Wed 29th May @ noon, Rm 312.222

Abstract:

Fluid inclusion gas analysis by mass spectrometry is a rare yet valuable geochemical tool used to tease out additional information from geothermal and hydrothermal systems but also from other geologic materials.  This talk is subdivided into two sections, the first dealing with the methodology and gas interpretation.  The second is a series of case histories that range from ore deposits to space exploration to ancient oxygen, and more.

Fluid inclusion gas interpretation can: discriminate fluid sources, identify processes, constrain redox, apply gas geothermometry, correct isochores, and provide key data for calculating metal solubility of hydrothermal fluids.  Some recent key findings include measuring Neoproterozoic oxygen levels at 10-12% pO2 from halite.  Also, methane was the killer cause of the end-Permian mass extinction.  At the Hishikari gold deposit in Japan, the best grades correlate with condensation rather than boiling.  For Mississippi-Valley type Pb-Zn mineralisation, two mechanisms and potentially three fluid sources are evident.  Methane was found in Martian meteorites, providing a potential food source for life on Mars, if it once existed.

The Browne Formation in Australia has been the focus of interest owing to its state of preservation and recently for the measurements of atmospheric oxygen from halite inclusions. Primary halite inclusions were analysed and the atmospheric oxygen found to be 10-12% pO2, suggesting that abundant oxygen was present to allow for the evolution of animal life prior to the Cambrian explosion.

Short bio:

Nigel is an Assistant Professor at the Department of Earth Sciences at Western University. Nigel is a geochemist who specializes in fluid inclusion and geochemical applications to geothermal systems, hydrothermal ore deposits, and petroleum basins.