Subsolidus segregation of quartz in metamorphic differentiation of metasedimentary rocks

Resumo

Thermodynamic modeling of the SiO₂–TiO₂–Al₂O₃–Fe₂O₃–MnO–MgO–CaO–Na₂O–K₂O–P₂O₅–H₂O (STAFMMCNKPOH) system at 600°C, 5 kbar has been applied to investigate dissolution and re-precipitation of quartz. Comparing silica molality in the STAFMMCNKPOH and SiO₂–H₂O systems, there is seen to be no effect of mineral assemblage on quartz solubility. From quantitatively estimated water/rock ratio required to dissolve quartz completely, one can deduce that the segregation of quartz appears to be due to diffusive transport of silica in inner pore fluid rather than to advective transport (in fluid flow).