Collaborative Research: Resolving the Nature and Extent Archean Crustal Components in Southwestern Laurentia Using Hf and U-Pb Analysis of Zircon and Baddeleyite

本项目旨在解决关于北美西南部前寒武纪岩石圈最早演化和深部结构的长期争议。该地区是研究大陆形成过程的一个全球重要的实地实验室。目前的争论集中在需要解决年轻弧的增生与旧地壳物质的再循环的相对重要性，和/或与裂缝相关的基性地壳的增加。本项目的目的是：1)确定莫哈韦省神秘太古宙和其他前1.8 Ga岩石圈成分的性质，并阐明它们合并到1.8-1.6 Ga造山系统的时间和过程；2)发现更多确定的穿刺点（相对于澳大利亚、南极洲等），可用于Nuna （1.8 Ga）和Rodina （1.0 Ga）的超大陆重建；3)为西南各年龄沉积盆地的碎屑锆石研究提供了一个全面的基底物源年龄模板。方法是对西南地区最古老岩石中的锆石进行U/Pb放射性定年和Hf同位素表征。初步研究表明，这些岩石含有更古老的颗粒，其历史将通过这些方法来破译。研究小组将分析从最古老的岩体中继承的锆石，这些锆石起到了探测下地壳融化的作用；从最古老的变质沉积岩中提取的碎屑锆石，这些锆石表明了侵蚀的源区以及由此产生的沉积盆地和沉积体系。该项目涉及美国学术界的pi、美国地质勘探局以及澳大利亚学术界和矿产行业的合作者之间的合作。合并后的数据集将与pi之前几十年的工作以及来自美国国家科学基金会EarthScope实验的新地球物理图像相结合。这项工作的重要性将是对北美大陆这部分基底结构的构造和演化进行新的综合，这将对地球科学的许多子领域有用，包括构造学，我们大陆的深时间地质历史，地下地球物理解释的地面真相，以及矿产勘探的应用。该项目还有一个强有力的外联部分，通过培训包括少数民族学生在内的学生地球科学家，并与公园合作，对公众进行非正式的地球科学教育，将研究和教育结合起来。

This project aims to resolve a long-standing controversy regarding the earliest evolution and deep structure of the Precambrian lithosphere of southwestern North America. This area is a globally important field laboratory for studies of the processes that form continents. Current debate has focused on the need to resolve the relative importance of accretion of juvenile arcs versus recycling of older crustal materials, and/or rift-related addition of mafic crust. The objectives of this project are to: 1) resolve the nature of the cryptic Archean and other pre-1.8 Ga lithospheric components in the Mojave Province and elucidate the timing and processes of their incorporation into an assembling 1.8-1.6 Ga orogenic system; 2) discover more definitive piercing points (relative to Australia, Antarctica, etc.) that can be used for supercontinent reconstructions of Nuna (1.8 Ga) and Rodina (1.0 Ga); and 3) provide a comprehensive basement provenance age template in support of the wide array of detrital zircon studies of sedimentary basins of all ages in the Southwest. The approach is to use U/Pb radiometric dating and Hf isotopic characterization of zircons from the oldest rocks in the Southwest. Pilot studies show that these rocks contain still older grains, whose history will be decipherable using these approaches. The research team will analyze inherited zircons from the oldest plutons, which act as probes what was being melted in the lower crust, and detrital zircons from the oldest metasedimentary rocks, which are an indication of eroding source regions and resulting sedimentary basin and depositional systems.The project involves collaboration between PIs in U.S. academia, the USGS, and Australian collaborators from academia and the mineral industry. The combined datasets will be integrated with several decades of previous work by the PIs and with emerging new geophysical images from the NSF EarthScope experiment. The importance of the work will be a new integrated synthesis of the structure and evolution of the basement architecture of this part of the North American continent that will be useful for many subfields in the geosciences, including tectonics, deep time geologic history of our continent, ground-truth of geophysical interpretations of the subsurface, and applications for minerals exploration. The project also has a strong outreach component that integrates research and education via training of student geoscientists, including minority students, and working with the Parks for informal geoscience education of the public.