Collaborative Research: Geochemical Imaging of Post-Pangean Lithospheric Structure in the Southern Appalachians

合作研究：阿巴拉契亚山脉南部后盘古大陆岩石圈结构的地球化学成像

• 批准号: 1305609
• 负责人: Craig Grimes
• 金额: $ 12.39万
• 依托单位: Ohio University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-27 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1305609&HistoricalAwards=false
• 关键词: Collaborative; Research; Geochemical; Imaging; Post

The combined Alleghanian-Hercynian-Variscan orogeny (approximately 300 million years ago) marks the culmination of Earth?s most recent example of the formation and dispersal of a supercontinent (Pangea). The southern Appalachian Mountains record a critical zone in the formation of Pangea because they mark the collision of the precursors of three modern continents (North America, South America, and Africa). Pangea's subsequent rupture produced these three continents and continues with the expansion of the Atlantic Ocean. The research team of faculty and students from the University of Florida and Mississippi State University are conducting detailed geochemical investigations into the spatial distribution, ages, and geochemical compositions of a suite of granitic igneous bodies that intruded crystalline rocks that formed up to one billion years earlier in the roots of the mountain belt and are now in Georgia, Florida, Alabama, and South Carolina. These granitic bodies are the only known magmatic manifestation of the destruction of two ancient oceans (Iapetus and Rheic). Understanding the age and origin of the granitic bodies is critical to understanding the growth of continents in general and, particularly, how continental crust was exchanged during the Pangean supercontinent cycle. In particular, they are focusing on identifying the boundary and the operative tectonic and magmatic processes that characterized convergence of the continents that ultimately formed Pangea. The convergent boundary has tentatively been identified on the basis of geophysical data to occur in a zone known as the Suwannee suture; the proposed suture lies sub-parallel to the Florida-Georgia border. A new boundary was established after the rupture of Pangea, which produced the modern Atlantic Ocean and the African, South American, and North American continents. The location of this rupture is not known, but is being further constrained by this project.Faculty and students (graduate and undergraduate) involved in this project are sampling the granitic rocks derived from melting of the lower continental crust as part of an integrated geochronologic, thermochronologic, and geochemical study of the spatial and temporal relationships between Alleghanian tectonism and magmatism. These data will provide unique constraints on lithospheric structure and evolution in the Pangean collision zone. The region chosen contains numerous Alleghanian magmatic rocks that intrude a range of pre-Alleghanian terranes typically considered part of ancient North America, as well as some considered to be fundamentally Gondwanan or peri-Gondwanan (e.g., African or South American). The uranium-lead zircon geochronology and isotopic composition of the granitic bodies are being used to geochemically image both sides of the proposed Suwannee suture to better understand the juxtaposition of the different continental fragments in 4-D. This "geochemical imaging" of lithospheric structure is: 1) providing a critical complement to on-going geophysical studies in this region that are integral to the mission of the EarthScope Program in North America, 2) providing important insight into the global tectonic enigma of largely amagmatic ocean closures, and 3) contributing to our understanding of the basement architecture of the eastern Gulf of Mexico petroleum province. The project supports an important regional scientific collaboration between researchers at the University of Florida and Mississippi State University. It is contributing to the training of graduate and undergraduate students in a STEM discipline. Because of the demographics of the student populations at both universities, it has the potential to contribute to the broadening of participation of underrepresented groups in the geosciences. The ongoing results of this research are being communicated in guidebooks, professional meeting symposia, and refereed scientific publications.This project is being supported by the NSF Tectonics and EarthScope Programs

阿勒格尼亚人 - 赫西尼 - 瓦里斯坎造山基（大约3亿年前）标志着地球的最新典型的形成和分散的超大陆（pangea）的最新例子。阿巴拉契亚南部的山脉记录了Pangea形成的关键区域，因为它们标志着三个现代大陆（北美，南美和非洲）的前体的碰撞。 Pangea随后的破裂产生了这三大洲，并随着大西洋的扩张而继续。佛罗里达大学和密西西比州立大学的教职员工和学生研究团队正在对一组花岗岩火成岩的物体的空间分布，年龄和地球化学组成进行详细的地球化学调查，这些岩石侵入了山脉和山上的山上，这些岩石侵入了多达十亿年的山脉和山上，这些岩石在山上和山脉中又构成了山脉。这些花岗岩体是两种古老海洋（Iapetus and Rheic）破坏的唯一已知的岩浆表现。了解花岗岩体的年龄和起源对于了解一般的大陆的生长，尤其是在Pangean超大陆循环中如何交换大陆地壳是至关重要的。特别是，他们专注于确定最终形成pangea的大陆收敛的边界以及手术构造和岩浆过程。在地球物理数据的基础上，暂时确定了收敛边界，该区域发生在称为Suwannee缝合线的区域中。所提出的缝合线位于与佛罗里达 - 斜视边界平行的。 Pangea破裂后，建立了一个新的边界，该破裂产生了现代大西洋以及非洲，南美和北美大陆。这种破裂的位置尚不清楚，但正在受到该项目的进一步限制。参与该项目的教师和学生（研究生和本科）是从下层大陆地壳的融化中取样的花岗岩岩石，作为综合地球学，热力学，热力学，热力学和纳米尔人之间的综合地球学，热力学和地球化学研究的一部分。这些数据将对Pangean碰撞区的岩石圈结构和演变提供独特的限制。所选择的地区包含众多阿勒格尼亚岩石岩石，这些岩石侵入了一系列前阿尔格纳尼亚人的地形，通常被认为是古代北美的一部分，有些人从根本上被认为是冈瓦南或佩吉·冈德瓦南（例如，非洲或南美）。花岗岩体的铀铅锆石的年代学和同位素组成被用来对拟议的Suwannee缝合线的两侧进行地球化形象，以更好地了解4-D中不同大陆碎片的并置。岩石圈结构的这种“地球化学成像”是：1）为该地区正在进行的地球物理研究提供关键的补充，这些研究与北美Earthscope计划的任务不可或缺，2）对全球构造构造的重要见解，在很大程度上是在很大程度上是杂乱无章的大洋封闭，以及3）对地下室的理解贡献了米型的大家长。该项目支持佛罗里达大学和密西西比州立大学研究人员之间重要的区域科学合作。它为在STEM学科的研究生和本科生的培训做出了贡献。由于两所大学的学生人口的人口统计，它有可能促进代理中代表性不足的群体的参与。这项研究的持续结果正在指南，专业会议专题讨论会和被裁判的科学出版物中进行传播。