Acta Scientiarum Naturalium Universitatis Pekinensis

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Fluid-Rock Equilibrium System of Archean Wanzi Rock Series in Taihang Mountains

LIU Shuwen, LIANG Haihua, HUA Yonggang   

  1. Department of Geology, Peking University, Beijing, 100871
  • Received:1998-02-16 Online:1999-03-20 Published:1999-03-20


刘树文, 梁海华, 华永刚   

  1. 北京大学地质学系,北京,100871

Abstract: The Archean metamorphic layering rock series in the Taihang Mountains consist mainly of Al-rich gneiss, various marbles, granulitites and others. There is marked difference in Equilibrium fluids' composition between Al-rich gneiss and marbles. Metamorphic fluid equilibrating with diopside-marble and fosterite-marble presents x(H2O)=0.02-0.07, however, these equilibrating with Al-rich gneiss has higher water, x(H2O)=0.27-0.747. There is a great disparity among different rocks in fluid composition in a small area. Fluid composition is controlled by lithology. The mole fraction of water in metamorphic fluid of Al-rich gneiss is higher and the one in marbles is extremely lower, implying that inner buffering plays a leading role in the fluid/rock equilibrium system of the Wanzi layering rock series. This forms a sharp contrast to the fluid/rock equilibrium system with infiltration playing a dominant role in the Fuping gneiss complex. The infiltration of the Fuping gneiss complex and buffering of the Wanzi layering rock series in the fluid/rock equilibrium system suggest that they formed at different tectonic levels of the earth.

Key words: fluid composition, buffers, Wanzi layering rock series, Taihang mountains

摘要: 太行山太古宙湾子变质层状岩系主要由富铝片麻岩、各类大理岩、变粒岩等组成。富铝片麻岩和大理岩类岩石中平衡流体成分相差甚大:与透辉大理岩和橄榄大理岩平衡的变质流体成分x(H2O)=0.02~0.07,近于纯二氧化碳;与富铝片麻岩平衡的流体成分则含有相对较高的水,x(H2O)=0.27~0.747。不同成分的岩石在很小区域内变质流体成分存在较大差别,它们主要受岩性控制。富铝片麻岩水的摩尔分数较高,大理岩水摩尔分数极低,反映了它们的流体岩石平衡体系以内部缓冲作用为主。这与阜平片麻杂岩的以渗透作用为主的流体岩石平衡体系形成了鲜明的对比,反映了湾子变质层状岩系与阜平片麻杂岩形成于不同的构造层次。

关键词: 流体成分, 缓冲作用, 湾子岩系, 太行山

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