Relinquishment report for EL 25681 Roper River, December 2009

Abstract

Exploration license EL 25681 Roper River is in the West MacArthur Basin, Northern Territory of Australia, entirely within Goondooloo Station. It is about 40 kilometres west of Mataranka, north of the Roper River. The geology of the area is comprised of Proterozoic sandstones, siltstones and mudstones of the Moroak Sandstone, Velkerri , Kyalla Member and Chalmers River Formation. These are overlaid locally by Cambrian Antrim Plateau Volcanics and intruded by Proterozoic dolerite and diorite. The initial exploration objective was either an Unconformity-type Uranium Deposit similar to those of the Alligator River Province, or a palaeochannel deposit similar to the Honeymoon Well project in South Australia. During the 2008 reporting period a review of available open-file information on the license was performed, seeking evidence to facilitate the exploration for uranium within the area. The most readily accessible data was airborne geophysics, geological mapping, mineral occurrence and topographic information. Airborne radiometric anomalies were investigated on the ground, using a portable gamma ray spectrometer, and sampled for analysis where of interest. Most of the anomalies were associated with black soils, though two of them correlated with lateritic duricrust outcrops. Determinations of uranium, thorium and potassium were made using the gamma ray spectrometer, while rock chip samples were also investigated with a Niton field-portable XRF device. Soil geochemical samples were taken in areas that lacked outcrop, and submitted for ICP-MS multi-element assay. In the absence of any encouragement for uranium mineralisation the area was assessed as having some potential for sedimentary iron occurring as bedded iron units within the McArthur River Group sandstones at the stratigraphic position of the Sherwin Iron Member. Areas recommended for relinquishment were those in which the iron formation, based on published mapping, was not present. A ground survey located the peak of the anomaly and a spectrometer was used to identify the equivalent uranium content. Where locations were anomalous in uranium a Nitron portable XRF was used to determine a more accurate value for uranium content. Most of the anomalies were over black soil alluvial plains and uranium contents, even at the peak of the anomalies, was never more than 15 ppm (equivalent). Ferruginous sandstone outcrops were found in places to be anomalous for uranium although uranium (equivalent contents were generally less than 20ppm. It was therefore recommended that no further exploration for uranium be carried out.