EL 32705 Annual Technical Report 2023 16 November 2022 to 15 November 2023 Arrinthrunga

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. A ground spectrometer survey undertaken during the first year of the Licence failed to ground truth this airborne anomaly. Subsequent acquisition and examination of the raw airborne data clearly indicated that the single point reading underpinning the 'anomaly' was spurious, likely the result of an instrument malfunction during the airborne survey. Nevertheless, nine rock chip samples were taken 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 Co) and zinc (to 2020ppm Zn) 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 associated base metals, whether or not in economic concentrations, was considered in relation to the sabkha-type facies represented by the Arrinthrunga Formation. Subject to further study, ongoing field geochemical investigations during the second year of the Licence were considered to assess this base metal potential of the property. A desktop study has since been undertaken. As a result of this study, it is concluded that, despite the apparent enhancement of base metal concentrations in the manganiferous ferricrete sampled, the geological setting is nevertheless conducive to sediment-hosted ore deposition and warrants broader rock-chip and soil geochemical investigations as an initial assessment of this proposition. Unfortunately, funding was not available to undertake these field investigations during Year 2 of the Licence, as intended, and they are deferred for undertaking during Year 3.