Aplication Of Fluid Inclusions In Fault Structure Research

Fluid inclusions are the samples of thermal fluid in structure events and are preserved in a great quantity within fault rocks. Various associations of fluid inclusions are present in the distinct faults with different property in different depth.This paper is concerned with fluid inclusions in quartz from three different property faults with a reverse fault, a ductile shear belt and a detachment fault. Based on previous research, some preliminary conclusions about fluid inclusions in different tectonic environments have been drawn as follows: 1. In extensional tectonic environment of the detachment fault, fluid inclusions with bigger size of grains from 5μm to 20μm, and most of them are H2O-Na Cl-CO2 three-phase inclusions and H2O-Na Cl two-phase inclusions. 2. In compressional tectonic environment of the reverse fault, fluid inclusions with bigger size of grains from 2μm to 6μm and arrange in fixed directions. Most of them are H2O-Na Cl two-phase inclusions, but H2O-Na Cl-CO2 three-phase inclusions are rare. 3. In ductile shear belt, the fluid inclusions rarely occur and have strong deformation. The size of grains less than 5μm. The melt and pure CO2 inclusions appear.By measuring and calculating fluid inclusions, the dissolution line of fluid trapped in quartz can be identified. Combine with dissolution line, geothermal gradient and geostress gradient, a new quantity was proposed in this thesis:Allowable Error Depth( δD).Allowable Error Depth( δD) is a reference quantity, which can be used in aided computing or correcting the fluid inclusions trapping pressure and trapping temperature. Compare with the traditional calculation method of trapping pressure and trapping temperature, the new δD method can get more accurate data.By the new method, different phase fluid inclusions in one syngenetic structure sample have been discovered. This discovery suggests that the fluid inclusions record a process of the fault evolution rather than a fragment of the fault evolution. Moreover, by use this method can find the thermal event in fault evolution. In the end, a hypothesis about fluid migration in fault evolution is designed to explain multiphase fluid inclusions are preserved in one sample.