Venturex holds mineral resources totalling 24Mt at 1.3% Cu, 3.7% Zn and 18g/t Ag within its East Pilbara Project. The resources are spread over six deposits within three fields that are part of a group of mineralised systems termed Volcanogenic Massive Sulphide (VMS) deposits. VMS mineralisation currently contributes approximately 20% of global zinc and copper production.
VMS mineralisation typically occurs as clusters of deposits formed on ancient sea floors which are around volcanic or sub-volcanic centres. Typically, these clusters can have resources totalling 40-50 million tonnes and in some cases giant fields contain in excess of 100 million tonnes. As well as VMS systems forming at several locations within the prospective terrane, mineralisation can also occur at several discrete levels within the stratigraphic sequence therefore once a VMS deposit has been identified there is significant potential to find incremental mineralisation above and below the known mineralisation and along strike.
Examples of this class of deposit occur in Australia on the west coast of Tasmania in Proterozoic fold belts and include Rosebery, Hellyer and Que River and in the Archaean of Western Australia include Golden Grove (Scuddles and Gossan Hill mines) and the Jaguar Project (Teutonic Bore, Jaguar and Bentley mines). The DeGrussa copper-gold mine and the nearby, recently discovered Monty deposit in the Byrah Basin are examples of Proterozoic VMS deposits in Western Australia.
Critical to successful exploration for VMS mineralisation is the identification of the prospective geological settings that lead to the deposition of metal into the sequence. Venturex has identified the geological horizons that host the VMS mineralisation in the Whim Creek basin and along the Panorama trend. Previous exploration work in all areas has been too shallow and sparse to effectively define the scale or quality of the known mineralisation and the Company therefore believes that there is significant exploration potential on the tenements of these two areas.
Venturex holds granted exploration and mining tenements covering approximately 27 kilometres of strike along the Panorama Trend which is a known VMS mineralised horizon. The Panorama Trend hosts the Sulphur Springs and Kangaroo Caves copper-zinc deposits as well as a number of advanced base metal exploration prospects. VMS mineralisation is associated with felsic volcanic and volacaniclastic rocks within a tectonostratigraphic domain trending north to northeast around a granitoid dome.
Since the discovery of Sulphur Springs in 1982, the majority of previous exploration has centred on Sulphur Springs, with lesser work undertaken at Kangaroo Caves. Only sporadic, shallow work has been carried out on the remainder of the prospective mineralised volcanic stratigraphy the Company now controls. The final package of ground was only acquired by the Company in 2013 by direct purchase from CBH and SIPA.
The exploration maturity of the region is relatively low reflecting the long periods of low base metal prices and the preferred focus of near prospect exploration by previous holders of the Sulphur Springs deposit. The region is considered to have significant potential for the discovery of large VMS systems and for the expansion of known resources, particularly at depth below existing mineralisation and possibly at further stratigraphic levels.
Whim Creek Greenstone Belt
The Whim Creek Project covers part of the Whim Creek Greenstone Belt which forms the north-western part of the Archaean Central Pilbara Tectonic Zone. The Whim Creek Greenstone Belt is an arcuate belt 85km long and 5 to 10km wide extending around the Caines Well Batholith. The northern side of the greenstone belt is truncated by the Sholl Shear and the south-eastern side is in faulted contact with sedimentary rocks of the Malina Basin (Huston 2006).
The basal unit of the Whim Creek Greenstone Belt is the Whim Creek Group consisting of the Warambie Basalt, rhyolite and volcaniclastic rocks of the Mons Cupri Volcanics overlain by conglomerate, sandstone, shale and felsic tuffs of the Bookingarra Group. The Bookingarra Group consists of the Cistern Formation, (conglomerate, tuffaceous sandstone and siltstone) overlain by the Rushall Shale and mafic rocks of the Louden and Mt Negri Volcanics (Huston 2006).
The base metal mineralisation style at Whim Creek, Mons Cupri and Salt Creek is volcanic massive sulphide and all the known VMS mineralisation in the Whim Creek greenstone belt is hosted in the Bookingarra Group. The Whim Creek Deposit is hosted in the Rushall Slate and the Mons Cupri Deposit is hosted in the upper part of the Cistern Formation.
The Liberty Indee Project covers the north plunging Croydon Anticline within the southern part of the Archaean Mallina Basin. The Mallina Basin is separated from the Whim Creek Basin to the West by the sub-vertical Loudens Fault. The Croydon anticline is cored by mafic to ultramafic sills assigned to the Millindinna Intrusion. These are flanked by the Constantine Sandstone which is the basal unit of the De Grey Group.
VMS style mineralisation is located near the contact between the mafic–ultramafic sill and the Constantine Sandstone. Detailed mapping at the Evelyn deposit has also identified narrow zones of dacite to rhyolite volcanics along this contact. The current stratigraphic interpretation correlates the Constantine Sandstone with the Cistern Formation of the Whim Creek Basin (Smithies 1998). The inference from this is the Evelyn VMS mineralisation formed at a similar time to the Whim Creek, Mons Cupri & Salt Creek deposits (see the Whim Creek Cu-Zn-Ag Project).