New Perspectives Workshop, September 2014
Presented by AIG Victoria and AusIMM Central Victoria Branch, Romsey Victoria
From crustal-scale 3D models to targets: an example workflow for Victorian orogenic gold systems
Tim Rawling* and Tim Moore
Australian Geophysical Observing System (AGOS), School of Earth Sciences, University of Melbourne, Parkville, Victoria 3010, Australia.
Recent advances in 3D geological modeling software and 2.5D and 3D geophysical forward and inversion modeling algorithms have made these tools ubiquitous in most aspects of geological endeavor. The usability of the newer software interfaces have also blurred the lines between the geologist, geophysicist and 3D modeler, leading to the development of fields such as structural geophysics. However, whist usage workflows for these tools are well embedded within exploration companies, they are typically used mostly at the “pointy” end of the exploration cycle – ie once some level of well or drilling control has been established – from prospect scale exploration to resource development.
A number of government geological organisations now build regional and crustal scale 3D models in much the same way that they once created traditional map sheets (Rawling et al 2011). The models can be used to constrain simulation models that provide significant insights into the way that fluids flow through the earths crust and in particular where these fluids may be focused and result in the development of a variety of ore systems (Schaubs et al 2011). Whist these tools have been available for some time now, the use of integrated regional-scale 3D geological, geophysical and numerical models at the area selection stage of the exploration cycle, is growing but still limited in part due to the lack of robust workflows allowing these less well constrained datasets to be used in a meaningful way.
Here we present an exploration workflow that utilises geophysically constrained regional 3D geological models to target orogenic gold systems in Victoria. We show how the identification of geometry of regional structures can be used to simulate and predict how auriferous fluids would move through the crust during orogenesis. These simulation results are integrated with the regional 3D models to generate potential targets based on the geometry of major faults that provide the plumbing architecture at the time of major fluid flow and then test these targets using a variety of geostatistical analysis.
The final workflow and targeting outcomes are based entirely on freely available datasets produced by the Geological Survey of Victoria and open source geospatial analysis software making the workflow particularly suitable to small exploration houses without access to large budget for the desktop studies.
Schematic workflow “from maps to models to targets
Rawling, T. J., Osborne, C. R., McLean, M. A., Skladzein, P. B., Cayley, R. A., and Williams, B., 2011, Geoscience Victoria 3D Victoria Report 14 – 3D Victoria Final Report: Department of Primary Industries
Schaubs, P., Zhang, Y., and Hill, J., 2011, Deformation – fluid flow numerical models of the Bendigo-Ballarat and Stawell Zones: Understanding fluid flow pathways for gold mineralisation in Western Victoria CSIRO.
About the Speaker
Tim Rawling is the Director of Infrastructure Development with the Australian Geophysical Observing System (AGOS). His recent research has involved the development of regional/crustal-scale 3D and 4D geological models as well as new exploration methodologies involving 3D modeling and finite element simulation. Tim’s background is in structural geology and IT and he has previously worked as a consultant exploration geologist, as the manager of the 3D modelling and simulation programs at the Geological Survey of Victoria, as the MCA lecturer at the University of Melbourne, a commercial programmer and as a researcher at Monash University and the University of Arizona.