The geological characteristics of oceanic-type UHP metamorphic belts and their tectonic implications: Case studies from Southwest Tianshan and North Qaidam in NW China
The geological characteristics of oceanic-type UHP metamorphic belts and their tectonic implications: Case studies from Southwest Tianshan and North Qaidam in NW China
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DOI：
10.1007/s11434-008-0386-2
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发表时间：
2008-09
影响因子：
--
通讯作者：
Lifei Zhang;Z. Lü;Guibin Zhang;Shuguang Song
中科院分区：
文献类型：
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作者：
Lifei Zhang;Z. Lü;Guibin Zhang;Shuguang Song
总结了洋壳深俯冲形成的超高压变质带的地质特征。大洋型超高压变质带具有典型洋壳的原石器组合特征，峰期变质温度为600°，在进退变质演化过程中分别经历蓝片岩相，冷俯冲地温梯度低。对大洋型超高压变质带的深入研究，对于建立冷俯冲带变质反应系列，了解水流体如何运移到深部地幔，划分冷俯冲带超高压变质作用类型具有重要意义。大洋超高压变质岩的抬升和折返机制是超高压变质作用研究中最具挑战性的问题之一，对于理解固体地球的地球动力学机制具有重要意义。大洋型超高压变质带作为俯冲到地幔深部再抬升到地表的旅行者，见证了从俯冲到折返的整体过程，是研究俯冲带元素地球化学行为和循环的理想靶区。一个会聚造山带的构造演化通常可以分为大洋俯冲和随后的大陆俯冲和碰撞两个阶段，其中最著名的两个造山带是阿尔卑斯山和喜马拉雅。因此，洋型超高压变质带的研究是当前板块构造理论的前沿。本文以中国为例，回顾了西南天山和柴达木北部洋型超高压变质带的研究现状和存在的问题。
The geological characteristics of ultrahigh-pressure (UHP) metamorphic belts formed by deep subduction of oceanic crust are summarized in this paper. Oceanic-type UHP metamorphic belt is characterized by its protolithic assemblage of typical oceanic crust, the peak metamorphic temperature <600°,P-Tpath undergoing blueschist facies during prograde and retrograde metamorphic evolution, respectively, with low geothermal gradient of cold subduction. The further study of oceanic-type UHP metamorphic belt is very significant for constructing metamorphic reaction series of cold subduction zone, for understanding how aqueous fluids were transported into deep mantle and for classifying the types of UHP metamorphism in cold subduction zone. The uplift and exhumation mechanism of oceanic UHP metamorphic rocks is one of the most challenging problems in the study of UHP metamorphism, which is very important for understanding the geodynamic mechanism of solid Earth. As a traveler subducted into the mantle depth and then uplifted to the surface, oceanic-type UHP metamorphic belts witness the bulk process from the subduction to exhumation and is an ideal target to study the geochemical behavior and cycling of elements in subduction zones. The tectonic evolution of one convergent orogenic belt can be usually divided into two stages of oceanic subduction and followed continental subduction and collision, and the two best-established examples of orogenic belts are Alps and Himalaya. Therefore, the study of oceanic-type UHP metamorphic belt is the frontier of the current plate tectonic theory. As two case studies, the current status and existing problems of oceanic-type UHP metamorphic belts in Southwest Tianshan and North Qaidam, NW China, are reviewed in this paper.