TY - JOUR
T1 - Gilt by association? Origins of pyritic gold ores in the Victory mesothermal gold deposit, Western Australia
AU - Palin, J M
AU - Xu, Ying
PY - 2000
Y1 - 2000
N2 - Sulfur isotope data and calculated fluid-rock reaction paths constrain the origin of pyritic gold ores in the Victory inesothermal gold deposit of Western Australia. Pyrite ? 34S values range from -4.4 to +5.1 and are negatively correlated with gold tenor in mafic host rocks, indicating a significant increase in fluid oxidation state accompanied mineralization. Geologic evidence argues strongly that mineralization occurred with wall-rock sulfidation, but this process alone cannot produce the degree of fluid oxidation necessary to explain the sulfur isotope range. In contrast, either carbonation of ferric iron-bearing minerals or separation of immiscible fluid phases, both of which are consistent with the available geologic data, can drive fluid oxidation to the point of aqueous sulfate dominance. Coupled decreases in gold solubility and sulfide sulfur isotope values that are predicted by such a scenario provide an explanation for the trend between ? 34S and gold tenor observed at Victory. Because both wall-rock carbonation and fluid phase separation involve loss of aqueous sulfide but do not require precipitation of iron sulfides, these processes may explain the poor correlation between gold tenor and pyrite abundance in many mesothermal deposits and the occurrence of some gold ores in iron-poor rocks.
AB - Sulfur isotope data and calculated fluid-rock reaction paths constrain the origin of pyritic gold ores in the Victory inesothermal gold deposit of Western Australia. Pyrite ? 34S values range from -4.4 to +5.1 and are negatively correlated with gold tenor in mafic host rocks, indicating a significant increase in fluid oxidation state accompanied mineralization. Geologic evidence argues strongly that mineralization occurred with wall-rock sulfidation, but this process alone cannot produce the degree of fluid oxidation necessary to explain the sulfur isotope range. In contrast, either carbonation of ferric iron-bearing minerals or separation of immiscible fluid phases, both of which are consistent with the available geologic data, can drive fluid oxidation to the point of aqueous sulfate dominance. Coupled decreases in gold solubility and sulfide sulfur isotope values that are predicted by such a scenario provide an explanation for the trend between ? 34S and gold tenor observed at Victory. Because both wall-rock carbonation and fluid phase separation involve loss of aqueous sulfide but do not require precipitation of iron sulfides, these processes may explain the poor correlation between gold tenor and pyrite abundance in many mesothermal deposits and the occurrence of some gold ores in iron-poor rocks.
U2 - 10.2113/gsecongeo.95.8.1627
DO - 10.2113/gsecongeo.95.8.1627
M3 - Article
VL - 95
SP - 1627
EP - 1637
JO - Economic Geology; Bulletin of the Society of Economic Geologists
JF - Economic Geology; Bulletin of the Society of Economic Geologists
ER -