Graduate Theses, Dissertations, and Problem Reports 2015 Integrated geochronology and petrogenesis of volcanic suites for tectonic sedimentary studies: Karoo Basin, South Africa Matthew P. McKay Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation McKay, Matthew P., "Integrated geochronology and petrogenesis of volcanic suites for tectonic sedimentary studies: Karoo Basin, South Africa" (2015). Graduate Theses, Dissertations, and Problem Reports. 6200. https://researchrepository.wvu.edu/etd/6200 This Dissertation is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. 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McKay Dissertation submitted to the Ebery College of Arts and Sciences at West Virginia University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Geology and Geography Amy Weislogel, Ph.D., Chair Andrea Fildani, Ph.D. Kathleen Benison, Ph.D. Thomas Kammer, Ph.D. Jaime Toro, Ph.D. Department of Geology and Geography Morgantown, West Virginia 2015 Keywords: U-Pb zircon, geochronology, petrogenesis, Karoo Basin, Gondwana Copyright 2015 i i ABSTRACT Integrated geochronology and petrogenesis of volcanic suites for tectonic sedimentary studies: Karoo Basin, South Africa Matthew P. McKay By integrating high-precision, U-Pb zircon geochronology with zircon and whole rock/ tuff geochemistry, the tectonic history of an active margin can be assessed independently from strata preserved in sedimentary basins. This approach is particularly useful in regions where sub- sequent active tectonism has resulted in extensive igneous intrusion, tectonic dissection, or struc- tural deformation of crustal suites, obscuring the record of previous geologic events. In this work I present 603 U-Pb zircon age coupled with zircon geochemical analyses collected from Sensitive High Resolution Ion Microprobe (SHRIMP) microanalyses, 15 U-Pb zircon Thermal Ionization Mass Spectrometry (TIMS) ages, and 109 U-Pb Laser Ablation-Inductively Coupled Plasma Mass Spectrometer (LA-ICPMS), and 41 whole rock geochemical analyses to assess 1) the utility and limitations of U-Pb zircon tuff geochronology when estimating absolute depositional ages of strata for chronostratigraphy, 2) the petrogenesis of volcanic tuffs from zircon U-Pb age and rare earth element (REE) compositions, and whole rock major and trace element concentrations, 3) advan- tages and limitations of geochronologic techniques (TIMS vs. SHRIMP vs. LAICPMS) and 4) the interaction between plate margin magmatism, orogenic deformation, and sedimentation into a tectonically active basin. ii DEDICATION This work is dedicated to Katie, the letter “z”, Archibald’s BBQ in Northport, AL, and the men and women of the U.S. Coast Guard. “You’ve gotta go out, but you don’t have to come back.” Semper Paratus iii ACKNOWLEDGMENTS Funding for this project was made possible by the SLOPE4 research consortium, American Association of Petroleum Geologists, Society for Sedimentary Geology, West Virginia University, Chesapeake Energy, Geological Society of America, and Dr. Robert Shumaker. Field assistance was provided by R. Brunt, D. Hodgson, S. Flint, A. Fildani, A. Weislogel, J. Dean, C. Findlay, and K. McKay. Special thanks to H. Patel for lab assistance and M. Coble for expert analytical sup- port (SHRIMP). I appreciate the support of my Ph.D. committee and the discussion and feedback provided by my co-authors (A. Fildani, A. Weislogel, R. Brunt, D. Hodgson, S. Flint, A. Hessler, M. Coble, W. Jackson, Jr.). I am grateful for support from my adviser, Dr. Amy Weislogel, and Dr. Andrea Fildani, who were both instrumental in the completion of this project. -M iv TABLE OF CONTENTS ABSTRACT.....................................................................................................................................ii DEDICATION................................................................................................................................iii ACKNOWLEDGMENTS..............................................................................................................iv PROLOGUE......................................................................................................................................1 CHAPTER 1: U-Pb ZIRCON TUFF GEOCHRONOLOGY FROM THE KAROO BASIN: IMPLICATIONS OF ZIRCON RECYCLING ON STRATIGRAPHIC AGE CONTROLS Abstract.................................................................................................................................3 Introduction...........................................................................................................................4 Geologic background............................................................................................................6 U-Pb methods and analyses..................................................................................................7 U-Pb results and interpretation.............................................................................................9 Tanqua depocenter: western basin............................................................................11 Ecca Group..................................................................................................11 Beaufort Group...........................................................................................12 Laingsburg depocenter: southwest basin................................................................12 Beaufort Group...........................................................................................13 Prince Albert transect: south-central basin.............................................................14 Ripon depocenter: eastern basin.............................................................................15 Ecca Group..................................................................................................15 Beaufort Group...........................................................................................16 Discussion...........................................................................................................................17 Tuff distribution and composition-Gondwanan tuff gap........................................17 Maximum depositional ages from U-Pb zircon analyses.......................................18 Implications for magmatism in southern Gondwana..............................................25 Summary.............................................................................................................................27 Acknowledgements.............................................................................................................27 References..........................................................................................................................28 CHAPTER 2: PETROGENESIS AND PROVENANCE OF DISTAL VOLCANIC TUFFS: A WINDOW INTO A DISSECTED, MAGMATIC PROVINCE Abstract...............................................................................................................................35 Introduction..........................................................................................................................36 Geologic background..........................................................................................................37 Whole rock geochemistry....................................................................................................40 Methods...................................................................................................................40 Results.....................................................................................................................42 Zircon U-Pb ages and REE compositions...........................................................................42 Methods...................................................................................................................42 U-Pb zircon maximum depositional ages...............................................................44 Ecca Group..................................................................................................45 Beaufort Group...........................................................................................45 v Trace elements in zircon..............................................................................46 Ti in zircon..................................................................................................46 Discussion............................................................................................................................48 Petrogenesis of Karoo tuffs from whole rock geochemistry...................................48 Zircon petrochronology of Karoo tuffs...................................................................49