University of Tasmania, Australia

Volatile and metal budgets in silicic large igneous provinces

Silicic large igneous provinces involve magma volumes in the order of 10⁴ to 10⁵ km³ being generated in geologically short periods of time. These magmas have enormous potential to concentrate and exsolve volatiles and metals during the final stages of fractionation and solidification. However, the mechanisms of concentration and exsolution, and compositions and amounts of metals and volatiles are poorly known. This project focuses on tracking the evolution of volatiles and metals in the Gawler silicic large igneous province in South Australia. The province is well preserved, well exposed and well understood in terms of architecture and setting. Preliminary research indicates that the volcanic units and intrusions formed from fluorine-rich magmas, and that the high fluorine content influenced the timing and mechanisms of metal transport in the magmas and magmatic-hydrothermal fluids.

The aims are to:

• Document the abundance and location of metals and volatile species in a complete section through the Gawler Range Volcanics and the associated Hiltaba Suite granite
• Determine the principal stages in metal and volatile concentration and loss from the magmas, comparing intrusive versus extrusive emplacement environments
• Establish the proportion of metals and volatiles outgassed to the atmosphere and hydrosphere versus sequestered in magmatic-hydrothermal fluids.

The project will involve a small amount of field work, primarily aimed at sampling the volcanic and intrusive units of the Gawler silicic large igneous province. The major research methods will be geochemical analysis of whole rock samples, minerals and selected melt and fluid inclusions, using a range of microanalytical techniques (LA-ICPMS, Raman, PIXE, EPMA).

OR