Name: Gruyere mine.

Location: The Gruyere deposit is located within the Yamarna Terrane of the eastern Yilgarn, in Western Australia.

Mine Owner/s: Gruyere Mining Co, a joint venture (JV) between Gold Fields and Gold Road Resources.

Brief Description: Gruyere has three openpits comprising the mineral reserve, as well as seven openpits and one underground mine, contributing to the mineral resource.

The pit is designed to be mined in stages over the life-of-mine.

Brief History: Gold Road discovered the mineralisation at Gruyere in 2013.

The Gruyere project was successfully completed and commissioned in 2019, with first gold delivered in June 2019.

Commercial levels of production were achieved at the end of September 2019, with ramp-up to name plate capacity achieved in the December 2019 quarter.

Primary Metals/Minerals: Gold.

Secondary Metals/Minerals: None stated.

Geology/Mineralisation: The Gruyere deposit is located on a flexure point within the regional-scale Dorothy Hills greenstone belt and shear zone. Orogenic gold mineralisation is hosted within the steep easterly-dipping Gruyere porphyry, a medium-grained quartz monzonite porphyry that has intruded the country rocks.

The host Gruyere porphyry averages 90 m in horizontal width through the deposit, with a maximum width of 190 m in the centre of the deposit and tapering to a width of about 5 m to 10 m at the northern and southern extremities.

The entire Gruyere porphyry is variably altered and gold grade is related to variations in style and intensity of alteration, structure, veining and sulphide species.

YAM14 is located 8 km south of the Gruyere deposit and is similarly located on a flexure of the Dorothy Hills shear zone. Mineralisation at YAM14 is shear related and hosted within an intermediate sedimentary package at the contact with a rhyolitic tuff.

Elevated gold grades are associated with shearing, increased quartz-veining and albite-chlorite-pyrite-arsenopyrite alteration. Gold mineralisation within the Attila-Alaric trend – Attila, Alaric, Montagne, Argos and Orleans projects – comprises steeply dipping shear-hosted gold in volcaniclastic sequences, with gold associated with zones of albite ± sericite ± chlorite ± pyrite mineralisation.

Reserves: Total proven and probable reserves as at December 31, 2019, were estimated at 90.43-million tonnes grading 1.24 g/t gold.

Resources: Total mineral resources as at December 31, 2019, were estimated 153.55-million tonnes grading 1.34 g/t gold.

Mining Method: The Gruyere mine uses mining contractors to mine the openpit, using conventional drill, blast, load and haul activities.

Major Infrastructure and Equipment: All ore mined is processed in the Gruyere plant, which comprises primary crushing, semiautogenous grinding/ball milling, gravity and carbon-in-leach circuits. The processing plant was initially designed to process 7.5-million tonnes a year, but subsequent studies have shown that this can be increased to 8.2-million tonnes a year.

Prospects: according to the latest mineral resources and reserves supplement  to Gold Fields integrated annual report, minor exploration will be undertaken at the JV that may include targeted satellite pit infill drilling on the Golden Highway and possibly further near-mine openpit extensions.

Contact Details:
Gold Road Resources
Tel +61 8 9200 1600
Email perth@goldroad.com.au
Website https://goldroad.com.au.