Biogenic hydrocarbons in fluid inclusions from the aberfoyle tin-tungsten deposit, Tasmania, Australia

Trace components in fluid inclusions from the Aberfoyle tin-tungsten deposit in Tasmania, Australia, were examined by thermal decrepitation-mass spectrometry. The technique involves the decrepitation of fluid inclusions by stepwise heating in the source of a mass spectrometer. In addition to water, other species identified were carbon dioxide and hydrocarbons. Detailed analysis of these hydrocarbons showed that they ranged in carbon number from C₁ up to at least C₃₃ and probably comprised, in part, biological marker compounds, previously unreported in such high-temperature environments. Their presence suggests that the fluid responsible for mineralisation was not entirely magmatic but contained a non-magmatic component evolved through fluid-rock interaction in the sedimentary country rocks.