SMEDG – Notice of Meeting

Thursday, 22nd October, 2009. 5.30pm for 6pm Rugby Club, Rugby Place, Circular Quay

Nigel J. Cook

Geology & Geophysics, School of Earth and Environmental Sciences, University of Adelaide

“Sulphides and their Dirty Secrets”

Common sulphide minerals such as pyrite and sphalerite can carry a wide range of trace elements both as solid solution and as submicro- to nanoscale inclusions. Well-known examples include ‘invisible gold’ in pyrite and valuable by-products such as germanium and indium that are concentrated in sphalerite.

High-precision in situ analytical methods allow measured concentrations to be correlated with preserved ore textures in the refractory phases, clearly illustrating the importance of post-depositional processes on element distribution at the grain scale. Similarly, multi-element analysis allows for correlation between different elements to identify substitution mechanisms and for the generation of models for element behaviour during remobilisation; including a critical assessment of the paradigm of invisible gold concentration being linked to arsenic content. Further breakthroughs include understanding how smallest-scale crystal structures (e.g., polytype or structural defects) can influence the ability of sulphides to carry minor and trace elements or host ‘dirty’ inclusions.

Drawing on examples from different types of ore deposits worldwide, the talk examines the range of exciting new opportunities for applied research using the current generation of microanalytical facilities. As well as pyrite and sphalerite, the talk will address other common sulphides, such as bornite and molybdenite, with respect to correlation between crystal structure, textures and trace element concentration, and how this carries implications for both mineral exploration and ore exploitation.