Use of potential field data and modelling to complement detailed geological mapping in the Goulburn?Braidwood area, New South Wales

Abstract

The Goulburn and Braidwood airborne geophysical surveys that cover part of the Southern Highlands of New South Wales have been flown as part of the National Geoscience Mapping Accord and the NSW Government?s $30 million Exploration NSW initiative. The new airborne magnetic and radiometric survey data show that many of the geological boundaries on Department maps can now be improved in areas of sparse outcrop. Interpretation of the new data will greatly assist the definition of rock types and geological structures that may be associated with gold, silver, lead, zinc and copper mineralisation and for construction materials such as sand and gravel. The airborne magnetic dataset has assisted in delineation of a number of major structural domains characterised by marked variations in strain and structural style. The survey areas are critically sited at the convergence of geological terranes already studied further to the north. These terranes are bounded by major fault structures ? some of which appear to converge and then diverge. Recent geological mapping, assisted by the interpretation of all the geophysical data, allows recognition of the complex volcanic and clastic stratigraphy of the mid-Late Silurian sequences. This has led to the recognition that the Hill End Trough and Ngunawal Basin (Captains Flat area) are most likely to both be part of a continuous marine basin, and expands the area prospective for VHMS Cu?Pb? Zn?Ag?Ba?Au deposits along the Frogmore Fault Zone in the west, and along the Yarralaw Fault Zone in the east. Potential field modelling has contributed to a moreconfident interpretation of the third dimension, and has provided control in the preparation of cross-sections.