Annual report on EL 25681 Roper River

Abstract

Exploration license EL25681 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 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. In the Unconformity-type deposits, the uranium is associated with chloritised sandstone, while the palaeochannel deposits rely on uranium fixation by change of oxidation state with organic material. 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 have been investigated on the ground, using a portable gamma ray spectrometer, and have been 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. Despite focussing closely on obtaining the most promising samples, the highest uranium assay obtained was 7.73ppm. There is no apparent source of uranium nor any likelihood of economic uranium mineralisation within the black soils, sandstones or lateritic duricrust.