Some effects of tectonic recrystallisation on fluid inclusions in vein quartz

Abstract

Filling temperature data obtained from tectonic vein quartz varies according to the state of intracrystalline deformation. Strain free domains within grains exhibit abundant primary fluid inclusions, from which internally consistent temperatures are recorded. The onset of optical features associated with intracrystalline deformation by dislocation creep is accompanied by a decrease in the number of fluid inclusions and an increase of filling temperatures. At higher states of strain tectonic recrystallisation, evidenced by the formation of new subgrains, leads to the complete destruction of inclusion arrays. Empty cavities are swept out of the new grains during recrystallisation, into subgrain walls. Heterogeneous deformation of vein quartz at the intracrystalline level may be due in part to selective hydrolytic weakening in areas where fluid inclusions have leaked and thereby increased the structural water content.