VIMP Data Sets a National Standard

Minerals

The minerals component of the Victorian Initiative for Minerals and Petroleum is designed to promote and aid mineral exploration by providing pre-competitive data and information as an incentive to increase the level of exploration in the state. This component of the work has largely been carried out by GeoScience Victoria.

The results of new detailed airborne magnetic and radiometric surveys together with new gravity data over Victoria conducted under this initiative have been lauded by industry as being a great incentive to encourage mineral exploration in the state.

The new generation of geological mapping and regolith mapping in strategic areas of the state integrates geological mapping with the interpretation of the geophysical data to produce a single composite understanding of the rocks and their relationships and mineralisation models. Analysis of existing and newly acquired datasets will enable explorers to identify and test previously unidentified targets. This work has culminated in the publication of “The Tasman Fold Belt System in Victoria”. This volume represents a major advance the understanding of the crustal architecture of Victoria. Geological data from the initiative and open file exploration reports is available as a digital geoscientific data package. Explanatory reports accompany the geological maps. Geoscientific Data Package A geoscientific data package (external link) has been compiled for Victoria and is available on DVD. The data include geology, geophysics, geochemistry, boreholes, tenements, mineral deposits and cultural features. The package is invaluable to explorers for project generation and better exploration targeting. Data is available free of charge to explorers, and updates are periodically released as new data become available. The geoscientific data package is the most popular GSV product available, saving explorers valuable time in researching their area of interest. The data is also available for online viewing and download via GeoVic. Airborne Geophysical Surveys Best coverage in Australia During the period 1988 to 2001 major airborne geophysical programs were undertaken in Victoria as part of the Victorian Initiative for Minerals and Petroleum and the National Geoscience Mapping Accord to improve the quality and coverage of magnetic and radiometric data in large areas of the state.

The program involves the acquisition of high quality magnetic and radiometric data using fixed wing (200 or 400 m line spacing) and helicopter acquisition (200 m line spacing). Victoria now has the most complete airborne geophysical data (external link) coverage of any state in Australia. Over 1 million line kilometres of high-resolution magnetic, radiometric and digital terrain data have been completed under VIMP. This provides 95% coverage of the state with high quality data.

Offshore surveys were flown to support petroleum exploration, with onshore surveys supporting minerals and petroleum exploration. GeoScience Victoria and industry routinely use data from these surveys, in the form of digital images and grids, in geological map boundary and regolith map boundary interpretation. Ground Gravity Surveys Ground gravity survey coverage of 95% of the state, with readings at 1.5 to 2 km spaced centres, has been completed under VIMP. This data represents the most detailed and complete gravity coverage of any state in Australia.

Radiometric image, Cobaw Granite, Central Victoria

With a trend for exploration away from outcrop areas to areas under cover, both the ground gravity and airborne magnetic and radiometric data are proving to be of crucial value to exploration companies searching for buried mineral and petroleum deposits. New Generation Geological Mapping Geological mapping The GSV geological mapping program is focussed on the production of integrated geological and geophysical interpretations of key areas of the state to support mineral exploration. The mapping program has been directed towards remapping of the central Victorian goldfields and completing an east-west mapping transect through the backbone of Palaeozoic rocks in Victoria. New generation geological mapping covers approximately 70% of the prospective outcrop areas.

Gravity surveying, Wilsons Promontory

The new high-resolution geophysical data from VIMP has fundamentally changed the way geological mapping is carried out in the GSV. Integration of geological and geophysical data, together with working in multidisciplinary project teams over the last decade has enabled GSV to produce geological maps at 1:50 000 scale and geophysical interpretation maps at 1:100 000 scale which have set the standard Australia-wide for maps at these scales. Results of the new generation geological mapping have been incorporated in the production of a landmark volume The Tasman Fold Belt System in Victoria in November 2001. This book, together with accompanying 1:1 000 000 scale maps, synthesises the geology, geophysics and mineralisation of the Palaeozoic rocks of Victoria. Geological interpretations Most of Victoria’s 2500 t of gold has come from orogenic deposits (eg Bendigo, Ballarat, and Castlemaine) in the Palaeozoic rocks of Lachlan Fold Belt. The host rocks extend under shallow cover to the north and south in an area similar in size to the known gold fields. These areas are unexplored and offer potential for the discovery of large gold deposits. Bedrock mapping, a program of 1:250 000 scale basement geological interpretation of geophysical data commenced in the mid 1990s in areas of post-Palaeozoic cover in western Victoria. These interpretations enable explorers to look through the cover to target buried repetitions of mineralisation worked in the Palaeozoic outcrop areas. The current project area is the St Arnaud 1:250 000 map sheet area.