Mt Woods 2D Seismic Reflection Survey, Gawler Craton, South Australia: An Integrated Minerals Exploration Case Study

Abstract

Five seismic reflection profiles for ca 130 line km were acquired over the southern Mt Woods Inlier, near the Prominent Hill IOCG deposit in South Australia. The aim was to provide high resolution images of the under-cover region in the shallow to mid crust, to augment existing potential field and drilling data and, through a combined interpretation, to optimise exploration targeting. The application of seismic reflection using vibroseis sources in hard rock terranes presented significant challenges to processing and interpretation. Notwithstanding this, the resulting 2D images clarified a number of important fault and fold patterns that were also apparent in, but poorly constrained by, the potential field data. The major faults include: the Southern Overthrust imaged as a major north dipping feature that truncates a series of gently dipping reflectors within the Palaeoproterozoic and Archaean basement, and the Bulgunnia Fault as a complex set of steeply dipping divergent faults. The major folds are large amplitude refolded features that include the Kennedys Dam antiform and Larissa synform. The White Hills mafic complex, which has an impressive positive gravity and magnetic response, occupies a broadly synformal position. The Gawler Range Volcanics and their contact with Palaeoproterzoic metasediments is well imaged using the seismic method. A thrust duplex structural setting has been inferred around the Prominent Hill deposit.