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Highland Valley - Krain |
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British Columbia, Canada |
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Cu Mo
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Super Porphyry Cu and Au
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The Krain deposit is located within the lower Jurassic Guichon Creek Batholith, near Kamloops in British Columbia, Canada.
For details of the geological setting see the Highland Valley overview record.
This deposit is unique in the district in that it is partly covered by post-mineral volcanics which have preserved its oxidised cap, which is up to 100 m thick. The deposit lies on the southern boundary of an extensive area of post-mineral cover, consisting of continental volcanic and interbedded sedimentary rocks of the early Tertiary Kamloops Group. Mineralisation occurs within the Guichon Granodiorite variety of the Highland Valley phase of the Guichon Creek Batholith, and within younger anastomosing dykes and small stocks (see the section above for a geological description of the phases and setting of the Guichon Creek Batholith). The dykes and stocks exhibit textures ranging from porphyritic to hypidiomorphic-granular, while the more equi-granular varieties closely resemble the quartz-diorites of the Bethlehem phase of the batholith. The mineralised porphyry system at Krain occurs within a broad north-westerly trending zone that contains other prospects and the Bethlehem deposit 7 km to the south. This broad zone is characterised by numerous sub-parallel NW trending porphyry dykes, as well as prominent fracture related, but non-pervasive chlorite-epidote-chalcopyrite ±pyrite±bornite hydrothermal vein and fracture selvage assemblages. At Krain mineralisation is closely associated with an elongate 1000 x 200 m dyke-like stock which is un-roofed in a small area in the centre of the deposit. To the north-west and south-east along strike the stock plunges gently away from the high point in the prospect centre, while it dips about 70°to the south-west. Fracturing, brecciation, alteration and mineralisation are all most strongly developed in and around this high-point of the stock/dyke (Christie, 1976).
Well defined zonal patterns of primary sulphide mineralisation and silicate alteration are recognised around the core. The areas of highest fracture density, which are adjacent to the stock, are also the best areas of mineralisation. Within the core and near the contacts of the stock, chalcopyrite-bornite assemblages are found associated with molybdenite bearing quartz veinlets. Peripheral to this mineralisation, chalcopyrite-pyrite assemblages occur in fracture-stockwork fillings in which pyrite becomes more abundant outward, both within the wall-rocks and in the stock. Maximum total sulphide content is around 5%, and this occurs in a zone approximately coincident with the outer limit of 0.1% Cu grades. Associated zoned silicate alteration is pervasive and diminishes outwards from sericite-clay-chlorite assemblages in the core, through clay-chlorite and chlorite assemblages in the chalcopyrite zone, to chlorite-epidote assemblages in the pyrite zone. Beyond the approximate outer limit of 0.05% Cu, silicate alteration is no longer pervasive, although chlorite-epidote form pronounced fracture selvage halos which gradually diminish to fracture coatings over transition zones as much as 1000 m wide. The ore zone, as outlined by the 0.1% Cu cut-off line is an irregular elliptical area at surface of some 1000 x 400 m. These grades appear to persist for at least 500 m below the surface.
Published reserve figures include:
14 Mt @ 0.56% Cu, 0.02% Mo (Res. 1976, Christie, 1976).
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1996.
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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Christie, J.S., 1976 - Krain: in Sutherland Brown, A. (ed.)., 1976 Porphyry Deposits of the Canadian Cordillera, Canadian Institute of Mining and Metallurgy, Special Volume 15, pp. 182-185.
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McMillan W J, 2005 - Porphyry Cu-Mo Deposits of the Highland Valley District, Guichon Creek Batholith, British Columbia, Canada: in Porter, T.M. (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide, v.1 pp. 259-274
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| References in PGC Publishing Books: | |
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McMillan W J, 2005 - Porphyry Cu-Mo Deposits of the Highland Valley District, Guichon Creek Batholith, British Columbia, Canada, in Porter T M, (Ed), Super Porphyry Copper and Gold Deposits: A Global Perspective, v1 pp 259-274
 Abstract
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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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