Round 16 Geophysics and Drilling Collaborations Program Final Report Moline Gravity Project

Abstract

The Moline Project comprising ML 24173, MLN 1059, MLN 41 and EL 28616, is located approximately 250 km southeast of Darwin. The titles cover the Moline Goldfields, as well as numerous small gold and base metal occurrences and historical gold mines which were last worked in the 1990's. The Moline Goldfields lie within the Pine Creek Orogen, a tightly folded sequence of Lower Proterozoic rocks, up to 14 km in thickness, laid down on a rifted granitic Archaean basement between ~2.2 and 1.87 Ga. The geology of the area has been described by Stuart-Smith et al. (1987) and Ahmad et al. (1993). The sequence is dominated by pelitic and psammitic (continental shelf shallow marine) sediments with locally significant inter-layered tuff units. Pre-orogenic mafic sills of the Zamu Dolerite event (~1.87 Ga) intruded the lower formations of the South Alligator Group. During the Top End Orogeny (Nimbuwah Event ~1.87-1.85 Ga) the sequence was tightly folded, faulted and pervasively altered. Metamorphic grade averages greenschist facies; phyllite occurs in sheared zones. The Cullen intrusive event introduced a suite of fractionated calc-alkaline granitic batholiths into the sequence between ~1.84 and 1.74 Ga. These high temperature I-type intrusives induced strong contact metamorphic aureoles ranging up to (garnet) amphibolite facies, and created regionally extensive biotite and andalusite hornfels facies. The area has been the subject of intense exploration and mining activities interspersed with periods of sporadic activity over a long period of time. Recent exploration has focused on evaluating beneath known mineralisation with limited success. Sovereign Metallurgical, operator of the project was granted funding for the Moline Gravity Project Collaborative Program of 500m x 500m ground gravity survey to increase data resolution designed to provide evidence for intrusions at depth and identify deeper seated structures which are not evident in the current magnetic or regional gravity datasets. The newly acquired data requires processing before integrating with existing datasets.