Formation of gold deposits: A metamorphic devolatilization model

Abstract

A metamorphic devolatilization model can explain the enrichment, segregation, timing, distribution and character of many goldfields such as those found in Archean greenstone belts, slate-belts and other gold-only provinces. In this genetic model, hydrated and carbonated greenschist facies rocks, particularly metabasic rocks, are devolatilized primarily across the greenschist-amphibolite facies boundary in an orogenic setting. Devolatilization operates on the scale of individual mineral grains, extracting not just H2O and CO2 but also S and, in turn, Au. Elevated gold in solution is achieved by complexing with reduced S, and by H2CO3 weak acid buffering near the optimal fluid pH for gold solu..