Chemistry of low-temperature hydrothermal gold, platinum, and palladium (±uranium) mineralization at Coronation Hill, Northern Territory, Australia

Abstract

Mineralization at Coronation Hill occurs below a major unconformity that separates a deformed and metamorphosed basement from a cover sequence of little-deformed hematitic quartz sandstone and sedimentary breccias. Geologic, fluid inclusions, stable isotope, and thermodynamic data indicate that mineralization at Coronation Hill occurred by reaction of highly oxidized and acid basin brines originating from the cover sequence and hydrosphere, with feldspathic and reducing rocks and fluids of the crystalline basement. The two styles of metal enrichment - dominant gold and platinum-group elements (PGE) ores, and subordinate mixed U-Au-PGE ores - can be explained as a result of varying degrees of acid neutralization by feldspars and reduction by carbonaceous matter and ferrous iron in various host rocks. The chemistry of ore deposition has been modeled by the numerical equilibration of the fluid with potash feldspar plus a very small amount of graphite. -from Authors Show more