Cretaceous and Eocene U-Pb Zircon Migmatite Ages from the East Humboldt Range Metamorphic Core Complex, Nevada

....................................................................................................................................... iii LIST OF TABLES ................................................................................................................................. v LIST OF FIGURES .............................................................................................................................. vi CHAPTER 1: INTRODUCTION ............................................................................................................ 1 CHAPTER 2: GEOLOGIC BACKGROUND ............................................................................................ 3 CHAPTER 3: ZIRCON BEHAVIOR DURING ANATEXIS ........................................................................ 8 CHAPTER 4: METHODS ................................................................................................................... 10 CHAPTER 5: RESULTS...................................................................................................................... 13 5.1 Zircon Images and Morphologies ............................................................................... 13 5.2 Thin Sections ............................................................................................................... 14 5.3 U-Pb Geochronology ................................................................................................... 16 5.4 Collective Evaluation of Geochronology ..................................................................... 18 5.5 Th-U Chemistry of Zircons ........................................................................................... 20 CHAPTER 6: GEOCHRONOLOGY INTERPRETATIONS ...................................................................... 22 6.1 Real Age Range Hypothesis ......................................................................................... 23 6.2 Pb Loss Hypothesis ...................................................................................................... 23 6.3 Spot-Overlap Hypothesis ............................................................................................ 24 6.4 Geochronology Interpretation Conclusion ................................................................. 25 CHAPTER 7: DISCUSSION ................................................................................................................ 26 7.1 Implications for Protolith ............................................................................................ 26 7.2 Implications for Migmatization .................................................................................. 28 7.3 Implications for Core Complex Evolution .................................................................. 30 CHAPTER 8: CONCLUSIONS ............................................................................................................ 33 APPENDIX 1: FIGURES AND TABLES ............................................................................................... 34 REFERENCES ................................................................................................................................... 59 CURRICULUM VITAE ....................................................................................................................... 65