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Shotgun |
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Alaska, USA |
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Au Ag Cu
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Shotgun gold deposit comprises a stockwork of Au-As mineralisation in a Late-Cretaceous (69.7±0.3 Ma) granite porphyry stock, approximately 150 km north of Dillingham in SW Alaska.
It is a low oxygen fugacity porphyry Au-As deposit that has characteristics of both intrusion-related gold and porphyry copper deposits. Although it has different mineralisation and alteration assemblages, it is texturally identical to Cu-Mo porphyries. The deposit has average estimated concentrations of 1.4 ppm Au, 6.1 ppm Ag, 0.5% As, 0.07% Cu, 40 ppm Mo, and 8 ppm Bi, with the bulk of the gold occuring in an intense quartz stockwork and breccias. Sulphides include, arsenopyrite>>pyrite>pyrrhotite>chalcopyrite. It lacks K alteration although it contains vein and pervasive albite-quartz-sericite-carbonate. Early high-temperature, low-fugacity sulphide mineralisation (arsenopyrite-loellingite-pyrrhotite) gave way to later, lower-temperature, moderately high-fugacity sulphide conditions (pyrite-bornite-chalcopyrite). Deposition temperatures have been measured at between 470 and 630 °C.
The ores at Shotgun contain primary native gold, native bismuth, Bi-Te sulphides, cubanite, maldonite, scheelite and sphalerite, as well as supergene covellite, chalcocite, marcasite, and native copper.
The Shotgun deposit is essentially an intrusion-related Au-As-Bi deposit emplaced at pressures and temperatures typical of a porphyry system.
The inferred resource using a 0.5 g/t Au cutoff is 30 tonnes gold (approx 1 Moz).
Preliminary metallurgical results indicate >90% gold is recoverable by cyanide leaching.
The most recent source geological information used to prepare this decription was dated: 2001.
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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Baker, T., Ebert, S., Rombach, C. and Ryan, C.G., 2006 - Chemical Compositions of Fluid Inclusions in Intrusion-Related Gold Systems, Alaska and Yukon, Using PIXE Microanalysis: in Econ. Geol. v.101, pp. 311-327.
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Rombach, C.S. and Newberry, R.J., 2001 - Shotgun deposit: granite porphyry-hosted gold-arsenic mineralization in southwestern Alaska, USA: in Mineralium Deposita v.36, pp. 607-621.
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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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