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Ministry of Energy Mines and Responsible for Core Review

J - Manto

BC Profile # Deposit Type Approximate Synonyms USGS Model #
J01 Polymetallic manto Ag-Pb-Zn Polymetallic replacement deposits 19a
J02 Manto and stockwork Sn Replacement Sn, Renison-type 14c
  J03* Mn veins and replacements covered by I05 and J01 19b
J04 Sulphide manto Au Au-Ag sulphide mantos - -
 

POLYMETALLIC MANTOS Ag-Pb-Zn


J01
by J.L. Nelson
British Columbia Geological Survey
 

Nelson, J.L. (1996): Polymetallic Mantos Ag-Pb-Zn, 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 101-104.

 

IDENTIFICATION

 

SYNONYM: Polymetallic replacement deposits.

 

COMMODITIES (BYPRODUCTS): Ag, Pb, Zn (Au, Cu, Sn, Bi).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International): Midway (104O 038) and Bluebell (082ENW026); Sa Dena Hes (Yukon, Canada), Prairie Creek (Northwest Territories, Canada), Leadville District (Colorado, USA), East Tintic District (Utah, USA), Eureka District (Nevada, USA), Santa Eulalia, Naica, Fresnillo, Velardena, Providencia (Mexico).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Irregularly shaped, conformable to crosscutting bodies, such as massive lenses, pipes and veins, of sphalerite, galena, pyrite and other sulphides and sulphosalts in carbonate hosts; distal to skarns and to small, high-level felsic intrusions.

 

TECTONIC SETTING: Intrusions emplaced into miogeoclinal to platformal, continental settings.

 

DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: In northern Mexico, most are hosted by Cretaceous limestones. In Colorado, the principal host is the Devonian- Mississippian Leadville limestone; in Utah, the Permian Torweap Formation hosts the Deer Trail deposit. The most favourable hosts in the Canadian Cordillera are massive Lower Cambian and Middle Devonian limestones, rather than impure carbonates and dolostone-quartzite units.

 

AGE OF MINERALIZATION: Canadian Cordilleran examples are Cretaceous to Eocene age; those in the southern Cordillera are typically Tertiary.

 

HOST/ASSOCIATED ROCK TYPES: Hosted by limestone and dolostone. The carbonates are typically within a thick sediment package with siliciclastic rocks that is cut by granite, quartz monzonite and other intermediate to felsic hypabyssal, porphyritic lithologies. There may be volcanic rocks in the sequence, or more commonly above, which are related to the intrusive rocks.

 

DEPOSIT FORM: Irregular: mantos (cloak shaped), lenses, pipes, chimneys, veins; in some deposits the chimneys and/or mantos are stacked.

 

TEXTURE/STRUCTURE: Massive to highly vuggy, porous ore. In some cases fragments of wallrock are incorporated into the ore. Some deposits have breccias: fragments of wallrock and also of sulphide ore within a sulphide matrix.

 

ORE MINERALOGY (Principal and subordinate): Sphalerite, galena, pyrite, chalcopyrite, marcasite; arsenopyrite, pyrargyrite/proustite, enargite, tetrahedrite, geocronite, electrum, digenite, jamesonite, jordanite, bournonite, stephanite, polybasite, rhodochrosite, sylvanite, calaverite. Chimneys may be more Zn-rich, Pb-poor than mantos.

 

GANGUE MINERALOGY (Principal and subordinate): Quartz, barite, gypsum; minor calc- silicate minerals.

 

ALTERATION MINERALOGY: Limestone wallrocks are commonly dolomitized and/or silicified, whereas shale and igneous rocks are argillized and chloritized. Jasperoid occurs in some U.S. examples.

 

WEATHERING: In some cases, a deep oxidation zone is developed. Mexican deposits have well developed oxide zones with cassiterite, hematite, Cu and Fe carbonates, cerusite and smithsonite.

 

ORE CONTROLS: The irregular shapes of these deposits and their occurrence in carbonate hosts emphasize the importance of ground preparation in controlling fluid channels and depositional sites. Controlling factors include faults, fault intersections, fractures, anticlinal culminations, bedding channelways (lithologic contrasts), karst features and pre-existing permeable zones. In several districts karst development associated with unconformities is believed to have led to development of open spaces subsequently filled by ore. Some deposits are spatially associated with dikes.

 

GENETIC MODEL: Manto deposits are high-temperature replacements as shown by fluid inclusion temperatures in excess of 300 C, high contents of Ag, presence of Sn, W and complex sulphosalts, and association with skarns and small felsic intrusions. They are the product of pluton-driven hydrothermal solutions that followed a variety of permeable pathways, such as bedding, karst features and fracture zones.

 

ASSOCIATED DEPOSIT TYPES: There is probably an overall outward gradation from granite- hosted Mo-Cu porphyries (L04), endoskarns (K) and possibly W- and Sn mineralization (L06?), through exoskarns (K01, K02) and into Ag-Pb-Zn veins (I05), mantos (J01) and possibly Carlin-type sediment-hosted Au-Ag deposits (E03). Only some, or possibly one, of these types may be manifest in a given district. Ag-Pb-Zn vein, manto and skarn deposits belong to a continuum which includes many individual occurrences with mixed characteristics.

 

COMMENTS: In the Canadian Cordillera, most mantos are located in the miogeocline (western Ancestral North America, Cassiar and Kootenay terranes) because of the essential coincidence of abundant carbonate and presence of felsic intrusions. There is one known example in Upper Triassic limestone on Vancouver Island, which probably formed distal to skarn mineralization related to a mid- Jurassic intrusion. Most mantos in the Canadian Cordillera are Late Cretaceous to Eocene, coinciding with the age of youngest, F-rich intrusions of the A-type (anorogenic) granite suite. In Mexico, mantos are associated with Early to mid-Tertiary volcanic rocks and cogenetic intrusions. The Colorado deposits may be associated with Tertiary sills, and the Deer Trail deposit in Utah has given a 12 Ma sericite age.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: B.C.: Ag, Pb, Zn, Sn in stream silts, F in waters. U.S.: Districts show outward zoning from Cu-rich core through broad Ag-Pb zone to Zn- Mn fringe. Locally Au, As, Sb, Bi. Jasperoid contains elevated Ba + Ag.

 

GEOPHYSICAL SIGNATURE: Subsurface granite associated with Midway deposit has negative magnetic signature.

 

OTHER EXPLORATION GUIDES: Concentration of Ag-Pb-Zn vein deposits in or near carbonates.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Individual deposits average about a million tonnes grading tens to hundreds of grams/tonne Ag and approximately 5 to 20% combined Pb-Zn. Mexico: Santa Eulalia district produced about 24 Mt in this century, grading about 300 g/t Ag, 8% Pb, 9% Zn. U.S.: Leadville deposit mined 30 Mt 70-130 g/t Ag, 12-15% Pb-Zn. B.C.: Midway geological resource is 1 Mt grading 400 g/t Ag 7% Pb, 9.6% Zn. In many mining districts the early production came from oxidized ore zones that can have higher grades and be easier to mine.

 

ECONOMIC LIMITATIONS: Generally, although not always, these deposits tend to be small, highly irregular and discontinuous. The Mexican deposits have yielded large quantities of ore because, due to low labour costs, mining provided an effective and low-cost exploration tool.

 

IMPORTANCE: As sources of base metals, manto deposits are overshadowed on a world scale by the giant syngenetic classes such as sedimentary exhalitive and volcanogenic massive sulphides. However, because of their high precious metal contents, they provide exciting targets for small producers.

 

REFERENCES

 

Hewitt, W.P. (1968): Geology and Mineralization of the Main Mineral Zone of the Santa Eulalia district, Chihuahua, Mexico; Society of Mining Engineers, Transactions, Volume 241, pages 228-260.

Jensen, M.L. and Bateman, A.M. (1981), Economic Mineral Deposits, 3rd edition, John Wiley and Sons, New York, 593 pages.

Maldonado, E.D. (1991): Economic Geology of the Santa Eulalia Mining District, Chihuahua; in Economic Geology, Mexico, Salas, G.P., Editor, Geological Society of America, The Geology of North America, Volume P-3, pages 241-257.

Morris, H.T. (1986): Descriptive Model of Polymetallic Replacement Deposits; in Mineral Deposit Models, Cox, D.P. and Singer, D.A., Editors, U.S. Geological Survey, Bulletin 1693, pages 90-91.

Nelson, J.A. (1991): Carbonate-hosted Lead-Zinc (ñ Silver, Gold) Deposits of British Columbia; in Ore Deposits, Tectonics and Metallogeny in the Canadian Cordillera, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1991-4, pages 71-88.

Ohle, E.L. (1991): Lead and Zinc Deposits; in Economic Geology, U.S., Gluskoter, H.J., Rice, D.D. and Taylor, R.B., Editors, Geological Society of America, The Geology of North America, Volume P-2, pages 43-62.

Prescott, B. (1926): The Underlying Principles of the Limestone Replacement Deposits of the Mexican Province - I; Engineering and Mining Journal, Volume 122, pages 246-296.

1. Manto is a Spanish mining term denoting a blanket-shaped orebody which is widely used for replacement deposits of Mexico. It has been used to describe the orientation of individual lenses and also to describe a class of orebodies.

 

MANTO AND STOCKWORK Sn


J02
by David Sinclair
Geological Survey of Canda, Ottawa
 

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.

 

IDENTIFICATION

 

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).

 

GEOLOGICAL CHARACTERISTICS

 

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).

 

EXPLORATION GUIDES

 

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.

 

ECONOMIC FACTORS

 

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.

 

REFERENCES

 

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.

 

 

MN VEINS AND REPLACEMENTS


J03
covered by I05 and J01 
 

*  Note:  All BC deposit profile #s with an asterisk have no completed deposit profile.  USGS deposit model #s with an asterisk had no published model in the late 1990s. 

Examples of Manto Deposits

BC Profile # Global Examples B.C. Examples
J01 East Tintic district (Utah), Naica (Mexico), Sa Dena Hess (Yukon) Bluebell, Midway
J02 Renison Bell & Cleveland (Australia), Dachang district (China) - -
  J03* Lake Valley (New Mexico), Phillipsburg (Montana) - -
J04 Ketza River (Yukon) Mosquito Creek , Island Mountain