THE INFLUENCE OF CO2 ON THE SOLUBILITY OF QUARTZ IN SINGLE-PHASE HYDROTHERMAL FLUIDS: IMPLICATIONS FOR THE FORMATION OF STOCKWORK VEINS IN PORPHYRY COPPER DEPOSITS

摘要

Porphyry copper deposits consist of low-grade stockwork and disseminated sulfide zones that contain characteristic vein generations formed during the evolution of the hydrothermal systems. The present contribution examines the influence of variable CO2 concentrations on the solubility of quartz in single-phase hydrothermal fluids forming stock-work veins in porphyry deposits at temperatures of 150 degrees to 550 degrees C and pressures ranging from 100 to 2,000 bar at concentrations up to 8 mol % CO2. The calculations demonstrate that quartz solubility in hydrothermal fluids decreases with increasing CO2 content. Retrograde quartz solubility is less pronounced in CO2-bearing fluids and is not observed in single-phase fluids having CO2 concentrations exceeding 6 mol %.