Poison Mountain - Copper Creek, Fenton Creek

British Columbia, Canada

Main commodities: Cu Au Mo
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The Poison Mountain porphyry copper - gold deposit is on the southwest flank of Poison Mountain, 37 km west of the Big Bar cable ferry on the Fraser River in British Columbia, Canada.

Published reserve and production figures are quoted immediately above.

    159 Mt @ 0.33% Cu, 0.007% Mo, 0.12 g/t Au, 3.1 g/t Ag (Resource. 1984, Dawson, et al. 1991).
    280 Mt @ 0.26% Cu, 0.14 g/t Au, 0.007% Mo, 0.51 g/t Ag - Copper Creek Zone, 1993
    18.3 Mt @ 0.31% Cu 0.13 g/t Au - Fenton Creek Zone, 1993

The Poison Mountain porphyry copper-molybdenum deposit is associated with one of three north-west to northerly trending Eocene porphyries that intrude north-west striking arkosic sandstones, greywackes, conglomeratic sandstones and argillites of the Lower Cretaceous Jackass Mountain Group, 3.2 km to the north-east of the north-west trending major Yalakon Fault. These are the North, Main and East Porphyries (Seraphim & Rainboth, 1976).

Two of these porphyry bodies the North and the Main, are zoned with hornblende-quartz monzonite cores and biotite-quartz monzonite perimeters. The cores of these porphyries are relatively un-altered, with only limited replacement of hornblende by chlorite, and a few patches of carbonate and clay-mineral alteration. In contrast, in the border zones, hornblande is not evident magascopically, although it originally constituted 15 to 20% of the rock. It is almost totally replaced by fine grained green-brown biotite, minor magnetite, chalcopyrite and a few coarse grains of apatite. The grey groundmass is a fine grained mosaic of quartz, plagioclase, magnetite, chalcopyrite, biotite and apatite. No K-feldspar has been identified, and plagioclase is only locally sericitiosed along fractures.

The un-mineralised East Porphyry is a relatively unaltered and uniform body of coarse plagioclase porphyry, and is probably the youngest. The Main and the North Porphyries are some 1500 x 600 m, and 400 x 400 m respectively at surface, while the East Porphyry is 300 to 600 m wide and extends from more than 3 km (Seraphim & Rainboth, 1976).

Both the zoned porphyries, the North and Main, have associated Cu-Mo mineralisation. The mineral concentrations approach ore grade in a horseshoe shaped semi-annular zone associated with the eastern and southern sections of the Main Porphyry, approximately coincident with the biotite altered border phases of the intrusions and adjacent biotite hornfelsed sedimentary rocks. The zone is around 200 m wide and extends for 1500 m along the southern rim of the porphyry, and for 600 m along its eastern margin. (Seraphim & Rainboth, 1976)

The sulphides in decreasing abundance are pyrite, chalcopyrite, molybdenite and bornite, with quartz, gypsum and calcite. The sulphides exist as vein and fracture fillings, and as disseminations. Chalcopyrite and bornite are almost equally divided between disseminations, chiefly replacing mafic minerals, and fracture fillings in quartz veins and 'dry' fractures. Pyrite, together with magnetite and hematite, is widespread and forms an irregular halo in the host rocks around both the mineralised zone in the Main and North Porphyries (Seraphim & Rainboth, 1976).

Calcite and gypsum also occur as hydrothermal minerals, while chlorite-epidote alteration occurs sporadically within Jackass Mountain Group rocks for several km around the deposit.

The intrusion, potassic alteration and mineralization at Poison Mountain have been dated at about 59 to 56 Ma (Paleocene) (Seraphim & Rainboth, 1976).

The most recent source geological information used to prepare this summary 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.

  References & Additional Information
   Selected References:
Seraphim R H and Rainboth W  1976 - Poison Mountain: in Sutherland Brown A (Ed.), 1976 Porphyry Deposits of the Canadian Cordillera, Canadian Institute of Mining and Metallurgy,   Special Volume 15, pp 323-328

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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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