Trace Metals in Geothermal Fluids: I. Metal Behaviour at the Deep Source

Abstract

The solubility of gold and bornite-magnetite have been calculated at magmatic conditions in order to investigate gold and copper mobilities in magmatic fluids. These calculations show that metal solubilities are dominated by chloride complexes, although may be important under certain conditions. Metal volatility calculations show that copper is transported exclusively as chloride species while gold is present as a sulphide in the low density aqueous phase. This suggests a strong control on the ratios in the low density aqueous phase formed after phase separation. Highly reduced fluids would be deficient in copper while oxidizing fluids would carry large copper concentrations but insignificant gold.