Tania Dhu

Geophysical modelling of the Gawler Province, SA – interpreting geophysics with geology

Multi-scale edge detection was applied to potential field data over the Gawler Province in the central part of South Australia. Also known as worming, the multi-scale edge analysis technique can aid identification of structural controls and depth extents of anomalies. A geological interpretation of the multi-scale edge detection results was then undertaken; integrating drill-hole information, ground mapping and tectonic understanding with geophysical modelling to gain a better comprehension of the dominant structures present. The multi-scale edge detection process provides potential solutions for the lack of outcrop, particularly that which is representative of three-dimensional architecture. The latter is particularly important in understanding how terrains are juxtaposed or dissected tectonically which, in turn, influences the style of any mineral system that may be present. Moreover, correct identification of structural geometry and cross-cutting relationships allows a more confident assessment of fault kinematics and potential dilatancy. In particular, the degree of uranium mineralisation in iron-oxide-copper-gold systems in the Gawler Province may be dependent on the interconnectivity of fault plumbing in three dimensions to nearby uraniferous Mesoproterozoic granitoids.

Detailed radiometric surveying at Radium Hill, South Australia

In June 2007 a ground radiometric survey utilising quad bikes, was conducted over the Radium Hill townsite, former minesite area and processing plant. An eight litre crystal pack was used along with an Exploranium GR-320 gamma ray spectrometer set to continuous (streaming) mode. A total of 148.8 line kilometres of radiometric data was collected over NS lines spaced at 100m intervals. Average ground speeds of ten kilometres per hour combined with the large crystal pack enabled good quality, highly detailed data to be collected on the ground over rough terrains. Data was continuously sampled at one second intervals and the entire survey was conducted in 10 days including mobilisation and demobilisation. The terrain was not suitable for large vehicles due to the danger of below surface mine adits, hence, the only alternative to surveying on quad bikes would be to survey on foot. It is estimated both that to get the same quality of data over this size survey area would require two operators 60 days, and also the use of such a large crystal pack would result in detailed data comparable with that derived from airborne surveys. Technical Area: Mine site environmental and engineering geophysics

New South Australian geophysical data ? PACE Northern G2 gravity survey

A combined heli-borne ground gravity acquisition program of approximately 17,000 gravity stations was acquired over the Northern G2 region within South Australia, as part of The Plan for Accelerating Exploration (PACE) program. The resolution of the gravity data was dramatically enhanced from the existing gravity coverage with a station spacing of approximately 7 kilometres to a 1.5 kilometre grid within the PACE survey. There have been several discoveries in the south of this region, leading to this area becoming a focus for data acquisition. Acquisition of geophysical data, especially gravity on a regional scale is a key strategy of the PACE program. It is expected that the new gravity data will provide exploration companies with many geophysical targets ready to drill. Technical Area: Geophysics in Government Surveys