Calidus Resources Limited (ASX:CAI) has received “outstanding” results from further rock-chip sampling and mapping by Pirra Lithium at its Spear Hill discovery in Western Australia announced in January 2022.
Pirra Lithium is owned equally by Calidus and Haoma Mining NL.
Assays have been received for a further 70 rock-chip samples of the pegmatite and adjacent country rocks. The samples were collected from the main pegmatite, to the west-northwest of those reported earlier and from an interpreted fault offset of the dyke to the north-east.
Calidus Managing Director, Dave Reeves, said the assays confirm that the main pegmatite is lithium-bearing for more than 2.5km along strike, and verify that a second, less well-defined pegmatite about 250m to the north of the discovery pegmatite is mineralised with assays yielding 0.35-0.77% Li2O.
These strong assays show clearly that we have a significant lithium pegmatite with high grades. In light of these results, we are gearing up for a maiden drilling program later this quarter, Mr Reeves said.
“There is immense prospectivity across the large tenement package and rights owned by Pirra Lithium. Our exploration to date has only scratched the surface of a small part of the tenure.”
Spear Hill
The Spear Hill area, about 50km SW of Marble Bar, is part of the historic Shaw River tin field. The area has been mined for alluvial tin since about 1893 with a little more than 6,500t of tin concentrate won from the field up until 1975.
The Shaw River tin field lies almost entirely within granitic rocks of the Shaw River batholith. The batholith is a composite feature of old (>3,400-million-year-old) granitic gneisses, granites, and slivers of greenstone, intruded by 2,950-millionyear-old granites and fractionated 2,890–2,830-million-year-old granites of the Split Rock Supersuite.
Across the Pilbara Craton, including at Wodgina, Pilgangoora, and Global Lithium’s Archer deposit near Marble Bar, lithium is hosted in pegmatites associated with granites of the Split Rock Supersuite4 .
In the late 1980s Greenex documented the presence of lepidolite in pegmatites5 in the Shaw River tin field in their pre-feasibility study of alluvial tin-tantalum deposits for Western Australia Rare Metals Co. Ltd and Greenbushes Ltd.
Recently Kalamazoo Resources announced the presence of lithium pegmatites6 and a large lithium index anomaly in soils adjacent to Pirra’s Moolyella tenement east of Marble Bar.
Riversgold Ltd revealed mapped pegmatites with 1.47-1.97% Li2O southwest of Pirra’s Spear Hill prospect.
Geology Overview
The lithium-bearing pegmatite was previously mapped on P45/2975 just over 3km ENE of Spear Hill and about 300m north of the Hillside–Marble Bar Road. The pegmatite was mapped for about 1.2km along strike and appears to be broadly parallel to the foliation or gneissic layering in the enclosing granitic rocks. The pegmatite strikes ESE and probably dips shallowly to the NNE. The width of the pegmatite at surface ranges from less than 10m to more than 30m, but the true thickness is not yet known owing to uncertainty about the dip angle.
Further mapping has established another 1.2km of strike of poorly exposed pegmatite on E45/5834 to the NE of the pegmatite body on P45/2975.
Exploration Licence E45/5834 is in application and there is no guarantee that it will be granted; however, the company knows of no impediment to the tenement being granted. The additional mapping appears to confirm that the pegmatite dips shallowly to the NNE.
The newly identified pegmatite is interpreted to have been offset by about 700m from that mapped on P45/2975 and crosses the Marble Bar–Hillside Road. On the west side of the road, the pegmatite is between 10 and 70m wide at surface (the true width is not known) and locally bifurcates.
Another narrow pegmatite is present in the footwall to the main body adjacent to the Marble Bar–Hillside Road. East of the road, the pegmatite is exposed as sub crop and trains of float amongst sheetwash deposits and appears to taper towards the eastern edge of E45/5834. The width of the pegmatite there is not known owing to the abundance of shallow cover.
Based on field reconnaissance to-date, lithium mineralisation appears to be dominated by lepidolite. Further work, including drilling and mineralogical studies, will be undertaken to determine the main lithium bearing minerals and their compositions and relative abundances.
Future work
A PoW application has been lodged with DMIRS for a maiden drilling programme. A heritage survey is currently underway across an area covering the mapped pegmatite and surrounds.
Field mapping is continuing in the area around Spear Hill with the aim of identifying further occurrences of lithium pegmatite and associated metasomatism. Historic exploration data (stream sediment, soil, and rock-chip geochemistry) and reprocessed Government geophysics are being reviewed to identify priority exploration targets across the Pirra tenement package.