Annual Technical Report GR449 MLN 582, MLN 1121, MLN 1122, MLN 1123, MLN 1124 and MLN 1125 5 January 2017 to 4 January 2018

Abstract

The McArthur River mine is one of the world's largest zinc, lead and silver mines, situated approximately 65 km south-west of Borroloola, near the Gulf of Carpentaria in the Northern Territory. It is operated by McArthur River Mining (MRM), a subsidiary of the Swiss mining company Glencore. Although discovered in 1955, when it was originally named the HYC ('Here's Your Chance') deposit, mining operations did not commence until 1995. Initially an underground mining operation, the mine transitioned across to an open-cut operation in 2006. The sediment-hosted stratiform HYC deposit is approximately 1.5 km long and 1 km wide with an average thickness of 55m. The HYC deposit has similarities with ore-bodies at Mount Isa in Queensland. The mine site is contained within five contiguous leases (MLN 1121, MLN 1122, MLN 1123, MLN 1124 and MLN 1125), located on McArthur River Station Pastoral Lease, with MLN 582 located west of these contiguous leases by a distance of approximately 4.5 km. During the reporting period a drilling campaign was completed across MLN 1121, MLN 1122, MLN 1123 and MLN 1124 which was designed to identify zones or features of relatively high hydraulic conductivity representing potential conduits for groundwater flow recharge to the old underground; better define the hydraulic properties of the northern section of the Western Fault block; identify and determine the impact of the Whelans Fault on groundwater recharge and pit wall stability in the Footwall Quarry; better define regional groundwater flow adjacent to the Western Production Run-off Dam (WPROD); and, resource development of the south-west limits of the HYC deposit. The drilling campaign consisted of 28 diamond drill holes totalling 4,154m, 7 reverse circulation drill holes totalling 140m, and 6 sonic drill holes totalling 62m. The findings from the 2017 drilling programme are highlighted by; the Western Fault block to be a low conductive structural feature, especially across the Western Fault and Cooley textural contact; and, the Mt Stubbs and Bald Hill fault intercept to be highly conductive and karstic. No drilling activities were conducted on MLN 582 or MLN 1125 as they are located outside the current operational area.