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Mungari Operation - White Foil, Frogs Leg, Cutters Ridge; Kundana - Millennium, Centenary, Pope John, Moonbeam and Christmas; East Kundana - Falcon, Raleigh, Rubicon, Hornet, Pegasus

Western Australia, WA, Australia

Main commodities: Au
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The Mungari gold mining operation is an amalgamation of a number of deposits within the southern Kundana Goldfield, ~600 km east of Perth and 20 km west to NW of Kalgoorlie, Western Australia.
(#Location: 30° 46' 35"S, 121° 14' 49"E).

For details of the geological setting, see the Coolgardie - Kundana Goldfield record and the broader Yilgarn Craton record. The deposits are located towards the western margin of the Kalgoorlie Terrane.

The principal mines feeding the central Mungari treatment plant in 2022 include the White Foil and Cutters Ridge open pits and the Frog’s Leg, Kundana (Millennium, Centenary, Pope John, Moonbeam and Christmas) and East Kundana (Raleigh, Falcon, Rubicon, Hornet and Pegasus) underground mines. Previous operating mines in the immediate district include Barkers and Strzelecki.

The White Foil deposit was discovered in 1996, followed by the Frog’s Leg deposit in 1999. Limited open-pit mining was undertaken at White Foil between 2002 and 2003 and at Frog’s Leg between 2003 and 2004. In 2008, the Frog’s Leg mine transitioned to underground and the first gold pour was achieved from that mine the same year. Construction of a processing plant for the two mines was started in 2013 and completed the following year. The open-pit mining operations at White Foil were also restarted in 2014. Evolution Mining acquired the White Foil and the Frog’s Leg mines along with the Mungari processing plant from the previous owner, La Mancha Group International, in August 2015. The Kundana and East Kunduna mines, which are within 8 km of Mungari’s mill, were acquired from Northern Star Resources Limited and the EKJV in 2021 and more than doubled the Mungari Mineral Resources and Ore Reserves.

The White Foil deposit comprises a quartz stockwork hosted by a gabbro that is broadly differentiated into a quartz-rich phase in the west and is part of the Powder Sill intrusive complex. This quartz rich phase is the most hydrothermally altered unit and contains the bulk of the gold mineralisation. The deposit is bounded to the west by hangingwall volcaniclastic rocks. To the east mineralisation becomes more irregular and is uneconomic in the more melanocratic phase of gabbro. Mineralisation is controlled by sheeted systems of stockwork veining that is accompanied by strong alteration and sulphidation of the host quartz gabbro. The mineralised zone is 70 m wide by 400 m long, dips to the WSW at between 50 to 60° and is open at depth. It is controlled by a NNW trending shear associated with the major regional scale Zuleika Shear Zone that is located ~3 km to the west and juxtaposes the Ora Banda domain to the east and the Coolgardie domain to the west. White Foil and the Mungari processing plant are 1.25 to 2 km SW of Frog's Leg. The latter lies along the same NW to NNW oriented zone of shearing as most of the other deposits of the operation, which are distributed over an ~8 km interval of that structural trend, with the exception of Cutters Ridge, which is ~9 km to the WSW. The deposits on this trend are, from SE to NW - Frog’s Leg, Rubicon-Hornet-Pegasus, Raleigh-Falcon, Christmas, Pope John and Millenium (Evolution Mining, 2021).

The Frog’s Leg deposit is located within the sheared contact between the regional Victorious Basalt and volcaniclastic rocks of Black Flag Group. The sheared Victorious Basalt is known locally as the porphyritic 'cat rock'. Mineralisation occurs as sub-parallel, laminated quartz veins associated with brecciation and alteration zones over widths ranging from 2 to 20 m and along strike lengths of 0.3 to 1 km. These lodes occur within the shear zone as NNW-SSE striking steep structures with dips of from vertical to 80°W. This shear zone is also related to the Zuleika Shear Zone (Evolution Mining, 2021).

The Kundana deposits comprise what is known as K2-style mineralisation which consists of narrow veins hosted by shear zones located along steeply dipping overturned lithological contacts. The K2 structure occurs along the contact between a black shale unit, the Centenary shale, and intermediate volcaniclastics of the Black Flag Group. Pope John is on the Centenary K2 trend. The deposit extends between the Pope John Fault in the north through to the Lucifer Fault in the south. At the Lucifer Fault, the K2 horizon is offset by ~200 m to the south west and becomes the Moonbeam deposit. The Pope John lode is locally offset by several smaller mine scale faults in between the two larger regional faults. The K2 mineralisation is typical of the area with a high-grade laminated quartz vein being the primary gold hosting unit with minor halo grade disseminated around this structure in the Centenary Shale and Black Flag volcaniclastics. The Kundana Gold Operations, incorporating Millennium, Centenary, Pope John, Moonbeam and Christmas, are accessed via a portal from the open pit (Evolution Mining, 2021).

Kundana East includes the significant Falcon deposit, which is the down plunge continuation of Raleigh. It is interpreted to represent a series of mineralised splays off low angle structures that persist through lithological contacts from the K2B contact between the i). Victorious Basalt and Bent Tree Basalt, and the ii). K2A contact between the Bent Tree Basalt and upper felsic and volcaniclastic/sedimentary rocks of the Black Flag Group. The Falcon mineralisation sits in the hangingwall of the regional K2 structure. Falcon mineralisation comprises laminated to brecciated to extensional-style quartz veining internal to a sheared biotite-sericite-ankerite altered siltstone/sandstone unit and an intermediate volcaniclastic unit. Mineralisation is present within veins, on vein selvedges, and within the altered host rock, with coarse gold often observed. There is a strong visual correlation between arsenopyrite and gold mineralisation. As of July 2021, mineralisation at Falcon had been outlined over a strike length of 1500 m, with individual mineralised envelopes ranging from 200 to 1000 m along strike, and from 50 to 300m down dip. Mineralised envelope true widths ranged from 0.5 to 8.0m. Mineralisation was known to occur from the base of cover to around 750 m below surface (Evolution Mining, 2021).

Ore Reserves and Mineral resources as at 31 December, 2021 (Evolution Mining Reserves and Resources Satement, 2022) were:
Mineral Resources
  Open-Pit at a 0.4 g/t Au cut-off
    Indicated Resource - 44.3 Mt @ 1.18 g/t Au
    Inferred Resource - 10.5 Mt @ 1.36 g/t Au
    Indicated + Inferred Resource - 54.8 Mt @ 1.21 g/t Au, for 66.3 tonnes of contained gold
  Underground at a 1.80 g/t Au cut-off
    Measured Resource - 1.7 Mt @ 5.39 g/t Au
    Indicated Resource - 10.1 Mt @ 4.26 g/t Au
    Inferred Resource - 9.4 Mt @ 3.58 g/t Au
    Measured + Indicated + Inferred Resource - 21.2 Mt @ 4.05 g/t Au, for 86 tonnes of contained gold
  TOTAL Mineral Resource - 76.1 Mt @ 2.0 g/t Au, for 152.3 tonnes of contained gold
Ore Reserves
  Open-Pit at a 0.73g/t Au cut-off
    Proved Reserve - 3.0 Mt @ 1.54 g/t Au
    Probable Reserve - 14.2 Mt @ 1.29 g/t Au
    Proved + Probable Reserve - 17.2 Mt @ 1.33 g/t Au, for 22.9 tonnes of contained gold
  Underground at a 4.82 g/t Au cut-off
    Proved Reserve - 0.8 Mt @ 4.89 g/t Au
    Probable Reserve - 2.6 Mt @ 4.33 g/t Au
    Proved + Probable Reserve - 3.5 Mt @ 4.46 g/t Au, for 15.5 tonnes of contained gold
  TOTAL Ore Reserve - 20.6 Mt @ 1.86 g/t Au, for 38.4 tonnes of contained gold
NOTE: Mineral Resources are inclusive of Ore Reserves.

The most recent source geological information used to prepare this summary was dated: 2021.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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