Summary:
The Tabba Tabba pegmatites are hosted in the Tabba Tabba Greenstone Belt, with the pegmatite preferentially hosted by a dolerite sill thought to be contemporaneous with the Millindinna Intrusive. The dolerite intrudes meta sediments of the Mallina Formation which have been metamorphosed into cordierite-biotite schists. The sill is north-northeast striking, coincident with the strike of the Tabba Tabba Greenstone Belt and the related Tabba Tabba Shear Zone. At Tabba Tabba, the dolerite sill has been intruded by a swarm of northtrending, east-dipping pegmatite dykes, becoming more north-westerly in their strike in the northern extents of the Project.
The largest pegmatite at Tabba Tabba is Leia, which has a known strike of greater than 2.5km. Leia outcrops from surface and plunges at roughly 20° to the north, with the central zone containing mineralised pegmatite at widths greater than 100m true thickness. Most of the mineralization occurs in a zone approximately 1.5km in length and in section view, the pegmatite appears to have a sigmoidal geometry. The second largest pegmatite is the Luke Pegmatite, with mineralised stacked pegmatites up to 50m thick inside a zone of up to ~100m cumulative thickness of pegmatite. The Leia and Luke pegmatites are comprised of quartz, albite, muscovite and garnet, and are variably mineralised along their strike and dip geometries. Metallurgy has confirmed the mineralised zones are dominated by the lithium-bearing mineral spodumene.
The Tabba Tabba Tantalum Deposit is hosted by a different phase of pegmatite, with tantalite dominating the ore mineralogy. Hutt and Han pegmatites are dominated by petalite, whilst Chewy is mineralised with both Petalite and Spodumene variably along its length.
Drilling has shown that the pegmatites typically occur as dykes dipping sigmoidal to the east at 0-60° and strike parallel to sub-parallel to the dominant NNW trending fabric within the greenstones. Pegmatites of the Leia, Luke and Chewy domains appear to form in thickly stacked sigmoidal vein arrays, whilst the Hutt and Han pegmatites appear to form in more thinly stacked sheeted arrays.
The Tabba Tabba tantalum Pegmatite has a symmetrically disposed outer cleavlandite zone, mica zone and a megacrystic K feldspar zone with a centrally disposed quartz zone associated with an albitic replacement unit. The zones generally dip in sympathy with pegmatite margins. The main Tabba Tabba Pegmatite presents as a thick (frequently greater than 20m) funnel-shaped dyke which strikes northwest and dips 30°-40° northeast. The geometry is possibly due to erosion of the top portion of the pegmatite. It can be followed in outcrop along strike for at least 400m and historical drilling has intercepted it up to 80m down dip.
The pegmatite is thickest at surface, thinning and bifurcating at depth, and is mineralogically zoned. Three distinct quartz cores have been recognised, and tantalum mineralization is mainly restricted to the albite replacement and lithium alteration zones and is composed of tantalite, wodginite and (in the lithium alteration zone) microlite. Three distinct mineralized zones occur as sheets which average 2m to 3m in thickness, but may be up to 6m thick, which strike and dip in sympathy with the pegmatite margins.
Dimensions:
The modelled mineralisation is hosted in an area striking for 3,500ms (south to north from Luke to The Hutt) and down to a depth of approximately 500m vertical beneath surface in multiple domains.