Exploration for volcanic-hosted sulfide deposits in western Tasmania

Abstract

The Cambrian Mt. Read Volcanics are currently being actively explored by numerous companies for volcanic-hosted massive sulfide deposits of a similar type to those currently producing (Mt. Lyell, Rosebery, and Hercules), all of which resulted from discoveries by the early prospectors between 1883 and 1898. The only significant modern discovery has been the Que River deposit, scheduled to commence production in 1981.A review of the two main deposit types assists in the identification of those characteristics that may be detected by current exploration techniques and indicates the limitations of specific techniques.The region is characterized by rugged terrain, thick vegetation, locally abundant glacial overburden, and a cool wet climate. These factors result in access and logistical problems similar to those experienced in northern Canada and Scandinavia. Reconnaissance stream sediment surveys (and airborne electromagnetic surveys in less rugged areas), supported by regional geologic mapping and mineral occurrence data, define prospective sequences and areas. Detailed prospect evaluation programs involve the initial cutting of grid lines through the rain forest, systematic geologic mapping, geochemical surveys of C horizon soil samples, ground magnetic and induced polarization surveys. The resultant anomalies are evaluated by costeaning and pitting before testing by diamond drilling.Although the exploration strategy and techniques discussed reflect the experiences of the Mt. Lyell Mining and Railway Company Limited since 1966, they may be considered as representative of western Tasmanian exploration practices in general.