The Trigg Hill Project (ELA 45/5728) is located in East Pilbara, Western Australia and approximately 75km SE of Pilbara Minerals Ltd’s Pilgangoora Lithium mine and 77km SE of the Wodgina Lithium and Tantum mine.
The Trigg Hill mine is an old tantalum and tin mine operated during 1960s and early 1980s. Pegmatite outcrops occur within the Trigg Hill-Curlew pegmatite swarms and cover approximately 5km2 with surface spodumene and lepidolite reported.
In August 2021, Eastern Resources entered into a Heads of Agreement to acquire a 100% interest in the Trigg Hill project
Figure : Location of Trigg Hill
Regionally, the Trigg Hill project is located within the East Pilbara granite-greenstone terrain, which is characterised by granitic rocks of the Shaw Batholith. The granites have intruded older Archean rocks of the Pilbara Supergroup, composed of mafic and felsic volcanic rocks, with minor sedimentary and intrusive rocks. The granitic rocks contain extensive swarms of late-stage pegmatites, the source of the tin and tantalum mineralisation in the area.
Pegmatite dykes related to the various granitic plutons have been intruded into the greenstone sequences and occur in swarms. These are variably fractionated and several have been located that fall at the end of the fractionation sequence in the Lithium- Caesium-Tantalum (LCT) category.
Figure : Simplified Geology with known and potential pegmatites
The tantalum mineral formanite was first discovered at Trigg Hill in 1906, During the 1960s, 340kg of tin-tantalum concentrates were produced. Several small pits and trenches were made in a large tantalum and rare earth bearing pegmatite. Pilgan Mining Ltd exploited in a small-scale operation eluvial and alluvial material surrounding the Trigg Hill pegmatite from 1980-82. They treated 21,000 cubic metres of material and produced an estimate ten tons of tantalum and tin concentrates. Trigg Hill is the Type locality of mineral formanite, analysis of formanite by Simpson (1948) contained 54% Ta205, 27.7% (Y, Er)2O3 1.8% Nb2O5 and 3% other REO Th, U.
The Curlew emerald deposit (excised) was discovered prior to 1940 and was mined from 1976 to 1982 with variable success. Emeralds, beryl, scheelite and molybdenite are associated with a narrow LCT pegmatite vein. The more prospective pegmatites are the larger LCT pegmatites within the swarm that surrounds the emerald mine. These pegmatites contain formanite and cassiterite and in 2018 limited sampling by Lithium Australia confirmed the presence of lepidolite with pegmatite rock chip samples up to 2.9% Li2O
The pegmatites in the project area have potential for tantalum, REO, lithium and tin. The larger zoned LCT pegmatites will be more prospective for the presence spodumene whilst lepidolite can occur in narrow dykes.