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Genesis and geochronology of alkaline volcanism in the Pinacate Volcanic Field Northwestern Sonora, Mexico Item Type text; Dissertation-Reproduction (electronic) Authors Lynch, Daniel James, 1940- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 10/10/2021 04:47:41 Link to Item http://hdl.handle.net/10150/565497 GENESIS AND GEOCHRONOLOGY OF ALKALINE VOLCANISM IN THE PINACATE VOLCANIC FIELD NORTHWESTERN SONORA, MEXICO by Daniel James Lynch II A Dissertation Submitted to the Faculty of the Department of Geosciences ,In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 19 8 1 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Final Examination Committee, we certify that we have read the dissertation prepared by ____Daniel James Lynch II______________________ entitled Genesis and Geochronology of Alkaline Volcanism in the Pinacate Volcanic Field, Northwestern Sonora, Mexico and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy C P f c . / r / 9 f / Date Dfc. [?, Date — UA * D f c IT, Date Date Date Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. Dissertation Director STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgement of source is made. Requests for permission for extended quotation from or re­ production of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgement the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED! /1. *i ; Cs ACKNOWLEDGEMENTS The work was done while I was employed in the Laboratory of Isotope Geochemistry in the Department of Geosciences at the University of Arizona. Support was furnished by the National Science Foundation under Grant Number EAR-78-11535, Paul E. Damon, Principal Investigator. Additional support was provided by the State of Arizona and by the Consejo Naturales no Removables of the government of Mexico. I especially wish to thank Dr. Paul Damon for his support and supervision of this dissertation. Not only this work, but my general education benefitted from long discussions with Drs. Mohammed Shafiqullah, William B. Bull and George H. Davis. The manuscript was improved with suggestions from Dr. Charles A. Wood, NASA Houston, and Peter Kresan of the University of Arizona, made in addition to those of my committee members. During the course of my field investigations, I shamelessly pressed my wife, Elaine, and my friends John Proids, Hugh Warren and Dave Dennis into service as sherpas to lug rocks down the mountain. A1 and Juanita Healey flew me on two photographic missions around the field. Song-Lin Cheng aided with the chemical and strontium analyses. Robert Bucher, quintessential jack of all trades, did the glass blowing for argon analyses and lettered my illustrations. My thanks to the numerous denizens of the mineral separation laboratory, now long vanished, who worked at sample preparation. ' Finally, I offer my profoundest gratitude to MFD for leaving Santa Clara for me. TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS....................................... vii LIST OF TABLES................................................ ABSTRACT........... xi 1. INTRODUCTION - THE VOLCANIC FIELD AND ITS SETTING............. 1 Purpose and Scope................... Geography and History of Exploration. Location and Climate............ Early Inhabitants and Exploration Previous Geologic Investigation.. Geology of the Finacate Region...... L«J Ul Ui OX 00 VO Geologic Evolution of the Region......... 11 Contemporaneous Volcanic Fields...................... 12 Development of the Gulf of California.......... 15 Site Geology........................... .17 The Country Rocks............ 20 The Landscape and Ephemeral Water........... ...24 Sand of the Gran Desierto............................ 27 2. THE PINACATE VOLCANOES....................................... 30 Structural Features of the Volcanic Field............ ....34 Cone Alignments...................................... 34 Relationships of Faulting and Volcanism..............37 Effects of Gulf of California Tectonism............. 42 The Pinacate Series Lavas................................ 43 Petrography.......................................... 45 Geochemistry......................................... 49 Strontium Isotope Ratios......................... 51 Geochronology of the Pinacate Volcanism..............53 Pinacate Volcanic Features............................... 57 Lava Flows........................................... 57 Cinder and Agglutinate Cones....................... .58 Histories of Two Typical Pinacate Volcanoes..........65 Carnegie Cone.................................... 65 Tecolote Cone.................. ...67 Other Noteworthy Features....... 76 Hilltop Volcanoes................................ 76 The "Pit" Crater................. 76 iv V TABLE OF CONTENTS — Continued Page 3. THE GREAT MAAR CRATERS.............................. 80 Descriptions and Scenarios................................... 84 Elegante Crater.......................................... 84 MacDougal and Molina Craters............................. 91 Sykes Crater..... ................ ................ .......95 Cerro Colorado Crater.................................... 97 Crater Elena Tuff Cone......... 100 Moon Crater............................................. 101 The Other Hydro-Volcanic Features...................... 103 A Hydrovolcanic Model....................................... 103 4. VOLCAN SANTA CLARA.......................................... 112 Nature and Implications of the Alkaline Rock Series...... 118 The Santa Clara Volcanic Series......................... 120 Distribution of the Lavas.......................... .120 Geochronology...................................... 123 Character of the Rock.............................. 125 Petrography............... ......................... 126 The Nodules......................................... 127 Geochemistry............................. .......... 129 Major Elements............. .................. .129 Trace Elements .......... ........................ 136 Strontium Isotopes........ ..................... 145 Benmoreite "B", the Compositional Reversal........... 145 Summary..................................................148 Similar Alkaline Volcanic Fields........................ 148 5. ORIGINS OF PINACATE AND SANTA CLARA - A GENERAL MODEL........ 152 The Nature and Source of the Alkali- Olivine-Basalt Magma Type...........152 Origin of the Pinacate and Santa Clara Magma Bodies...... 159 A General Volcanic Model ....... ................. 162 vi TABLE OF CONTENTS — Continued Page APPENDIX I: GEOGRAPHY AND ACCESS........................... 170 Worldwide Volcano Locator........................ *......170 Maps and Photographic Coverage.......................... 171 Access......... .........................................172 APPENDIX II: EXPERIMENTAL TECHNIQUES....................... 173 Sample Collection and Preparation....................... 173 "Whole Rock" Age Determination.......................... 173 Strontium Isotope Analysis....... 175 Whole Rock Chemistry.....................................177 APPENDIX III: SAMPLE DATA.................................. 179 REFERENCES CITED 233 LIST OF ILLUSTRATIONS Figure Page 1. VOLCAN SANTA CLARA AND THE PINACATE VOLCANOES............. 2 2. GEOLOGIC PROVINCES SURROUNDING THE PINACATE REGION........ 10 3. LATE NEOCENE VOLCANIC FIELDS OF THE PINACATE REGION....... 13 4. LANDSAT/ERTS VIEW.......................................... 18 5. GEOLOGIC PHOTOGRAPH OF THE PINACATE AREA.................. 21 6. RIO DE SONOYTA AT BATAMOTE............................... ..25 7. SAND PATTERNS AROUND PYRAMID CONE (CC 5940)............ ....28 8. SKYLAB 4 PHOTOGRAPH OF THE PINACATE AREA...................31 9. CONES OF THE SOUTH FLANK................................... 32 10. STRUCTURAL FEATURES MAP.................................... 35 11. STRUCTURAL ROSE DIAGRAM.................................... 36 12. STRESS REGIMES OF FAULTING AND MAGMA INTRUSION.............39 13. COMPOSITIONAL FIELDS OF THE ALKALINE ROCKS..... ........... 44 14. BARKER DIAGRAMS OF THE PINACATE SERIES ROCKS...............50 15. LOCATIONS OF DATED SAMPLES................................. 55 16. PHILLIPS BUTTES............................................ 62 17. CARNEGIE CONE ON THE SUMMIT PLATFORM....................... 64 18. SPATTER CONES.............................................. 66 19. PAHOEHOE SPATTER

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