First steps into the unknown: potential field surveying as an affective first step in exploration -­‐ a uno fault example south Australia, Australia

Abstract

The Uno Province in South Australia is a current focus of mineral exploration. The province is bounded to the north by the Gawler Range Volcanics, a large felsic igneous province of Mesoproterozoic age that overlies the Palaeproerozoic basement. The nature of the boundary is postulated to be structurally controlled by the east-west trending Uno fault. However, little is known of the morphology of the fault. The fault, over time, has been continually extrapolated eastward with minimal geological rationale. Information and knowledge adhering to the nature of the fault, its possible extent and the exact boundaries between geological units adjacent to it, does not yet exist. To provide new constraints on the fault, two lines of gravity data were procured in June 2015. The lines were approximately 52 km and 27 km long and comprised 156 stations spaced approximately 250 m to 1 km apart. It’s hoped that description of the planning phases and the two transect lines of variable gravity station spacing produced a valuable replicable method for this line of work. Regional elevation changes are small (less than 150m) so that only simple gravity reduction methods were applied and the data were tied into a reference South Australian gravity framework. The lines were designed to cross the boundary of the GRV approximately at right angles, although stations had to be located along roads for logistical reasons. Two-dimensional modelling of the fault using representative densities for the major lithological units shows that the Uno Fault represents a clear boundary in physical properties, but the data could not determine fault from unconformity. The continuation of the fault was not detected to the east in the Siam line. Anomalous areas other than the fault were investigated and discussed including parts of the Hutchinson Group and the geometry of the Hiltaba Suite. Conclusions were bounded by the uncertainties inherent in non-unique solutions. However, possible explanations for gravitational trends along both lines have been stated and may aid in the continued exploration of this area for minerals.