Preferential water leakage from fluid inclusions by means of mobile dislocations

Abstract

THE fluid density, carbon dioxide content, and therefore the pressure-temperature conditions derived from fluid inclusions in meta-morphic rocks are commonly inconsistent with coexisting mineral assemblages. Here we report hydrothermal experiments mimicking isobaric cooling and isothermal decompression, which indicate changes in density and composition without significant change in volume of H2O–CO2 inclusions in quartz. A simultaneous change to CO2-rich compositions and lower densities indicates that water is leaking from the inclusions. We argue that preferential water leakage is made possible by microscopic unmixing of the H2O–CO2 mixture caused by physical and chemical interactions with the inclusion wall. Water transport then occurs by the movement of water-saturated dislocations through the hydrothermally recrystallizing quartz.