American Rare Earths Broken Hill Initiative
In 2018 ARR was granted three new exploration licences in the Broken Hill Region, significantly increasing its overall exposure to this world class mineral province and securing a number of under-explored base, precious and industrial mineral prospects. The new leases EL8773 (Main Line) and EL8775 (Broken Hill NW) apply to base, precious metals and industrial minerals (Groups 1, 2 & 5) whereas EL8776 (Triple Chance) covers industrial minerals only. Initial work on EL8773 has involved detailed logging and re-assay of historical 1957 drill core from the Burtt & Cattersons prospect.
Burtt & Catterson’s Cu-Co Prospect (EL 8773 Main Line)
This tenement covers an area of approximately 20 square km and allows exploration for base, precious and industrial minerals (Groups 1, 2 & 5). The southern part is along strike from the world class Broken Hill Line of Lode and covers the Burtt & Catterson’s workings, approximately 8.5km south-west of Broken Hill (Figure 1). The site is marked by several historical bulldozer costeans, shallow pits, and two shafts, 114’ (35m) and 70’ (21 m) deep. The Burtt & Catterson’s mineralisation occurs in rocks of the Cues Formation (Thackaringa Group), and is regarded as ‘Great Eastern’ type, where copper and cobalt sulphides are associated with metamorphosed chemical sediments, including pyritic siliceous ironstone and blue quartz–garnet rocks. Three diamond holes were drilled at the prospect in the 1950s, but only cursory surface exploration has since been undertaken. Assay intervals published in old Zinc Corporation and CRA Exploration reports show thin bands (0.3–0.6m) with up to 4% copper contained in thicker silica and iron-rich lode rock intercepts. In addition, one 5.5m interval in drill hole 57BC-1 historically assayed at 0.16% (1600ppm) cobalt.
Apart from rare cases such as the Thackaringa Pyrite–Cobalt deposits (ARR and Cobalt Blue Holdings Ltd) and Copper Blow (Silver City Minerals Ltd), exploration for deposits hosted by the Thackaringa Group rocks were for many years discounted in favour of nearby Broken Hill-type Pb–Zn–Ag prospects. An upsurge in world demand for cobalt has changed this perspective and sparked a revival of exploration for economic copper and strategic metals in the iron-rich (pyrite or hematite/magnetite-bearing) horizons that occur throughout the Thackaringa Group.
Rock chip sampling by ARR at Thackaringa, and Silver City Minerals and others around Broken Hill (see Silver City Minerals Ltd ASX release 17 September 2018), has demonstrated that widespread Cu–Co geochemical anomalism at surface is associated with the Thackaringa Group rocks. Current work is aimed at defining these anomalies through more comprehensive sampling and ground-based geophysical techniques such as induced polarisation (IP).
Apart from the clear potential for base and precious metals in this expanded tenement package, the ARR Board believes that the industrial mineral potential of the Broken Hill Region has been systematically ignored over recent years. Several large, advanced, mining and infrastructure projects in the area will potentially bring additional and improved services and/or generate their own industrial mineral demands, delivering a change to the economic case.
Under the terms of the Thackaringa Joint Venture (TJV), ARR retains the rights to base and precious metals on the Thackaringa tenements, where it is actively exploring for Broken Hill (Pb-Zn-Ag) style mineralisation.
The Broken Hill Group, which hosts the world class Broken Hill Pb-Zn-Ag (300Mt of ore containing 30Mt Pb, 24Mt Zn, 1B oz Ag and 1M oz Au), is widely distributed across the Thackaringa Project with multiple prospects prioritised for further exploration (Figures 3 & 4).
Recent geological mapping and sampling combined with newly acquired high resolution geophysics has greatly enhanced exploration targeting. Newly discovered prospects characterised by outcropping quartz gahnite rocks — a key vector for Broken Hill Pb-Zn-Ag style deposits — and rock chip sampling has defined extensive Cu-Pb-Zn-Au-Ag mineralisation.
A major step forward in Thackaringa district exploration began in late 2017 after the flying of a major heliborne electromagnetic (VTEM) survey covering both EL6622 and EL8143. The survey was fully funded by COB as part of the Thackaringa Cobalt Project joint venture. District-scale geological mapping and 3D modelling has greatly enhanced the context around a wide range of geochemical and geophysical anomalies, including currently known prospects.
Numerous geochemical and geophysical targets will be tested during sterilisation drilling at the Thackaringa Cobalt Project in parallel with ongoing advanced feasibility studies.
Broken Hill Group Prospects
ARR’s Broken Hill type prospects include Pyramid Hill and Himalaya North.
- Occurs in the lower Broken Hill Group
- Outcropping ‘lode rocks’ persistent over 500m of strike
- Rock chip assays up to 7.5% Cu, 40g/t Ag, 1g/t Au, 0.1% Ni, 0.2% Pb & 0.4% W
- Only 150m of the mapped extent has been tested by shallow drilling
- Historical drill intersections include 5m at 0.23% Cu, 1g/t Ag, 0.66g/t Au, 0.04% Zn, 103ppm Co & 569ppm Ni from 64m (11RCPM01)
- Hosted by the lower Broken Hill Group
- A stacked sequence of ‘lode rocks’ mapped over 1,500m strike
- Rock chip assays up to 2.6% Cu, 5.9% Pb, 62g/t Ag & 0.8% Zn
- An area of multiple quartz gahnite occurrences
- Shallow reconnaissance drilling tested 200m of the mapped extent with intersections including 2m at 0.17% Cu, 0.17% Zn, 0.04% Pb & 7g/t Ag from 41m (11RCHN3)
Thackaringa Group Prospects
The Thackaringa Cobalt–Pyrite deposits occur in the Himalaya Formation of the Thackaringa Group. ARR has identified numerous copper-rich Broken Hill type targets within the underlying Cues Formation (Figures 1 & 2) including Old Coolgardie West and Ram Paddock:
Old Coolgardie West
- Anomalous rock chip samples over 800m of strike
- Assays up to 5.2% Cu, 140g/t Ag, 0.2g/t Au, 0.2% Ni & 0.1% Pb
- The zone contains extensive garnet amphibolite and laminated calc-silicate with a strong magnetic response.
- Iron oxide Cu–Co±Ni±Au target
- Rock chip assays up to 1050ppm Co, 850ppm Cu, 420 ppm Ni, and 500ppm Zn