Alteration mapping of the Tarcoola Goldfield (South Australia) using a suite of hyperspectral methods

Abstract

A suite of hyperspectral methods (Hyperion, HyMap, HyLogger, PIMA II and ASD) was used to examine the mineralogy of the Tarcoola Goldfield in central South Australia, 650 km northwest of Adelaide. The area has produced over 75 000 ounces of Au from quartz veins crosscutting Proterozoic shallow marine sedimentary rocks on granitic basement. A further measured resource of 65 000 ounces Au has been identified in recent drilling. The mineralization and associated alteration are characteristic of several new gold prospects located in the central Gawler Craton. Spectral logging of drill core supports a hydrothermal paragenesis with overprinting supergene enrichment. Kaolin/iron oxide mineral distribution defines the weathered zone in which the presence of smectite or alunite correlates with supergene Au enrichment. Hydrothermal alteration, as hematite and sericite, is pervasive in the unweathered host rocks and a positive correlation between phengitic white mica content and elevated Au values is observed. At Tarcoola, surface spectral signatures show clear zonation, defined by crystalline illite, which are associated with both stratigraphically-controlled, and cross-cutting, mineral alteration. Airborne and ground spectral techniques have a role in exploration for Au in the Gawler Craton in highlighting areas of possible hydrothermal alteration in weathered surface outcrop.