Wed 1st November @ noon, Rm 312.222
Abstract:
The anomalous sulfur isotopic signature ∆33S0 ≠ 0‰ that occurs in a restricted range of sulfur-bearing rock types throughout the geological record has been used to assess the surficial nature of the biological and atmospheric and hydrological sulfur cycle through time. It is widely accepted that ∆33S0 anomalies (∆33S0 > ±0.2‰) were formed in the Archean eon, largely through mass independent fractionation of sulfur (MIF-S) in an oxygen-poor atmosphere and imparted to the Archean supracrustal rock record (as MIF-S0). In this talk, I demonstrate examples of how we are harnessing the indelible MIF-S0 signature to trace sulfur pathways to mineral systems where the signature is recycled as MIF-S1. For instance, study of the Waroonga Archean orogenic gold deposit demonstrates that gold-bearing arsenopyrite yield ∆33S1 = +0.3‰, indicating that sulfur, the complexing ligand for gold transport, was sourced at least partially from the Archean sediment record. When these spatially- and temporally-constrained measurements are combined with detailed chemical maps of arsenopyrite, we demonstrate that the Archean sediment reservoir was likely devolatilised at depth. Ore deposits (leaving aside their economic significance) are loci where mass and energy concentrative processes take place, being the ideal natural laboratories to study volatile pathways. The outcomes from these studies have the potential to greatly enhance the application of MIF-S1 (∆33S1) as a powerful tracer of sulfur pathways through the lithosphere.
Short bio:
Crystal attended Acadia University for her BSc. She then completed regional-scale mapping projects for her MSc at Memorial University of Newfoundland, and PhD at the University of New Brunswick in the Canadian Shield of Labrador and Nunavut. Presently, as a postdoctoral researcher at the Centre for Exploration Targeting, University of Western Australia, she studies how the nature of volatiles can enhance our understanding of lithospheric-scale tectonic processes by linking mineral systems, tectonics and geochemistry.
