Proterozoic Assembly Of North America: Insight From The Interactions Of Deformation, Metamorphism And Magmatism In The Southwestern United States
PROTEROZOIC ASSEMBLY OF NORTH AMERICA: INSIGHT FROM THE INTERACTIONS OF DEFORMATION, METAMORPHISM AND MAGMATISM IN THE SOUTHWESTERN UNITED STATES Robert Alexander Hunter, Ph. D. Cornell University One of the major goals of the geoscience community is to develop an accurate tectonic history of North America. Understanding how our continent evolved through time has numerous implications for our ability to develop accurate models of the tectonic evolution of continents - how they form, deform, and break. The interactions of deformation, metamorphism, and plutonism, three fundamental geological processes at work throughout the evolution of continents, record information that can be used to better understand the mechanisms and events that have shaped our continent. This dissertation employs metamorphic petrology, structural geology, geochemistry and geothermobarometry to interrogate the interactions of deformation, metamorphism and plutonism on multiple scales across the southwest United States. On a microscope scale, this dissertation shows that deformation and metamorphism can work in a positive feedback loop, facilitated by solution mass transfer, to localize both deformation and metamorphism, producing areas of high strain that have more closely approached metamorphic equilibrium. This result informs our understanding of crustal behavior at mid-crustal depths during orogenesis. On the mountain range scale, this dissertation combines petrographic analysis, structural geology, geochemistry and geothermobarometry to show that metamorphism in the Tusas and Picuris Mountains of northern New Mexico is consistent with one metamorphic event following a pressure-temperature-time trajectory consistent with progressive loading during the formation of a fold and thrust belt. This result informs our understanding of the tectonic history of North America, and has implications for the petrogenesis of aluminosilicate triple-point rocks in the region. Finally, on a continental scale, this dissertation uses previously published geochronologic data to identify spatial patterns in the age of igneous bodies across the southwest United States. These results were used to characterize mesoproterozoic tectonism and develop a model for melt production of these plutons. This result informs not only our understanding of crustal growth and rejuvenation during orogeny, but also provides a comprehensive dataset and novel approach that may both be employed in future research.
Deformation; Metamorphism; Plutonism
Kay, Robert Woodbury; Kassam, Karim-Aly Saleh
Ph. D., Geological Sciences
Doctor of Philosophy
dissertation or thesis