A TEM Study on Fluid Inclusions in Coesite-bearing Jadeite Quartzite in Shuanghe in the Dabie Mountains

摘要

Fluid inclusions at a nano to sub-micron scale in quartz from jadeite quartzite at Shuanghe, Dabie Mountains, have been investigated by using the transmission electron microscopy (TEM). Most fluid inclusions are spherical or negative crystal shaped, forming wide swarm-like trails. The TEM reveals that the relationship between coesite and the host quartz is syntaxic and provides strong evidence of the occurrence of high-salty fluids at peak metamorphic conditions. The fluid inclusions are often connected to dislocations, which are undetected at the scale of optical microscopy. Nondecrepitation leakage of fluid inclusions may occur by pipe diffusion of molecule H_2O or CO_2 along dislocations from the inclusions into the host quartz, thus leading to original inclusion density and composition changes. It should be taken into lull account for the correct petrological interpretation of micro-thermometric results.