Heavy Rare Earths Ltd (ASX: HRE) has commenced on-ground exploration for rare earths has commenced at its 100% owned Duke project in the Northern Territory.
The Duke project comprises two adjacent granted exploration licences EL33101 and EL33194 that together cover an area of 255 sq. km. They are located on the Phillip Creek pastoral lease approximately 50 kilometres north-west of Tennant Creek and 25 kilometres west of the Stuart Highway.
Exploration on and around HRE’s tenement package has in the past focused on ironstone hosted Cu-Au-Bi and IOCG deposits, but this is the first time the area will be subject to exploration for rare earths.
The exploration model being investigated by HRE is an unconformity-type REE deposit similar to those at Northern Minerals’ Browns Range project in Western Australia. The unconformity in question occurs between the Proterozoic Warrego Granite and metamorphic rocks of the Flynn Group and overlying sandstone and conglomerate of the Tomkinson Creek Group.
Reconnaissance Visit – April 2023
HRE undertook a reconnaissance visit to the project area in April 2023 to assess access. During the visit prominent thorium (Th) anomalies from a previous explorer’s airborne magnetic/radiometric survey over the project area were investigated on the ground using a portable XRF (pXRF) and gamma-ray spectrometer.
In addition, core from diamond drill hole PCRD001 drilled in 2009 to test a uranium anomaly from the same airborne survey (and in the same general area of the Th anomalies) was examined at the Northern Territory Geological Survey’s core library in Alice Springs. PCRD001 intersected Warrego Granite from five metres depth.
pXRF analysis confirmed the presence of elevated rare earths both at outcrop and in the Warrego Granite. In situ analysis of silcrete outcrops and zones of quartz veining returned values ranging from below detection limits up to 0.21% TREE (total rare earths). Forty spot pXRF analyses on Warrego Granite intersected by PCRD001 averaged 745 ppm TREE with a maximum of 0.2% (2000 ppm) TREE.
A total of seven samples (five rock chip and two drill core samples) were assayed by LabWest Minerals Analysis in Perth. Five of the seven samples returned >300 ppm TREE with a maximum of 732 ppm TREE. Rare earth enrichment is confirmed in an extensive zone of hydrothermal quartz veining, in surficial silcrete, and in the Warrego Granite. The latter is particularly significant because the granite may be a suitable source for an overlying ion-adsorption type REE deposit in laterite (saprolite), and locally up to 20 metres of saprolite was intersected in this area during drilling carried out during the 1970s.
First-pass Exploration – August 2023
Encouraged by these results, the Company has now commenced a systematic campaign of soil sampling comprising 420 samples over an area of about 23 sq. km. It is planned to cover the above-mentioned area of Th anomalism, a large zone of quartz veining and a sizeable but discrete Cu-Au-Bi-in-soil anomaly identified in previous exploration but never drilled. Samples will be collected along 400 metre-spaced lines on 200 metre centres.
The survey is expected to take two to three weeks to complete and assay will be via the innovative UltraFine+TM method which targets the extremely fine component of soils (<2 μm). There is minimal outcrop of Proterozoic rock across the survey area, which is mainly covered by sheet and dune sand, and sandy soil.
In addition to the soil survey, the effectiveness of stream sediment sampling will be assessed to explore the more difficult-to-access northern, western and eastern portions of the project area.
