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Donlin Creek |
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Alaska, USA |
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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 Donlin Creek gold deposit, is located ~400 km NW of Anchorage, and 200 km NE of the inlet port of Bethel in southwestern Alaska.
It has been dated at approximately 70 Ma and is hosted in the Kuskokwim flysch basin of Late Cretaceous age, that was developed in the back section of an arc region of an active continental margin, on previously accreted oceanic terranes and continental fragments. The mineralisation is structurally hosted by a competent suite of hypabyssal, mainly rhyolitic to rhyodacitic, and commonly porphyritic intrusives that form an 8 x 3 km dyke complex. This complex is part of a regional approximately 77 to 58 Ma magmatic arc.
The deposit is subdivided into more than ten different prospects within the complex. Most are composed of dense quartz ± carbonate veinlet networks that fill NNE striking extensional fractures in the NE trending igneous rocks. The principal alteration processes are sericitisation, carbonatisation and sulphidation, with the dominant sulphides being arsenopyrite, pyrite and younger stibnite. Gold occurs within the arsenopyrite and is refractory.
The Dome prospect on the northern margin of the cluster of mineralised locations comprises copper and gold bearing stockwork veins which are overprinted/cut by younger, lower temperature, auriferous veins that represent the main Donlin Creek gold mineralising event. The epizonal Donlin Creek deposits are interpreted as orogenic - intrusion related, and have many differences to epithermal or Carlin type occurrences. It has been suggested that the ore forming fluids were derived by either broad scale metamorphic devolatilization above rising mantle melts or exsolution from a magma that was dominated by a significant flysch melt component.
Reserves and resources as at 12 April, 2012, (Novagold Resources Inc, website, 2012) were:
Proven + probable reserves - 504.8 Mt @ 2.09 g/t Au,
Measured + indicated resource - 541.3 Mt @ 2.24 g/t Au
Inferred resource - 92.2 Mt @ 2.o2 g/t Au.
For detail consult the references listed below.
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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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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Goldfarb, R.J., Ayuso, R., Miller, M.L., Ebert, S.W., Marsh, E.E., Petsel, S.A., Miller, L.D., Bradley, D., Johnson, C. and McClelland, W., 2004 - The Late Cretaceous Donlin Creek Gold Deposit, Southwestern Alaska: Controls on Epizonal Ore Formation: in Econ. Geol. v.99, pp. 643-671.
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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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