MEASUREMENT PROBLEMS ................................ 22 STABILITY OF TEKTITE NRM TO SHOCK .................... 25 THE SUSCEPTIBILITY MEASUREMENTS ...................... 40 P r o c e d u r e ..................... 42 Discussion of Susceptibility Data ............ 44 Impact Glasses ................................ 47 Applications of Susceptibility Data ............ 49 Microtektites .................................. 53 A Possible Formation Model .................... 54 Implications of Susceptibility and Intensity Data ................ 56 viii Page SUSCEPTIBILITY AND INTENSITY CHANGES ACROSS A TEKTITE . 58 SUSCEPTIBILITY OF SPECIMENS FROM THE MOLDAVITE STREVÏN FIELD . 62 ORIGIN OF THE NATURAL REMANENT MAGNETIZATION ............... 69 Isothermal Remanent Magnetization ................... 70 Partial Thermoremanent Magnetization ................ 79 Chemical and Viscous Remanent Magnetization ......... 80 Thermoremanent Magnetization......................... 81 PROPERTIES OF THE N R M ....................................... 83 Relationship of Carrier Size to N R M ................. 85 Tektite Demagnetization Curves ...................... 88 Estimation of Magnetic Carrier Sizes.................. 82 Impactite Demagnetization Curves ..................... 84 SATURATION STUDIES ........................ .............. Impactites......................................... Implications of Saturation Studies .................. CARRIER CHANGES IN OXIDIZING AND NON-OXIDIZING ENVIRONMENTS ........................ 114 THERMAL DEMAGNETIZATION AND SEM STUDIES ............... 121 Impact Glasses ........................ 131 SUMMARY OF RESULTS ................................... 134 THE QUESTION OF TEKTITE ORIGIN ............................ 136 Formation of Teardrop Tektites ...................... 139 Tektite Formation According to the Lunar Hypothesis. 141 Aerothermal Stress Shell ............................ 146 Strain Pattern ...................................... 148 Strain Effects on Synthetic and Natural Tektite Glass. 149 Selection of Cores ................................... 151 Preparation of Cores ................................ 153 Experimental Procedure .............................. 155 Estimation of the Paleointensity Field .............. 157 PALEOINTENSITY MEASUREMENTS ON OTHER TEKTITES............... 162 Australasian Tektites ........ ..... 162 Origin of Moldavites, Bediasites, and Ivory Coast Tektites........... 163 IX Page FORMATION MODELS ...................................... 166 CONCLUSIONS .......................................... 171 SELECTED REFERENCES .................................. 173 PERSONAL COMMUNICATIONS .............................. 180 APPENDIX ................................................ 182 TABLES Table Page 1. Intensity changes after cleaning . .............. 8 2. Comparison of NRM before and after destructive tests ....................... 39 3. Typical magnetic properties
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