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

讨论了蛇绿岩形成侵位的构造背景。阿曼和阿联酋的Samail蛇绿岩是世界上最大、研究最深入的蛇绿岩之一，是研究这些过程的理想场所。本研究项目利用高精度的锆石U-Pb年代学和放射性同位素、常量元素和微量元素地球化学方法，研究了蛇绿岩从地壳形成到蛇绿岩下逆冲构造的演化过程。这项工作将集中在侵入蛇绿岩地幔和地壳的晚期岩浆系列，以及变质鞋底内的变质岩和相关的浅色豆荚。地壳和地幔晚期岩浆系列具有同位素和微量元素特征，可归因于蛇绿岩下方的逆冲或俯冲，结合测年和地球化学分析，将确定相对于地壳生长的逆冲或俯冲的时间。来自变质鞋底的类似分析将在逆冲板块内提供补充记录。完整的数据集将提供蛇绿岩构造发展的详细时间记录，并有助于区分现有的蛇绿岩形成模式。蛇绿岩是在大洋扩张中心形成的薄片地壳，随后被推到大陆上。由于蛇绿岩比原地大洋地壳更容易接近，而且经常暴露在地壳和上地幔的横截面上，因此对蛇绿岩的研究在目前洋壳结构和形成过程的模型的发展中发挥了重要作用。然而，蛇绿岩与原地洋壳之间存在化学差异，这表明蛇绿岩可能形成于更复杂的构造环境。为了了解蛇绿岩观测如何应用于洋壳的形成，有必要了解蛇绿岩形成和侵位过程中的构造环境。几位作者提出，蛇绿岩可能形成于新俯冲带的初始发展阶段，因此，对蛇绿岩的研究也可能为深入了解俯冲开始的过程提供帮助。这项拟议的研究将产生Smail蛇绿岩形成的时间和化学记录，从而深入了解蛇绿岩的起源和潜在的俯冲启动过程。

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.