大别超高压变质带流体包裹体的组合关系与演变

Fluid inclusion associations and their development in the Dabie UHP zone

对大别超高压变质带主要构造单元各类地质体岩石中的流体包裹体进行了岩相学和相变温度的观察与测定。流体包裹体类型和成分特征显示 ,与超高压变质、早期退变质有关的流体成分主要属于盐 -H2 O体系 ,减压熔融释放的流体成分主要属于NaCl-CO2 -H2 O体系 ,脆性变形期间涉及的成分流体主要属于NaCl-H2 O体系。由于超高压变质岩系的快速折返抬升造成的压力迅速降低等影响 ,各个事件中形成的流体包裹体都发生了程度不同的颈缩及爆裂等捕获后变化 ,其密度大都已不能反映捕获时的状态。超高压变质和退变质岩石中常常叠加了与不同流体事件有关的流体包裹体组合 ,因此 。

The fluid inclusions in several types of rocks in the Dabie UHP zone were systematically investigated in the aspects of petrography and temperature of phase change. The results indicate that the fluid components related to UHP and early retrograde metamorphism belonged to salt_H 2O system, those released from partial melting to NaCl_CO 2_H 2O system and those related to brittle deformation to NaCl_H 2O system. As the effect of pressure decreased in the quick exhumation episode of UHPM rocks, and such changes after trapping as necking_down and explosion occurred in varying degrees in fluid inclusions of all events, the present densities of the fluid inclusions mostly do not reflect the state of the trapping, and their isochores are not suitable for the estimation of trapping temperatures and pressures. The fluid inclusion associations related to distinct fluid_related events were often superimposed on the rocks in UHP and retrograde metamorphism, and hence the geological explanation for chemical and isotopic composition of fluid inclusions based on bulk inclusion analysis is subject to some risk.