大别山碧溪岭和黄镇榴辉岩中绿辉石的结构水:对原岩性质和动力学过程的制约

Water in clinopyroxenes from eclogites of Bixiling and Huangzheng, Dabicshan and geodynamic implications.

运用傅立叶变换红外光谱(FTIR)技术,对大别山碧溪岭和黄镇榴辉岩中的绿辉石进行了详细的结构水观察。绿辉石中普遍含有结构水,以OH^-的形式存在,含量可达～2000ppm(H_2O wt.)。碧溪岭绿辉石的水含量在露头尺度(-150km)上是不均一的,而黄镇绿辉石是均一的(至少在3km的尺度上)。碧溪岭绿辉石水含量的不均一分布和黄镇绿辉石水含量的均一分布都反映的是原岩特征,碧溪岭榴辉岩原岩经历的水-岩相互作用是“隧道式”的而黄镇是“弥散式”的碧溪岭榴辉岩的原岩可能是基性的侵入岩而黄镇榴辉岩的原岩可能是玄武岩。碧溪岭绿辉石的水含量(<1400ppm)明显低于黄镇绿辉石(～1850ppm),这是原岩水含量差异的体现,原岩性质的不同和经历的水-岩相互作用方式的不同造成了原岩水含量的差异。

Clinopyroxenes in eclogites from Bixiling and Huangzhen, Dabieshan have been investigated by FTIR. Structural water occurs in all omphacites as hydroxyl ( OH-) with content up to similar to 2000ppm ( H2O wt.) . Water content is heterogeneous on the outcrop ( similar to 150m) scale at Bixiling and homogeneous at Huangzheng on the 3km scale, and the distribution characteristics were inherited from their protoliths. The water - rock interaction which Dabieshan eclogites' protoliths experienced was channeled for Bixiling and pervasive for Huangzheng. The protolith of Bixiling eclogites was probably gabbroic intrusion and that of Huangzheng eclogites was probably basalt. Water content of Bixiling clinopyroxenes ( < 1400ppm) was significantly lower than that of Huangzheng clinopyroxenes ( similar to1850ppm), which aroses from different protolith and the way of water - rock interaction before subduction.