Geophysical signatures of small-scale base metal occurrences in south eastern New South Wales

Ground-based, time-domain electromagnetic, magnetic and gravity datasets were obtained for the southern Gurubang and Rosebank VHMS deposits located approximately 15 km east of Cooma, NSW. The deposits are hosted in a mid-late Silurian sequence of rock composed of shallow marine sediments and felsic volcanic rocks. The aim of this research was to ascertain the usefulness of highresolution geophysical techniques in targeting and evaluating small-scale polymetallic massive sulphide deposits, and to investigate how the detailed geophysics relates to the overall geological framework of the prospect areas. The acquired data was analysed using a forward modelling approach. Due to both deposits containing high concentration of conductive minerals, a coincident loop time-domain electromagnetic 2D survey effectively delineated the sulphide mineralisation and was useful in interpreting and adapting deposit parameters such as the azimuth, dip and strike length. Based on the physical nature of the target deposits, it was determined that high-resolution magnetic and gravity surveys would not be effective methods in directly delineating these smaller-scaled (10’s of m’s) mineral deposits. However, magnetics and gravity did prove effective in depicting the surrounding geology, including potential volcanic intrusions and basement lithologies and structures.