Influence of dislocations on water leakage from fluid inclusions in quartz: a quantitative reappraisal
Cordier, Patrick; Doukhan, Jean Claude; Ramboz, Claire
European Journal of Mineralogy Volume 6 Number 6 (1994), p. 745 - 752
published: Nov 30, 1994
manuscript accepted: Apr 7, 1994
manuscript received: Oct 11, 1993
ArtNo. ESP147050606001, Price: 29.00 €
Abstract Selective leakage of H2O from homogeneous fluid inclusions in quartz has been proposed as a possible mechanism for the formation of pure CO2 inclusions in metamorphic rocks. Such a leakage can occur because water is soluble and diffuses in the quartz lattice. Dislocations are preferential sites for the water point defects and preferential diffusion paths. A large density of dislocations is likely to enhance water leakage. Several models have been proposed to interpret this water leakage in natural systems. They are reappraised in the present paper from a quantitative point of view. We show that sweeping out water of fluid inclusions through mobile dislocations would require a tremendous amount of deformation. Pipe diffusion along dislocations does not significantly enhance the kinetics of water leakage. Under normal metamorphic conditions the solubility of water is too low to account for water leakage by re-hydration of the host matrix; however, its diffusivity is high enough to allow exchanges between fluid inclusions and the environment. This is the most likely process for water leakage from fluid inclusions in natural rocks.