Short and long wavelength geophysical features reflecting geology and structure in the Doradilla tin-copper-nickel district, 45 km south-east of Bourke, NSW

Abstract

Integrated interpretation of regional geophysical surveys and geological data by the Geological Survey of New South Wales highlights complex magnetic intensity features in the vicinity of the mineralised Doradilla district near Bourke, northern NSW. The district hosts mineral occurrences of copper, tin and nickel which are subject to current exploration and evaluation programs, but geological understanding is limited due to flat terrain and thick regolith cover. This study analyses radiometric, magnetic and gravity datasets which have potential to contribute information on the geology at different penetration levels: in outcrop, near to the surface, and also at deeper crustal levels. The study examines an elongate high radioelement feature and its relation to terrain, regolith, local geology, and neighbouring granites. Sources for short wavelength aeromagnetic anomalies in the area are interpreted and correlated with present understanding of lithologies and mineralisation. Longer wavelength magnetic features are studied using low pass filtering to investigate possible buried intrusive bodies. A coincident gravity low is investigated using multi-scale edge detection contours to indicate major crustal gradients. The results indicate a deeply seated granite intrusion, overlying near-surface structures, and alteration and intrusion effects in outcrop. Characteristics of the Doradilla district are found to match previously recognised geophysical criteria for granite-sourced tintungsten mineralisation. The project demonstrates the value which regional geophysical datasets offer when analysing mineral systems.