The Neglected Involvement of Organic Matter in Forming Large and Rich Hydrothermal Orogenic Gold Deposits

Orogenic gold deposits have provided most of to humanity. These were formed by fluids carrying dissolved at temperatures 200–500 °C and crustal depths 4–12 km. The model involves mobilization as HS? complexes in aqueous solution buffered CO2, with precipitation following changes pH, redox activity (fO2), or H2S activity. In this contribution, the involvement carbonaceous organic matter is addressed considering formation large and/or rich orogenic three stages: source gold, its solubilization, precipitation. First, accumulates nodular pyrite within carbonaceous-rich sedimentary rocks bacterial reduction sulfates seawater black shales. Second, can be transported hydrocarbon-metal colloidal nanoparticles for which hydrocarbons generated from thermal maturation gold-bearing shales abiotic origin. capacity solubilizing greater than those fluids. Third, precipitated efficiently graphite derived containing reducing organic-rich rocks. Black are thus a key component standpoints source, transport, Unusual CO2-rich, H2O-poor documented some largest richest deposits, regardless their age. interpreted result chemical reactions involving hydrocarbon degradation, hence supporting fundamental role forming exceptional deposits.