Petrological and Tectonic Investigations of High Pressure Metamorphism in NE Oman

阿曼东北部Saih Hatat盆地基底和陆相台地沉积中赋存蓝片岩、c型榴辉岩等高压变质岩。蓝片岩和榴辉岩在构造上构成了一个由两个含低品位高压变质组合的逆冲桩覆盖的连贯原位地形。整个层序被塞梅尔蛇绿岩推覆体覆盖。这些高压变质岩的构造背景是独特的，因为它们出现在没有经历大陆碰撞的被动大陆边缘，并且它们与未变质的特提斯塞梅尔蛇绿岩推覆体的结构关系。国家科学基金会被要求提供为期两年的支持，继续对阿曼东北部的高压变质进行详细的野外、岩石学、地球化学和地质年代学研究。本研究旨在(a)限制变质作用的压力-温度条件，重建不同构造地形的压力-温度-时间路径(b)建立高压变质岩不同岩性的成岩网格；(c)确定这些构造域的变质作用年龄和隆升速率。本研究结果将约束阿曼高压变质作用与蛇绿岩侵位之间的关系，并将用于开发一个构造模型，该模型将对大规模构造事件具有足够的时间控制。本研究的最终目的是解释为什么高压变质作用是在大陆边缘下没有大陆-大陆碰撞或洋壳俯冲的情况下形成的。

Blueschists, type-C eclogites and other high pressure metamorphic rocks occur in the basement and continental platform deposits of the Saih Hatat culmination in northeastern Oman. The blueschists and eclogites constitute a coherent in situ terrain structurally overlain by two thrust piles containing lower-grade high pressure metamorphic assemblages. The entire sequence is overlain by the Semail ophiolite nappe. The tectonic setting of these high pressure metamorphic rocks is unique given their occurrence in a passive continental margin that has not undergone continent-continent collision and their structural relations to the unmetamorphosed Tethyan Semail ophiolite nappe. The NSF is requested to provide two-year support to continue a detailed field, petrological, geochemical and geochronological study of high pressure metamorphism in NE Oman. This study is aimed at (a) constraining the pressure-temperature conditions of metamorphism and reconstructing the pressure-temperature-time paths of the different structural terrains (b) developing petrogenetic grids for the various lithologies of the high pressure metamorphic rocks; and (c) establishing the ages of metamorphism and uplift rates of these domains. The results of this study will constrain the relationship between high pressure metamorphism and ophiolite emplacement in Oman and will be used to develop a tectonic model that will have sufficient temporal control on the large-scale tectonic events. The ultimate goal of this research is to explain why high pressure metamorphism developed in the absence of continent- continent collision or oceanic crust subduction beneath the continental margin.