Low temperature eclogite facies rocks discovered in the Eastern Himalayan Syntaxis: Poly-cyclic metamorphic evolution and implications
Low temperature eclogite facies rocks discovered in the Eastern Himalayan Syntaxis: Poly-cyclic metamorphic evolution and implications
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东喜马拉雅地区发现的低温榴辉岩相岩石：多旋回变质演化及其意义
DOI：
10.1111/jmg.12689
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发表时间：
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影响因子：
3.4
通讯作者：
Zhang Yanling
中科院分区：
文献类型：
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作者：
Li Wangchao;Yin Changqing;Zhang Zeming;Peter A Cawood;Li shun;Zhang Jian;Ding Huixia;Qian Jiahui;Zhang Yanling
我们报告了在新特提斯洋岩石圈俯冲过程中形成的印度-雅鲁藏布江缝合带最东端的多旋回高压低温（HP-LT）岩石的首次出现。岩石学、矿物成分和P-T假剖面建模揭示了两次低温榴辉岩相变质事件，初始高压P-T条件为16.4-18.7 kbar和510-520°C，折返至10.5-12.0 kbar和580-590°C，随后的第二次高压P-T条件为~16 kbar和~560°C，折返至≤9 kbar和≤600°C。独居石测年和结构关系表明，晚期折返、冷却和石榴石破碎发生在c. ~25-22 Ma。我们解释的第一次埋葬事件，代表俯冲的新特提斯洋在东部印度河-雅鲁藏布江缝合带。最初的折返、再埋藏和最后的折返代表了俯冲通道中大规模对流循环系统中的物质输送。俯冲通道中的对流翻转显然是产生多旋回变质作用和发掘LT榴辉岩相岩石的机制。
We report the first occurrence of poly‐cyclic high‐pressure low‐temperature (HP‐LT) rocks from the easternmost Indus‐Yarlung suture zone, formed during subduction of Neo‐Tethyan oceanic lithosphere. Petrology, mineral composition and P–T pseudosection modelling reveal two low‐temperature eclogite facies metamorphic events with an initial high‐pressure P–T condition of 16.4–18.7 kbar and 510–520°C, exhumation to 10.5–12.0 kbar and 580–590°C and a subsequent second high‐pressure P–T condition of ~16 kbar and ~560°C and exhumation to ≤9 kbar and ≤600°C. This history implies a complex ‘yo‐yo type’ P–T path. In situ monazite dating and textural relationships show that late‐stage exhumation, cooling and garnet breakdown occurred at c. ~25–22 Ma. We interpret the first burial event to represent subduction of the Neo‐Tethys Ocean at the eastern Indus‐Yarlung suture zone. Initial exhumation, reburial and final exhumation represent material transport in a large‐scale convective circulation system in the subduction channel. Convective overturn in the subduction channel evidently serves both as a mechanism to produce poly‐cyclic metamorphism and to exhume LT eclogite facies rocks.