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首页> 外文期刊>Proceedings of the National Science Council, Republic of China, Part A. Physical Science and Engineering >Ultrahigh-Pressure Metamorphism: an Overview
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Ultrahigh-Pressure Metamorphism: an Overview

机译：超高压变质作用：概述

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摘要

The ultrahigh-pressure (UHP) metamorphism was defined as the metamorphism occurring under pressure conditions higher than the quartz-coesite equilibrium curve. Based on the discovery of microdiamond and coesite inclusions, UHP metamorphic rocks of crustal origin have been reported from five continent-collision orogenic belts around the world. This shows that crustal rocks can be subducted to mantle depths (>100 km) during continental collision. Several minerals/mineral assemblages characteristically relevant to UHP conditions have also been established established through experimental studies. A fast exhumation rate, the absence of a fluid phase and the continuous refrigeration effect during exhumation are required to preserve UHP minerals at the Earth's surface. However, the restricted occurrence of UHP minerals makes it difficult to confidently establish a regional scale for some UHP terranes. It was demonstrated that water activity in fluid phase during UHP metamorphism was low. "Excess Ar" was also shown to be commonly incorporated within UHP minerals, causing difficulties in Ar geochronology. Age dating of UHP rocks combined with petrologic pressure-temperature studies revealed that the exhumation rate of UHP rocks from mantle depths to -the lower crustal level was higher than 7-14 mm/yr. The geodynamic model for the exhumation mechanism(s) of these UHP terranes, however, remains controversial due to the lack of key constraints.
机译：超高压（UHP）变质被定义为在高于石英-Coiteite平衡曲线的压力条件下发生的变质。基于微金刚石和柯氏岩包裹体的发现，已经从世界上五个大陆碰撞造山带中发现了地壳来源的超高压变质岩。这表明在大陆碰撞期间地壳岩石可以俯冲到地幔深度（> 100 km）。通过实验研究，还建立了一些与超高压条件有关的矿物/矿物组合。为了将UHP矿物保存在地球表面，需要快速的发掘速率，没有液相以及在发掘过程中具有持续的制冷效果。但是，UHP矿物的出现受到限制，因此很难自信地为某些UHP地层建立区域规模。结果表明，UHP变质过程中的液相水活度较低。还显示出“过量Ar”通常掺入UHP矿物中，从而导致Ar年代学方面的困难。 UHP岩石的年龄定年结合岩石学的压力-温度研究表明，UHP岩石从地幔深度到低地壳水平的掘出速率高于7-14 mm / yr。但是，由于缺乏关键约束，这些UHP地形挖掘机制的地球动力学模型仍然存在争议。

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