The 58km2 Wallbrook tenement package (including Nexus’ surrounding exploration tenement), is considered highly prospective for the discovery of significant gold mineralisation.View ASX Announcements
Nexus has acquired the Wallbrook exploration tenements from Saracen for consideration of 1,490,000 Nexus shares. This investment is consistent with the Company strategy of investing in advanced gold exploration assets (ASX release 17 January 2018 – Nexus to Acquire Wallbrook Gold Project from Saracen and ASX release 23 January 2018 - Nexus Wallbrook Gold Project UpdateNexus Wallbrook Gold Project Update). The transaction includes an Ore Purchase Agreement, whereby any future ore mined from the Project tenement may be purchased by Saracen for processing through its 2.4Mtpa CIL processing plant at Carosue Dam Operations – 35km to the south of the project area via existing haul road network.
The region is dominated by metamorphosed volcaniclastic sediments, andesite, basalt and other sedimentary and variously metamorphosed rock units. These rock units have been intruded by numerous small, variably mineralised, porphyritic intrusions. The majority of these intrusions identified to date are under cover or very weathered. Their composition varies from syenite to quartz monzonite to tonalite. These intrusions are discordant with respect to the lithological layering and major regional structures, suggesting emplacement late in the tectonic evolution of the greenstone belt, indicating mineralisation associated with the intruded porphyries may be relatively “local” to the position of the intruded porphyry.
Gold mineralisation has been identified and mined historically in a belt stretching from the Porphyry mining district to the Wallbrook area 8km to the southeast. Over 350,000 ounces of gold have been produced from multiple operations from 1921 to 2012. This same region today contains a current JORC 2012 mineral resource inventory of 31Mt @ 1.5g/t for 1.5M ounces gold (all Saracen Resources, see their 2017 Annual Report). None of these historically mined ounces nor the current mineral resource inventory are contained on Nexus tenements.
The main sites of gold mineralisation in the district are on the margins of porphyritic intrusions. Mineralisation is known to occur within the margins of these porphyries themselves, and also developed within the intruded sheared and altered greenstone sequence lithologies and as mineralised quartz vein stockworks.
Previous Exploration Activities
The Wallbrook project contains no prior commercial mining operations. A number of shafts exist at the Eastwood Reefs prospect, which was mined by prospectors in the early 1900’s.
An extensive search of the Western Australian Department of Mines and Petroleum (DMP) database has shown Wallbrook to have undergone a number of periods of exploration activities by different exploration companies between 1977 to 2011. These activities including geological mapping and rock chip sampling, geophysical surveys, as well as RAB, RC and diamond drilling campaigns. The majority of the Wallbrook geology is under cover with limited areas of outcrop identified at the Eastwood Reefs, Jedi and Paint prospects.
There are 552 rock chip results available with 79 samples returning >1g/t Au and 34 samples returning >3g/t Au.
There have been 12 series of drill programs between 1977 and 2011. RAB drill holes represent 1772 holes for 39,000m, with the majority of these holes less than 10m in depth effectively representing surface geochemistry. RC drill holes represent 275 holes for 21,000m (average depth 76m), and a sole diamond drill hole 159m deep.