CYPRUS MASSIVE SULPHIDE Cu (Zn) / G05

Cortesia del Gobierno de BRITISH COLUMBIA. Ministerio de Enegia y Minas

Metallics And Coal

GEOLOGICAL CHARACTERISTICS	ECONOMIC FACTORS
EXPLORATION GUIDES	REFERENCES

IDENTIFICATION

Cyprus massive sulphide, cuprous pyrite.

Cu, (Au, Ag, Zn, Co, Cd).

(British Columbia - Canada/International): Chu Chua (092F140), Lang Creek (104P008), Hidden Creek (103P021), Bonanza (103P023), Double Ed (103P025), ; Cyprus; York Harbour and Betts Cove (Newfoundland, Canada); Turner-Albright (USA); Lokken (Norway).

GEOLOGICAL CHARACTERISTICS

Deposits typically comprise one or more lenses of massive pyrite and chalcopyrite hosted by mafic volcanic rocks and underlain by a well developed pipe-shaped stockwork zone.

Within ophiolitic complexes formed at oceanic or back-arc spreading ridges; possibly within marginal basins above subduction zones or near volcanic islands within an intraplate environment.

Lenses commonly are in tholeiitic or calcalkaline marine basalts, commonly pillowed, near a transition with overlying argillaceous sediments. Many lenses appear to be structurally controlled, aligned near steep normal faults.

Any age. Deposits in British Columbia are primarily Mississippian-Permian or Late Triassic.

Tholeiitic or calcalkaline pillow and flow basalts, basaltic tuff, chert, argillite. Overlying "umbers" consist of ochre [Mn- poor, Fe-rich bedded mudstone containing goethite, maghemite (Fe3O4-Fe2O3 mixture) and quartz] or chert.

Concordant massive sulphide lens overlying cross-cutting zone of intense alteration and stockwork mineralization and hydrothermally altered wallrock, and overlain by chert.

Massive, fine-grained pyrite and chalcopyrite, sometimes brecciated or banded?; massive magnetite, magnetite-talc and talc with variable sulphide content; associated chert layers, locally brecciated, contain disseminated sulphides; disseminated, vein and stockwork mineralization beneath lenses.

Pyrite, chalcopyrite, magnetite, sphalerite, marcasite, galena, pyrrhotite, cubanite, stannite-besterite, hematite. Sometimes goethite alteration of top of sulphide layer.

Talc, chert, magnetite, chlorite.

Chlorite, talc, carbonate, sericite and quartz veins in the core of the stringer zone, sometimes with an envelope of weak albite with illite alteration.

Prominent structural control with clustering or alignment of sulphide lenses along early normal faults, near transition from mafic pillow basalts; less commonly mafic tuff; to overlying fine pelagic material.

Seafloor deposition of sulphide mounds contemporaneous with mafic volcanism, such as spreading ridges.

Vein and stockwork Cu (-Au) mineralization; Mn and Fe- rich cherts; massive magnetite (-talc) deposits.

EXPLORATION GUIDES

Cu, Zn; common depletion of Ca and Na; less common, local minor Na enrichment; possible local K enrichment; prominent Fe and Mn enrichment in footwall stringer zone.

Sulphide lenses usually show either an electromagnetic or induced polarization signature depending on the style of mineralization and presence of conductive sulphides.

Mafic ophiolitic volcanic rocks; transition to argillite; clustering or alignment of deposits indicative of fault control; ochre and exhalite (chert) horizons; regional pyritic horizons.

ECONOMIC FACTORS

Published average is 1.6 Mt containing 1.7 % Cu, 0-33 g/t Ag; 0-1.9 g/t Au, 0-2.1 % Zn ( Cox and Singer, 1986). B.C. examples: Chu Chua reserves - 1.043 Mt, 2.97 % Cu, 0.4 % Zn, 8.0 g/t Ag, 1.0 g/t Au; Anyox deposits - 0.2 to 23.7 Mt, approx. 1.5% Cu, 9.9 g/t Ag and 0.17 g/t Au.

Deposits at Anyox produced 335,846 tonnes copper, 215,057 kg silver and 3,859 kg gold. Worldwide these deposits are generally significant more for their higher grades and polymetallic nature, than their size.

REFERENCES

• Cox, D.P. and Singer, D.A., Editors (1986): Mineral Deposit Models; U.S. Geological Survey, Bulletin 1693, 379 pages.

• Höy, T., (1991): Volcanogenic Massive Sulphide Deposits in British Columbia; in Ore Deposits, Tectonics and Metallogeny in the Canadian Cordillera, McMillan, W.J., Coordinator, B. C. Ministry of Energy, Mines and Petroleum Resources, Paper 1991-4, pages 89-123.

• Franklin, J.M., Lydon, J.W. and Sangster, D.M., (1981): Volcanic-associated Massive Sulfide Deposits; Economic Geology, 75th Anniversary Volume, pages 485-627.

• Lydon, J.W., (1988): Volcanogenic Massive Sulphide Deposits, Part 2: Genetic Models; Geoscience Canada; Volume 15, pages 43-65.

• Constantinou, G. and Govett, G.J.S., (1972): Genesis of Sulphide Deposits, Ochre and Umber of Cyprus; Institution of Mining and Metallurgy, Transactions, Volume 8, pages B36-B46.

• Spooner, E.T.C., (1980): Cu-pyrite Mineralization and Seawater Convection in Oceanic Crust - The Ophiolite Ore Deposits of Cyprus; in The Continental Crust and its Mineral Deposits, Strangway, D.W., Editor, Geological Association of Canada, Special Paper 20, pages 685-704.

Mineral Deposit

Cortesia del Gobierno de BRITISH COLUMBIA. Ministerio de Enegia y Minas