EL 1321 Davis Dome, Ngalia Basin year ending 15-03-1979.

Abstract

The Ngalia Basin is located about 300 km north-west of Alice Springs. It is an elongated, intracratonic depression filled by Upper Proterozoic, Palaeozoic and Cainozoic sediments and surrounded by a basement of Precambrian crystalline and meta-sedimentary rocks. It is about 420 km long, east-west, and is about 70 km wide, north-south, at its widest part. Strong folding and faulting have disturbed and disrupted the strata. Thrusting along the northern margin of the Ngalia Basin has moved Precambrian granitic basement south, in general, over the younger formations, which in many places near the margin, are overturned. Folding and faulting of varying intensity was probably related to this thrusting. Uranium was originally discovered by Central Pacific Minerals NL within the Ngalia Basin itself in 1971, in the Mount Eclipse Sandstone (of Carboniferous Age) which is the formation of greatest interest for uranium exploration. CPM had a virtual monopoly on exploration till 1975. The area under discussion fell within EL 402/EL 605. AFMECO Pty Ltd started a reconnaissance study (mapping, sectioning, drilling) of the Mount Eclipse in the western sub-basin in 1977, concentrating on areas of outcrop close to the basement, and on areas with surface anomalies and channelling facies. During the 1977 field season very little prospective ground was available, and this area was drilled during this preliminary programme on the basis of high background shales and siltstones being present. The work of the 1978 field season in the western sub-basin has had the objective of testing, by drilling, the down dip extension of surface anomalies discovered by CPM and now protected by CPM claims and SMLs. The one drill hole, DAV1, reached a total depth of 904.6 in. The drill site was located on the crest of Davis Dome, which is down dip of CPM's Bigrlyi No. 15 Anomaly. Detailed field work (mapping, sectioning, structural study) accompanied the drilling to improve the understanding of the geology and to make possible a regional reconstruction of the palaeo-geography, in order to locate the most promising areas for uranium mineralisation. The drill hole DAV1 penetrated all units from Unit 7 to perhaps the upper part of Unit 2, its total depth was 904m. A single Radiometric Anomaly was present at 899.3 m.