3D structural modelling and implications for targeting gold mineralisation in western Victoria

Abstract

A 150×150 km area of western Victoria has been modelled in three dimensions to a depth of ∼20 km. This was constructed through integrated analysis and serial cross-sections of geological and geophysical datasets, utilising mapped positions of major faults, intrusive bodies and lithostratigraphic packages as primary inputs. These are extrapolated to depth and under cover through interpretation of upward continued multiscale wavelet edges of aeromagnetic and gravity data, inversion of the gravity field and the positions of acoustic boundaries. The objective was to develop an understanding of crustal structure in the context of gold mineralisation potential. The upper crustal structure is modelled as comprising a planar array of northwest-trending, steep to moderate inclined mainly east-dipping faults (Moyston, Pleasant Creek). These are interpreted to merge with a basal detachment (Western Fault). This elongate dome-shaped detachment overlies a buried wedge of inferred Proterozoic basement. We suggest that gold distribution in the upper crust may be influenced by the position in the mid-crust of the leading edge of the wedge and its interface with the mafic substrate that largely encloses it. The Coongee Fault appears to be a first-order regional-scale control on the localisation of gold deposits adjacent to basaltic dome prospects in the Stawell corridor. It represents a backthrust, with superimposed sinistral transpression, and is interpreted to have developed above the mid-crustal ramp detachment. Cross-faults that intersect the Coongee Fault may have high exploration potential for localising both orogenic- and intrusion-related gold.

Key words:

• Delamerian Orogen
• faults
• geophysics
• gravity
• Lachlan Orogen magnetics
• structure

Acknowledgements

We are grateful to the Director of the Predictive Mineral Discovery Cooperative Research Centre and the Directors of Leviathan Resources for financial support during this study. The project would not have come together without the strong support of the Stawell Mines geological team. Fractal Graphics are thanked for provision of the multiscale wavelet data, and aspects of their interpretation by Darren Holden, derived from the potential-field data supplied by GSV and Leviathan Resources. Bob Smith and Kim Frankcome are also thanked for their generous contribution of data and discussion of our interpretation of their inversions. Reviews by Kevin Hill and Vince Morand have improved this paper.