EL 32705 Annual Technical Report 2022 16 November 2021 to 15 November 2022

Abstract

Exploration Licence 32705, comprising 25 graticular sub-blocks, was granted to Burgeo Pty Ltd on 16 November 2021. This Licence was sought to cover a strong, isolated radiometric anomaly evident on the 1:2,500,000 Radiometric Map of the Northern Territory (Dhu T, 2020), which, from a review of previous exploration by others in this district, had not hitherto been addressed. The anomaly is located at 595,900mE;7,506,400mN (MGA94, Zone53) and is underlain by gently dipping fine sandstones, siltstones and intercalated limestones of the late Cambrian Eurowie Sandstone Member within the Arrinthrunga Formation of the southern Georgina Basin. Interest in this airborne radiometric anomaly is derived, not so much from the uranium (or thorium) potential per se, but as a possible indicator of associated high field strength elements - rare earths, tantalum, niobium, zircon, as well as tin and tungsten. The purpose of the work program during the first year of tenure was to ground-truth this radiometric anomaly by GPS-controlled traversing of the anomaly site with a hand-held spectrometer (Radiation Solutions Inc RS-125) and back-up using a 'legacy' Scintrex BGS-1S scintillometer. Access to the site was made by helicopter from Alice Springs on 7 June 2022 and, over a period of several hours, total count readings were taken manually at sixty stations on nominal 50m x 200m centres to effectively cover the site of the anomaly. Maximum response was barely twice background. It was therefore concluded that the anomaly was either misplaced or the result of an instrument malfunction at the time of the airborne survey (Huckitta, 1981. p548; Percival, P.J., 2014). Despite this negative result nine rock chip samples were taken at the time in the vicinity of the anomaly and assayed for a suite of 62 major, minor and trace elements. Predictably, no concentrations of high field strength elements (or U, Th or K) were indicated. However, several samples of ferricrete returned elevated concentrations of cobalt (to 1145ppm) and zinc (to 2020ppm) with slightly elevated copper and nickel. Notably these several ferricrete samples are also enriched in manganese (average about 5% MnO) so that a degree of manganese scavenging is evident. Nevertheless, a primary source of cobalt (and zinc), whether or not in economic concentrations, may be envisaged. The sabkha-type facies represented by the Arrinthrunga Formation presents a compatible geological setting for such deposition. Subsequent acquisition and examination of the located flight line data from the 1981 Huckitta airborne radiometric survey indicates that the perceived radiometric anomaly is registered as an extreme single point total count reading of 95,221 cps (compared to the next highest of 4,316cps from 4,340 survey readings) within an expansive background of around 1,900cps. Tellingly, the following two readings of all channels and including altitude, each 74m further south along the flight line, are assigned erroneous designations. An instrument malfunction or atmospheric/cosmic spike has generated the 'anomaly'.