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

美国西部的前寒武纪岩石的年龄从大约5.5亿年到20多亿年不等，记录了创造和改变北美大陆的早期构造过程和重大地质事件。最近在亚利桑那州和新墨西哥州的前寒武纪岩石中进行的两项碎屑锆石年代学研究发现，其中一些岩石的沉积时间大约在1.45~1.5Ga之间，约2亿年。比之前认为的要年轻。这些新发现需要对美国西南部约1.7至1.4 Ga之间的构造演化进行重大的重新解释。该研究项目将对新墨西哥州中部和北部的前寒武纪变质沉积岩进行详细的碎屑锆石年代学研究，以帮助圈定这些较年轻的变质沉积岩的区域范围，并更好地了解沉积盆地的几何学和当时该地区的构造背景。此外，还将通过岩相学分析、适当的常量元素和微量元素温压测定、平衡相图(假组份)和独居石年代学来表征这些岩石的变质历史，以确定沉积后的压力-温度-时间-变形历史和构造过程。碎屑锆石年代学和变质独居岩年代学相结合的方法将制约这些变质沉积岩的最大和最小沉积年龄。这些新数据将用于测试和改进构造模型，这些模型描述了美国西部大陆岩石圈是如何以及何时形成的，以及它是如何在前寒武纪中期演化的。初步数据表明，会聚的、可能是增生性的构造过程可能发生在1.5~1.4Ga之间。如果更多的数据支持这一假设，这将构成我们对北美增长和构造演化的理解的根本转变。本科生研究和教育是这一研究项目的重要组成部分。该项目将为本科生研究人员提供重大研究计划的经验，有机会前往主要研究机构并使用尖端研究仪器，并通过数据获取和解释发展关键的分析技能。本科生研究人员还将获得向更大的地质界展示他们的结果的经验。

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.