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Craigmont |
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British Columbia, Canada |
| Main commodities:
Cu
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Super Porphyry Cu and Au
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The Craigmont Cu-Fe skarn deposit is adjacent to the southern margin of the lower Jurassic Guichon Creek Batholith, near Kamloops in British Columbia, Canada.
For details of the geological setting see the Highland Valley record.
The host to ore are the sedimentary and volcanic rocks of the upper Triassic Nicola Group. In the mine area this group is represented by a complex sequence at least 600 m thick which has been subdivided into Basalt, Rhyolite, Carbonate and Clastic Sediments Units. All strike and dip parallel to the contact of the batholith, and are within the batholith contact aureole. Only the Clastic Sediment Unit however, is in contact with the batholith. The majority of the skarn and ore is within facies that comprise lime sandstone, lime siltstone, quartzo-feldspathic siltstone and argillite. The first stage of development of the ore is magnetite rich, with actinolite-epidote-magnetite skarn developed within basaltic rocks and Fe-bearing siltstones of the facies listed above, while barren grossular garnet-epidote-calcite-pyrite skarns are found in Fe-poor rhyolitic bands of the same facies and the Carbonate Unit. In the second stage massive barren grandite garnet skarn replaced mineralised first stage skarns in the vicinity of diorite plugs and specularite ore formed in brecciated first stage skarn and clastic rocks away from the plugs. While the first stage skarn requires no addition of thge main rock forming elements, only a redistribution and concentration of the elements already present, Cu was apparently added, or was subjected to a better process of redistribution and concentration compared to the other elements. The second stage similarly requires only redistribution and recrystalisation of first stage skarns and ore (Morrison, 1980).
Cu and Fe are the only elements in economic concentrations and chalcopyrite is the onoly significanr Cu mineral. The chalcopyrite is disseminated and is interstitial to magnetite in the first stage mineralised skarns, and is interstitial to the second stage specularite in the matrix of the breccias of that stage. Chalcopyrite also occurs with pyrite as stringer ore in bleached sediments and rhyolite tuffs in the stratigraphic footwall of the main orebodies. The Craigmont deposit has more in common with Cu-Fe deposits found in meta-sedimentary and meta-volcanic rocks than with those generally associate with porphyry copper deposits (Morrison, 1980). Morrison (1980) considers Craigmont to be more likely a product of concentration of metals already within the Nicola Group by the Guichon Creek Batholith, than of the mineralising event that produced the porphyry Cu deposits of the central Guichon Creek Batholith. This is reinforced by the identification of Cu-Fe rich units within the host rocks which extend away from the batholith, and apparently control the distribution of much of the ore within the sequence which is restricted to the aureole.
Published reserve and production figures comprised:
33.7 Mt @ 1.77% Cu, 19% Fe (Prod. 1961-82, Dawson, etal. 1991)
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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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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