Characterising and mapping alteration
South Australia’s Olympic Cu-Au Province hosts some of the world’s great iron oxide copper gold (IOCG) deposits, such as Olympic Dam, Prominent Hill and Carrapateena. The same thermal event resulted in variants of this deposit class throughout the Olympic Province and includes skarn-dominated mineralisation where hydrothermal fluids interacted with calcareous lithologies. The Punt Hill region, located 105 km NNW of Port Augusta and in the vicinity of the Carrapateena deposit, includes some of the best examples of widespread skarn development in the eastern Gawler Craton. To advance the understanding of mineral systems developed in this region, the South Australian Geological Survey (GSSA) in collaboration with Monax Mining Limited, used the Punt Hill region as a case study for developing a multi-disciplinary approach to characterise, map and predict alteration associated with skarn-dominated mineralisation.
The GSSA used historical drillholes and drill core provided by Monax Mining Limited to systematically acquire co-located geochemical, spectral and petrophysical data. These data were collected from a regional and prospect-scale distribution of drillholes. Spectral scans of drill core, in the visible to thermal infrared wavelength range, were made using the HyLogger-3™ hyperspectral core scanner. Selected sample intervals were analysed for 65 elements by ICP methods, and fluorine by specific ion electrode. Drillhole sampling was supplemented by measurements of magnetic susceptibility and specific gravity. Inversion models of regional aeromagnetic and gravity data were generated to improve the understanding of the 3-dimensional distribution of magnetic susceptibility and density in the region.
A 3D model of the Punt Hill region was constructed to view, integrate and interpret all datasets generated in this project. A deposit-scale model (1 km2) around the Groundhog prospect was also constructed and is incorporated in the Punt Hill 3D data package. This model serves as a 3D mineral potential map that displays components of mineral systems developed in the Punt Hill region down to ~5 km depth.
Interpolated copper values shown on the modelled volume of Wallaroo Group (restricted to zones with abundant retrograde alteration minerals), Groundhog 3D model. Plotted next to drillhole traces are specific gravity values (coloured points) and a geochemical index (line plot)
Note: these models are presented as a 'proof of concept' only and their accuracy (spatial or otherwise) should not be relied upon for exploration or other decision making processes.
Publication Date: May 2017
For more information, contact:
Geological Survey of South Australia
+61 8 8429 2556