Final report, investigations on AP2593, Tanumbirini Northern Territory

Abstract

Geochemical results showed low levels of concentration of base metals and uranium over the area studied, and no further work is planned. The 281 square mile area was taken up as the subject for search for base metals and uranium in the Upper and Lower Proterozoic rocks which crop out over most of the area of the AP. Drainage geochemistry was carried out over the whole of the area, which was also subjected to reconnaissance airborne radiometric survey. Geochemical values for base metals are too low to be of interest, and although weak persistent radioactivity was noted over certain formations, ground follow-up work, including analysis of the drainage samples for uranium, revealed nothing of economic interest in the area and it is proposed to relinquish the area. Two groups of Proterozoic rocks are represented in the area of the AP, and are overlain in part by younger formations. The Proterozoic sequences of interest include: Corcoran Formation - shale micaceous siltstone, blocky fine quartz sandstone. Abner Sandstone. Roper Group Crawford Formation - sandstones, feldspatbic sandstone. Mainoru Formation - siltstone, shale, sandstone. Limmen Sandstone - sandstone, feldspathic sandstone, siltstone. Masterton Formation - breccia, agglomerate, Tawallah Group volcanic conglomerate, Wollogorang Formation dolomitic siltstones, silty dolomite, Rosie Creek Sandstones feldspathic quartz- sandstone with glauconite. In this area the Tawallah Group rocks occupy the core of a faulted anticlinal structure, and the overlying Roper Group units dip west on be western flank of this feature. The Cambrian Bukalara Sandstone and the Cretaceous Mullamen Beds unconformably overly the above rocks over parts of the area. The area was held by Geopeko in 1965 66 as part of a larger AP. A report by BT Williams indicates that the area was taken up by Geopeko to investigate the possibility that ciolomites might be present which resembled those at McArthur River, as a target for lead zinc exploration. This work predated the publication of the final 13 MR 1:250,000 Tanumbirini geological map sheet. A photo interpretation map was prepared and a short field visit to check on lithologies was made. A petrological study of three specimens from the Tanumbirini Volcanic Member demonstrated that rocks of this Member represented 1remobi1 ised and segregated sands and muds?. From this it was concluded that the Member did not represent a source rock for mineralisation. No samples were taken from the Tanumbirini area for assay. Kenneth McMahon and Partners examined and reported on the area in 1968, again before publication of the final BMR geological map. McMahon?s field work involved the preparation of a l:14,000 geological map over 60 square miles and the collection of 207 drainage, 6 soil and 6 rock samples by means of helicopter. Geochemical results of only those stream sediment samples considered significant, totaling 26 in number, are reproduced in their report, the analyses being performed by Sampey. Metal values of these are all very low. A small malachite showing in fractured rocks of the Masterton Formation was described, and minor pyrite and chalcopyrite was noted in dolomite of the Wollogorang Formation. Drainage sampling was carried out over the whole of the area of the A.P. and 183 geochemical drainage samples were collected. Relief in the region is such that active erosion is taking place on most rock units, excepting those soft formations which underlie strike valleys. The samples were analysed for lead, zinc, copper, nickel and uranium in The Zinc Corporation laboratories at Broken fill, and the results are on the attached plans. During the course of a rapid radiometric reconnaissance of the area, using a Scintrex BGS l portable scintillometer carried in a helicopter it was noted that certain formations were anomalously radioactive, notably the poorly exposed Corcoran Formation in the western part of the area of the A,P, and to a lesser extent outcrops of the Tanumbirini Volcanic Member, and parts of the Masterton and Woollogorang Formations. The location of the areas of radiometric anomaly detected in the aerial reconnaissance is shown on the attached plan. Analysis of the geochemical samples for uranium failed to establish the presence of any abnormal concentration of uranium in stream sediments, and no further work in the area is proposed. In pursuing the aerial reconnaissance beyond the limits of the A.P. it wa recorded that rad4.oactivity is common over outcrops of tL. Cororan Formation, and this observation led to the application for further ground in the area. Geochemical results showed low levels of concentration of base metals and uranium over the area studied, and no further work is planned. In pursuing the above investigations, expenditure totalling $10,636 was incurred.