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Sunrise Dam, Sunrise, Cleo |
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Western Australia, WA, Australia |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Sunrise Dam-Cleo operation is located ~55 km to the south of Laverton, 220 km NNE of Kalgoorlie, and 770 km NE of Perth, in the Eastern Goldfields province of the Archaean Yilgarn craton, in Western Australia.
Exploration tenements were first acquired over the Sunrise Dam area in 1983 by Canyon Resources Pty Ltd, the parent company of the then unlisted Delta Gold NL, targeting areas of outcropping banded iron formation and areas with favourable magnetic signatures. Exploration by Delta Gold in joint venture with Placer Pacific involved composite float sampling which produced interesting results, although significant areas of anomalous gold were not outlined until 1988. The first economic supergene gold mineralisation was encountered in July 1990 in transported sediment cover and by 1992 the extent of the full supergene deposit was indicated with a resource estimate in July 1994 of 4.8 Mt @ 3.0 g/t Au. The supergene open pit mine was opened in May 1995 with ore transported to Granny Smith for treatment.
In the meantime, Shell/Billiton Australia Ltd, whose interests were later acquired by Acacia Resources Limited in 1994, had begun ground acquisition in the area in 1987. Scout RAB drilling defined the Golden Delicious deposit (6.1 Mt @ 1.3 g/t Au, including 2.4 Mt at 1.8 g/t Au below barren weathered colluvium/alluvium) and then the main Cleo mineralisation 8 km to the SW. In 1993, the fourth drill hole at Cleo intersected 54 m @ 10 g/t Au. By September 1997, the total resource at Cleo was 18.35 Mt @ 4.2 g/t Au. Acacia had commenced open pit production at Cleo in February 1997. In June 1998, Acacia Resources was acquired by Anglogold Ashanti. The main Sunrise Dam-Cleo primary deposit extended north into the Delta-Placer Pacific leases and production from the two titles was combined into a single operation managed by Anglogold Ashanti with ore proportionately delivered to the Granny Smith and the new AngloGold Ashanti treatment plant on site. On exhaustion of the Placer-Delta resource, the Sunrise Dam operation was wholly owned and operated by Anglogold Ashanti. Underground mining commenced in 2003 with a number of different mining methods being applied, depending on the style of mineralisation and grade of the geological domain. By 2014, the open pit had been completed at a final depth of 500 m below surface and the mine was wholly an underground operation. Total production to 2016 was ~267 t of gold with ~110 t of contained gold in resources. In 2021, mining re-commenced at the Golden Delicious satellite pit, whilst a the and new higher-grade and Frankie orebody discovered in 2020, close to exisiting underground infrastructure, was accessed and exploited by the end of 2021. Other underground lode zones including Flamingo, Vogue and Carey Shear continue to expand underground resources (AngloGold Ashanti Operational Profile, 2022 and Diggers and Dealers Presentation, 2021).
Sunrise Dam is located on the eastern margin of the Kurnalpi Terrane of the Eastern Goldfields Superterrane, part of the Yilgarn Craton. It lies within the Laverton Tectonic Zone that straddles the boundary between the the Kurnalpi and Burtville terranes to the west and east respectively, overlapping sections of both. For detail of the regional setting of the Kurnalpi Terrane, see the Yilgarn Craton record.
The ore at the ~2670 Ma Sunrise Dam deposit is developed within both Archaean basement and overlying transported cover. The basement ore lies within the Laverton Tectonic Zone of the Yilgarn craton, characterised by major north-south shears and associated faults. The dominant host is strongly deformed, greenschist facies andesitic to basaltic/mafic-ultramafic volcaniclastic rocks and magnetite-rich shales and turbidites (banded iron formation), which have been intruded by both quartz-feldspar porphyry sills and dykes (e.g., Dolly porphyry) and localised ultramafic and lamprophyre dykes. The timing of gold mineralisation relative to the metamorphic peak has not been ascertained, although similar deposits elsewhere in the Yilgarn craton are inferred to have formed syn- to post- peak metamorphism. Gold mineralisation is found intermittently within a NE trending corridor over a length of 4.5 km, coincident with a strongly magnetic BIF rich sequence.
Gold mineralisation is structurally controlled and vein hosted, occurring in two main styles, namely: i). gently dipping shear-related and high strain veins; and ii). stockwork zones in steeply dipping planar faults with brittle characteristics, commonly concentrated at lithofacies contacts within the volcanic stratigraphy or porphyry margins, and within hinge domains in the magnetite shales (BIF). Gold is found in all lithologies, but is best developed in the Fe rich bands, in association with pyrite replacement of BIF. These mineralisation styles occur as:
Group I orebodies, which occur in shallowly dipping foliation parallel veins within a strong penetrative fabric that consists of a sericite±chlorite cleavage and/or schistosity. Veins typically contain quartz-carbonate±pyrite±arsenopyrite and quartz-sericite-carbonate-pyrite-chlorite alteration.
Group II lodes are steeply dipping and characterised by steep veins and breccias up to a few metres in width. Breccias comprise angular clasts of sericite-altered host-rock volcanics up to several cms across, locally with jigsaw fits, set in a quartz and quartz-carbonate matrix. Veins may be up to 5 m wide, and consist of carbonate-pyrite-arsenopyrite-quartz. Gently NW-dipping, laminated quartz-carbonate veins containing gold, arsenical sulphides and tellurides are also observed within Group II orebodies, and are interpreted to have formed during D4 dextral normal faulting.
Group III orebodies are hosted within steeply dipping stockwork breccia zones up to 20 m wide, and less commonly as vein zones. Stockwork veins commonly contain carbonate-chlorite-quartz±sericite±pyrite±arsenopyrite, with adjacent alteration typically consisting of sericite-quartz-pyrite-ankerite±arsenopyrite. The breccia is characterised by sericite-altered host-rock volcanics clasts and quartz and carbonate matrix.
Group IV lodes are hosted within the quartz-feldspar Dolly porphyry, with mineralisation being typically arsenic rich, occurring and within steep narrow (0.2 to 0.5 cm wide) gold-bearing quartz-pyrite-arsenopyrite veins.
These variably oriented gold-hosting structures and mineralisation styles are the result of a complex structural and mineralisation history involving at least six phases of deformation as observed at Sunrise Dam, namely:
• D1 - formed several major shallow- to moderately dipping northwest-trending shear zones (Cleo, Margies, Mako, Sunrise, Midway-GQ, and Carey). These include low-angle ductile shear zones, characterised by a penetrative S1 fabric, mostly parallel to the structures, are up to 40 m wide, and are vertically stacked above one another. Steeply dipping shear zones are also interpreted as initial D1 structures that subsequently underwent D3 reactivation.
• D2 - produced north- and south-plunging upright folds with steep axial surfaces, in response to east-west to WNW-ESE shortening, and S2 cleavage which crenulates S1. No mineralisation is associated with D2 structures, although the bulk of the ore accompanied D3 and D4.
• D3 - characterised by thrusting along gently dipping D1 shear zones and sinistral shearing along steeply dipping structures, accompanied by Group I and II orebodies (see below) in the respective structures. Quartz-feldspar porphyries (e.g., the Dolly dyke) are interpreted to have intruded during late D2 to D3 and locally host narrow gold-bearing quartz-pyrite veins (Group IV orebodies). These quartz porphyries are deformed by D3 shear zones and cut by S3 fabrics.
• D4 - resulted in dextral faults as a response to NE-SW shortening accompanied by steeply dipping stockwork vein (D4a) and breccia systems (D4b) that comprise the Group III orebodies.
• D5 - produced strike-slip faults as a result of SE compression.
• D6 - characterised by dextral conjugate faults caused by east-west shortening. Neither D5 nor D6 structures are mineralised.
In the transported cover, secondary (supergene) gold with extremely high gold grades was hosted by fluvial sediments within two distinct horizons, each of 2 to 12 m in thickness over a 600 x 200 m area and at a depth of from 5 to 40 m. These were developed near the base of Tertiary palaeochannels and horizontal blankets of mineralisation related to iron redox fronts and associated palaeo-water table.
The ore below the unconformity is developed in both oxidised and fresh bedrock, occurring as a shallow west dipping zone covering a plan area of 1600 x 700 m, and extending as a series of shoots to depths of more than 1400 m below the surface. These shoots are known as the Sunrise Deeps discovery.
In December 2000 the AngloGold Cleo resource totalled 40.8 Mt @ 3.39 g/t Au, while in December 1998 the Placer Dome Granny Smith section of the deposit had a resource of 11.3 Mt @ 3.2 g/t Au. Together these total more than 170 t of contained Au.
At 31 December 2010, (AngloGold Ashanti reserve statement):
Proved + Probable Reserves were: 13.89 Mt @ 3.08 g/t Au, and
Measured + Indicated + Inferred Resources were: 36.68 Mt @ 2.85 g/t Au (which includes the reserves, and totals 104.38 t of Au),
Additional low grade resources and stockpiles were: 22.8 Mt @ 2.70 g/t Au (for an additional 61.55 t Au)
Production in the year 2006 totalled 14.463 tonnes of Au and by 2010, 12.316 tonnes Au.
Total cumulative production to 2010 was 149 t (4.8 Moz) of gold at an average grade of 4.2 g/t Au.
At 31 December 2016, (Nugus et al., 2017):
Proved + Probable Reserves were: 22.23 Mt @ 1.88 g/t Au, and
Measured + Indicated + Inferred Resources were: 89.65 Mt @ 2.04 g/t Au (which includes the reserves) for 183 t of gold,
Total resources below infrastructure was 18.07 Mt @ 2.01 g/t Au containing 36 t of gold.
Total cumulative production to the ned of 2016 was ~267 t of gold.
At 31 December 2018, (AngloGold Ashanti reserve statement):
Measured + Indicated + Inferred Resources were: 84.0 Mt @ 2.16 g/t Au (which includes the reserves) for 181.6 t of gold.
The most recent source geological information used to prepare this decription was dated: 1999.
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.
Sunrise Dam
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Selected References:
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Baker T, Bertelli M, Blenkinsop T, Cleverley J S, McLellan J, Nugus M and Gillen D, 2010 - P-T-X Conditions of Fluids in the Sunrise Dam Gold Deposit, Western Australia, and Implications for the Interplay between Deformation and Fluids: in Econ. Geol. v105 pp 873-894
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Brown S M, Fletcher I R, Stein H J, Snee L W, Groves D I 2002 - Geochronological constrains on pre-, syn- and postmineralization events at the world-class Cleo Gold deposit, Eastern Goldfields Province, Western Australia: in Econ. Geol. v97 pp 541-559
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Brown S M, Groves D I, Newton P G N 2002 - Geological setting and mineralization model for the Cleo Gold deposit, Eastern Goldfields Province, Western Australia: in Mineralium Deposita v37 pp 704-721
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Brown S M, Johnson C A, Watling R J, Premo W R 2003 - Constraints on the composition of ore fluids and implications for mineralising events at the Cleo Gold deposit, Eastern Goldfields Province, Western Australia: in Australian J. of Earth Sciences v50 pp 19-38
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Gellatly, D.C., Ion, J.C., Ryal,l A.W., Thomson, R.M. and Holmes, J.S., 1995 - The Sunrise Gold Deposit - A Greenfields Discovery: in New Generation Gold Mines, Case Histories of Discovery, Conf. Proc., Perth, Nov, 1995 AMF, Adelaide pp. 10.1-10.9.
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Newton, P.G.N., Gibbs, D., Grove, A., Jones, C.M. and Ryall, A.W., 1998 - Sunrise-Cleo Gold Deposits: in Berkman D A, Mackenzie D H (Eds), Geology of Australian and Papua New Guinean Mineral Deposits The AusIMM, Melbourne pp. 179-186.
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Sung Y-H, Brugger J, Ciobanu C L, Pring A, Skinner W and Nugus M, 2009 - Invisible gold in arsenian pyrite and arsenopyrite from a multistage Archaean gold deposit: Sunrise Dam, Eastern Goldfields Province, Western Australia: in Mineralium Deposita v.44 pp. 765-791
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Wang, R., Cudahy, T., Laukamp, C., Walshe, J.L., Bath, A., Mei, Y., Young, C., Roache, T.J., Jenkins, A., Roberts, M., Barker, A. and Laird, J., 2017 - White Mica as a Hyperspectral Tool in Exploration for the Sunrise Dam and Kanowna Belle Gold Deposits, Western Australia: in Econ. Geol. v.112, pp. 1153-1176.
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Zhang, Y., Schaubs, P.M., Sheldon, H.A., Poulet, T. and Karrech, A., 2103 - Modelling fault reactivation and fluid flow around a fault restraining step-over structure in the Laverton gold region, Yilgarn Craton, Western Australia: in Geofluids v.13, pp. 127-139.
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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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