Exploration Targeting from Prospectivity Modelling of Multiple Deposit Types in the Lachlan Fold Belt, NSW

Prospectivity modelling has been completed over the Lachlan Fold Belt, New South Wales, Australia, using the GIS based weights of evidence modelling technique to target porphyry Cu-Au, associated skarn Cu-Au, orogenic Au and VMS Au mineralisation. The Lachlan Fold Belt is a 700 km wide belt of Paleozoic accretionary terrains, stretching from Queensland to Tasmania. Porphyry and skarn mineralisation was associated with Ordovician shoshonitic magmatism, which was followed by Silurian regional metamorphism and deposition of orogenic gold deposits. Contemporaneous VMS-style mineralisation resulted in deposits in intra-arc rift basins of the Macquarie Arc. In preparation for the prospectivity modelling, lithological and structural data, extensive geophysical surveys and stream, drill-hole and rock chip geochemistry were used to create predictive maps that represent various parts of the mineral systems being modelled. Included in the models are maps that identify possible sources of heat and mineralised fluids, structures used for fluid migration, mineral trap zones, and outflow zones that may indicate a subsurface deposit. Prospectivity maps have been created for each mineralisation style and new areas of each deposit type located. The models have also independently identified areas of proven mineralisation, including Cadia, Northparkes, Woodlawn and other large producing mines. The prospectivity maps were reclassified to generate targets by delineating highly prospective areas from each model. Targets were compared and overlap examined among the four models, before further analysis of high priority targets. Single targets or clusters of targets were individually assessed by incorporating information such as tenure, geology, geochemistry and geophysical signature. Economic and risk factors were assessed and the targets ranked and mapped according to high and low exploration risk. Following this analysis, targets of interest can be highlighted as potential projects for acquisition, or used to prioritise new exploration data collection.