Cobalt—Styles of deposits and the search for primary deposits
<p>Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly…
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USGS Logo Cobalt—Styles of Deposits and the Search for Primary Deposits By Murray W. Hitzman, Arthur A. Bookstrom, John F. Slack, and Michael L. Zientek Open-File Report 2017-1155 U.S. Department of the Interior U.S. Geological Survey
U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S. Geological Survey William H. Werkheiser, Deputy Director exercising the authority of the Director U.S. Geological Survey, Reston, Virginia: 2017 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit ://www.usgs.gov/ or call 1-888-ASK-USGS (1-888-275-8747). For an overview of USGS information products, including maps, imagery, and publications, visit ://store.usgs.gov/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Hitzman, M.W., Bookstrom, A.A., Slack, J.F., and Zientek, M.L., 2017, Cobalt—Styles of deposits and the search for primary deposits: U.S. Geological Survey Open-File Report 2017-1155, 47 p., ://doi.org/10.3133/ofr20171155. ISSN 2331-1258 (online)
Contents Slide Presentation 1 Abstract 2 References Cited 44
Conversion Factors International System of Units to U.S. customary units Multiply By To obtain Length centimeter (cm) inch (in.) millimeter (mm) inch (in.) meter (m) foot (ft) kilometer (km) mile (mi) meter (m) yard (yd) Mass gram (g) ounce, avoirdupois (oz) metric ton (t) ton, short [2,000 lb] metric ton (t) ton, long [2,240 lb] Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as °F (1.8 × °C) + 32.
Abbreviations Ag As Au Bi bn bt CACB CCB Co cob Congo (Kinshasa) cp cpy cr Cr Cu EEZ Fe hm IOCG Ma Mg mgt Mn MnS MVT Ni Os Pb PGE ppm py q Re REE saf to U VMS ZCB Zn silver arsenic gold bismuth bornite biotite carbon Central African Copperbelt Congo Copperbelt chlorine cobalt cobaltite Democratic Republic of the Congo chalcopyrite (appears in this form on page 22 only; elsewhere, cpy) chalcopyrite carrollite chromite copper exclusive economic zone iron hematite iron oxide-copper-gold mega-annum magnesium magnetite manganese alabandite Mississippi Valley-type nickel osmium lead platinum-group element part per million pyrite quartz rhenium rare-earth element safflorite toumaline uranium volcanogenic massive sulfide Zambian Copperbelt zinc
U.S. Department of the Interior U.S. Geological Survey Cobalt—Styles of Deposits and the Search for Primary Deposits Murray W. Hitzman, Arthur A. Bookstrom, John F. Slack, and Michael L. Zientek USGS Logo
Abstract Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly used in magnets and rechargeable batteries. More than 50 percent of primary cobalt production is from the Central African Copperbelt. The Central African Copperbelt is the only sedimentary rock-hosted stratiform copper district that contains significant cobalt. Its presence may indicate significant mafic-ultramafic rocks in the local basement. The balance of primary cobalt production is from magmatic nickel-copper and nickel laterite deposits. Cobalt is present in several carbonatehosted lead-zinc and copper districts. It is also variably present in Besshi-type volcanogenic massive sulfide and siliciclastic sedimentary rock-hosted deposits in back arc and rift environments associated with mafic-ultramafic rocks. Metasedimentary cobalt-copper-gold deposits (such as Blackbird, Idaho), iron oxide-copper-gold deposits, and the five-element vein deposits (such as Cobalt, Ontario) contain different amounts of cobalt. None of these deposit types show direct links to mafic-ultramafic rocks; the deposits may result from crustal-scale hydrothermal systems capable of leaching and transporting cobalt from great depths. Hydrothermal deposits associated with ultramafic rocks, typified by the Bou Azzer district of Morocco, represent another type of primary cobalt deposit. In the United States, exploration for cobalt deposits may focus on magmatic nickel-copper deposits in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska; also, possibly basement rocks in southeastern Missouri. Other potential exploration targets include—
The Belt-Purcell basin of British Columbia (Canada), Idaho, Montana, and Washington for different styles of sedimentary rock-hosted cobalt deposits;
Besshi-type VMS deposits, such as the Greens Creek (Alaska) deposit and the Ducktown (Tennessee) waste and tailings; and
Known five-element vein districts in Arizona and New Mexico, as well as in the Yukon-Tanana terrane of Alaska; and hydrothermal deposits associated with ultramafic rocks along the west coast, in Alaska, and in the Appalachian Mountains. USGS Logo
Cobalt—Properties and Uses Cobalt is a silvery gray metal. Key properties: o Ferromagnetism (even at high temperature). o Hardness and wear‐resistance when alloyed with other metals. o Low thermal and electrical conductivity. o High melting point. o Intense blue color when combined with silica. o Cathodes in rechargeable batteries—lithium‐ion, Ni‐Cd, Ni‐metal‐hydride. o Superalloys for turbine engines in jets and terrestrial energy generation. o Magnet applications—marine propulsion, missile guidance, sensors, and radar. o Cemented carbides—cutting tools and wear‐resistant components (for use in construction, oil and gas extraction, mining, metalworking). USGS Logo
Cobalt—Critical Mineral? "Critical" means you need it; "strategic" means you don't have it
Cobalt is not currently considered a "critical" mineral, but it has the potential to become one in the future (McCullough and Nassar, 2017).
Most cobalt is produced as a byproduct (of copper or nickel mining), which limits the flexibility of producers to respond to changes in market demand and results in periods of oversupply or shortage.
More than 50% of primary cobalt production is from Congo (Kinshasa)—a country that ranks high on the 'risk of doing business' index because of its political instability; another 16% of primary cobalt production is from Russia, Cuba, and China combined (U.S. Geological Survey, 2017, p. 52-53).
The United States imports 75% to 80% of its supply. Most of the remaining 20% to 25% is from recycled scrap. The leading source of refined cobalt is China (U.S. Geological Survey, 2017, p. 52-53). USGS Logo
Cobalt—Current Sources of Primary Production The majority of the world's cobalt currently comes from Congo (Kinshasa). A number of other countries each contribute less than 10% to the total. In all cases except the Bou Azzer district (Morocco), cobalt is produced as a byproduct of other metals (Cu, Ni). USGS Logo Pie Chart on Cobalt
USGS Logo Cobalt—Geochemistry The ionic radii of Co2+ and Co3+ are similar to the ionic radii of Mg2+, Mn4+, Fe2+, Fe3+, and Ni2+. Cobalt can substitute for any of these elements in many minerals. The highest average cobalt content occurs in ultramafic rocks (dunite, serpentinite; ~110 ppm) mafic igneous rocks (basalt; 47 ppm) shales (19 ppm) granite (3 ppm).
Cobalt—Primary (Hypogene) Mineralogy Sulfides: o Carrollite o Linnaeite Co3S4 o Pentlandite o Siegenite (Co, Cobaltiferous iron sulfides: o Pyrite o Pyrrhotite Sulfarsenides: o Cobaltite CoAsS o Glaucodot Arsenides: o Safflorite o Skutterudite USGS Logo
Cobalt—Secondary (Supergene) Mineralogy Carbonate minerals: o Cobaltoan dolomite Other minerals: o Asbolane o Cobaltiferous oxyhydroxides (geothite, limonite)—it is unclear if the cobalt is within crystal structures or adsorbed onto surfaces o Erythrite o Heterogenite USGS Logo
USGS Logo Cobalt—Occurs in a Wide Variety of Deposit Types
Submarine nodules and crusts
Ni‐Co laterites
Magmatic Ni‐Cu sulfide deposits
Sedimentary rock‐hosted deposits o Stratiform copper deposits o Mississippi Valley‐type (MVT) deposits o Other carbonate‐hosted Cu‐(Zn‐Pb) deposits
"Synsedimentary and (or) diagenetic"—a spectrum of types
Co‐Cu‐Au deposits in metasedimentary rocks
Iron oxide‐copper‐gold (IOCG) deposits
Five‐element vein deposits (Ag‐Ni‐Co‐As‐Bi) (Kissin, 1992)
Hydrothermal deposits associated with ultramafic rocks
USGS Logo Cobalt—Submarine Resources The largest known cobalt resources are found in submarine Fe‐Mn nodules and crusts. Mining them is currently not economic because of legal and technical issues (inability to process the material economically). 180° 180° 135° 135° 90° 90° 45° 45° 0° 0° 45° 45° 90° 90° 135° 135° 180° 180° 50° 40° 40° 30° 30° 20° 20° 10° 10° 0° 0° 10° 10° 20° 20° 30° 30° 40° 40° 80° 80° 70° 70° 60° 60° 50° 50° 50° 60° 60° 70° 70° 80° 80° Clarion-Clipperton zone Cook Islands EEZ Pioneer Prime crust zone Madeira-Torre Rise Nodules Crusts Modified from Slack and others, in press.
USGS Logo Cobalt—Deposit Types in Production Laterites (weathered ultramafic rock) o Australia o Brazil o Cuba o New Caledonia From Slack and others, in press.
USGS Logo Cobalt—Ni‐Co Laterites
Consist of— o Overburden. o Limonite (higher Co grades). o Saprolite (higher Ni grades). o Weathered ultramafic rock.
Range in thickness from 10 to 40 m.
Cobalt contained in asbolane, clays (nontronite, montmorillonite), erythrite, goethite, heterogenite, limonite.
Manganiferous Nkamouna Co‐Ni deposit (Cameroon) has cobalt as principal metal recovered.
Mined laterites generally contain >1% Ni, cobalt contents: o Highest: Nkamouna—0.22% Co. o Other higher grade: Moa, Cuba—0.18% Co; Jacaré, Brazil—0.13% Co; New Caledonia—~0.1% Co. o Most have <0.1% Co; as low as 0.04% Co. Modified from Slack and others, in press. Map - Co balt 30° 20° 10° 0° 10° 20° 30°
USGS Logo Cobalt—Deposit Types in Production o China o Cobalt is a byproduct of sulfides mined for Ni‐Cu‐(PGEs) in mafic‐ultramafic intrusions.
Laterites (weathered ultramafic rock) o Australia o Brazil o Cuba o New Caledonia
Magmatic Ni‐Cu sulfide deposits o Canada o Russia o Cobalt is correlated with nickel grade; the higher the Ni grade, the higher the amount of Co. o Cobalt recoveries from magmatic ores are low— generally 20% to 66%. From Slack and others, in press.
USGS Logo Cobalt—Magmatic Ni‐Cu Sulfide Deposits
Wide range of cobalt grades:
Cobalt is a byproduct of sulfides mined for Ni‐Cu‐(PGEs) in mafic‐ ultramafic intrusions.
Sulfides occur in disseminated, net‐ textured, and massive zones— o As basal accumulations in komatiitic flows (Raglan, Kambalda), differentiated sills (Noril'sk‐Talnakh), and layered intrusions (Sudbury, Duluth). o As stratabound units in layered intrusions (Bushveld, Stillwater). o In discordant magmatic conduits (Voisey's Bay, Eagle).
Cobalt is found primarily in pentlandite, and in lesser amounts, in linnaeite. Modified from Slack and others, in press. Map - Co bal t M ag mat Ni-C u Su lfi de Dep osi ts 180° 135° 90° 45° 0° 45° 90° 135° 180° 0° 0° ° 0° Kambalda 0.21% Raglan 0.06% Voisey's Bay 0.09% Sudbury 0.04% Eagle 0.08% Bushveld 0.03% Noril'sk‐Talnakh 0.06% Duluth 0.01%
USGS Logo Cobalt—Deposit Types in Production
Laterites (weathered ultramafic rock) o Australia o Brazil o Cuba o New Caledonia
Magmatic Ni‐Cu sulfide deposits o Canada o China o Russia
Sedimentary rock‐hosted stratiform copper deposits o Congo (Kinshasa) o Zambia From Slack and others, in press.
USGS Logo Cobalt—Sedimentary Rock‐Hosted Stratiform Copper
Cobalt grades:
Only one sedimentary rock‐hosted stratiform copper district contains economic cobalt resources—the Central African Copperbelt (CACB).
In this district, only some deposits have economic (byproduct) cobalt: o Western portion of the Zambian Copperbelt (ZCB). o Most of the Congo Copperbelt (CCB), with the exception of the new Kamoa‐Kakula deposit. o Tilwezembe structure (in the CCB) contains the most cobalt‐rich deposits; several have grades sufficient for primary cobalt production (Kisanfu).
Cobalt occurs as carrollite (hypogene). Map - Co balt Sed ime nta ry Roc kHo ste d S rat ifo rm C oppe r 30° 20° 10° 0° 10° 20° 30° Modified from Slack and others, in press. Kisanfu 1.1% Kolwezi 0.4% Mukondo 0.7% Tenke 0.3% Tilwezembe 0.6% Luanshya 0.2% Nchanga 0.4% Nkana 0.1%
USGS Logo Sp a t ial Distr ibution of Copper De posits Copper (Mt) Kolwezi Tenke‐Fungurume Fishtie Spatial Distribution of Central African Copperbelt Copper Deposits
USGS Logo S pat ial Dis tribution of Cobalt Deposi ts Cobalt (Mt) Tenke‐Fungurume Spatial Distribution of Central African Copperbelt Cobalt Deposits
USGS Logo Cobalt—Sedimentary Rock‐Hosted Stratiform Copper
Although sedimentary rock‐hosted stratiform copper deposits currently account for ~60% of the world's cobalt production, virtually all this output is from one district (CACB).
An abundance of gabbroic intrusive rocks in the western ZCB and the presence of hydrothermal Ni deposits in the CACB (for example, Enterprise; Capistrant and others, 2015) suggest that mafic rocks may be an important metal source.
Other sedimentary rock‐hosted stratiform copper districts generally contain no or very minor amounts of cobalt (for example, Spar Lake [Montana], Kupferschiefer [central Europe], and Dzhezkazgan [Kazakhstan]). This type of deposit should not be considered a typical cobalt exploration target.
USGS Logo Cobalt—Other Deposit Types Sedimentary rock‐hosted deposits
Mississippi Valley‐type (MVT) deposits
Other carbonate‐hosted Cu‐(Zn‐Pb) deposits "Synsedimentary and (or) Diagenetic"—a spectrum of deposits Co‐Cu‐Au deposits in metasedimentary rocks IOCG deposits Five‐element vein deposits (Ag‐Ni‐Co‐As‐Bi) Hydrothermal deposits associated with ultramafic rocks
USGS Logo Cobalt—Mississippi Valley‐Type (MVT) Deposits Several southeastern Missouri lead district (Old Lead Belt and Viburnum Trend) deposits have copper‐rich zones beneath the lead orebodies that have in the past been mined for copper with byproduct cobalt. Cobalt occurs primarily in siegenite. Southeastern Missouri is an anomalous MVT district:
Pb>>Zn; presence of Cu‐(Co, Ni).
Deposits formed close to Precambrian basement. MVT carbonate‐hosted Zn‐Pb deposits generally do not contain cobalt. Pho tograph of Gray Matallic Slegenite with Brassy Chalcopyrite in Dull Grapy Limeston e Gray metallic siegenite with brassy chalcopyrite in dull gray limestone. From Fredericktown, Missouri. Field of view is about 1.5 cm across. Photograph by W. Cordua, Minerals of Wisconsin, ://WGNHS.UWEX.edu/minerals/siegenite.
USGS Logo Cobalt—Other Carbonate‐Hosted Cu‐(Zn‐Pb) Deposits Diverse group of deposits, some of which contain cobalt:
Ruby Creek (Bornite), Alaska—High‐grade portions of the deposit contain up to 0.1% Co in early cobaltiferous pyrite and later carrollite replacing this pyrite.
Walford Creek Cu‐Zn deposit (Australia) contains cobaltiferous pyrite (Vardy zone; 6.6 Mt at 0.16% Co; Aeon Metals Ltd., 2017, p. 8).
Mt. Isa Cu and Zn‐Pb orebodies (Australia) contain cobaltiferous pyrite. Carrollite Intergrow with Bornite and Map of Chalcopyrite and Replacing Cobaltiferous Pyrite Carrollite intergrown with bornite and chalcopyrite and replacing cobaltiferous pyrite, Ruby Creek deposit, Alaska (Hitzman, 1986, fig. 17). bn, bornite; cp, chalcopyrite; cr, carrollite; py, pyrite
USGS Logo Cobalt—"Synsedimentary and (or) Diagenetic" Deposits Spectrum of deposits—Besshi‐type volcanogenic massive sulfide (VMS) deposits.
VMS deposits with enhanced cobalt—often termed "Besshi" after Cu‐Zn‐(Ag,Au) deposits in Japan—that contain ~0.05% Co in cobaltiferous pyrite, are generally iron sulfide rich, and occur in reduced C‐rich (some Mn‐rich) sediments with associated mafic‐ ultramafic rocks in back arc and oceanic rift environments. o Besshi (Japan)—30 Mt at 0.05% Co. o Windy Craggy (Canada)—138 Mt at 0.66% Co. o Outokumpu (Finland)—29 Mt at 0.25% Co. o Ducktown (Tennessee)—163 Mt, Co grade is unknown. Photograph of Pyritic Massive Sulfide from the Windy Craggy Deposit Pyritic massive sulfide from the Windy Craggy deposit. Image courtesy of Jan Peter.
USGS Logo Cobalt—"Synsedimentary and (or) Diagenetic" Deposits Spectrum of deposits—Black shale deposits.
In black (C‐rich) shales deposited in a rift basin with ultramafic rocks (now talc‐carbonate).
Shales may contain manganese as alabandite (MnS).
Cobalt occurs primarily in cobaltiferous pyrite.
Primary example is the Talvivaara deposit (Finland)—1,550 Mt at 0.02% Co, 0.22% Ni, 0.13% Cu, and 0.49% Zn.
USGS Logo Cobalt—Other Sediment‐Hosted Deposits Spectrum of deposits—Shale‐hosted deposits.
Sullivan deposit (Canada) contained cobalt in arsenopyrite (not recovered).
Sheep Creek (Black Butte), Montana, contains 9.1 Mt at 0.12% Co in cobaltiferous pyrite (minor amount of siegenite). Photograph of Stratiform Pyrite and Cross Section of Sheep Creek, Montana Cross section, Sheep Creek, Montana (Graham and others, 2012, fig. 7). Stratiform pyrite, Sheep Creek, Montana (Graham and others, 2012, fig. 5e).
USGS Logo Cobalt—"Synsedimentary and (or) Diagenetic" Deposits Spectrum of deposits—Mn‐rich deposits.
Atlantis II Zn‐Cu‐(Ag, Co) (Red Sea) o Mudstones and chemical sediments in small basins in oceanic rift with evaporites above mafic volcanic and intrusive rocks. o Upper Mn‐rich zone and lower Fe‐rich zone (~89 Mt). Mn and Fe as oxyhydroxides with 0.05% Co.
Boleo Cu‐Zn‐(Co) (Mexico) o Mudstones interbedded with siltstones and conglomerates deposited adjacent to evaporites and above basalts in proto‐Gulf of California rift. o Stacked mantos of sulfide and Fe‐ and Mn‐oxide‐rich material (sulfide— 264 Mt of 0.06% Co—in oxyhydroxides and cobaltiferous pyrite).
USGS Logo Spectrum of Co‐bearing "Synsedimentary and (or) Diagenetic" Deposits
These deposits formed on or near the sea floor surface by exhalation and infiltration of hydrothermal fluids (heated seawater) that reacted with sediments and mafic‐ultramafic rocks to derive Fe‐Cu‐Zn‐Co‐Ni.
These are fundamentally iron sulfide (and in some cases iron and manganese oxide) deposits with relatively minor amounts of trace metals.
The presence of manganese is probably controlled by water depth and the oxidation state of both the hydrothermal fluids and the ocean water.
The tectonic environments vary from incipient rifts with oceanic crust to back arc basins. The presence of evaporites in the section probably helps to increase hydrothermal fluid salinity and the ability of the fluids to carry additional cobalt.
USGS Logo Cobalt—Co‐Cu‐Au in Metasedimentary Rocks Stratabound to discordant zones of semimassive to locally massive sulfides within deformed siliciclastic metasedimentary rocks. Contain cobaltite with lesser amounts of (and later formed) chalcopyrite, pyrite, pyrrhotite, and cobaltiferous arsenopyrite. Primary example is the Blackbird district (Idaho) for which historical production plus current reserves total 17 Mt at 0.7% Co, 1.4% Cu, and 1 ppm Au (individual deposits are open at depth). Cross section, Blackbird district: Sulfides are predominantly stratabound within metamorphosed Mesoproterozoic biotite‐rich banded siltites of the Apple Creek Formation. Modified from Bookstrom and others, 2014. Cross Section, Blackbird District - Quartz Cobaltite, Bobttitite, Phyllite, and Argillite
USGS Logo Cobalt—Blackbird District, Idaho
Host sediments are older than 1,410 Ma.
Absence of significant mafic rocks in the area.
The mineralized banded siltite unit was also pervasively biotitized (Fe2+, Cl‐rich).
The cobaltite‐biotite‐(tourmaline‐xenotime‐Au) ore (dominant) is younger than the xenotime dated 1,370 Ma but older than the xenotime dated 1,316 to 1,270 Ma (Aleinikoff and others, 2012); the Re‐Os age is 1,349+76 Ma (Saintilan and others, 2017). Time period includes an orogenic event.
The mineralizing fluids were probably reduced and highly saline.
There was an overprinting Cretaceous‐age quartz‐chalcopyrite‐pyrite‐ cobaltiferous arsenopyrite‐(Au) event. Map of Blackbird District, Idaho Photograph by Art Bookstrom.
USGS Logo Cobalt—Iron Oxide‐Copper‐Gold (IOCG) Deposits
IOCG deposits are a still poorly understood class of deposits apparently formed by crustal‐scale hydrothermal systems that consist of significant iron oxides (magnetite and [or] hematite) with chalcopyrite and gold. They commonly contain a variety of trace metals, including U, Ag, Co, Ni, Bi, and often have extensive zones of potassic alteration enclosing the ore.
Currently, no IOCGs are producing byproduct cobalt, although a number contain significant resources. The NICO deposit in Canada (Cu‐poor IOCG variant) is slated to come into production as a primary cobalt producer. Pho tog raph of Iron Oxide-Copper-Gold Deposits Guelb Moghrein (Kirschbaum, 2011). Olympic Dam (Australia) 650 Mt at 0.02% Ernest Henry (Australia) 166 Mt at 0.05% Boss Bixby (Missouri) 40 Mt at 0.04% NICO (Canada) 31 Mt at 0.12% Guelb Moghrein (Mauritania) 24 Mt at 0.14%
USGS Logo Cobalt—Five‐Element Vein Deposits Ag‐Ni‐Co‐As‐Bi‐(U‐REE) veins have been recognized as a distinctive ore type since the early 20th century (Bastin, 1939) and were the historic silver mines of Europe (Erzebirge [Czechoslovakia, Germany]; Schwarzwald [Germany]; Kongsberg [Norway]). In Canada, major districts are Cobalt‐Gowganda, Thunder Bay, and Echo Bay. In the United States, similar deposits were mined at Wickenberg (Arizona) and Black Hawk (Silver City, New Mexico). All these deposits produced silver, some produced uranium, and a few produced cobalt. Grades and tonnage at many deposits are hard to determine owing to old records. o Keeley‐Frontier Mine (Cobalt district) produced nearly 1,500 Mt at grades of 0.5% Co and 1,644 g/t Ag (The Northern Miner, 2017).
USGS Logo Cobalt—Five‐Element Vein Deposits (Continued) These deposits generally occur in crystalline terranes (metamorphic or granitic rocks) and do not appear to be genetically associated with magmatic rocks (mafic or felsic). The deposits typically consist of open‐space‐filling veins up to several meters in width that pinch and swell. Maximum depths to which veins have been mined is approximately 500 m and, in some districts, the veins are barren at depth. There is virtually no wallrock alteration around the veins. Where wallrock alteration is present, it is weak chloritization.
USGS Logo Five‐Element Vein Deposits—Sequential Mineralogical Stages (1) Early quartz with minor amounts of pyrite, sphalerite, galena. (2) Uraninite‐quartz. (3) Native silver with Ni‐Co arsenide minerals and sometimes native bismuth with calcite or dolomite. (4) Pyrite, sphalerite, galena, chalcopyrite with native silver and argentite and calcite, and minor amounts of quartz, fluorite, and barite. (5) Late‐stage calcite, sometimes with barite or fluorite.
USGS Logo Cobalt—Five‐Element Vein Deposits Several fluid inclusion studies indicate progression to the highest temperature (300 to 500 °C) during the Ag‐Ni‐Co stage, down to 150 °C during the sulfide stage, and to below 125 °C for late‐stage calcite. Evidence of multiple pulses of fluids, multiple T maxima. High‐ temperature‐stage fluids (Ag, Co, Ni, As) were NaCl saturated. Evidence of boiling in some districts, and trapping pressures at Cobalt, Ontario, suggest ore deposition at 700 m (Kerrich and others, 1986).
USGS Logo Cobalt—Metased Co‐Cu‐Au—IOCG—Five‐Element Vein These deposit types, though distinct, have some similarities: o Metal suite (Co, Ni, Ag, Au) with differences regarding amount of Fe, Cu, As, U, and Bi. o Formed by hydrothermal fluids that do not appear to be directly related to igneous activity. o Fluids with high salinity and low reduced sulfur content (generally low iron sulfides) at temperatures of ~500 to 250 °C. Causative fluids formed by deep crustal heating?
USGS Logo Candelaria District, Chile—A Model to Tie Together IOCG, Metased Co‐Cu‐Au, and Five‐Element Vein Deposits? limestone skarn siltstone andesite intrusive Potassic alteration (biotite) Sodic-calcic alteration mgt-cpy-Au hm-cpy-Au Calcite (+Ag, Co) 5 km 1 km hornfels W
IOCG system with deep magnetite zone and hematite zone above the magnetite zone.
Massive biotitite— analogy to Blackbird?
System is capped by calcite veins containing Ag and Co (five‐element veins).
USGS Logo Cobalt—Hydrothermal Deposits Associated with Ultramafic Rocks (Bou Azzer District, Morocco) From Oberthür and others, 2009, fig. 1.
The Bou Azzer district of Morocco is a primary producer of cobalt (with byproduct nickel and gold).
More than 60 individual deposits are known.
District contains approximately 6 Mt at 1% Co, 1% Ni, and 3 g/t Au. Cobalt - Hydrothermal Deposits Associated with Ultramafic Rocks
USGS Logo Cobalt—Hydrothermal Deposits Associated with Ultramafic Rocks Deposits occur as quartz‐calcite veins immediately adjacent to Neoproterozoic serpentinites that are part of an ophiolite along a Pan‐African suture zone. Mineralization occurred during the Hercynian orogeny (~310 Ma; Oberthürand others, 2009). Photograph of Cobalt - Hydrothermal Deposits From Oberthür and others, 2009, fig. 2.
USGS Logo Cobalt—Bou Azzer Cobalt Deposit
There is a sequential increase in Co and As precipitation through time from Ni monoarsenides (nickeline) to Ni‐Co diarsenides (rammelsburgite) to cobalt triarsenides (skutterudite) to sulfarsenides (arsenopyrite) to copper sulfides. Quartz and carbonate minerals fill spaces and fractures between ore minerals.
The mineralogical paragenetic sequence is probably the result of decreasing temperatures, increasing pH, and decreasing oxygen fugacity—possibly owing to mixing of hydrothermal and meteoric fluids.
Co, Ni, Fe, Cu and As were probably leached from the serpentinites by relatively low pH, saline fluids.
The predominance of Co over Ni arsenide minerals despite the high Ni‐Co ratio in the serpentinites is probably owing to the difference in the solubility of the elements in the hydrothermal fluid (Ahmed and others, 2009).
USGS Logo Cobalt—Summary and Speculation Many cobalt deposits are associated with mafic‐ultramafic rocks. The association can be: o Close—Ni‐Co laterites, magmatic Ni‐Cu sulfide deposits, hydrothermal deposits associated with ultramafic rocks. o Intermediate—Besshi‐type VMS deposits, black shale deposits. o Distant—Central African Copperbelt, southeastern Missouri. The association is least evident in the metasedimentary Co‐Cu‐Au, IOCG, and five‐element vein deposits.
USGS Logo Cobalt—Summary and Speculation (Continued) The CACB is probably cobalt‐ rich owing to mafic‐ultramafic rocks in the underlying basement. Most deposits in the Belt‐ Purcell basin also contain at least minor amounts of cobalt, suggesting that it may be similar to the CACB. Other styles of sedimentary rock‐hosted cobalt deposits may be present in this basin. Modified from Bookstrom and others, 2016.
USGS Logo Cobalt—Summary and Speculation (Continued) Primary Co deposits are restricted to hydrothermal deposits associated with ultramafic rocks and possibly some five‐element vein deposits. Both deposit types— o Have relatively poorly defined exploration models. o Are small targets with weak alteration halos. o Probably represent primarily Ni‐As‐Co‐Ag geochemical anomalies (elements that have not been routinely analyzed for in the past). o Are not significant geophysical targets. o Represent targets for which little exploration has yet been done.
USGS Logo Cobalt—U.S. Exploration
Magmatic Ni‐Cu in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska. Also basement rocks in southeastern Missouri?
Belt‐Purcell basin for different styles of sedimentary rock‐hosted cobalt deposits.
Besshi‐type VMS deposits—Is cobalt present in any of the ore lenses at the Greens Creek (Alaska) deposit? Cobalt resource present in Ducktown (Tennessee) waste and tailings?
Known five‐element vein districts in Arizona and New Mexico and potential for additional districts in crystalline rocks in and adjacent to the Basin and Range Province. Additionally, in the Yukon‐Tanana terrane of Alaska, which has geologic similarities to European Hercynian terranes.
Hydrothermal deposits associated with ultramafic rocks along the west coast, in Alaska, and in the Appalachian Mountains.
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