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Sams Creek |
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South Island, New Zealand |
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Au
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Super Porphyry Cu and Au
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The Sam's Creek gold deposit is located 25 km south of Takaka in northwest Nelson, northern South Island, New Zealand.
The Sam's Creek area lies within the Eastern Sedimentary Belt of the Takaka terrane, a belt of Lower Palaeozoic metasedimentary rocks which were deformed and metamorphosed under lower greenschist facies conditions prior to intrusion of the Late Devonian (367 Ma) Rameka Complex. The terrane was subsequently intruded by granite and granodiorite of the Early Cretaceous Separation Point Suite. Three phases of deformation have been identified in the region: i). a first phase of recumbent folding (F 1 ), ii). a second of inclined folds (F 2 ) about subhorizontal north-south trending axes, iii). and a third (F 3 ) of localised northeast to southeast trending folds.
A peralkaline granite porphyry dyke which hosts gold-bearing sulphide-quartz-siderite veins at Sams Creek has a thickness of 30 to 40 m and lateral extent of at least 7 km. The granite dyke, which has thin lamprophyre dykes along its contacts, intrudes Ordovician-Silurian metapelite and quartzite. Gold is associated with arsenopyrite and pyrite in an irregular stockwork of deformed sulphide-quartz-siderite veins that are confined to the granite porphyry dyke.
The unaltered granite porphyry is composed of scattered phenocrysts of perthite (0.5 -5 mm in length), arfvedsonite, aegerine and quartz (up to 4 mm) in a fine grained (~0.2 mm) hypidiomorphic granular aggregate of perthite, quartz, plagioclase, arfvedsonite and aegerine. Myrmekitic intergrowths of quartz and plagioclase are common. Ilmenite, rutile and fluorite are accessory minerals.
The mineralised veins, the granite and lamprophyre dykes have all been deformed by more than one phase of folding, the youngest of which is Early Cretaceous. The granite has been hydrothermally altered, with early magnetite-siderite ±biotite alteration overprinted by sulphide and quartz-siderite veins and quartz-perthite-albite-siderite-pyrite-rutile ±sericite alteration assemblages. The sulphide veins are composed of arsenopyrite +pyrite ±gold ±galena ±sphalerite ±chalcopyrite ±pyrrhotite ±graphite, with minor quartz and siderite. The gold contains significant silver (up to 30.8 wt%) and ranges from 692 to 844 fineness.
The 2004 resource estimate at Sams Creek is 10.7 Mt @ 2.12 g/t Au containing 22.7 tonnes of Au at a 0.7 g/t Au cut-off and limited to a depth of 140 m.
The most recent source geological information used to prepare this decription was dated: 2004.
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.
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Selected References:
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Brathwaite R L and Faure K, 2004 - The Sams Creek Peralkaline Granite Hosted Gold Deposit, Northwest Nelson,New Zealand - A New Variant on Alkaline Intrusion-Related Gold Deposits: in Hi Tech and World Competitive Mineral Success Stories Around the Pacific Rim Proc. Pacrim 2004 Conference, Adelaide, 19-22 September, 2004, AusIMM, Melbourne, pp 127-133
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Faure K and Brathwaite R L, 2006 - Mineralogical and stable isotope studies of gold-arsenic mineralisation in the Sams Creek peralkaline porphyritic granite, South Island, New Zealand: in Mineralium Deposita v40 pp 802-827
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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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