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Catface |
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British Columbia, Canada |
| Main commodities:
Cu Mo
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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 Catface porphyry copper-molybdenum deposit is located on the west coast of Vancouver Island, some 13 km NW of Tofino in British Columbia, Canada, (#Location: 49° 15' 23" N 125° 58' 51" W).
Published resource figures include:
188 Mt @ 0.42% Cu, 0.0084% Mo at 0.30% Cu cut-off and 1.1:1 stripping ratio
(Indicated resource Falconbridge, 1990),
151 Mt @ 0.45% Cu (Resource, 1984, Dawson, 1991),
158.4 Mt @ 0.44% Cu, at 0.31% Cu cutoff -or- 78.2 Mt @ 0.53% Cu, at 0.4% Cu cutoff .
(Resource, Doublestar Resources Ltd, 1999).
The main Catface Cu-Mo deposit is hosted by intrusive rocks of the Mesozoic and/or Paleozoic Westcoast Complex and a hood or capping of volcanics of the Devonian to Permian Sicker Group or to the Upper Triassic Karmutsen Formation of the Vancouver Group. The volcanics, which have been weakly hornfelsed near the intrusions, are the oldest rocks on the property and comprise a few thousand metres of basaltic and andesitic flows, tuff breccias and agglomerates, with some lesser intercalated limestones elsewhere in the district.
The intrusives include:
i). the extensive lower Jurassic (192 Ma) West Coast Diorite, of the Island Plutonic Suite found along the west coast of Vancouver Island and to the west of the deposit;
ii). the Early to Middle Eocene Tofino Intrusive Suite, previously the Catface Quartz Monzonite phase, which is generally coarse grained and leuco-cratic and occurs as a sill like mass emplaced along the volcanic-diorite contact. Its age is uncertain, suspected of being either Jurassic or late Cretaceous to early Tertiary, related to the Island Plutonic Suite. It contains xenoliths of volcanic rocks and has been subjected to propylitic alteration to produce an assemblage that includes chlorite, epidote, zoisite and sericite. Kaolinite, quartz, biotite and magnetite alteration minerals are also recognised. The largest exposure outcrops over an area of 3000x1500 m in the prospect area;
iii). Hecate Bay Quartz Diorite, which a medium grained, equi-granular leucocratic rock which intrudes the volcanics, the West Coast Diorite and the quartz monzonite. It is dated at early Tertiary (48±12 Ma);
iv). Porphyritic Quartz Diorite and Granodiorite, which occur in bulbous dyke like forms, outcropping over an area of some 770x700 m in the prospect area, and extending to depths of at least 600 m. These are believed to be related to the Hecate Bay Quartz Diorite;
v). Porphyry dykes, which are pre-ore and constitute up to 5% of the rocks in the prospect area and include andesite, dacite and quartz-feldspar porphyry that trend north to northwest and dip 50 to 70° east.
The main mineralised rocks are the quartz-monzonite and volcanic rocks, each of which contain about one third of the total sulphides, with the remainder being within the quartz-diorite and the dykes. Brecciated and fragmental volcanics and well fractured to brecciated quartz-monzonite are the most favourable hosts, while sections of the porphyritic quartz-diorites are the least favourable.
Faulting predates mineralisation and strikes both northerly and easterly. Jointing in the younger intrusive rocks trends north to northeast and dips at 50 to 70° east. A less persistent joint set in these intrusions trends east to southeast and dips steeply north. Joints in the volcanic rocks trend 156° and dip 51° east.
The main mineralised zone, as defined by an arbitrary 0.2% Cu cut-off, has a bulbous outline and measures some 900 m along a NW axis and averages 600 m in width, and extends to a depth of around 350 m. The distribution of mineralisation is largely controlled by the density of faulting and fracturing. Within this mass, there is a bornite zone with accompanying chalcopyrite and trace pyrite and pyrrhotite, which measures 700 m north-south by 450 m east-west, and coincides approximately with more intense silicification. The bornite zone partially encircles a low grade central core of uncertain size and shape which coincides with less fractured and altered porphyritic quartz-diorite. This bornite annulus in turn grades outwards into an surrounding chalcopyrite-pyrite zone, with some pyrrhotite. These zones transgress all rock boundaries.
Hydrothermal alteration is only weakly to moderately developed, although a broadly annular pattern of zoning is recognised, coinciding with the distribution of mineralisation. In the central low grade core, which is several hundred metres in diameter, feldspars have been altered to sericite and kaolinite, while mafic minerals have been chloritised, and silicification, including quartz in fractures, is represented. Some 2 km from the centre the alteration has faded away and is not recognised. Secondary biotite is recognised in clusters in the intrusives and is associated with sulphide veinlets.
Copper minerals include chalcopyrite, bornite and some chalcocite, with significant secondary carbonate and copper oxide minerals occurring on fractures. Other minerals recognized include pyrite, pyrrhotite, covellite, idaite, digenite, native copper, cuprite, valleriite, tenorite, limonite, goethite, magnetite, hematite, cupriferous chalcedony-opal and scheelite.
Chalcopyrite is the most common sulphide within the main deposits, with lesser bornite, occurring as veinlets, dry fracture coatings, or as disseminations associated with mafic minerals. Chalcopyrite is very widespread in all rocks within and outside of the prospect, although the best mineralisation is located in the volcanic rocks and in the younger porphyritic phases, but the grade is not consistent. Molybdenite occurs throughout the deposit as finely disseminated flakes, as rosettes in quartz veins, or as coatings in or near quartz filled fractures, and is associated with the Cu minerals. Pyrite, although less abundant than chalcopyrite, also occurs in most rocks in and around the deposit.
The most recent source geological information used to prepare this decription was dated: 2006.
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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McDougall J J, 1976 - Catface: in Sutherland Brown A (Ed.), 1976 Porphyry Deposits of the Canadian Cordillera, Canadian Institute of Mining and Metallurgy, Special Volume 15, pp 299-310
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