Report on prospecting for EL 123 and AP 2225 South Alligator

Abstract

This report summarises exploration completed during the year 1972 on Exploration Licence (E.L.) 123. The area is of an irregular geometrical form and extends along the South Alligator River from north of the Pine Creek - Oenpelli road as far south as Coronation Hill. Location Map of E. L. Nos. 119,120, 123. For practical reasons the area has been divided into two parts, namely Area 2 and Area 4 (or Central Valley area). Exploration of area 2 was initiated by the reinterpretation of airborne radiometric and magnetic data from a survey, conducted by Geophysical Resources Development Company (GRD) during 1970. This reinterpretation resulted in the ground investigation of twelve new anomalies, the inspection of four relocated old anomalies and a re-examination of two previously investigated anomalies. One of the new anomalies, designated 2J, was found to warrant drilling and a programme of rotary percussion drilling totaling 1,285 feet was completed. Work on Area 4 consisted of ground investigation of twenty anomalies indicated by the G. R. D. interpretation of 1971. Six of these anomalies were grouped and designated the Sandstone Anomaly which was investigated by detailed geological mapping and rotary percussion drilling totaling 2,002 feet. The unconformity between the Lower and Middle Proterozoic, often marked by the base of the Kombolgie Formation, was examined by rim traversing. This included the geological and radiometric investigations of two windows in the Kombolgie Formation. The use of Mercury 'sniffing' as an exploration tool was investigated.