The Browns Range project previously formed part of the Gardiner-Tanami Project, but since 2009 has become a focus for the Company’s Rare Earth Element (REE) exploration program. The project consists of two (2) granted exploration licenses and one tenement application. The tenements cover an area of 400 km2 within Western Australia, located adjacent to the WA/NT border approximately 150 km southeast of Halls Creek.
Interest
Northern owns 100% of all mineral rights on the Browns Range Project.
Location
The Browns Range Project is located in the Tanami region around the WA/NT border, 150 km southeast of Halls Creek, WA.
Target & Geology
The target is hydrothermal xenotime mineralisation, xenotime being a rare earth phosphate mineral and a rich source of yttrium and high value Heavy Rare Earths (HREE). Xenotime was first identified in the Browns Range area in the 1980s by PNC Exploration while exploring for uranium. PNC named the area of quartz-xenotime mineralisation “Area 5 Prospect” and tested one of the larger quartz-xenotime veins (10-30cm wide, 15m long) by costeaning and shallow drilling, obtaining results up to 16% yttrium (Y), 0.2% uranium (U), 0.5% light REE (LREE) and 12% HREE.
The Area 5 Prospect is located on the western side of the Browns Range Dome, a Paleoproterozoic dome formed by a granitic core intruding the Paleoproterozoic “Browns Range Metamorphics” (meta-arkoses, feldspathic metasandstones and schists) and an Archaean orthogneiss and schist unit to the south. The dome and its aureole of metamorphics are surrounded by the Mesoproterozoic Gardiner Sandstone of the Victoria-Birrindudu Basin. Area 5 was described by PNC Exploration as consisting of outcrops of arkose, conglomerate and minor quartz mica schist. Sub-cropping ultramafic rocks and a banded iron formation (BIF)/quartz pebble conglomerate occur in the area. Calc-silicate rocks are also recorded 4 km to the east. Elongate, probably discontinuous magnetic ultramafic bodies, up to 400m wide, appear to have been intruded along faults trending 060˚.
Work completed by Northern Uranium
Previously unknown xenotime mineralisation was encountered 4 km to the north-northeast of the Area 5 Prospect during recent Northern Uranium exploration programs. These newly discovered hydrothermal quartz-xenotime stockworks are similar to the Area 5 occurrences, with xenotime concentration being up to 3-4 wt-%. Preliminary analyses of the mineralisation has indicated unusually high concentrations of HREE, including several rare earths that have increased in value due to their growing demand, restricted availability and strategic importance. Isotopic dating of the xenotime suggests that the quartz-xenotime mineralisation may be linked to regional scale tectonic reactivation, implying ore-deposit potential in the Browns Range Dome area.
Proposed Work program
The Area 5 Prospect and the new discovery 4 km to the NNE are in areas of anomalous uranium radiometrics and topographic highs. The topographic highs may be due to erosion-resistant outcropping quartz stockworks and are immediate targets for on-ground investigations. Based on anomalous uranium radiometrics the REE target zone is open in several directions and extends over some 9km.
The REE exploration program will include review and re-processing of the Hymap hyperspectral airborne mapping data and airborne radiometrics. The presence of minor uranium in xenotime means that any subtle airborne radiometric anomalies will require checking on the ground. Hymap may be useful in detecting the quartz stockworks (+/- xenotime) and associated alteration clay signature. After the initial reconnaissance, promising areas will be selected for detailed geological and structural mapping, rock chip sampling and ground radiometrics. Follow-up in areas of interest will include detailed geochemical soil sampling and/or systematic detailed ground radiometrics to outline potential drill targets.