Link between gold provinces

Abstract

Low-salinity, high-temperature (>200°C), reducing fluids are poorly represented in ore-forming processes, yet appear to account for 90% of the primary gold mined to date. Metamorphism of chlorite-calcite-albite-quartz assemblages at the greenschist-amphibolite facies boundary occurs around 480° ± 20°C (for 3-5 kbar) and produces large volumes of low-salinity, H2O-CO2 fluid similar in composition to those recorded in many gold deposits. Widespread pyrite in the above assemblage typically leads to elevated levels of dissolved sulfur. Such conditions are ideal for gold transport as a molecular Au-S complex and can lead to deposits rich in gold relative to silver and base metals. Low-salinity fl..