Final report for Wellington Range 2016-2017 CORE Collaborations Funding

Abstract

Cameco Australia Pty Ltd (Cameco) and Rio Tinto Exploration Pty Ltd (RTX) have entered into a Joint Venture (JV) to explore for unconformity style uranium mineralisation in the Wellington Range (EL 5893), King River (EL 25064 and EL 25065), and Waidaboonar (EL 24017 and EL 27059) tenements in Arnhem Land. As part of a tenement wide data review process the JV has identified several areas where there are significant knowledge gaps in the understanding of the distribution of prospective basement lithological units. The most significant knowledge gaps occur in the northern-most JV tenement, EL 5893, where there are significant thicknesses of Cretaceous sedimentary cover blanketing the area and where there has been limited historic drilling. In 2016 the JV applied for CORE Geophysics and Drilling Collaborations Program (CORE) funding to complete three diamond drillholes within EL 5893. The total CORE funding approved by the Northern Territory Department of Mines and Energy totalled $100,000. All three of the proposed holes were completed but due to significant savings realised in the cost of the drilling the final CORE contribution to the overall program was $87,268 (exclusive of GST). The CORE collaborations drillholes completed have provided information that will assist in generating an improved geological framework for this part of Arnhem Land. The co-funded diamond hole completed at Angularli Target 3 commenced coring in Mamadawerre Sandstone at a depth of 45.8 m. Drilling continued through sandstone to a depth of 172 m where an unconformity between the Mamadawerre Sandstone and the underlying Paleoproterozoic basement was intersected. The metasedimentary rocks below the unconformity included intercalated pelite and amphibolite overlying a sequence of crystalline semi-pelite. Diamond drillhole WRDD0136 collared in Mamadawerre Sandstone. The drillhole intersected the Proterozoic unconformity at a depth of 229.05 m. Variably altered Paleoproterozoic metasediments were noted between 229.05 and 263.25 m. The base of the metasedimentary package was marked by a 30 cm wide chlorite altered fault gouge. Below the fault variably bleached Mamadawerre Sandstone was intersected to the base of the drillhole. The drillhole completed at Condor South (WRDD0138) intersected a approximately 150 metre thick sequence of metasedimentary rocks composed of sedimentary facies similar to that observed in the Ranger/Jabiluka area. The drillhole intersected a sequence of pelitic, semi-pelitic and psammitic metasedimentary rocks interbedded with amphibolite units. This sequence was underlain by 18 m wide, variably silicified marble unit. The footwall to the marble unit comprises interbedded highly aluminous pelite interbedded with psammite which unconformably overlies interpreted Archean gneiss basement. The metasedimentary sequence is intruded by a series of 0.1 m to 40 m wide pegmatitic units. This discovery demonstrates that there is further potential for Ranger/Jabiluka style mineralisation along the northern strike extension of the Nanambu/Cahill unconformity.