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 H 2 O and CO 2 but also S and, in turn, Au. Elevated gold in solution is achieved by complexing with reduced S, and by H 2 CO 3 weak acid buffering near the optimal fluid pH for gold…

• BG
  Barrick Gold Corporation
• NC
  Newmont Corporation