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Ministry of Energy Mines and Responsible for Core Review

D - Continental Sediments and Volcanics

BC Profile # Deposit Type Approximate Synonyms USGS Model #
D01 Open-system zeolites - - 25oa
D02 Closed-basin zeolites - - 25ob
D03 Volcanic redbed Cu Basaltic Cu 23
D04 Basal U - - - -
  D05* Sandstone U Roll front U, Tabular U 30c
D06 Volcanic-hosted U Epithermal U, Volcanogenic U 25f
D07 Iron oxide breccias & veins ±P±Cu±Au±Ag±U Olympic Dam type, Kiruna type 29b,25i
 

OPEN-SYSTEM ZEOLITES


D01

by R.A. Sheppard 1 and G.J. Simandl 2
1United States Geological Survey, Federal Center, Denver, Colorado, USA
2British Columbia Geological Survey, Victoria, B.C., Canada

Sheppard, R.A. and Simandl, G.J. (1999): Open-system Zeolites; in Selected British Columbia Mineral Deposit Profiles, Volume 3, Industrial Minerals, G.J. Simandl, Z.D. Hora and D.V. Lefebure, Editors, British Columbia Ministry of Energy and Mines, 1999-10.

 

IDENTIFICATION

 

SYNONYM: In the field it may be practically impossible to distinguish these deposits from burial metamorphic zeolites.

 

COMMODITIES: Clinoptilolite, mordenite, chabazite, phillipsite, heulandite.

 

EXAMPLES: (British Columbia (MINFILE #) - Canada/ International): Clinoptilolite, Asp Creek (092HSE164), Bromley Vale Zeolite (092HSE166), Tailings Tephra (092HSE167), Sunday Creek (092HSE168); clinoptilolite, John Day Formation, (Oregon, USA), clinoptilolite and mordenite, Miocene Paintbrush Tuff, Calico Hills and Crater Flat Tuffs, Nye County (Nevada, USA), phillipsite and chabazite, Yellow tuffs near Naples (Italy), clinoptilolite, Death Valley Junction, (California, USA).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Microcrystalline zeolites (clinoptilolite, chabazite, mordenite, phillipsite) hosted by relatively thick, generally non-marine, tephra sequences. The ore zones are 10s to 100s of metres thick and commonly exhibit a more or less vertical zonation of zeolites and associated silicate minerals within the host sequence. The zeolites crystallized in the post-depositional environment over periods ranging from thousands to millions of years.

 

TECTONIC SETTINGS: Active or unmetamorphosed, continental, arc-related or other insular volcanic complexes.

 

DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: Non-marine and shallow marine basins in volcanic terrains. Depositional basins may be fault bound. Many deposits form in fluviatile and lacustrine volcanic sequences, but some are hosted by shallow marine or subaerial tuffaceous deposits. Typical regional depositional environments contain thick sequences of vitric tuffs affected by diagenesis or very low grade metamorphism.

 

AGE OF MINERALIZATION: Mesozoic to Holocene, but most are Cenozoic. Zeolite deposits in British Columbia are Cretaceous or Tertiary.

 

HOST/ASSOCIATED ROCK TYPES: The zeolite-bearing rocks are hosted by volcanic ash and tuff beds with minor intercalated flows. Silicic tuffs commonly were deposited as non-welded ash flows. Other rock types include fluviatile mudstone, sandstone, conglomerate and diatomite.

 

DEPOSIT FORM: Stratabound, stratiform or lens-shaped, mineral zonation may cross-cut the bedding. Thickness of the zeolitic tuffs in major deposits may range from 100's to 1000's of metres. Areal extent is commonly 100's to 1000's of square kilometres. Minor deposits and minable portions of above described zeolitic tuffs may be less than 30 metres in thickness.

 

TEXTURE/STRUCTURE: Finely crystalline, commonly bedded, similar to bedded diatomite or bentonite. The common local attribute is vertical zonation of authigenic silicate minerals. In silicic tuff sequences, the alkali-rich siliceous zeolites (clinoptilolite and mordenite) in the upper part of the deposit are commonly replaced at depth by analcime, potassium feldspar and/or albite. A similar sequence occurs in burial diagenetic deposits.

 

ORE MINERALOGY (Principal and subordinate): Clinoptilolite, chabazite, mordenite, phillipsite.

 

GANGUE MINERALOGY (Principal and subordinate): Authigenic smectite, mixed layer illite-smectite, opal - (cristobalite/tridymite), quartz, plagioclase, microcline, sanidine, biotite, muscovite, calcite; pyrogenic crystal fragments, volcanic rock fragments, unreacted vitric material.

 

ALTERATION MINERALOGY: Zeolitization is the ore forming process (see ore mineralogy). Early zeolite minerals are further modified during burial diagenesis. In silicic tuff sequences, the alkali-rich siliceous zeolites (clinoptilolite and mordenite) in the upper part of the deposit are commonly replaced at depth by analcime, potassium feldspar and/or albite. In some cases the zonation may be enhanced or overprinted by hydrothermal alteration related to intrusive activity.

 

WEATHERING: Zeolitic tuffs commonly resist weathering and may be ledge formers.

 

ORE CONTROLS: Grain size and permeability of host tuff; flow of meteoric water downward in an open hydrologic system; hydrolysis and solution of vitric material by the subsurface water in the upper part of the system raised the pH, activity of SiO2 and content of dissolved solids to values where zeolites crystallized. These result in a vertical or near-vertical zonation of zeolites and other authigenic minerals. Composition of the vitric material and the characteristics of the solutions may have dictated which zeolite species precipitated. For example, clinoptilolite and mordenite are common in silicic tuffs, but chabazite and phillipsite are common in mafic or trachytic tuffs. In many cases the composition of the glassy protolith is believed to determine the mineralogy of the deposit. Trachyte to phonolite glassy protoliths with low Si/Al ratios (£ 3.0) may favour the formation of phillipsite and chabazite, while a more felsic protolith may favour formation of clinoptilolite. Chabazite forms within the systems characterized by low Na/K ratio, whereas phillipsite dominates where the protolith has a high Na/K ratio. Conversion of zeolite to an assemblage of alkali feldspar-quartz can occur at a later stage if the stability field of zeolites is exceeded.

 

ASSOCIATED DEPOSIT TYPES: Deposits that may occur in the same geographic area include pumice (R11), bentonite (E06), diatomaceous earth (F06), volcanic-hosted precious opal (Q11), peat (A01) and coal (A02 and possibly A03).

 

GENETIC MODELS: It is nearly universally accepted that zeolite formation is linked to syn- and post- depositional reaction of volcanic glass with relatively alkaline solutions. The zonation of the open-system type of zeolite deposit is in many cases similar to the upper zones of burial diagenesis (burial metamorphism) that affected thick sequences of silicic, vitric tuffs. Zeolitization temperatures are believed to be less than 100° C, but higher temperatures are estimated for some of the deposits. In many cases, there is controversy as to whether the fluids are "low temperature hydrothermal solutions", "diagenetic fluids" or "heated meteoritic waters". The genetic process probably varies from one deposit to an other. There may be some overlap between different fluid types in the same deposit and also in the terminology used by individual authors.

 

COMMENTS: In British Columbia, clinoptilolite is a major constituent of zeolite deposits.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: None recognized. In most cases, zeolites can be detected and positively identified only by direct analytical techniques, such as x-ray diffraction. Lithogeochemistry may be a useful tool.

 

GEOPHYSICAL SIGNATURE: Possible use of color-composite imagery from airborne multispectral scanner data to distinguish zeolitic tuffs.

 

OTHER EXPLORATION GUIDES: Very low grade or unmetamorphosed volcaniclastic sequences typically containing large proportions of ignimbrites. Vertical zonation of zeolites and associated authigenic silicate minerals in thick (100s to 1000s of metres) tuffaceous sequences. This vertical zonation commonly is (from top to bottom) unaltered vitric material - smectite to clinoptilolite to mordenite to opal-(cristobalite-tridymite) to analcime to potassium feldspar to quartz and then to albite and quartz. This zonation may cut across bedding.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: The value of zeolite deposits varies depending on the end product use and zeolite species present. Properties, such as cation exchange capacity for radionuclides, heavy metals or NH+4, are more meaningful than grade. This is because these properties are commonly different for the same zeolite species originating from two distinct deposits. The zeolite content of better deposits currently mined is estimated to have zeolite content above 60 %, but may reach over 80%. Deposits supplying materials to control the odor to local farms may have zeolite content well below 50%, but must be close to the market.

 

ECONOMIC LIMITATIONS: Virtually all mines are open pit. The cost of the transportation to the market is the most important non-technical parameter. The Si/Al ratio, cation exchange capacity and adsorption capacity for various gases are important technical parameters. Hardness and attrition resistance of zeolitic tuff (commonly affected by abundance of opal-cristobalite-tridymite or quartz) are important in processing and end use. Crystal size of the zeolite is < 2m m to 30m m and can affect the adsorption of gases and the extent and rapidity of cation exchange. Color (due to iron staining) and the abundance of non-zeolitic minerals may limit use. Environmental regulations vary from one jurisdiction to another. Some of the zeolite minerals such as erionite and mordenite may be classified as asbestiform. Free silica occurs commonly in the zeolite ores. Excessive concentrations of asbestiform particles or free silica in the ground product may limit its marketability.

 

END USES: Natural zeolites are used for effluent treatment, mine waste management, pet litter, barn deodorizers, soil conditioners, aquaculture, animal feed additive and construction materials, including pozzolan materials. Higher-priced synthetic zeolites dominate in manufacturing, oil industry / chemical applications and detergent industry. Natural zeolites are used in ion-exchange and adsorption applications, for example, clinoptilolite to remove NH4+ in tertiary sewage treatment and phillipsite to remove Cs and Sr from radioactive materials. Removal of heavy metals from industrial and mine drainage, currently achieved by direct addition of lime or soda, may be done in the future by zeolites. Heavy metal removal, particularly in acid mine drainage, has potential for a growing market.

 

IMPORTANCE: Important sources of natural clinoptilolite and mordenite. Bentonite, attapulgite and other materials known for their high absorbency may be cost effective alternatives to zeolites for specific ion exchange applications.

 

REFERENCES

 

Broxton, D.E., Bish, D.L. and Waren, R.G. (1987): Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada; Clays and Clay Minerals, Volume 35, pages 89-110.

Colella, C. (1996): Ion Exchange Equilibria in Zeolite Minerals; Mineralium Deposita, Volume 31, pages 554-562.

de’Gennarro, M. and Langella, A. (1996): Italian Zeolitized Rocks of Technological Interest; Mineralium Deposita, Volume 31, pages 452-472.

Ghiara, M.R., Franco, E., Luxoro, S., Gnazzo, L. (1995): Diagenetic Clinoptilolite from Pyroclastic Flows of Northern Sardinia; in Proceedings III, Convegno Nazionale di Scienza e Tecnologia delle zeoliti, Cetraro, Sept. 1995: De Rose Montalto, Cosenza; Editor R. Aiello, pages 349-353.

Gottardi, G. and Obradovic, J. (1978): Sedimentary Zeolites in Europe; Fortschritte der Mineralogie, Volume 56, pages 316-366.

Hay, R.L. (1963): Stratigraphy and Zeolitic Diagenesis of the John Day Formation of Oregon; Berkley, University of California Publications in Geological Sciences, Volume 42, pages 1999-262.

Hay, R.L., and Sheppard, R.A. (1981): Zeolites in Open Hydrologic Systems; in Mineralogy and Geology of Natural Zeolites, F.A. Mumpton, Editor, Mineralogical Society of America Reviews in Mineralogy, Volume 4, pages 93-102.

Holmes, D.A. (1994): Zeolites; in Industrial Minerals and Rocks, 6th edition , D.D. Carr, Senior Editor, Society for Mining, Metallurgy and Exploration, Inc., Littleton, Colorado, pages 1129-1158.

Mumpton, F.A. (1983): Commercial Utilization of Natural Zeolites; in; Industrial Minerals and Rocks, S.J. Lefond, Chief Editor, American Institute of Mining, Metallurgical and Petroleum Engineers Inc., New York, pages 1418-1431.
Pansini, M. (1996): Natural Zeolites as Cation Exchangers for Environmental Protection; Mineralium Deposita, Volume 31, pages 563-575.

Sheppard, R.A. (1991): Descriptive Model of Sedimentary Zeolites - Deposit Subtype: Zeolites in Tuffs of Open Hydrologic Systems; in Some Industrial Mineral Deposit Models: Descriptive Deposit Models, G.J. Orris and J.D. Bliss, Editors, U.S. Geological Survey, Open-File Report 91-11A, pages 13-15.

Sheppard, R.A. (1985): Death Valley Junction - Ash Meadows Zeolite Deposit, California and Nevada: 1985 International Clay Conference, Field Trip Guidebook, pages 51-55.

Stamatakis, M.G., Hall, A., and Hein, J.R. (1996): The Zeolite deposits of Greece; Mineralium Deposita, Volume 31, pages 473-481.

Temel, A. and Gundogdu, M.N. (1996): Zeolite Occurrences and the Erionite-mesothelioma Relationship in Cappadocia, Central Anatolia, Turkey; Mineralium Deposita, Volume 31, pages 539-547.

 
 

CLOSED-BASIN ZEOLITES


D02

by R.A. Sheppard 1 and G.J. Simandl 2
1United States Geological Survey, Federal Center, Denver, Colorado, USA
2British Columbia Geological Survey, Victoria, B.C., Canada


Sheppard, R.A. and Simandl, G.J. (1999): Closed-basin Zeolites; in Selected British Columbia Mineral Deposit Profiles, Volume 3, Industrial Minerals, G.J. Simandl, Z.D. Hora and D.V. Lefebure, Editors, British Columbia Ministry of Energy and Mines, Open File 1999-10.

 

IDENTIFICATION

 

SYNONYMS: "Closed-system" zeolite deposits.

 

COMMODITIES: Analcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite.

 

EXAMPLES: (British Columbia (MINFILE #) - Canada/International): Lake Tecopa (California, USA), Bowie Deposit (Arizona, USA), Jersey Valley Deposit (Nevada, USA), Lake Magadi (Kenya).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Microcrystalline zeolite-bearing vitric tuff that consists chiefly of analcime, chabazite, clinoptilolite, mordenite, phillipsite and sometimes erionite. Deposit may consist of one or several stacked zeolite layers separated by sub-economic or barren beds.

 

TECTONIC SETTINGS: Varied tectonic settings. Closed hydrographic basins in either block-faulted terrains (such as the Basin and Range province), trough valleys associated with rifting (such as the Eastern Rift Valley of Kenya) or as Tibet-type grabens formed in a compression environment (such as Emet and Kirka basins, Turkey).

 

DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: These deposits form in lacustrine basins that receive silica-rich, vitric, volcanic material. The saline lake water is commonly of sodium carbonate-bicarbonate variety, with a pH of 9 or greater. These lakes are common in arid and semi-arid regions where annual evaporation exceeds rainfall.

 

AGE OF MINERALIZATION: Late Paleozoic to Holocene; most deposits are Cenozoic.

 

HOST/ASSOCIATED ROCK TYPES: Most favourable hostrocks are rhyolitic to dacitic, vitric tuffs, especially those that are alkali-rich. Associated rocks are bedded evaporites (trona, halite, borates), mudstone, diatomite, bedded or nodular Magadi-type chert, oil shale, conglomerates and sandstones.

 

DEPOSIT FORM: Stratabound; several distinct, overlying beds may be zeolitized. The thickness of the zeolitic tuffs commonly ranges from 10 cm to 10 m. Areal extent is commonly tens to hundreds of square kilometres.

 

TEXTURE/STRUCTURE: Finely crystalline individual tuff beds show lateral zonation from unaltered glass near the shore, to zeolites and then to potassium feldspar in the center of the paleobasin.

 

ORE MINERALOGY (Principal and subordinate): Analcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite. Several of these ore minerals commonly coexist within a given deposit.

 

GANGUE MINERALOGY (Principal and subordinate): Authigenic smectite, mixed layer illite/smectite, silica (opal, cristobalite/tridymite), quartz, searlesite, dawsonite, potassium feldspar, ± calcite, ± dolomite, biotite, sanidine, sodic plagioclase, hornblende, volcanic glass.

 

ALTERATION MINERALOGY: In certain highly alkaline and saline lacustrine deposits, siliceous and alkalic zeolites have been replaced during late burial diagenesis by analcime or potassium feldspar in the central part of the basin.

WEATHERING: Zeolitic tuffs resist weathering and are ledge formers in the lacustrine sequence. Local yellow to brown stains related to hydrous iron oxides.

 

ORE CONTROLS: Chemical composition of the protolith glass and grain size and permeability of the host vitric tuff are the key parameters. Salinity, pH, and ratios of alkali and alkaline-earth ions in the pore water are other important factors. Zeolite deposits are not preserved in rocks where metamorphism exceeded zeolite facies conditions.

 

ASSOCIATED DEPOSIT TYPES: Continental-basin bedded evaporites (trona, halite, borates), diatomite (F06), and finely crystalline, disseminated fluorite in lacustrine rocks. Li-rich trioctahedral smectites (hectorite, saponite and stevensite) may be closely associated with borates.

 

GENETIC MODELS: Microcrystalline zeolites form during early diagenesis of silicic, vitric tuffs deposited in closed hydrographic basins. The zeolites crystallize in the post-depositional environment over thousands to hundreds of thousands of years by reaction of the vitric material with saline, alkaline pore water trapped during lacustrine sedimentation. Locally, zeolites also form from detrital clays, feldspar, and feldspathoids and from chemically precipitated aluminosilicate gels in the same depositional environment.

 

COMMENTS: There are zeolite-bearing tuffs in British Columbia, however, no associated evaporite minerals, no boron enrichment, and no lateral zonation characteristic of closed-basin zeolites are reported.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: The lacustrine environment of sodium carbonate-bicarbonate type that is favourable for closed basin zeolites may also be enriched in boron and lithium.

 

GEOPHYSICAL SIGNATURE: Possible use of color-composite imagery from airborne multispectral scanner data to distinguish zeolitic alteration.

 

OTHER EXPLORATION GUIDES: Unmetamorphosed or very low metamorphic-grade environments. Molds of evaporitic minerals, associated dolomitic mudstone, occurrence of Magadi-type chert. Concentric zonation and lateral gradation in a basinward direction of unaltered volcanic glass to alkali-rich, silicic zeolites to analcime and then to potassium feldspar in the central part of the depositional basin. Zeolites are finely crystalline and resemble bedded diatomite, feldspar or bentonite in outcrop. Combination of X-Ray diffraction and ammonia cation exchange capacity (CEC) are essential in the early screening of zeolite prospects.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: The cutoff grade varies greatly. For example, a 10 to 20 centimetre thick ore bed at Bowie contains 60 to 80% chabasite. Obviously, this zone would not have been economic if the main ore mineral was clinoptilolite. Most of the commercial clinoptilolite deposits contain between 50% and 90% zeolite.

 

ECONOMIC LIMITATIONS: Distance to the market is an important limitation for materials used in agricultural and construction applications. High-value specialty zeolites are international travelers. Production is typically from open pits with as much as 30 m of overburden. Mining costs reported by Holmes (1994) vary from US$ 3 to 6 per ton. Ground natural zeolites are selling for US$30 to 120 for low-value industrial use, but small tonnages of specialty products for the radioactive waste market can sell for more than $US 1000.00 per ton. Environmental regulations vary from one jurisdiction to an other. Some of the zeolite minerals, such as erionite and mordenite, may be classified as asbestiform, a designation that reduces the market for the product. Free silica occurs commonly in the zeolite ores. Excessive concentrations of free silica or fibrous particles in the ground product may severely limit its marketability.

 

END USES: Zeolites have many agricultural uses, for example as preservative agents (desiccants), soil conditioners, fertilizer extenders, herbicides, pesticide and fungicide carriers, animal food additives and odor controllers. They are used in aquaculture for ammonia removal. Other uses are as dimension stone, light weight aggregate, pozzolan and for treatment processes, such as natural gas purification, nuclear waste treatment and disposal, and oil spill, sewage and effluent cleanup. Chabazite and clinoptilolite are used in heat exchange systems. Most of the non-construction uses are based on the ion-exchange and adsorption properties of zeolites. Cation exchange capacity and adsorption capacity for various gases are important. For example, chabazite is used to remove CO2 and H2S from sour natural gas while clinoptilolite can remove NH4+ in tertiary sewage treatment and in pet-litter and base metals from effluents. The Si/Al ratio and exchangeable cation ratios of the zeolites affect certain uses. Crystallite size of the zeolite is < 2 m m to 30 m m and can affect the adsorption of gases and the extent and rapidity of cation exchange.

 

IMPORTANCE: This deposit type contains the largest variety of zeolite species and it is an important source of chabazite, erionite, and phillipsite. Naturally occuring zeolites are substantially less expensive than synthetic zeolites; however, the latter are preferred in many applications because they are monomineralic, have less variability in product properties, or have useful properties that can not be matched by natural products. Bentonite, attapulgite, activated carbon, silica gel are viable substitutes for zeolite in a number of applications.

 

REFERENCES

 

Colella, C. (1996): Ion Exchange Equilibria in Zeolite Minerals; Mineralium Deposita, Volume 31, pages 554-562.

Gündogdu, M.N., Yalçin, H., Temel, A. and Claue, N. (1996): Geological, Mineralogical and Geochemical Characteristics of Zeolite Deposits Associated with Borates in the Bigadiç, Emet and Kirka Neogene Lacustrine Basins, Western Turkey; Mineralium Deposita, Volume 31, pages 492-513.

Gottardi, G. and Obradovic, J. (1978): Sedimentary Zeolites in Europe; Fortschritte der Mineralogie, Volume 56, pages 316-366.

Holmes, D.A. (1994): Zeolites; in Industrial Minerals and Rocks, 6th edition , D.D. Carr, Senior Editor, Society for Mining, Metallurgy and Exploration, Inc., Littleton, Colorado, pages 1129-1158.

Ibrahim, K. and Hall, A. (1996): The Authigenic Zeolites of the Aritayn Volcanic Formation, Northeast Jordan; Mineralium Deposita, Volume 31, pages 514-522.

Mumpton, F.A. (1983): Commercial Utilization of Natural Zeolites; in; Industrial Minerals and Rocks, S.J. Lefond, Chief Editor, American Institute of Mining, Metallurgical and Petroleum Engineers Inc., New York, pages 1418-1431.

Pansini, M. (1996): Natural Zeolites as Cation Exchangers for Environmental Protection; Mineralium Deposita, Volume 31, pages 563-575.

Sheppard, R.A. (1991): Zeolitic Diagenesis of Tuffs in the Miocene Chalk Hills Formation, Western Snake River Plain, Idaho; U.S. Geological Survey, Professional Paper 1963, 27 pages.

Sheppard, R.A. (1982): Model for Zeolites in Alkaline-Lake Deposits; Characteristics of Mineral Deposit Occurrences, compiled by R.L. Erickson, U.S. Geological Survey, Open-File Report 82-795, pages 241-243.

Sheppard, R.A. and Gude, A.J., 3rd (1968): Distribution and Genesis of Authigenic Silicate Minerals in Tuffs of Pleistocene Lake Tecopa, Inyo Country, California; U.S. Geological Survey, Professional Paper 547, 38 pages.

Sheppard, R.A. and Gude, A.J., 3rd (1973): Zeolites and associated Authigenic Silicate Minerals in Tuffaceous Rocks of the Big Sandy Formation, Mohave County, Arizona; US. Geological Survey, Professional Paper 830, 36 pages.

Surdam, R.C. and Sheppard, R.A. (1978): Zeolites in Saline, Alkaline-Lake Deposits; in: Natural Zeolites: Occurrences, Properties, Use, L.B. Sand and F.A. Mumpton, Editors, Pergamon Press, New York, pages 145-174.

Temel, A. and Gundogdu, M.N. (1996): Zeolite Occurrences and the Erionite-mesothelioma Relationship in Cappadocia, Central Anatolia, Turkey; Mineralium Deposita, Volume 31, pages 539-547.

 

VOLCANIC REDBED Cu


D03

by D.V. Lefebure and B.N. Church
British Columbia Geological Survey


Lefebure, D.V. and Church, B.N. (1996): Volcanic Redbed Cu, in Selected British Columbia Mineral Deposit Profiles, Volume 1 - Metallic Deposits, Lefebure, D.V. and Hõy, T, Editors, British Columbia Ministry of Employment and Investment, Open File 1996-13, pages 5-7.

 

IDENTIFICATION

 

SYNONYMS: Basaltic Cu, volcanic-hosted copper, copper mantos.

 

COMMODITIES (BYPRODUCTS): Cu (Ag)

 

EXAMPLES (British Columbia - Canada/International): Sustut Copper (094D 063), Shamrock (092HNE092), NH (093L 082), North Star (094D 032); White River (Yukon, Canada), 47 Zone and June, Coppermine River area (Northwest Territories, Canada) Mountain Grill and Radovan (Alaska, USA), Calumet-Hecla and Kearsarga, Keweenaw Peninsula (Michigan, USA), Mantos Blancos, Ivan and Altamira (Chile).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Chalcocite, bornite and/or native copper occur in mafic to felsic volcanic flows, tuff and breccia and related sedimentary rocks as disseminations, veins and infilling amygdules, fractures and flowtop breccias. Some deposits are tabular, stratabound zones, while others are controlled by structures and crosscut stratigraphy.

 

TECTONIC SETTINGS: These deposits occur in intracontinental rifts with subaerial flood basalt sequences and near plate margins with island-arc and continental-arc volcanics.

 

DEPOSITIONAL ENVIRONMENT / GEOLOGICAL SETTING: Continental to shallow-marine volcanic settings which formed in “low to intermediate latitudes” with arid to semi-arid environments. The metamorphic grade is sub-greenschist.

 

AGE OF MINERALIZATION: Proterozoic to Tertiary.

 

HOST/ASSOCIATED ROCK TYPES: Amygdaloidal basaltic lavas, breccias and coarse volcaniclastic beds with associated volcanic tuffs, siltstone, sandstone and conglomerate are the most common rock types. The volcanics may cover the spectrum from basalt to rhyolite composition. Redbed sedimentary rocks are common and often exhibit shallow water sedimentary structures (small-scale crossbedding, mud cracks, algal mats). Any of these units may host the deposits, although typically it is the mafic volcanics that have widespread elevated background values of copper due to the presence of native copper or chalcocite in amygdules, flow breccias or minor fractures.

 

DEPOSIT FORM: Many deposits are tabular lenses from a few to several tens of metres thick which are roughly concordant with the host strata over several hundred metres. Other deposits are strongly influenced by structural controls and crosscut the stratigraphy as veins, veinlets, fault breccias and disseminated zones.

 

TEXTURE/STRUCTURE: Disseminations, open-space fillings, veins and some replacement textures. Open spaces may be amygdules, cavities in flowtop breccias or fractures. Mineralization is commonly fine-grained, although spectacular examples of copper “nuggets” are known.

 

ORE MINERALOGY (Principal and subordinate): Chalcocite, bornite, native copper, digenite, djurleite, chalcopyrite, covellite, native silver and greenockite. Iron sulphides, including pyrite, typically peripheral to the ore. Some deposits are zoned from chalcocite through bornite and chalcopyite to fringing pyrite. Copper-arsenic minerals, such as domeykite, algodonite and whitneyite, occur in fissure veins in the Keewenaw Peninsula.

 

GANGUE MINERALOGY (Principal and subordinate): Typically minor gangue; hematite, magnetite, calcite, quartz, epidote, chlorite and zeolite minerals.

 

ALTERATION MINERALOGY: Generally no associated alteration, although many deposits occur in prehnite-pumpellyite grade regionally metamorphosed volcanic rocks with minerals such as calcite, zeolites, epidote, albite, prehnite, pumpellyite, laumontite and chlorite.

 

WEATHERING: These deposits commonly have no associated gossans or alteration; locally minor malachite or azurite staining.

 

ORE CONTROLS: Deposits appear to be confined to subaerial to shallow-marine volcanic sequences commonly with intercalated redbeds. One of the major ore controls is zones of high permeability due to volcaniclastics, breccias, amygdules and fractures.

 

ASSOCIATED DEPOSIT TYPES: Sediment-hosted copper deposits (E04) often occur in the same stratigraphic sequences. The carbonate-hosted copper deposits at Kennicott, Alaska are associated with basaltic Cu deposits in the Nikolai greenstone.

 

GENETIC MODELS: Most authors have favoured metamorphism of copper-rich, mafic volcanic rocks at greater depth for the source of the metal-bearing fluids, and subsequent deposition higher in the stratigraphic sequence, in oxidized subaerial hostrocks at lower metamorphic grade. More recently analogies have been drawn to diagenetic models for sediment-hosted Cu deposits which predate the metamorphism. Low-temperature fluids migrating updip along permeable strata to the margins of basins, or along structures, deposit copper upon encountering oxidized rocks. These rocks are typically shallow-marine to subaerial volcanic rocks which formed in arid and semi-arid environments. Both models require oxidized rocks as traps, which requires the presence of an oxygen-rich atmosphere; therefore, all deposits must be younger than ~2.4 Ga.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: Simple ore mineralogy produces a very specific geochemical signature for Cu and usually Ag. Lithogeochemical and stream sediment samples may return high values of CuñAg, typically high Cu/Zn ratios and low gold values.

 

GEOPHYSICAL SIGNATURE: Induced polarization surveys can be used to delineate mineralized lenses and areas of more intense veining.

 

OTHER EXPLORATION GUIDES: Malachite-staining. A red liverwort-like organism (Tentopholia iolithus) is often found in abundance on the surface of outcrops with copper mineralization in northern British Columbia.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: The deposits range in size from hundreds of thousands to hundreds of millions of tonnes grading from less than 1% Cu to more than 4% Cu. Silver values are only reported for some deposits and vary between 6 and 80 g/t Ag. Sustut contains 43.5 Mt grading 0.82% Cu. The Calumet conglomerate produced 72.4 Mt grading 2.64% Cu.

 

ECONOMIC LIMITATIONS: Only a few deposits have been high enough grade to support underground mines and the majority of occurrences are too small to be economic as open pit operations.

 

IMPORTANCE: The Keweenaw Peninsula deposits in Michigan produced 5 Mt of copper between 1845 and 1968. Otherwise production from basaltic copper deposits has been limited; the only currently operating mines producing significant copper are in Chile. However, there are numerous deposits of this type in British Columbia which underlines the potential to find significant copper producers.

 

REFERENCES

 

Butler, B.S. and Burbank, W.S. (1929): The Copper Deposits of Michigan; U.S.Geological Survey, Professional Paper 144, 238 pages.

Cox, D.P. (1986): Descriptive Model of Basaltic Cu; in Mineral Deposit Models, Cox, D.P. and Singer, D.A., Editors, U.S. Geological Survey, Bulletin 1693, page 130.

Kindle, E.D. (1972): Classification and Description of Copper Deposits, Coppermine River; Geological Survey of Canada, Bulletin 214, 109 pages.

Kirkham, R.K. (1984): Volcanic Redbed Copper; in Canadian Mineral Deposit Types, A Geological Synopsis, Eckstrand, O.R., Editor, Geological Survey of Canada, Economic Geology Report 36, page 37.

Kirkham, R.K. (in press): Volcanic Redbed Copper; in Geology of Canadian Mineral Deposit Types, Eckstrand, O.R., Sinclair, W.D. and Thorpe, R.I., Editors, Geological Survey of Canada, Geology of Canada, Number 8, pages 243-254.

Lortie, R.H. and Clark, A.H. (1987): Strata-bound Cupriferous Sulphide Mineralization associated with Continental Rhyolitic Volcanic Rocks, Northern Chile: I. The Jardin Silver Copper-Silver Deposit; Economic Geology, Volume 82, pages 546-570.

Sato, T. (1984): Manto Type Copper Deposits in Chile; Bulletin of the Geological Society of Japan, Volume 35, pages 565-582.

Sood, M.K., Wagner, R.J. and Markazi, H.D. (1986): Stratabound Copper Deposits in East South-central Alaska: Their Characteristics and Origin; in Geology and Metallogeny of Copper Deposits, Friedrich, G.H. et al., Editors, Springer- Verlag, Berlin, pages 422-442.

White, W.S. (1968): The Native-Copper Deposits of Northern Michigan; in Ore Deposits of the United States, 1933-1967; The Graton-Sales Voume, Ridge, J.D., Editor, American Institute of Mining, Metallurgy and Petroleum Engineers, Inc., New York, pages 303-325.

Wilton, D.H.C. and Sinclair, A.J. (1988): The Geology and Genesis of a Strata-bound Disseminated Copper Deposit at Sustut, British Columbia, Economic Geology, Volume 83, pages 30-45.

 

IRON OXIDE BRECCIAS AND VEINS P-Cu-Au-Ag-U


D07

by David V. Lefebure
British Columbia Geological Survey


Lefebure, D.V. (1995): Iron Oxide Breccias and Veins P-Cu-Au-Ag-U, in Selected British Columbia Mineral Deposit Profiles, Volume 1 - Metallics and Coal, Lefebure, D.V. and Ray, G.E., Editors, British Columbia Ministry of Employment and Investment, Open File 1995-20, pages 33-36.

 

IDENTIFICATION

 

SYNONYMS: Olympic Dam type, Kiruna type, apatite iron ore, porphyrite iron (Yangtze Valley), iron oxide rich deposits, Proterozoic iron oxide (Cu-U-Au-REE), volcanic-hosted magnetite.

COMMODITIES (BYPRODUCTS): Fe, P, Cu, Au, Ag, U (potential for REE, Ba, F).

 

EXAMPLES (British Columbia - Canada/International): Iron Range (082FSE014; 082FSE015; 082FSE016; 082FSE017; 082FSE018; 082FSE019; 082FSE020; 082FSE021; 082FSE022; 082FSE023; 082FSE024; 082FSE025; 082FSE026; 082FSE027; 082FSE028); Sue-Dianne (Northwest Territories, Canada); Wernecke breccias (Yukon, Canada), Kiruna district(Sweden), Olympic Dam (Australia), Pea Ridge and Boss-Bixby (Missouri, USA), El Romeral (Chile).

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION: Magnetite and/or hematite breccia zones and veins which form pipes and tabular bodies hosted by continental volcanics and sediments and intrusive rocks. The deposits exhibit a wide range in their nonferrous metal contents. They vary from Kiruna type monometallic (Fe ± P) to Olympic Dam type polymetallic (Fe ± Cu ± U ± Au ± REE).

 

TECTONIC SETTING: Associated with stable cratons, typically associated with grabens related to rifting. Intracratonic extensional tectonics coeval with hostrock deposition. Upper crustal igneous or sedimentary rocks.

 

DEPOSITIONAL ENVIRONMENT/ GEOLOGICAL SETTING: Found crosscutting a wide variety of sedimentary and igneous rocks; magnetite-apatite deposits show an affinity for volcanics and associated hypabyssal rocks.

 

AGE OF MINERALIZATION: Proterozoic to Tertiary and believed to be virtually contemporaneous with associated suite of intrusive and/or volcanic rocks. Polymetallic Fe oxide deposits are commonly mid-Proterozoic age varying from 1.2 to 1.9 Ga.

 

HOST/ASSOCIATED ROCK TYPES: Veins and breccias crosscut, or are conformable with, a wide variety of continental sedimentary and volcanic rocks and intrusive stocks, including felsic volcanic breccia, tuff, clastic sedimentary rocks and granites. There may be a special association with a felsic alkalic rock suite ranging from “red” granite, and rapakivi granite to mangerite and charnockite and various volcanic equivalents. Fe oxides have been reported as common accessories in the associated igneous rocks. In some deposits the Fe oxide forms the matrix to heterolithic breccias which are composed of lithic and oxide clasts (usually hematite fragments), hematite-quartz microbreccia and fine-grained massive breccia. Some deposits have associated hematite-rich breccias, bedded Fe oxides and Fe oxide-bearing volcanic rocks which are conformable with associated volcanic rocks. Magnetite lavas and feeder dikes exist on the El Laco volcano in Chile. . DEPOSIT FORM: Discordant pod-like zones, veins (dike-like), tabular bodies and stockworks; in some deposits dikes are overlain by Fe oxide tuffs and flows. The veins and tabular zones extend horizontally and vertically for kilometres with widths of metres to hundreds of metres.

 

TEXTURE/STRUCTURE: Cu-U-Au mineralization is typically hosted in the Fe oxide matrix as disseminations with associated microveinlets and sometimes rare mineralized clasts. Textures indicating replacement and microcavity filling are common. Intergrowths between minerals are common. Hematite and magnetite may display well developed crystal forms, such as interlocking mosaic, tabular or bladed textures. Some of the deposits (typically hematite rich) are characterized by breccias at all scales with Fe oxide and hostrock fragments which grade from weakly fractured hostrock on the outside to matrix-supported breccia (sometimes heterolithic) with zones of 100% Fe oxide in the core. Breccias may be subtle in hand sample as the same Fe oxide phase may comprise both the fragments and matrix. Breccia fragments are generally angular and have been reported to range up to more than 10 m in size, although they arefrequently measured in centimetres. Contacts with hostrocks are frequently gradational over scale of centimetres to metres. Hematite breccias may display a diffuse wavy to streaky layered texture of red and black hematite.

 

ORE MINERALOGY (Principal and subordinate): The deposits vary between magnetite-apatite deposits with actinolite or pyroxene (Kiruna type) and hematite-magnetite deposits with varying amounts of Cu sulphides, Au, Ag, uranium minerals and REE (Olympic Dam type). Hematite (variety of forms), specularite, magnetite, bornite, chalcopyrite, chalcocite, pyrite; digenite, covellite, native copper, carrolite, cobaltite, Cu-Ni-Co arsenates, pitchblende, coffinite, brannerite, bastnaesite, monazite, xenotime, florencite, native silver and gold and silver tellurides. At Olympic Dam, Cu is zoned from a predominantly hematite core (minor chalcocite-bornite) to chalcocite-bornite zone then bornite-chalcopyrite to chalcopyrite-pyrite in the outermost breccia. Uraninite and coffinite occur as fine-grained disseminations with sulphides; native gold forms fine grains disseminated in matrix and inclusions in sulphides. Bastnaesite and florencite are very fine grained and occur in matrix as grains, crystals and crystal aggregates.

 

GANGUE MINERALOGY (Principal and subordinate): Gangue occurs intergrown with ore minerals, as veins or as clasts in breccias. Sericite, carbonate, chlorite, quartz, fluorite, barite, and sometimes minor rutile and epidote. Apatite and actinolite or pyroxene with magnetite ores (Kiruna type). Hematite breccias are frequently cut by 1 to 10 cm veins with fluorite, barite, siderite, hematite and sulphides.

 

ALTERATION MINERALOGY (Principal and subordinate): A variety of alteration assemblages with differing levels of intensity are associated with these deposits, often with broad lateral extent. Olympic Dam type: Intense sericite and hematite alteration with increasing hematite towards the centre of the breccia bodies at higher levels. Close to the deposit the sericitized feldspars are rimmed by hematite and cut by hematite veinlets. Adjacent to hematite breccias the feldspar, rock flour and sericite are totally replaced by hematite. Chlorite or k-feldspar alteration predominates at depth. Kiruna type: Scapolite and albite?; there may also be actinolite-epidote alteration in mafic wallrocks. With both types of deposits quartz, fluorite, barite, carbonate, rutile, orthoclase ± epidote and garnet alteration are also reported.

 

WEATHERING: Supergene enrichment of Cu and U, for example, the pitchblende veins in the Great Bear magmatic zone.

 

ORE CONTROLS: Strong structural control with emplacement along faults or contacts, particularly narrow grabens. Mid-Proterozoic rocks particularly favourable hosts. Hydrothermal activity on faults with extensive brecciation. May be associated with felsic volcanic and alkalic igneous rocks. In some deposits calderas and maars have been identified or postulated. Deposits may form linear arrays more than 100 km long and 40 km wide with known deposits spaced 10-30 km along trend.

 

ASSOCIATED DEPOSIT TYPES: Volcanic-hosted U (D06); alkaline porphyry Cu-Au deposits (L03); supergene uranium veins.

 

COMMENTS: Hitzman et al. (1992) emphasize that these are low-Ti iron deposits, generally less than 0.5% TiO2 and rarely above 2% TiO2 which allows distinction from Fe oxides associated with anorthosites, gabbros and layered mafic intrusions. Fe and Cu sulphides may be more common with hematite Fe oxides.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: Anomalously high values for Cu, U, Au, Ag, Ce, La, Co, ± P, ± F, and ± Ba in associated rocks and in stream sediments.

 

GEOPHYSICAL SIGNATURE: Large positive gravity anomalies because of Fe oxides. Regional aeromagnetic anomalies related to magnetite and/or coeval igneous rocks. Radiometric anomaly (such as airborne gamma-ray spectrometer survey) expected with polymetallic deposits containing uranium.

 

OTHER EXPLORATION GUIDES: Proterozoic faulting with associated Fe oxides (particularly breccias), possibly related to intracratonic rifting. Widespread hematite, sericite or chlorite alteration related to faults. Possibly form linear arrays 100 or more kilometres long and up to tens of kilometres wide.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Deposits may exceed 1000 Mt grading greater than 20 % Fe and frequently are in 100 to 500 Mt range. Olympic Dam deposit has estimated reserves of 2000 Mt grading 1.6% Cu, 0.06% U3O8, 3.5 g/t Ag and 0.6 g/t Au with a measured and indicated resource in a large number of different ore zones of 450 Mt grading 2.5% Cu, 0.08 % U3O8, 6 g/t Ag and 0.6 g/t Au with ~5,000 g/t REE. The Ernest Henry deposit in Australia contains 100 Mt at 1.6% Cu and 0.8 g/t Au. Sue-Dianne deposit in the Northwest Territories contains 8 Mt averaging 0.8% Cu and 1000 g/t U and locally significant gold. The Kiruna district contains more than 3000 Mt of Fe oxide apatite ore grading 50-60% Fe and 0.5 -5 % P. The largest orebody at Bayan Obo deposit in Inner Mongolia, China contains 20 Mt of 35 % Fe and 6.19% REE.

 

ECONOMIC LIMITATIONS: Larger Fe oxide deposits may be mined for Fe only; however, polymetallic deposits are more attractive.

 

IMPORTANCE: These deposits continue to be significant producers of Fe and represent an important deposit type for producing Cu, U and possibly REE.

 

REFERENCES

 

ACKNOWLEDGEMENTS: This deposit profile represents the results of a literature review. The only “ground truthing” is thanks to instructive conversations with Sunil Gandhi of the Geological Survey of Canada and Tom Setterfield of Westminer Canada Ltd.

 

Cox, D.P. (1986): Descriptive Model of Olympic Dam Cu-U-Au; in Mineral Deposit Models, Cox, D.P. and Singer, D.A., Editors, U.S. Geological Survey, Bulletin 1693, 379 pages.

Einaudi, M.T. and Oreskes, N. (1990): Progress Toward an Occurrence Model for Proterozoic Iron Oxide Deposits - A Comparison Between the Ore Provinces of South Australia and Southeast Missouri; in The Midcontinent of the United States - Permissive Terrane for an Olympic Dam Deposit?, Pratt, W.P. and Sims, P.K. Editors, U. S. Geological Survey, Bulletin 1392, pages 589-69.

Gandhi, S.S. (1994): Geological Setting and Genetic Aspects of Mineral Occurrences in the Southern Great Bear Magmatic Zone, Northwest Territories; in Studies of Rare- metal Deposits in the Northwest Territories, Sinclair, W.D. and Richardson, D.G, Editors, Geological Survey of Canada, Bulletin 475, pages 63-96.

Gandhi, S.S. and Bell, R.T. (1993): Metallogenetic Concepts to Aid in Exploration for the Giant Olympic Dam Type Deposits and their Derivatives; Proceedings of the Eighth Quadrennial IAGOD Symposium, in Ottawa, Ontario, August 12-18, 1990, International Asssociation on the Genesis of Ore Deposits, Maurice, Y.T., Editor, Schweizerbar’sche Verlagsbuchhandlung, Stutggart, pages 787-802.

Hauck, S.A. (1990): Petrogenesis and Tectonic Setting of Middle Proterozoic Iron Oxide- rich Ore Deposits; An Ore Deposit Model for Olympic Dam Type Mineralization; in The Midcontinent of the United States - Permissive Terrane for an Olympic Dam Deposit?, Pratt, W.P. and Sims, P.K. Editors, U. S. Geological Survey, Bulletin 1932, pages 4-39.

Hildebrand, R.S. (1986): Kiruna-type Deposits: Their Origin and Relationship to Intermediate Subvolcanic Plutons in the Great Bear Magmatic Zone, Northwest Canada; Economic Geology, Volume 81, pages 640-659.

Hitzman, M. W., Oreskes, N. and Einaudi, M. T. (1992): Geological Characteristics and Tectonic Setting of Proterozoic Iron Oxide (Cu-U-Au-REE) Deposits; Precambrian Research, Volume 58, pages 241-287.

Laznicka, P. and Gaboury, D. (1988): Wernecke Breccias and Fe, Cu, U Mineralization: Quartet Mountain-Igor Area (NTS 106E); in Yukon Exploration and Geology, Exploration and Geological Services Division, Yukon, Indian and Northern Affairs Canada, pages 42-50.

Oreskes, N. and Einaudi, M.T. (1990): Origin of Rare Earth-enriched Hematite Breccias at the Olympic Dam Deposit, Roxby Downs, South Australia; Economic Geology, Volume 85, pages 1-28.

Parak, T. (1975): Kiruna Iron Ores are not “Intrusive-magmatic Ores of the Kiruna Type”; Economic Geology, Volume 68, pages 210 -221.

Reeve, J.S., Cross, K.C., Smith, R.N. and Oreskes, N. (1990): Olympic Dam Copper- Uranium-Gold-Silver Deposit; in Geology of the Mineral Deposits of Australia and Papua New Guinea, Hughes, F.E., Editor, The Australasian Institute of Mining and Metallurgy, pages 1009-1035.

Research Group of Porphyrite Iron Ore of the Middle-Lower Yangtze Valley (1977): Porphyrite Iron Ore - A Genetic Model of a Group of Iron Ore Deposits in Andesitic Volcanic Area; Acta Geological Sinica, Volume 51, No. 1, pages 1-18.

Roberts, D.E. and Hudson, G.R.T. (1983): The Olympic Dam Copper-Uranium-Gold Deposit, Roxby Downs, South Australia; Economic Geology, Volume 78, pages 799-822.

  

*  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 Continental and Volcanic Deposits

BC Profile # Global Examples B.C. Examples
 D01 Ash Meadows (California), John Day Formation (Oregon)  Princeton Basin, Cache Creek area
 D02 Bowie (Arizona), Lake Magadi (Kenya)  
 D03 Keewenaw (Michigan), Coppermine (Northwest Territories) Sustut Copper, Shamrock, NH
D04 Sherwood (Washington) Blizzard, Tyee
D05* Colorado Plateau, Grants (New Mexico) - -
D06 Marysvale (Utah), Aurora (Oregon) Rexspar, Bullion (Birch Island)
 D07 El Romeral (Chile), Sue-Dianne (Northwest Territories) Iron Range