Determining the Areal Extent and Tectonic Significance of Mesoproterozoic (1.50-1.45 Ga) Sedimentation and Metamorphism along the Yavapai-Mazatzal Lithospheric Boundary, New Mexico

Bucknell University, Lewisburg PA

Investigators

Abstract

Precambrian rocks in the western United States range in age from about 550 million years old to more than 2 billion years old and record the early tectonic processes and major geological events that created and changed the North American continent. Two recent detrital zircon geochronology studies in Precambrian rocks of Arizona and New Mexico have discovered that some of these rocks were deposited between about 1.45 and 1.5 Ga some 200 million years. younger than previously thought. These new findings require a significant reinterpretation about the tectonic evolution of the southwestern United States between about 1.7 and 1.4 Ga. This research project will conduct a detailed detrital zircon geochronology study of Precambrian metasedimentary rocks across central and northern New Mexico to help delineate the regional extent of these younger metasedimentary rocks and to better understanding the geometry of the depositional basin and the tectonic setting of the region at this time. Additional work will characterize the metamorphic history of these rocks using petrographic analysis, appropriate major element and trace element thermobarometry, equilibrium phase diagrams (pseudosections), and monazite geochronology to determine the pressure-temperature-time-deformation history and tectonic processes that followed deposition. The combined approach of detrital zircon geochronology and metamorphic monazite geochronology in the same rocks will constrain the maximum and minimum depositional age of these metasedimentary rocks. These new data will be used to test and refine tectonic models that describe how and when the continental lithosphere of the western United States was formed and how it evolved in the mid-Precambrian. Preliminary data suggest that convergent, possibly accretionary tectonic processes may have occurred between 1.5 and 1.4 Ga. If additional data support this hypothesis, it would constitute a fundamental transformation in our understanding of the growth and tectonic evolution of North America. Undergraduate research and education is an essential component of this research project. This project will give undergraduate researchers experience with a major research initiative, the opportunity to travel to major research institutions and use cutting-edge research instrumentation, and develop critical analytical skills through data acquisition and interpretation. Undergraduate researchers will also gain experience presenting their results to the larger geological community.