Final report for EL 1229 Cockroach, NT

Abstract

The Exploration Licence was explored by means of geological and prospecting traverses with minor stream sediment and rock chip sampling. The Cockroach Exploration Licence is located mainly on Manners Creek and Tarlton Downs stations in the eastern part of the Northern Territory. The Licence covers an area in the central part of the Tobermory 1:250 000 Sheet. Exploration Licence 1228 mainly covers a carbonate and sandstone sequence of Upper Cambrian-Lower Ordovician Ninmaroo Formation and Tomahawk Beds. Exploration of these units, particularly the carbonate facies, was carried out mainly by geological and prospecting traverses. A small drainage system in the south-western corner of the Licence was sampled as part of a major geochemical survey in the adjoining Tarlton Downs Exploration Licence. Conclusions;1. Geological and prospecting traverses failed to find any surface lead, zinc or pyrite mineralization. All anomalous ferruginous material was considered to be due to scavenging of base metals by iron and manganese oxides during lateritic weathering. 2. The coarse fraction stream sediment geochemical survey resulted in a number of high lead anomalies. Follow-up work proved that the high lead values were contained in the iron and manganese oxide portion of the samples. Corresponding 80 mesh stream sediment samples only gave background values. 3. No evidence of surface or near surface mineralization was found by follow-up exploration of stream sediment anomalies. 4. Geochemical evidence strongly supports the theory that lead was progressively enriched in iron and manganese oxides during a prolonged weathering phase on an extensive pre-Triassic weathering surface. Later erosion has removed most of the Triassic cover and recycled possible lead rich iron and manganese nodules into the present drainage system. 5. The lack of any signs of surface mineralization, meaningful geochemical anomalies, and the overall geology of the area, together with the lack of encouraging results from exploration of other Licences in the general region indicate that the chances of finding viable lead and/or zinc mineralization in the area to be very low. 6. The Ninmaroo Formation, Tomahawk Beds and Kelly Creek Formation sediments were deposited on a broad shelf of a shallow epicontinental sea. The deposition of sandy facies, common in the western part of the area during Cambro-Ordovician times increased during the Lower Ordovician when the Kelly Creek Formation was deposited. RECOMMENDATION; It is recommended that Exploration Licence No.1230 Cockroach be relinquished.