Sinclair, W.D. (1996): Manto and Stockwork Sn, in Selected British Columbia Mineral Deposit Profiles, Volume 2 - Metallic Deposits, Lefebure, D.V. and Hõy, T., Editors, British Columbia Ministry of Employment and Investment, Open File 1996-13, pages 105-109.
SYNONYMS: Replacement Sn, distal Sn skarn, Renison-type.
COMMODITIES (BYPRODUCTS): Sn (Cu, Zn, Pb, Ag, Sb, Cd, Bi, In).
EXAMPLES (British Columbia - Canada/International): Renison Bell, Cleveland and Mt. Bischoff (Tasmania, Australia), Dachang and Gejiu districts (China).
CAPSULE DESCRIPTION: Disseminated cassiterite occurs in massive sulphide replacement bodies in carbonate rocks and in associated veins, stockworks and breccias. Felsic intrusions are nearby, or adjacent to the deposits and may also be mineralized.
TECTONIC SETTING: Postorogenic underlain by cratonic crust containing carbonate rocks.
DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: Carbonate rocks intruded by epizonal felsic intrusive rocks.
AGE OF MINERALIZATION: Mainly Paleozoic to Mesozoic, but other ages possible.
HOST/ASSOCIATED ROCK TYPES: Mainly limestone or dolomite; chert, pelitic and Fe-rich sediments, and volcanic rocks may also be present. Genetically-related granitic plutons and associated felsic dikes are typically F and/or B rich. They are commonly porphyritic.
DEPOSIT FORM: Variable: massive, lensoid to tabular, concordant sulphide-rich bodies in carbonate rocks; veins and irregular stockwork zones in associated rocks.
TEXTURE/STRUCTURE: Massive sulphide-rich bodies tend to follow bedding in host carbonate rocks; associated veins and stockworks include mineralized fractures, veinlets, quartz veins and breccias.
ORE MINERALOGY (Principal and subordinate): Cassiterite, chalcopyrite, sphalerite and galena; stannite, stibnite, bismuth, bismuthinite and a wide variety of sulphosalt minerals including jamesonite, bournonite, franckeite, boulangerite, geocronite, matildite and galenobismutite may also be present.
GANGUE MINERALOGY (Principal and subordinate): Pyrrhotite (often predominant sulphide) and/or pyrite, arsenopyrite, quartz, calcite, siderite, rhodochrosite, flourite and tourmaline.
ALTERATION MINERALOGY: Dolomite near massive sulphide bodies is typically altered to siderite, and, to a lesser extent, talc, phlogopite and quartz. Rocks hosting vein or stockwork zones may be tourmalinized. Greisen-type alteration, characterized by flourite and/or topaz, F-bearing micas and tourmaline, is best developed in and around genetically related felsic intrusive rocks.
WEATHERING: Oxidation of pyrite and pyrrhotite produces limonitic gossans. Deep weathering and erosion may result in residual concentrations of cassiterite in situ or in placer deposits downslope or downstream.
ORE CONTROLS: Carbonate rocks in the vicinity of F and B rich felsic intrusive rocks; faults and fracture zones in the carbonates and associated rocks provide channelways and also alternate sites of deposition for ore-forming fluids.
GENETIC MODEL: Magmatic-hydrothermal. Magmatic, highly saline aqueous fluids strip Sn and other ore metals from temporally- and genetically related magma. Early Sn deposition is dominantly from these magmatic fluids, mainly in response to increase in pH due to carbonate replacement. Mixing of magmatic with meteoric water during waning stages of the magmatic-hydrothermal system may result in deposition of Sn and other metals in late-stage veins and stockworks.
ASSOCIATED DEPOSIT TYPES: Sn-W skarn deposits (K06, K05), Sn-W vein deposits, Sb-Hg veins, placer deposits (C01, C02).
GEOCHEMICAL SIGNATURE: Sn, Cu, Pb, Zn, As, Ag, Sb, Hg, F, W, Bi and In may be anomalously high in hostrocks adjacent to and overlying mineralized zones; Sb and Hg anomalies may extend as much as several hundred metres. Sn, W, F, Cu, Pb and Zn may be anomalously high in stream sediments and Sn, W, and B (tourmaline) may be present in heavy mineral concentrates.
GEOPHYSICAL SIGNATURE: Massive pyrrhotite may be detected by magnetic surveys; massive sulphide zones may also be detected by electromagnetic and resistivity surveys.
OTHER EXPLORATION GUIDES: Deposits commonly occur in zoned, polymetallic districts; Sn and base metal bearing skarns and veins occur close to related intrusive rocks, carbonate- hosted Sn mantos and stockworks are at intermediate distances from the intrusive rocks, and Sb and Hg veins are the outermost deposits. Genetically related felsic intrusive rocks typically have high contents of silica (>74% SiO2) and F (>0.1% F); tourmaline may also be present.
TYPICAL GRADE AND TONNAGE: Deposits are large and high grade, containing millions to tens of millions of tonnes averaging about 1% Sn. The following figures are for production plus reserves: Renison Bell (Australia): 27 Mt at 1.1% Sn (Newnham, 1988) Cleveland (Australia): 5.3 Mt at 0.5% Sn, 0.2% Cu (Cox and Dronseika, 1988) Mt. Bischoff (Australia): 6.1 Mt at 0.49% Sn (Newnham, 1988) Dachang (China): 100 Mt at 1% Sn, 3-5% combined Cu, Pb, Zn and Sb (Fu et al., 1993) Gejiu (China): 100 Mt at 1% Sn, 2-5% Cu, 0.5% Pb (Sutphin et al., 1990).
IMPORTANCE: The large tonnage and relatively high grade of these deposits makes them attractive for exploration and development.The Renison Bell deposit in Australia and the Dachang and Gejiu deposits in China are currently major producers of tin on a world scale.
ACKNOWLEGEMENT: Rod Kirkham kindly reviewed this profile.
Cao, X. (1988): Integrated Geophysical and Geochemical Indicators of the Gejiu Tin Mine and its Neighbouring Areas; in Geology of Tin Deposits in Asia and the Pacific, Hutchison, C.S., Editor, Springer-Verlag, Berlin, pages 443-455.
Chen, Y., Huang, M., Xu, Y., Ai, Y., Li, X., Tang, S. and Meng, L. (1988): Geological and Metallogenic Features and Model of the Dachang Cassiterite-Sulphide Polymetallic Ore Belt, Guangxi, China; in Geology of Tin Deposits in Asia and the Pacific, Hutchison, C.S., Editor, Springer-Verlag, Berlin, pages 358-372.
Cox, R. and Dronseika, E.V. (1988): The Cleveland Stratabound Tin Deposits, Tasmania: A Review of their Economic Geology, Exploration, Evaluation and Production; in Geology of Tin Deposits in Asia and the Pacific, Hutchison, C.S., Editor, Springer-Verlag, Berlin, pages 112-123.
Fu, M., Changkakoti, A., Krouse, H.R., Gray, J. and Kwak, T.A.P. (1991): An Oxygen Hydrogen, Sulfur, and Carbon Isotope Study of Carbonate-replacement (Skarn) Tin Deposits of the Dachang Tin Field, China; Economic Geology, Volume 86, pages 1683-1703.
Fu, M., Kwak, T.A.P. and Mernagh, T.P. (1993): Fluid Inclusion Studies of Zoning in the Dachang Tin-Polymetallic Ore Field, People’s Republic of China; Economic Geology, Volume 88, pages 283-300.
Newnham, L. (1988): The Western Tasmanian Tin Province with special reference to the Renison Mine; in Geology of Tin Deposits in Asia and the Pacific, Hutchison, C.S., Editor, Springer-Verlag, Berlin, pages 101-111.
Patterson, D.J., Ohmoto, H. and Solomon, M. (1981): Geologic Setting and Genesis of Cassiterite-Sulfide Mineralization at Renison Bell, Western Tasmania; Economic Geology, Volume 76, pages 393-438.
Reed, B.L. (1986): Descriptive Model of Replacement Sn; in Mineral Deposit Models, Cox, D.P. and Singer, D.A., Editors, U. S. Geological Survey, Bulletin 1693, pages 61-63.
Sutphin, D.M., Sabin, A.E. and Reed, B.L. (1990): International Strategic Minerals Inventory - Tin; U.S. Geological Survey, Circular 930-J, page 52.
Yang, J., Li, D., Zhang, D., Li, S., Li, X. and Lu, X. (1988): Geochemical Characteristics of Indicator Elements and Prospecting Criteria for the Danchi Polymetallic Mineralized Belt of the Dachang Tin Field; in Geology of Tin Deposits in Asia and the Pacific, Hutchison, C.S., Editor, Springer-Verlag, Berlin, pages 339-350.