冀西北麻粒岩相花岗质片麻岩中矿物的流体包裹体特征及其地质意义

本文报道了冀西北地区麻粒岩相片麻岩中矿物内流体包裹体的特征并讨论了其地质意义。根据包裹体的形态、赋存状态并结合包裹体ＣＯ２密度的演化，在麻粒岩相花岗质片麻岩的矿物中可识别出四种类型的流体包裹体：１）一相富ＣＯ２包裹体、２）气液两相富ＣＯ２包裹体、３）三相含液态ＣＯ２包裹体，４）含石盐子晶的多相包裹体。不同类型包裹体的特征和密度等表明，该区花岗质片麻岩经历了三个阶段的变质过程。第一阶段，在麻粒岩相变质作用峰期之后捕获了高密度的富ＣＯ２包裹体。在第二阶段形成了两相富ＣＯ２包裹体。第三阶段捕获了低密度的三相含液态ＣＯ２包裹体。这种很低密度的流体包裹体反映了晚期变形和退变质期间的温压条件

Characterastics of Fluid Inclusions from Granitic Gneisses in Northwestern Hebei Province and Their Geological Significance

According to the morphology and attitude of inclusions and in considerations of the density evolution of CO 2, four types of the fluid inclusions in granitic gneisses metamorphozed to granulite facies could be divided, 1)single phase CO 2 rich inclusions, 2) CO 2 rich inclusions with gas fluid binary phases, 3)triple phase inclusions with fluid CO 2, and 4) polyphase inclusions with halite.The morphology, homogenization temperatures and densities of different types of the inclusions indicate that the granitic gneisses in the area underwent metamorphism in the three stages. In the first stage, single phase CO 2 rich inclusions with high density were trapped after the peak of granulite facies metamorphism. The homogenization temperature and density of the inclusions formed in the stage exhibit isotemperature depressional evolution. In the second stage, binary phase CO 2 rich inclusions with lower density were formed during amphibolite facies retrometamorphism. In the third stage, triple phase inclusions with fluid CO 2 and the lowest density were trapped. The lowest density of inclusions in granitic gneisses reflects the temperature and pressure conditions during shear deformation and retrometamorphism.