Minerals and Metals Group (MMG)
0.2Mt Zn, 0.2Mt Cu, 7.8Moz silver, 0.2Moz gold, 0.03Mt lead (proven and probable reserves) and 1.0Mt Zn, 0.7Mt Cu, 0.1Mt lead, 34Moz silver and 0.7Moz gold (resources)
Rhyadacitic volcaniclastic succession
Underground, sublevel open stoping
Crush, grind and flotation
The Golden Grove mine is located in Western Australia, approximately 450km north-east of Perth and 280km east of Geraldton. The mine has been producing zinc, copper and precious metal concentrates since 1990. It was initially owned and operated by Australian Consolidated Minerals.
Formerly known as Normandy Poseidon, Normandy Mining purchased the mine in November 1991. Newmont Australia acquired the assets of Normandy Mining in February 2002.
Newmont Australia sold the mine to Oxiana in June 2005 for A$265m ($203m). Oxiana collaborated with Zinifex in 2008 to form OZ Minerals. China Minmetals subsidiary Minerals and Metals Group acquired the property from OZ Minerals in June 2009.
The new $24m tailings storage facility was built at the mine site between 2009 and September 2010.
The property hosts the Scuddles and Gossan Hill zinc and copper mines, two underground mines that are 3km apart. The Scuddles mine was put under care and maintenance in July 2009. It was reopened in the second quarter of 2011.
The Golden Grove mine produced 23,619t of zinc in concentrate and 33,780t of copper in concentrate in 2013. A $100m expansion to boost the production was announced on 31 March 2011 and open pit mining at Golden Grove started in January 2012.
The expansion allows the mine to produce between 59,000t and 67,000t of copper metal a year. The initial mine life has been extended up to 2019.
Golden Grove reserves and geology
As of December 2013, the net reserve base of the mine included 0.2Mt Zn, 0.2Mt Cu, 0.03Mt lead, 7.8Moz silver and 0.2Moz gold. Total resources comprised 1Mt Zn, 0.7Mt Cu, 0.1Mt lead, 34Moz silver and 0.7Moz gold.
The deposit lies within the north-eastern edge of the Warriedar Fold Belt in the Golden Grove domain. The layered stratigraphy of the domain extends to approximately 30km.
Both Scuddles and Gossan Hill are volcanic-hosted massive sulphide (VHMS) type deposits, hosted within an underlying layered, 550m-thick rhyodacitic volcaniclastic succession known as the Golden Grove formation.
Depending on the facies, grain size differences, concentration of volcanic quartz grains and bedding features, the bedded tuffaceous volcaniclastic rocks of the formation are segmented into six categories. The primary rock types of the hanging wall include dacitic and rhyodacitic volcanic rock of the Scuddles formation.
A metamorphic assemblage typical of the biotite schist is found throughout the domain. At Gossan Hill, however, biotite is absent. Its absence and the presence of andalusite have caused alkali depletion, which is related to the intense hydrothermal alteration and mineralisation.
Alteration zones at the Golden Grove formation are characterised by locally extensive quartz, iron-rich chlorite and trace amounts of muscovite. At Gossan Hill, chlorite and ankerite-siderite alteration border the deposits and grade upwards into intense silification.
Mineralisation, mining and processing at the Western Australian mine
Zinc mineralisation at both Gossan Hill and Scuddles deposit occurs within a steeply west-plunging sequence hosting thin layers of chert and tuff.
The mineralisation overlies coarse felsic pyroclastic and epiclastic rocks.
The Gossan Hill deposit includes multiple lodes of zinc and copper mineralisation. The mineralised lodes extend 400m in strike length and 20m in width. Copper-bearing magnetite-rich epiclastic rocks are stratigraphically hosted below the zinc ore.
The zinc sulphide lodes are overlain by an oxidised near-surface silver gold resource, while an oxide copper resource lies over the copper sulphide lodes.
The primary ore minerals include sphalerite, chalcopyrite and lesser galena with a gangue of pyrite, magnetite and pyrrhotite.
Mining of the main zinc ore body is carried out using sublevel open stoping. The ore extracted from Gossan Hill is hauled to the surface via trucks. The ore is crushed and sent to the mill through a 3km overland conveyor.
Ore processing involves a two-stage grinding circuit, which is followed by flotation. The sulphides are separated using air agitation.
Open pit expansion at Minerals and Metals Group’s deposit
An open copper pit expansion was carried to boost the underground operations at Golden Grove. The $22m pit development was approved in the second quarter of 2011.
The groundbreaking ceremony of the expansion took place in November 2011. The project began its full production in 2012. Having a rated capacity of 1.8Mt per annum, the processing plant is being maintained throughout the project. Alliance was contracted to carry out the operations of the expansion project under the guidance of MMG Golden Grove Management.
The open pit is designed to produce nearly 235,000t of copper concentrate, containing 59,600t of copper metal in concentrate between 2012 and 2014. It contributed an additional 3Mt of copper ore reserves to the reserve base of Golden Grove.
The project included construction of an open pit mine, waste rock dump and associated infrastructure including transport and access roads.
Transportation and handling of concentrates
The copper, zinc, lead and gold concentrates extracted from the mine are transported to smelters in China, Korea, Japan, India and Thailand through the Port of Geraldton.