University of Texas at El Paso DigitalCommons@UTEP Open Access Theses & Dissertations 2019-01-01 Zircon (u-Th)/he Thermochronologic Investigation Of The Long-Term Thermal History Of Proterozoic Rocks In West Texas And Southern New Mexico Nathan Zachary Reade University of Texas at El Paso, [email protected] Follow this and additional works at: https://digitalcommons.utep.edu/open_etd Part of the Geology Commons Recommended Citation Reade, Nathan Zachary, "Zircon (u-Th)/he Thermochronologic Investigation Of The Long-Term Thermal History Of Proterozoic Rocks In West Texas And Southern New Mexico" (2019). Open Access Theses & Dissertations. 151. https://digitalcommons.utep.edu/open_etd/151 This is brought to you for free and open access by DigitalCommons@UTEP. It has been accepted for inclusion in Open Access Theses & Dissertations by an authorized administrator of DigitalCommons@UTEP. For more information, please contact [email protected]. ZIRCON (U-TH)/HE THERMOCHRONOLOGIC INVESTIGATION OF THE LONG-TERM THERMAL HISTORY OF PROTEROZOIC ROCKS IN WEST TEXAS AND SOUTHERN NEW MEXICO NATHAN ZACHARY READE Master’s Program in Geological Sciences APPROVED: Jason Ricketts, Ph.D., Chair Stanley Mubako, Ph.D. Jeffrey Amato, Ph.D. Charles Ambler, Ph.D. Dean of the Graduate School Copyright © by Nathan Zachary Reade 2019 ZIRCON (U-TH)/HE THERMOCHRONOLOGIC INVESTIGATION OF THE LONG-TERM THERMAL HISTORY OF PROTEROZOIC ROCKS IN WEST TEXAS AND SOUTHERN NEW MEXICO by NATHAN ZACHARY READE, B.S. THESIS Presented to the Faculty of the Graduate School of The University of Texas at El Paso in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Department of Geological Sciences THE UNIVERSITY OF TEXAS AT EL PASO May 2019 Acknowledgements Foremost, I would like to express the deepest appreciation to my committee chair and advisor, Dr. Jason Ricketts, for the continuous support and motivation, for his patience, enthusiasm and immense knowledge. Without his guidance, this thesis would not have been possible. In addition, I would also like to thank the rest of my committee members, Dr. Stanley Mubako and Dr. Jeffrey Amato, for their unwavering involvement in this project, insightful comments and constructive suggestions. I would like to thank all my friends, Julian Biddle, Garett Goff, Georgina Rodriguez- Gonzalez, Tony Garcia, Labdan Alqahtani, Kofo Fadeyi, Victor Garcia and Katalina Salas, for the endless conversations and all the fun we had these past two years. My sincere thanks also goes to the entire staff and faculty of UTEP Geological Sciences department. I could not have asked for a better department, which backed me every step of the way. Last but not the least, I would like to thank my family and girlfriend, for the never ending support and love. You all have push me to excel in my academics and without your continued motivation reaching this point would not have been possible. iv Abstract The tectonic history of west Texas and southern New Mexico is well documented, however existing geologic data only provide limited snapshots of the region’s prolonged and complex tectonic evolution. Zircon (U-Th)/He (ZHe) thermochronology is used to examine the long-term thermal history of Proterozoic rocks exposed in the southern Rio Grande rift. ZHe data were collected from the Carrizo Mountains (10 dates), Cookes Range (16 dates), and Franklin Mountains (30 dates) in order to constrain the long-term (>1 Ga) thermal history of rocks in this region and relate this history to known tectonic or climatic events. Individual ZHe dates range from 6-731 Ma in the Carrizo Mountains, 44-446 Ma in the Cookes Range, and 19-649 Ma in the Franklin Mountains. Each of these datasets show negative correlations with effective uranium concentrations. Forward and inverse modeling of samples from each of these ranges successfully constrains the >1 Ga thermal history of each of these ranges and documents periods of exhumation and/or burial associated with Precambrian assembly of the North America, the Paleozoic Ancestral Rocky Mountain event, Paleozoic-Mesozoic sedimentary burial, the Laramide orogenic event, and formation of the Rio Grande rift. The final inverse model for the Carrizo Mountains suggest a large pulse of cooling from ~1100-1000 Ma, likely associated with the collision of a microcontinent with the southern margin of Laurentia at that time. Farther to the north, thermal history modeling of the Franklin Mountains documents a previously unrecognized period of Precambrian burial and subsequent uplift. This may have been associated with the formation of an orthogonal rift during final assembly of Rodinia, or alternatively with the breakup of Rodinia. In the Cookes Range, the Precambrian thermal history is somewhat unconstrained. However, exhumation likely occurred during either final assembly or breakup of Rodinia. These times of exhumation in all three ranges v are therefore likely a record of the assembly and breakup of supercontinents. The data do not support models where Precambrian erosion was a result of Snowball Earth glaciations. vi Table of Contents Acknowledgements ........................................................................................................................ iv Abstract ............................................................................................................................................v Table of Contents .......................................................................................................................... vii List of Tables ................................................................................................................................. ix List of Figures ..................................................................................................................................x Chapter 1: Introduction ....................................................................................................................1 Chapter 2: Background ....................................................................................................................2 2.1 Regional Geologic History ...............................................................................................2 2.2 Carrizo Mountains Geologic History ................................................................................4 2.3 Cookes Range Geologic History .......................................................................................5 2.4 Franklin Mountains Geologic History ..............................................................................6 Chapter 3: Methodology ..................................................................................................................8 3.1 Summary ...........................................................................................................................8 3.2 Rock Descriptions .............................................................................................................8 3.3 ZHe Thermochronology....................................................................................................9 3.4 GIS Deformation Maps ...................................................................................................10 3.5 Sample Collection and Processing ..................................................................................15 3.6 Forward Modeling ..........................................................................................................15 3.7 Inverse Modeling ............................................................................................................16 Chapter 4: Results ..........................................................................................................................18 4.1 ZHe Dates .......................................................................................................................18 Carrizo Mountains .......................................................................................................18 Cookes Range ..............................................................................................................18 Franklin Mountains ......................................................................................................19 4.2 Forward Models ..............................................................................................................23 Carrizo Mountains .......................................................................................................23 Cookes Range ..............................................................................................................26 Franklin Mountains ......................................................................................................29 4.4 Inverse Models ................................................................................................................37 vii Carrizo Mountains .......................................................................................................37 Cookes Range ..............................................................................................................38 Franklin Mountains ......................................................................................................39 Chapter 5: Discussion ....................................................................................................................42 Chapter 6: Conclusion....................................................................................................................46