Australia

Ridgeway Mine

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Overview

Mine TypeUnderground
Commodities
  • Gold
  • Copper
  • Silver
Mining Method
  • Block caving
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Mine Life... Lock
ShapshotThe Ridgeway underground mine and Cadia Extended open cut mine were developed shortly afterwards and commenced production in 2002 and 2003, respectively, with Ridgeway expanding into block cave mining in 2009. Collectively, Cadia Hill and Ridgeway produced over 8Moz of gold and nearly 860kt of copper concentrate over their mine lives through 2018 following which the Cadia Hill deposit was largely exhausted and Ridgeway was placed on care and maintenance in March 2016 with minor production resumed during 2017 to supplement plant feed following the Cadia East seismic event in April 2017.

Ridgeway is currently on care and maintenance subject to further studies, all necessary approvals, permits, internal and regulatory requirements and further works.
Related AssetCadia Valley Operation

Owners

SourceSource
CompanyInterestOwnershipInvestor's Info
Newmont Corp. 100 % Indirect
Cadia is 100% owned by Newcrest through its wholly owned Subsidiary, Cadia Holdings Pty Ltd.

On November 6, 2023, Newmont Corporation completed the acquisition of Newcrest Mining Limited to create the world’s leading gold company with robust copper production.

Deposit type

  • Breccia pipe / Stockwork
  • Porphyry

Summary:

Cadia consists of the Cadia East, Cadia Extended, and Ridgeway deposits which consist of alkalic porphyry gold-copper style mineralization and the Big Cadia deposit which is a skarn-style occurrence.

The Ridgeway deposit is a subvertical body of quartz–sulphide vein stockwork mineralisation with an elliptical, pipe-like geometry, elongated along a northwest-striking axis. Stockwork dimensions are approximately 400 m east–west, 250 m north–south and the deposit extends to a depth in excess of 1,000 m.

The Ridgeway mineralisation is defined in a copper gold quartz veining zoned in a monzonite to quartz- monzonite plug 50 m to 100 m in diameter that has intruded the FRV. There is a disseminated copper rich chalcopyrite zone above a quartz vein-hosted gold rich zone. This is cut by the Claudia Fault. The mineralisation is as stockwork and sheeted quartz sulphide veins within a broadly stratabound zone associated with the monzodiorites.

Mineralisation is spatially and temporally associated with a composite intrusive plug consisting of multiple mafic monzonite to quartz monzonite phases that intruded the FRV. The earliest phase is a mafic monzonite, which is a northwest striking, subvertical body with horizontal dimensions of 200 x 50 m wide and a vertical extent of at least 500 m. It occurs as a subvertical plug along the southern side of the Ridgeway deposit.

Three phases of porphyritic intrusion (early-mineral monzonite, and inter- and latemineral quartz monzonite) post-date the mafic monzonite, and form a composite pipe along the northeastern margin of the mafic monzonite. This pipe has a horizontal footprint of about 130 x 40 m, oriented along a west–northwest trending axis. The pipe has been recognised over a vertical interval of >650 m and remains open at depth.

Hydrothermal alteration is broadly zoned from an inner calc-potassic (actinolite–biotite–orthoclase) and potassic (orthoclase–biotite–quartz) core, outwards through propylitic (chlorite–hematite– magnetite–epidote–albite–pyrite ± calcite) and sodic (albite–pyrite) assemblages (Wilson et al., 2003). The transition to more distal metal-poor propylitic alteration zones has been long recognised by the disappearance of hematite-dusted secondary albite (Holliday et al., 2002).

The Ridgeway deposit is centred on multiple steeply-dipping porphyries occurring at the confluence of two gently-dipping structural blocks. To the west of Ridgeway, stratigraphy gently dips east, whereas sedimentary units to the east dip west to west–northwest at 10–20°. These rocks are cut by multiple moderate-dipping reverse faults. A single prominent fault, the Tinnock Fault, occurs with ~500 m of stratigraphic offset (as defined by two stratigraphic pinpoints, including the two lowermost units of the Forest Reefs Volcanics), placing lower parts of the stratigraphy over higher parts. Numerous other moderately-dipping faults splay from this master fault and dismember parts of the Ridgeway deposit. In the deposit, these faults only displace the intrusions by several tens of metres (Harris et al., 2009).

Isopach maps combined with 3D modelling show that the ore-related intrusions at Ridgeway occur in the thickest parts of basin-fill successions preserved in both the Forest Reefs Volcanics and the upper parts of the Weemalla Formation. Basin-fill strata laterally vary and broadly thin to the south and west, defining half-graben basin geometries. Tilting (approximately 20° to the west/west–northwest) and structural offset of basinrelated sedimentary sequences implies the ongoing dismemberment and expansion of the basins. Well-constrained cross-sections show that the pencil-like intrusions at Ridgeway were probably localised along basin-bounding faults that occur at the margins of the thickest parts of the preserved basin-fill succession.

At Ridgeway, structurally controlled mineralisation is dominated by sub-vertical vein systems:
• North-, west–northwest- and northeast-striking mineralised stockworks and veins most intensely developed in the porphyry intrusions and wall rock;
• East-, northeast- and northwest-striking chalcopyrite-rich sheeted quartz veins.

The vein orientations were generally controlled by pre-existing fractures and the prevailing stress state, and in part by the geometry of the intrusions with which the mineralised veins are associated (Cuison, 2010).

The frequency of the veins and intensity of alteration decreases away from the intrusive complex margin (Wilson et al., 2003). Ore minerals include bornite and chalcopyrite with lesser covellite and gold and occur in veins and as disseminations (Wilson et al., 2003).

Sulphide minerals are zoned from a bornite to chalcopyrite (plus gold) core, outwards and upwards through a chalcopyrite-rich to an outer pyrite-rich domain.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityProductUnits2018201720162015
Gold Metal in conc./ doré koz 41751223
Copper Metal in concentrate M lbs 4.46.62479,366
Copper Concentrate kt 61243152

Operational metrics

Metrics2018201720162015
Ore tonnes mined 453 kt197 kt4,921 kt9,351 kt
Tonnes milled 442 kt1,147 kt4,006 kt9,349 kt

Production Costs

Commodity production costs have not been reported.

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Apr 16, 2024
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