Timescales of Development of Sub-Ophiolite Subduction: High Precision U-Pb Dating and Geochemical Characterization of Late Magmatism and Metamorphism in the Oman-U.A.E. Ophiolite

对蛇绿岩形成和侵位时的构造环境进行了讨论。阿曼和阿拉伯联合酋长国的Samail蛇绿岩是世界上最大的蛇绿岩，也是研究得最好的蛇绿岩之一，是研究这些过程的理想场所。本项目利用高精度U-Pb锆石年代学、放射性成因同位素、主微量元素地球化学等方法，研究蛇绿岩地壳形成到蛇绿岩下方逆冲发育的演化过程。研究的重点是侵入蛇绿岩地幔和地壳的晚期岩浆系列，以及变质底内的变质岩及其伴生的白质豆角岩。地壳和地幔中晚期岩浆系列的同位素和微量元素特征归因于蛇绿岩下方的逆冲或俯冲作用，结合年代测定和地球化学分析将确定逆冲或俯冲的时间与地壳生长有关。变质鞋底的类似分析将提供推力下板块内的补充记录。完整的数据集将提供蛇绿岩构造发育的详细时间记录，并有助于区分现有的蛇绿岩形成模型。蛇绿岩是在海洋扩张中心形成的地壳薄片，随后被推入大陆。由于蛇绿岩比海洋地壳更容易接近，并且经常暴露出地壳和上地幔的截面，因此对蛇绿岩的研究在目前海洋地壳结构和形成过程模型的发展中发挥了重要作用。但蛇绿岩与原位洋壳的化学成分存在差异，表明蛇绿岩可能形成于更为复杂的构造环境。为了了解蛇绿岩观测如何应用于海洋地壳的形成，有必要了解蛇绿岩形成和侵位时的构造环境。一些学者提出蛇绿岩可能形成于新的俯冲带的初始发育阶段，因此对蛇绿岩的研究也可能为俯冲起始过程提供新的认识。提出的研究将生成Semail蛇绿岩形成的时间和化学记录，为蛇绿岩的起源和潜在的俯冲起始过程提供见解。

The tectonic setting during ophiolite formation and emplacement are debated. The Samail ophiolite in Oman and the United Arab Emirates is the largest and one of the best-studied ophiolites in the world, and is an ideal place to study these processes. This research project uses high precision U-Pb zircon geochronology and radiogenic isotope, major and trace element geochemistry to study the evolution from formation of the ophiolite crust to development of thrusting below the ophiolite. The work will focus on late magmatic series that intruded the ophiolite mantle and crust, and metamorphic rocks and associated leucocratic pods within the metamorphic sole. The late magmatic series in the crust and mantle have isotopic and trace element signatures that have been attributed to thrusting or subduction below the ophiolite, and the combined dating and geochemical analyses will determine the timing of thrusting or subduction relative to crustal growth. Similar analyses from the metamorphic sole will provide a complimentary record within the under-thrust plate. The complete dataset will provide a detailed temporal record of the tectonic development of the ophiolite and help to differentiate between existing models of ophiolite formation. Ophiolites are thin slices of crust that formed at oceanic spreading centers and subsequently thrust onto the continents. Because ophiolites are easier to access than in-situ oceanic crust, and often expose cross sections through the crust and upper mantle, research on ophiolites has played a major role in the development of current models for the structure of the oceanic crust and the processes that form it. However, there are chemical differences between ophiolites and in-situ oceanic crust, which suggest ophiolites may form in more complex tectonic environments. To understand how observations from ophiolites can be applied to the formation of the oceanic crust, it is necessary to understand the tectonic setting during formation and emplacement of ophiolites. Several authors have proposed that ophiolites may form during the initial development of new subduction zones, and as a result, research on ophiolites may also provide insight into the processes of subduction initiation. The proposed research will generate a temporal and chemical record of the formation of the Semail ophiolite, providing insight into both the origin of ophiolites and potentially the processes of subduction initiation.