Report on 1975 investigations EL 123 South Alligator Valley

Abstract

This report summarises exploration activities completed during 1975 in Exploration License No 123. The reduced Exploration Licence lies within the Mount Evelyn district of the Northern Territory. Three separate areas totaling 117.5 square miles comprise the license and the exact boundaries. The central part of the general area is underlain by Lower Proterozoic rocks of the Goodparla Group and South Alligator Group, which are locally intruded by basic igneous rocks of the Zamu Complex. In the north eastern and south western sections, prominent plateaux are formed by a younger sandstone and volcanic sequence of Middle Proterozoic age. Graded roads, which extend between Pine Creek, El Sherana and Oenpelli, and ungraded bush tracks, provide good dry season access to all except the plateau areas. Exploration comprised investigations of the Window II area by geological mapping, Track Etch radon, seismic and soil geochemical surveys. Radon anomalies, delineated during 1974, were evaluated in the Window I area by detailed geological mapping, in the Anomaly 2J area by geological mapping, radon monitor and geochemical surveys, and in the Barramundie Creek area by detailed Track Etch radon and soil geochemical surveys. Three radon anomalies in the Barramundie Creek area were tested by 504 metres of percussion drilling. Conclusions; 1) Two distinct areas with Track Etch radon anomalies are present at Window II along a north west striking zone about 4 kms in length. The anomalies are present over outcropping sandstones and conglomerates of Middle Proterozoic age. These overlie Lower Proterozoic rocks forming a variable cover of between 20 and 100 metres. One of the anomalous areas is associated with high copper values in soils, 2) The Window II anomalies are considered to be derived from uranium within the Lower Proterozoic succession but they could be affected by acid volcanics if these are present at the base of the Middle Proterozoic, 3) Drilling should be carried out at the Window II anomaly peaks in order to determine their probable cause, 4) Track Etch radon anomalies along a reverse fault at the south west margin of Window I are probably related to uranium mineralisation and should be tested by drilling, 5) Radon emanometer anomalies in the Barramundie Creek area are related to superficial processes and not to underlying uranium mineralsation, 6) A Track Etch radon anomaly north of Anomaly 2J is related to superficial processes and not to underlying uranium mineralisation.