Porphyry Copper-Gold-Molybdenum Mineralization in The Island Copper Cluster, Vancouver Island
J.A. Perelló, J.A. Fleming, K.P. O'kane, P.D. Burt, G.A. Clarke, J.A. Himess, A.T. Reeves, 1994. "Porphyry Copper-Gold-Molybdenum Mineralization in The Island Copper Cluster, Vancouver Island", Selected Mineral Deposits of British Columbia, Canada: I. Porphyry Ore Deposits Of Southern British Columbia II. Mineral Deposits Of Northern Vancouver Island, C.R. Stanley, W.J. McMillan, Andre Panteleyev
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The Island Copper Cluster (ICC), situated at the northern end of Vancouver Island, consists of five porphyry copper-gold-molybdenum systems genetically associated with stock and dike-like rhyodacitic porphyries of Jurassic age (approximately 180 ma) that intruded the island arc, calc-alkaline basalts, andesites and pyroclastic rocks of the comagmatic Bonanza Group. The systems (Island Copper; Bay Lake; G Zone; Red Island; and Rupert Inlet) are coincident with a series of northwest-trending magnetic highs and regional faults aligned for more than 10 km. They all share many similarities in the alteration-mineralization geometries but vary largely in size and grades. Copper-bearing skarn and vein-type mineralization also constitutes an integral part of the porphyry systems.
The only economic deposit of the cluster is the Island Copper mine controlled and operated by BHP Minerals Canada Ltd., which had initial estimated reserves of 257 million tonnes at 0.52 per cent copper and 0.017 per cent molybdenum at a 0.3 per cent copper cutoff grade. At Island Copper, mineralization is associated with multiphase rhyodacitic intrusions and hydrothermal breccia bodies. Available data suggest that the porphyry system evolved dynamically from an early, probably juvenile-dominated stage, to one strongly influenced by meteoric waters, as the main heat source cooled . and further intrusion and brecciation took place. Three main stages of alteration and mineralization have been differentiated:
An Early Stage, related to the intrusion of a main rhyodacite porphyry, involved the development of four outwardly progressing zones: a) a copper-barren stockworked core of quartz-amphibole-albite-magnetite( apatite, scapolite); b) a biotite-magnetite zone
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Selected Mineral Deposits of British Columbia, Canada: I. Porphyry Ore Deposits Of Southern British Columbia II. Mineral Deposits Of Northern Vancouver Island
km 0 Depart from the Delta Town and Country Inn. Zero your odometer at the Inn. Turn right onto River Road (Highway # 17). Cross the overpass and take the freeway on-ramp onto Highway # 99 south toward Seattle.
km 8 Take Exit # 20 (Highway # 10) east toward Langley and Hope. The road climbs a hill from the Fraser River delta late Holocene (< 8000 years before present) Salish Sediments (shoreline sand and clayey silt; river gravel, sand, silt and clay; peat bogs and swamps) through Pleistocene Vashon Drift (Fraser Glaciation) and pre-Vashon deposits from the Olympia and Highbury non-glacial intervals and the Semiahmoo and Westlynn Glaciations (tills, glaciofluvial, glaciolacustrine, glaciomarine and deltaic sediments), onto early Holocene (10,000 to 8000 years before present) glacial retreat and melt-out deposits of the Sumas Drift, Ft. Langley Formation and Capilano Sediments (Armstrong, 1990).
Lacustrine (principally oxbow lake) environments of these units near Maple Ridge, British Columbia are the only good local source of fire clay. These are valuable deposits because of their low Ca concentrations, relative to Na and K, and true clay mineralogy. Other clay deposits within British Columbia are predominantly glacial, and thus generally contain only un-weathered clay-sized particles instead of clay minerals. Furthermore, the overall quartz diorite composition of the country rocks that underlie the Fraser River drainage basin generally results in Ca-rich bricks which form a generally undesirable white precipitate over time.
km 32 Highway# 10 turns left toward Fort Langley.
km 36 Highway # 10 turns right.
km39 Turn right onto Highway # 1 (the Trans-Canada Freeway) toward Hope. This freeway crosses the ‘Lower Mainland’, the agriculturally important Fraser River delta (here consisting predominantly of Ft. Langley Formation glacial and deltaic sediments; Armstrong, 1990), which narrows to a significant defile at the town of Hope.
Km 51 In clear weather, Mt. Baker (3285 m), a Cascade andesite stratovolcano is in view directly ahead. This most-northerly United States Cascade volcano last erupted in 1843 during the waning stages of its third cycle of volcanism (approximately 50, 31–34 and 17 million years ago). It is now considered to be dormant, although minor fumarolic activity has occurred within and immediately adjacent to its 90 m wide summit crater since 1975 (Armstrong, 1990). Mt. Baker is considered to be a ‘coherent’ Cascade volcano (McBimey, 1968), meaning that it is dominated by relatively quiescent andesitic lava and phreatic ash eruptions, without