Collaborative Research: Isotopic, Geochronologic, and Tectonic Character of the Western Piedmont, Virginia - Implications for the Closing of Iapetus

伊阿普图斯洋是一级早古生代洋区，将北美东部与冈德瓦南周围的地壳块体隔开。它的关闭将北美与阿巴拉契亚山脉的这些冈湾元素并列在一起，对全球水圈和大气施加了新的环流制度，是朝着盘古超级大陆最终消失的方向迈出的重要一步。尽管Iaptus在古生代的全球演化中很重要，但人们对其关闭的时间和性质知之甚少，主要是因为北美和冈德瓦元素之间的原始界面，即主要的Iapetan缝合，在美国阿巴拉契亚山脉没有被识别。根据区域地质关系和稀少的同位素数据，推测弗吉尼亚中部的乔帕瓦米西断裂代表了美国阿巴拉契亚山脉的主要伊帕坦缝合带。该项目通过综合断层两侧岩浆岩的Nd和Pb同位素研究结果；通过对断层两侧及其上方地层中碎屑锆石群体的U-Pb锆石年代学研究；通过对选定的岩浆单元的高分辨率U-Pb年代学以及对断层的运动学和年代学分析，来验证这一假说。这项研究是北卡罗来纳州立大学和德克萨斯农工大学的研究人员合作完成的。阿巴拉契亚地质学管理着北美人口最密集的人口的资源(矿物、水)，并影响着他们的福祉(地震灾害)；从逻辑上讲，对基岩地质的基本了解对于该地区的进一步发展和可持续发展至关重要。这项研究的结果还将通过多种途径进入更广泛的教育和外联领域。该项目部分资助了八名学生，其中包括两名女性。主要调查人员正在积极招募来自城市高中和少数族裔群体的新生参与这一项目。参与该项目的德克萨斯州农工学院鼓励学生自愿参加布拉索斯山谷自然历史博物馆既定的外展活动。研究生打算在专业会议和弗吉尼亚州科学教师协会的会议上展示他们的发现，并通过弗吉尼亚州科学标准研究所传播结果。一旦取得重大成果，项目人员将领导弗吉尼亚实地会议，这是一项迎合广泛参与者的年度实地考察活动。此外，加拿大合作者和一名南非硕士候选人的参与为该项目增加了国际成分。该项目产生的科学成果将通过在专业地球科学会议上的陈述和同行评议的科学文献来传播。

The Iapetus Ocean is a first-order early Paleozoic oceanic tract that separated eastern North America from peri-Gondwanan crustal blocks. Its closure, which juxtaposed North America with these Gond¬wan¬an elements in the Appalachians, imposed new circulation regimes upon the global hydrosphere and atmosphere and it was a major step toward the eventual amal¬gamation of the supercontinent of Pangea. Despite the importance of Iapetus in the global evolution of the Paleozoic, little is known about the timing and nature of its closure, mainly because the original interface between North American and Gondwanan elements, the main Iapetan suture, is unrecognized in the U.S. Appalachians. On the basis of regional geological relationships and scant isotopic data, it is hypothesized that the Chopawamsic fault in central Virginia represents the main Iapetan suture in the US Appalachians. This project is testing this hypothesis by inte¬grating the results of Nd- and Pb- isotopic studies of magmatic rocks on either side of the fault; by a U-Pb zircon geochron¬ologic study of detrital zircon populations from either side of, and in strata lying above, the fault; by using high resolution U-Pb geochronology on selected magmatic units, and by a kinematic and geochronologic analysis of the fault. This study is a collaborative effort between researchers at North Carolina State University and Texas A&M University.Appalachian geology governs resources (mineral, water) for, and influences the wellbeing (seismic hazards) of, the densest human population in North America; logically, a basic understanding of the bedrock geology is essential to further development and sustainability in the region. Results of this study will also take multiple paths into the broader domains of education and outreach. The project partially supports eight students, including two females. The principal investigators are actively recruiting incoming freshman from urban high schools and from minority groups to work on this project. Texas A&M students involved in the project are encouraged to volunteer and participate in established outreach functions with the Brazos Valley Museum of Natural History. Graduate students intend to present their findings at both professional meetings and at meetings of the Virginia Association of Science Teachers, and disseminate results through the Virginia Science Standards Institute. Once significant results are available, project personnel will lead the Virginia Field Conference, an annual field trip that caters to a broad array of participants. In addition, the involvement of Canadian collaborators and a South African MS candidate adds an international component to the project. Scientific results that derive from the project will be disseminated via presentations at professional geoscience meetings and the peer-reviewed scientific literature.