Progress report on exploration, EL 314

Abstract

This report describes the results of an exploration programme undertaken by Planet Resources Group NL during October 1973 within Exploration Licence 314, situated approximately 15 miles southeast of Adelaide River, Northern Territory. The scope of the programme was (a) locate by ground scintillometer traverses a number of airborne radiometric anomalies delineated by Geophysical Contractors Aero Surveys (Australia) Pty Limited during July, 1973; (b) to geologically.map and geochemically sample the anomalies; (c) undertake detailed ground radiometric surveys over the defined areas. A geochemical stream sediment sampling programme was also carried out within selected portions of the EL. All samples were analysed for copper, lead, zinc, nickel and cobalt by atomic absorption and for uranium by fluorimetry, by Robertson Research (Australia) Pty Limited, Bowral, NSW. Soil and stream sediment samples were sieved to -80 mesh prior to forwarding to the laboratory for analysis. Geophysical consultants, Layton and Associates, were retained by the Company to evaluate the results of the airborne radiometric and magnetometer survey completed by Aero Surveys. They found that no major uranium anomalies were evident on the analog spectrometer chart. However, four minor anomalies, designated Bi, B2, B3 and B5, were defined as being worthy of further investigation. The oldest rocks in the Exploration Licence comprise quartz-siltstone, carbonaceous siltstone and calcareous siltstone of the Lower Proterozoic Golden Dyke Formation. These are conformably overlain by siltstone, greywacke and silicified calcareous greywacke of the Burrell Creek Formation. Intrusive rocks are represented by basic sills of dolerite which intrude sediments of the Golden Dyke Formation. The dominant structural feature is the north-south trending, doubly pitching Howley Anticline, occurring in the west-central portion of the EL. The core of the structure is occupied by a conformably folded dolerite sill. The only previously exploited deposit within the EL is the Bridge Creek Gold-Copper-Lead Mine. This was a small deposit in which the mineralisation, comprising galena, chalcopyrite and arsenopyrite was associated with quartz veins within pyritic carbonaceous siltstones of the Golden Dyke Formation, near their contact with a dolerite sill. However, shallow exploration pits - both for lode and eluvial gold - are aligned along the axial portion of the Howley Anticline. Previous workers have referred to this mineralised trend as the ?Howley Line of Lode?. The ?Howley Line of Lode? persists southwards beyond the southern extremity of EL 314, and contains former medium sized producing mines such as the Fleur de Lys (Cu, U), the Cosmopolitan Howley (Au) and the Big Howley (Au) Mines. Geochemical soil and rock sampling within the Bl, B3 and B5 anomalous zones did not yield any significant uranium values, being consistently less than 5 ppm.U. Radiometric readings within these zones rose to a maximum of 1.5 times background. However the absence of any coincident geochemical response, either in uranium, copper or lead, appears to preclude the possibility of locating economic mineralisation. Geochemical sampling within the B2 grid area delineated a uranium anomalous zone rising to a maximum of 45 ppm U, from a background of 5 ppm U. 1.15. The anomalous zone is located along the western flank of a northerly trending sub-outcrop of gossanous carbonaceous siltstones of the Golden Dyke Formation, near its contact with a doleri.te sill. It is also coincident with a copper-lead geochemically anomalous zone. However, the latter zone has greater width and anomalous copper and lead values persist to the western limits of the sampled area. The afore mentioned gossanous carbonaceous siltstones have a radiometric anomaly centred on them, rising to a maximum of +2 times background. Thus the work in the B2 grid area confirmed a uranium anomalous zone, with a slight displacement between the axis of the uranium geochemical anomaly, and the axis of the radiometric anomaly. The structural setting of the uranium B2 anomaly within the axial portion of the Howley Anticline, its lithological association with carbonaceous siltstones of the Golden Dyke Formation, and its proximity to an intrusive dolerite sill bear similarities to features pertaining at the Fleur de Lys Copper-Uranium mine, and it is considered to warrant further testing to evaluate its significance. A geochemical stream sediment sampling programme was completed within certain portions of the EL, about the environs of the ?Howley Line of Lode?, and in the north-eastern extremity of the Licence. A stream sediment copper-lead-zinc anomaly was delineated in streams draining the Bridge Creek Mine area, and is considered to reflect the known mineralisation. A geochemically anomalous train in copper, lead and zinc was also obtained in the south-western portion of the Exploration Licence. The streams in this area drain the B3 anomalous zone, however there are no known occurrences of base metal mineralisation and further work is necessary to evaluate its significance. 1.23. A rock chip sample taken over a quartz outcrop in the vicinity of Mt. Pasqualan during a survey completed in July 1970 yielded 11.6 ppm. Au/ton. This area has not been subsequently investigated, and further work is necessary to determine the significance of this comparatively high value. Expenditure incurred on the Exploration Licence from the date of granting to January 1974 is $28,476.00.