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首页> 外文期刊>Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen >A clockwise P-T path of anatectic metapelites from Wadi Shiban: implication for crustal evolution in southwestern Yemen
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A clockwise P-T path of anatectic metapelites from Wadi Shiban: implication for crustal evolution in southwestern Yemen

机译：Wadi Shiban的钙质变质岩的顺时针P-T路径：也门西南部地壳演化的意义

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摘要

Microstructural relations and the inferred sequence of mineral reactions indicate that Wadi Shiban metapelites in southwestern Yemen developed in response to continuous P-T changes during a single metamorphic event. The rocks followed a clockwise P-T path involving decompression during cooling. The prograde evolution was characterized by muscovite and biotite volatile phase absent-melting reactions. Retrograde metamorphism involved formation of intergrowths of plagioclase + biotite + quartz muscovite or chlorite + plagioclase + quartz + biotite + magnetite on garnet grains in proximity to leucosomes as well as formation of late muscovite after sillimanite, alkali feldspar and garnet. Geothermobarometric calculations indicate 813 degrees C and similar to 7.5 kbar for the metamorphic peak followed by decompression at similar to 751 degrees C. The high T/P ratio (> 100 degrees C/kbar) inferred for the Wadi Shiban metapelites close to the metamorphic peak suggests an additional heat input, probably due to significant thinning of the mantle lithosphere causing rapid heating of the overlying crust. However, the P-T path indicates that the crust in southwestern Yemen involved initial crustal thickening and burial of the sediments (similar to 22 km deep), followed by rapid tectonic exhumation during cooling to a shallower level (similar to 7 km deep).
机译：微观结构关系和矿物反应的推断序列表明，也门西南部的瓦迪石板变质岩是在单个变质事件中响应连续的P-T变化而发育的。岩石遵循顺时针P-T路径，涉及冷却过程中的减压。白云母和黑云母挥发相不发生熔融反应就表明了其演化。逆行变质作用包括在石榴石粒上靠近白垩质的斜长石+黑云母+石英白云母或绿泥石+斜长石+斜长石+磁铁矿共生物的形成以及在硅线石，碱长石和石榴石后形成晚白云母。地热大气法计算表明，变质峰的温度为813摄氏度，接近7.5 kbar，随后在751℃时进行减压。推断出接近变质峰的Wadi Shiban变质岩的高T / P比（> 100摄氏度/ kbar）。暗示了额外的热量输入，这可能是由于地幔岩石圈的明显变薄导致了上覆地壳的快速加热。但是，P-T路径表明也门西南部的地壳涉及初始的地壳增厚和沉积物的埋葬（约22 km深），随后在冷却至较浅的水平（约7 km深）时迅速进行了构造掘出。

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