Experimental transport of Si,Al and Mg in hydrothermal solutions: an application to vein mineralization during high-pressure,low-temperature metamorphism in the French Alps

A study of hydrothermal vein mineralization in meta-argillites subjected to high-pressure, low-temperature metamorphism reveals that ferromagnesian (e.g., chlorite) and pure aluminosilicate (e.g., pyrophyllite) mineralization can be correlated with regimes of increasing and decreasing temperature, respectively. An experimental study of the transport of silica, aluminum and magnesium in hydrothermal solutions has been undertaken to simulate variations in the physical conditions during metamorphism and the accompanying mass transport in a closed system. Thermodynamic and kinetic analysis of the experimental results indicates that local equilibrium among aqueous and mineral phases controls the distribution and composition of hydrothermal vein mineralization and that vein mineralogy can be used to infer the sense of variation of pressure and temperature during metamorphism.