EL 605 Walburi, Uranium group annual report of activities 1972

Abstract

Regional radiometric prospecting of Mount Eclipse Sandstones extended the anomalous zone of radioactivity west of the Walbiri Prospect and a further six occurrences of radioactivity accompanied by carnotite were found. A car-borne radiometric survey in the Currinya EL over areas of calcrete was successful and located two broadly anomalous zones each about 1.2 by 2.5 kms in size. In both, trenching revealed carnotite in the calcrete. Drs Brondi and Carrara, sedimentologists, carried out a detailed study of the Walbiri Prospect, and their work has indicated the presence of a channel which extends both east and west of the Walbiri Prospect. A 5000 foot diamond drilling programme was completed at the Walbiri Prospect. Of the twelve holes drilled, only two showed no anomalous radioactivity, while one (NG DD11) gave an intersection of 6.97 metres of 6.2 lbs/s ton. Equilibrium was checked on two holes and found to be in order. However, radiometric assay values did not correlate and assays are currently being checked. Drilling showed that; (a) light grey reduced rocks continued from the surface down dip, (b) pyrite occurred in this sequence usually associated with carbonaceous material, (c) shale beds occur above and below the reduced sandstone layer which turn impermeable and therefore would provide the confining boundaries for the passage of fluids. The car-borne surveying has been highlighted by the discovery of carnotite mineralization in the Quaternary calcrete on EL 454, Currinya. This was found using the (105 12 spectrometer whilst systematically covering calcrete outcroppings and float at mile line spacing's. Two broadly anomalous areas were located, each being approximately l.5 miles by 0.75 miles in size. Subsequent trenching within the anomalous areas revealed carnotite mineralization associated with the calcrete (For

further information see Report NT 59). Further car-borne survey work has been orientated towards seismic line traversing in the western part of the Ngalia Basin. This has mainly entailed radiometric values over Quaternary alluvium. No anomalies have been located. The car-borne radiometric method has shown that it is extremely useful for covering a large expanse of accessible terrain, when targets are broadly anomalous areas. The method is limited if the ground is inaccessible to vehicles or possible targets are very small in size.