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Ministry of Energy Mines and Responsible for Core Review

B - Residual/Surficial

BC Profile # Deposit Type Approximate Synonyms USGS Model #
B01* Laterite Fe Gossan Fe - -
B02* Laterite Ni - - 38a
B03* Laterite-Saprolite Au Eluvial placers 38g
B04* Bauxite Al Lateritic bauxite 38b
B05 Residual kaolin Primary kaolin 38h*
B07* Bog Fe, Mn, U, Cu, Au - - - -
B08 Surficial U Calcrete U - -
B09 Karst-hosted Fe, Al, Pb-Zn - - - -
B10 Gossan Au-Ag Residual Au; Precious metal gossans - -
B11* Marl - - - -
B12 Sand and Gravel - - - -

 

Residual Kaolin

B05
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS:  Primary kaolin, china clay, chinastone.

 

COMMODITIES (BYPRODUCTS): Kaolin (sometimes silica sand, construction aggregate, mica).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International)Lang Bay (092F 137), Sumas Mountain (092GSE004), Buse Lake (092INE123); Spruce Pine district (North Carolina, USA), Germany, Cornwall, Saxony, France, Czech Republic, Ukraine

 

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  In situ alteration (or kaolinization) of feldspathic rocks, such as granite, gneiss, syenite, arkose and leucocratic volcanic ash, by tropical or sub-tropical weathering into kaolinite saprolite.  Weathered zones may thicken considerably where sheer and fracture zones or hydrothermally altered zones act as conduit for groundwater of meteoric origin. 

 

TECTONIC SETTINGS: Continental and continental margin setting. Stable continental basins and lowlands, foreland basins and shelves with grabens and downfaulted blocks.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: High rate of chemical weatherin with low rate of physical erosion, basement composed of feldspathic rocks and their weathered or altered equivalents, with ground water circulation.  Lacustrine basins and tropical swamp environment.  Kaolinization should be taking place in areas lacking physical erosion.

 

AGE OF MINERALIZATION: Globally, most of producing deposits are of Carboniferous to Lower Tertiary age. Kaolinite can be of any post Late Paleozoic age, and is forming currently in some tropical regions.  

 

HOST/ASSOCIATED ROCK TYPES: Feldspathic rocks of metamorphic origin – gneisses (Denmark, Spain, Ukraine), schists and phyllites (Germany, South Africa, Australia), granitic intrusions (North Carolina, Saxony, Cornwall, Czech Republic), arkoses and arkosic sandstones (Czech Republic, Germany, France) or volcanic ash (Buse Lake, Czech Republic) / Laterite, bauxite.

 

DEPOSIT FORM: Slab, irregular mantle, trough.  Weathered crust – saprolite with intensity and depth of kaolinization depending on permeability of the original host. Along faults, mylonitic and hydrothermally altered zones the kaolinic weathering can reach a depth of over 200 metres. The depth of the economically viable zone is quite variable and usually up to 50 metres as it depends on local subsidence, such as fault controlled blocks, the original surface morphology and host rock permeability.

  

ORE MINERALOGY [Principal and subordinate]: Kaolinite, halloysite, dickite, nakrite.  

 

GANGUE MINERALOGY [Principal and subordinate]: Quartz, sometimes feldspar, mica, pyrite, siderite, tourmaline, zircon, rutile.  
 

ALTERATION MINERALOGY: Basic mineralogy is not changed by alteration, but it may remove dark organic matter, iron hydroxide, carbonate, residual feldspar and in general improve the quality of kaolinite resource.  

 

WEATHERING: High alumina minerals like diaspor, gibbsite, boehmite.  Lateritic and/or pisolitic bauxite.

 

PRODUCT CONTROLSThe intensity of kaolinization and the presence of detrimental components, particularly iron and titanium are important. Some deleterious contamination depends on the type of original host rock and presence of minerals, such as biotite.

 

GENETIC MODELSThe alteration results from surface weathering and groundwater movement below the surface. Kaolin minerals form under physical and chemical conditions at relatively low temperature and pressure. The most common parent minerals are feldspars and muscovite. Feldspathic rocks weather readily to kaolinite and quartz under favourable conditions of high rainfall, rapid drainage, temperate to tropical climate, a low water table and adequate water movement to leach soluble components. Heat producing radiogenic decay within some granites may lead to convective circulation of heated groundwater and enhance the alteration process.

 

ASSOCIATED DEPOSIT TYPESSedimentary kaolin (E07), residual bentonite, coal (A02, A03, A04), silica sand, expanding shale (R02), cement "shales" (R01), some vermiculite deposits.

  

COMMENTSSome deposits have a multiple process of kaolinization, where hydrothermal alteration was overprinted by residual weathering. Cornwall and New Zealand are two examples. In both cases the residual overprint resulted in improved kaolin quality.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: Absence of sodium and potassium, increase in aluminium and silica.

GEOPHYSICAL SIGNATURESeismic and resistivity techniques are successfully used in kaolin exploration. Conductive clays respond to resistivity and low clay density provide enough contrast for seismic survey. Aerial electromagnetic survey can delineate weathered profile even under tens of metres thick overburden.

 

OTHER EXPLORATION GUIDES: Regional unconformities, coal and basal claystone in sedimentary basins.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGEResidual deposits have in general 15 to 20% kaolin recovery. Different end uses have specific requirements on the quality of processed kaolin. This may include presence of impurities, like iron hydroxides, titanium dioxide, sodium and potassium, some other clay minerals, brightness and particle size. Because of the need for sophisticated processing to obtain a quality commercial product, present commercial producers operate plants with capacity from 50,000 tonnes of processed kaolin per year and up.

 

ECONOMIC LIMITATIONSDistribution of kaolin deposits globally is very uneven. Therefore the trade in processed kaolin is routinely crossing both the continents and oceans. In North America, for example, the west coast paper industry is importing large quantities of kaolin from eastern states like South Carolina and Georgia. Also, processed kaolin from Brazil is currently selling in Europe and Asia. Replacement by other minerals is limited to only some end uses.

 

END USESThe annual US production of kaolin is in the order of 9 million tones per year. About half of kaolin in North America is used by paper industry, and about 25% in variety of ceramics. The rest is used in a numerous other end uses, like filler in plastics, rubber, and paints, cosmetics and pharmaceutics, catalyst and catalyst carrier, silicon chemicals, specialty cement, and refractory products.

 

IMPORTANCEImportant kaolin source worldwide, less in North America because of large secondary kaolin deposits in Alabama, Georgia and South Carolina.

 

REFERENCES

 

Bristow, C.M. (1987): World Kaolins - Genesis, Exploitation and Application”, Industrial Minerals, number 238, July, pages 45-59.

Clarke, G. (1985): Special Clays, Industrial Minerals, Number 216, September, pages 25-51.

Harben, P.W. and Kuzvart, M. (1996): Industrial Minerals – A Global Geology, Metal Bulletin PLC, London. UK, 462 pages.
Harvey, C.C. and Murray, H.H.(1997): Industrial Clays in the 21st Century: A Perspective of Exploration,


Technology
and Utilization, Applied Clay Science, Volume 11, pages 285-310.

Kuzvart, M. (1984): Industrial Minerals and Rocks, Elsevier, New York, 454 pages.

Malkovsky, M. and Vachtl, J., Editors, (1969): Kaolin Deposits of the World, A-Europe, B-Overseas Countries, Proceedings of Symposium 1, 23th International Geological Congress, Prague, 1968, 460 pages.

Murray, H.H., Bundy, W. and Harvey, C.C., Editors, (1993): Kaolin Genesis and Utilization; The Clay Minerals Society, Boulder, Colorado, 341 pages.

Pickering, S.M. and Murray, H.H. (1994): Kaolin; in Carr, D.D., Senior Editor, Industrial Minerals and Rocks, Society for Mining, Metallurgy and Exploration, Littleton, Colorado, page 255-277.

Psyrillos, A., Manning, D.A.C. and Burley, S.D. (1998): Geochemical Constraints on Kaolinization in the St Austell Granite, Cornwall, England, Journal of the Geological Society, London, Vol.155, 1998, pages 829-840.

Read, P.B. (1996): Industrial Mineral Potential of the Tertiary Rocks, Vernon and Adjacent Map Areas (82L), Ministry of Energy, Mines and Petroleum Resources, Geological Fieldwork 1995, Paper 1996-1, pages 207-218.

 
 

Carbonate-hosted, Nonsulphide Zn-Pb (supergene)

B09
by S. Paradis and G.J. Simandl
Geological Survey of Canada and British Columbia Geological Survey, Victoria, B.C., Canada

 

Paradis, S. and Simandl, G.J. (2011): Carbonate-hosted, Nonsulphide Zn-Pb (supergene) Mineral Deposit Profile B09; in Geological Fieldwork 2010, BC Ministry of Energy, Mines and Petroleum Resources, Paper 2011-1, pages 189-193.

 

IDENTIFICATION

 

SYNONYMS:  Zinc-oxides, Calamines, Galman

 

COMMODITIES (BYPRODUCTS): zinc, lead (silver, copper, barite, cadmium).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International): Redbird (082FSW024), Lomond (082FSW018), Reeves MacDonald (082FSW219), Caviar (082FSW060), HB (082FSW004), Oxide (082FSW022),

Cariboo Zinc (which comprises Canopener, DeBasher (093A 050), Flipper Creek, Dolomite Flats, Main (093A 065), Gunn and Que (093A 062); Leadville (Colorado, USA), Balmat (New York, USA), Sierra Mojada, Mapimi (Mexico), Accha, Mina Grande (Peru), Ariense (Brazil), Tynagh, Silvermines and Galmoy (Ireland), La Calamine (Belgium), Reocin (Spain), Silesia-Cracow district (Poland), San Giovanni (Italy), Lavrion (Greece), Touissit (Morocco), Um Gheig (Egypt), Zamanti district (Turkey), Jabali (Yemen), Angouran, Mehdiabad, Irankuh, Kuh-e-Surmeh (Iran), Shaimerden (Kazakhstan), Skorpion (Namibia), Padaeng (Thailand), Long Keng (Myanmar), Cho Dien (Vietnam), Jinding, Qiandong Shen Shen (China), Magellan (Australia).

 

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  Nonsulphide deposits are commonly hosted in carbonate rocks.  The main minerals are hemimorphite, smithsonite, hydrozincite, cerussite, Fe-oxyhydroxides (including goethite), and hematite.  The deposits are broadly divided into three subtypes:  the more common - 1) direct replacement and 2) wallrock replacement; and the less common - 3) residual and karst-fill.  Direct replacement deposits have similar shape as the sulphide protore from which they are derived and may contain vestiges of sulphide mineralization.  Wallrock replacement deposits are located at various distances from the protore, have simpler mineralogy and higher Zn/Pb ratio than direct replacement deposits, and occur as irregular masses encrustations, tabular bodies, and open-space fillings.  Residual and karst-fill deposits form generally small, high grade, irregular bodies of partly consolidated material that may have detrital component.  Some nonsulphide deposits may share characteristics of more than one of these subtypes. 

 

TECTONIC SETTINGS: Supergene nonsulphide deposits derived from Mississippi Valley-type (MVT) and Irish-type deposits are located in carbonate platform settings, typically in relatively undeformed orogenic foreland rocks, commonly in foreland thrust belts inboard of clastic rock-dominated passive margin sequences, and in continental rift systems.  Those derived from sedimentary exhalative (SEDEX) deposits are located in intracratonic or continental margin environments in fault-controlled basins and troughs.  Volcanic-hosted massive sulphide (VHMS)-derived supergene nonsulphide deposits are emplaced under extensional crustal regime, such as oceanic or back-arc spreading ridges, continental rifts, back-arc basins, oceanic ridges close to continental margins, and rift environment within, or perhaps behind, an oceanic or continental margin arc. 

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Hostrocks of supergene nonsulphide Zn-Pb deposits are mostly deposited in platform successions within shallow and deep water environments.  The nonsulphide deposits are found in both arid and tropical environments; however, many of the best supergene nonsulphide deposits recognized to date formed in semi-arid environments.  Some are found in cold, wet climates at higher latitudes. 

 

AGE OF MINERALIZATION: Ages of nonsulphide mineralization are commonly poorly constrained.  Ore formation coincides with or postdates the exhumation of the hostrocks and generally postdates the main tectono-metamorphic event.  Most of the nonsulphide deposits formed during the late Cretaceous to late Tertiary (i.e. Paleocene to Pliocene) and younger times.    

 

HOST/ASSOCIATED ROCK TYPES: Dolostone, limestone, dolomitized limestone and argillaceous carbonate are the most common hostrocks.  Siliciclastic rocks, such as calcsilicate rocks, carbonaceous black shale, siltstone, cherty argillite, quartz-rich conglomerate and arkosic meta-arenites, and volcaniclastic and metasedimentary rocks are also potential hosts.  

 

DEPOSIT FORM: The direct replacement deposits (also referred to as "red ores") occur as a) irregular and poorly defined masses that replaced primary sulphides and carbonate hostrocks, whereby selective replacement within specific horizons may yield stratabound morphologies; and b) veins and open-space fillings within primary breccias of sulphide mineralization and carbonate hostrocks, where the morphologies of the nonsulphide zones are comparable to those of the related primary sulphides (i.e. stratabound zones and/or crosscutting pipes, fracture-fill zones, veins).  The depth of oxidation can be variable from a few metres to several hundred metres.  The wallrock replacement deposits are Zn-rich irregular and lens-shaped or tabular (subvertical to subhorizontal) bodies adjacent to or distal to direct replacement bodies.  The residual and karst-fill deposits occur as accumulations of ferruginous, "earthy" and hemimorphite-clay mixtures, within karst cavities that cut through the replacement or open-space filling mineralization.  These deposits have, irregular geometry, and can form high-grade nonsulphide bodies.  Geometry is controlled by basement topography. 

 

TEXTURE/STRUCTURE: Nonsulphides form irregular stratabound masses, pods or lenses; breccias of sedimentary and tectonic origin, disseminations, fracture fill, and veins are also very common.  Due to intense oxidation, the primary textures of sulphides and hostrock are often obscured.  Ore textures are varied and complex, ranging from massive to highly brecciated, from compact to powdery and from vuggy to dense.  Nonsulphide minerals occur as earthy to crystalline aggregates replacing primary sulphides and/or carbonate hostrocks.  The form crusts, concretions, and stalactites on outer surfaces, and botryoidal, colloform and crystalline aggregates of euhedral and subhedral crystals in intergranular voids, cavities, fractures, and breccias. 

  

ORE MINERALOGY [Principal and subordinate]: Smithsonite, hemimorphite, hydrozincite, sauconite, cerussite, anglesite, litharge, pyromorphite, mimetite, and plumbojarosite; minrecordite, zincian aragonite, willemite, goslarite, loseyite, descloizite, hetaerokite, hydrohetaerolite, chalcophanite, hopeite, aurichalcite, woodruffite, tarbuttite, scholzite

 

Where the sulphide-bearing protolith was not entirely converted to nonsulphides, primary sulphides remain intermixed with the nonsulphide minerals to form "mixed ores".  The primary sulphides may contain anglesite-coated nodules of galena and remnants of sphalerite.  Chalcocite, malachite and azurite are present in some deposits.  

 

GANGUE MINERALOGY [Principal and subordinate]: Carbonates (dolomite, calcite, aragonite), hematite, goethite, other Fe-oxyhydroxides, gypsum, minor quartz.  
 

ALTERATION MINERALOGY: Coarse crystalline dolomite spatially associated with MVT-type protore may survive in proximity to nonsulphide deposits and contrast with regional finely crystalline dolostone.  Local alteration may also include silicification and rare secondary barite, both a result of the alteration and breakdown of feldspar (e.g. Skorpion).  The sulphide weathering and near surface alteration of protore corresponds to formation of supergene mineralization.  

 

WEATHERING: The nonsulphide mineralization forms by weathering of sulphides.  Multicyclic oxidation and leaching of nonsulphides is part of the ore-forming process and may affect even previously formed wallrock replacement bodies.  Such bodies may be gradually converted into porous brown to reddish smithsonite intergrown with hemimorphite.  Further leaching may result in mixture of hemimorphite, sauconite, hematite- or goethite-dominated iron oxides, and hematitic chalcedonic silica, and ultimately transformed into a barren goethite-chalcedonic silica rock. 

 

ORE CONTROLS: Most favourable conditions for oxidation are achieved in hot, arid or semiarid climates, which maximize the quantity of metals available for transport by supergene solutions.  Sedimentary successions containing carbonate rocks are the most common regional hosts for nonsulphide lead and zinc deposits.  In general, the oxidation of the protore takes place above water table.  Karst, faulting, fracturing and to lesser extent porosity are important in enhancing the depth and intensity of the oxidation.  Major faults represent channels for oxygenated solutions and permit oxidation to depths exceeding 500 metres.  Faults also increase the reactive surface of the hostrocks (i.e. provoking changes in pH and Eh).  Direct replacement deposits are confined to protore envelope.  Wallrock replacement orebodies are commonly located near the level of the paleo and/or present water table. 

 

GENETIC MODEL: Supergene nonsulphide Zn-Pb deposits form when base metal sulphide mineralization is subject to intense weathering and metals are liberated by the oxidation of sulphide minerals.  The formation of nonsulphide minerals is influenced by the composition, size and morphology of the pre-existing sulphide body.  During the formation of a direct replacement deposit, primary ore (protore) is oxidized, and base metals pass into solution and are redistributed and trapped within space originally occupied by the protore.  If the base metals liberated by the oxidation of sulphides are not trapped locally, they are transported by percolating waters down and/or away from the sulphide protore, and under favourable geological conditions may form wallrock replacement deposits.  Wallrock replacement deposits can be located in proximity to protore or several hundreds of metres away.  Lead is less mobile in the supergene environment than zinc, so in general, it is left behind as relict galena nodules and lead carbonate or lead sulphates.  Wallrock replacement deposits tend to have higher Zn content and higher Zn/Pb ratios than direct replacement deposits.  Residual and karst-fill deposits are formed as accumulations of mechanically and/or chemically transported zinc-rich material in karstic cavities or lows in basement topography.  Some nonsulphide zinc deposits are assigned a hypogene origin.  These deposits are characterized by willemite-franklinite-zincite assemblages (Hitzman et al..2003) and formed at higher temperatures than the supergene deposits.  Their temperature of formation is estimated from less than 100 degrees to nearly 300 degrees celsius.

 

ASSOCIATED DEPOSIT TYPES: Mississippi Valley-type Pb-Zn (E12), Irish-type carbonate-hosted Zn-Pb (E13), sedimentary exhalative Pb-Zn-Ag (E14), veins, and Pb-Zn skarns (K02); rarely volcanic hosted massive sulphide (G04 to G06). 

  

COMMENTS: British Columbia has prospective strata for supergene nonsulphide deposits in the miogeoclinal carbonate platform rocks of the Ancestral North America continental margin and in pericratonic rocks of the Kootenay terrane.  The association of many known carbonate-hosted nonsulphide zones with directly underlying massive sulphide ore bodies, in combination with nonsulphide mineralogical characteristics, suggests that a large proportion of known nonsulphide mineralized zones in southern and central British Columbia are of the direct replacement type.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: Colorimetric field test for secondary zinc minerals ("Zinc Zap") is very useful.  Portable hand-held x-ray fluorescence spectrometry was successfully tested in British Columbia on supergene nonsulphide Pb-Zn deposits.  Depletion in zinc, lead, copper, iron and manganese in and around former zinc-bearing sulphide gossans.  Readily detectable positive anomalies of zinc and lead in residual soils and stream sediments; elevated concentrations of copper, iron, silver, manganese, arsenic and cadmium can also be detected.  Analysis of heavy mineral concentrates (identification of Zn-Pb nonsulphides) in stream and overburden may be effective in areas lacking deep weathering.  Where residual sulphide oxidation is taking place, soil gas geochemical techniques (SO2 surveys) may be an applicable exploration technique.  Many supergene minerals, such as hydrozincite and smithsonite, give distinct spectral responses in the short-wave infrared portion of the spectrum.  Hyperspectral imaging holds promise as a useful tool for accurate mapping of structures, lithologies, and alteration .

GEOPHYSICAL SIGNATURE: There is no simple approach to use geophysical methods in exploration for nonsulphide-bearing Pb-Zn deposits.  The mineralogy, textures, homogeneity, friability, porosity, and degree of saturation by water vary widely.  These properties affect the density, resistivity, magnetic susceptibility, and seismic properties of the rocks.  Interpretation methodologies may be district specific.  Where sulphide mineralization is present at depth, methodology used in exploration for MVT, VHMS, and SEDEX deposits applies.

 

OTHER EXPLORATION GUIDES: Most of the supergene nonsulphide base metal deposits are derived from the oxidation, or near-surface weathering, of primary carbonate-hosted sulphide deposits, such as Mississippi Valley-type, sedimentary exhalative, Irish-type or vein-type deposits and, to lesser extent, Pb-Zn skarns and rarely volcanic-hosted massive sulphide.  Any carbonate-hosted, sulphide zinc district that has undergone geochemically mature weathering in semiarid to wet climatic (or paleoclimatic) conditions and concomitant tectonic uplift and/or water table depression is prospective for supergene nonsulphide deposits.  Within these settings, exploration could be further focused on areas where favourable water table level, optimum oxido-reduction conditions, permissive hydrological characteristics (permeability and porosity of the hostrocks, karsts, and fracture and fault zones), rocks with ability to control the pH of the metal-bearing solutions, topography and slow(?) rate of uplift, coexisted.  Discovery of outcropping supergene Zn-Pb nonsulphide deposits depends on recognition of common nonsulphide ore minerals.  Areas not affected by glaciation have higher potential to contain preserved, soft, nonsulphide deposits than glaciated ones.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Tonnages for nonsulphide Zn-Pb deposits range from <1 Mt to 50 Mt with grades of 2% to more than 30% zinc.  If mixed ores are considered, some deposits and districts have tonnages comparable to world-class sulphide deposits.  Skorpion (Namibia) has 60 Mt of mixed resource grading 6-8% zinc and 1-2% lead, and 24.6 Mt of oxide resource grading 10.6% zinc.  Mehdiabad (Iran) has a mixed oxide-sulphide resource of 218 Mt grading 7.2% zinc, 2.3% lead and 51 grams per tonne silver.  Direct replacement nonsulphide Zn-Pb deposits could be also significant sources of lead, as illustrated by the exploitation of the Magellan deposit, which has ore reserves of 8.5 Mt grading 7.12% lead.

 

ECONOMIC LIMITATIONS: The economic value of nonsulphide ores is dependent on the physical setting of individual deposit, the specific characteristics of the mineralogical association and the nature of the gangue minerals.  The large, near-surface deposits are amenable to high volume, open pit mining.  Underground mining is less common.  Depending on the type of ore and mineralogy, a dedicated processing plant may be required.  However, there is also the possibility that limited quantities of zinc-rich carbonates or silicate-bearing material (with low levels of impurities) may be used by conventional smelters as a sweetener (instead of Ca carbonate that is commonly used to control the pH) or as source of silica; this should be investigated.

 

IMPORTANCE: Nonsulphide deposits were the main source of zinc prior to the 1930s.  Following the development of differential flotation and breakthrough in smelting technology, the mining industry turned its attention almost entirely to sulphide ores.  Today, most zinc is derived from sulphide ore.  The nonsulphide deposits provided roughly 7% of the world's zinc production in 2009.  The successful operation of a dedicated processing plant at the Skorpion mine to extract zinc, through direct acid leaching, solid-liquid separation, solvent extraction and electro winning from nonsulphide ore has attracted more attention to these types of deposits.  These deposits are attractive targets because they are characteristically low in lead, sulphur and other deleterious elements, offer low-cost onsite production and are environmentally friendly.

 

REFERENCES

 

Gorzynski, G. (2001): REMAC zinc project, Reeves property and Redbird property - 2000 summary report, trenching and drilling program; Redhawk Resources Inc., 47 pages.

Heyl, A.V. and Bozion, C.N. (1962): Oxidized zinc deposits of the United States, Part 1, General geology; United States Geological Survey, Bulletin 1135-A, 52 pages.

Hitzman, M.W., Reynolds, N.A., Sangster, D.F., Cameron, R.A. and Carman, C.E. (2003):  Classification, genesis, and exploration guides for nonsulphide zinc deposits; Economic Geology, Volume 98, Number 4, pages 685-714.

Paradis, S., Simandl, G.J., Bradford, J., Leslie, C., Brett, C., and Schiarizza, P. (2010):  Carbonate-hosted sulphide and nonsulphide Pb-Zn Mineralization in the Barkerville area, British Columbia, Canada; in Geological Fieldwork 2009, British Columbia Ministry of Energy, Mines and Petroleum Resources, Paper 2010-1, pages 69-82.

Enkin, R. Paradis, S. and Simandl, G.J. (in press):  Physical properties of carbonate-hosted nonsulphide Zn-Pb mineralization in southern (NTS082F/03) and central British Columbia (NTS 093A/14E); in Geoscience BC Summary of Activities, Geoscience BC Report 2011-1.

Pirajno, F., Burlow R., and Huston, D. (2010): The Magellan Pb deposit, Western Australia; a new category within the class of supergene non-sulphide mineral systems; Ore Geology Reviews, Volume 37, pages 101-113.

Reichert, J. (2009):  A geochemical model of supergene carbonate-hosted nonsulphide zinc deposits; in Titley, S.R., ed., Supergene, Environments, Processes, and Products, Society of Economic Geologists, Special Publication number 14, pages 69-76.

Reichert, J., and Borg, G. (2008):  Numerical simulation and geochemical model of supergene carbonate-hosted non-sulphide zinc deposits; Ore Geology Reviews, Volume 33, pages 134-151. 

Sangster, D.F. (2003):  A special issue devoted to nonsulphide zinc deposits: a new look; Economic Geology, Volume 98, Number 4, pages 683-684.

Simandl, G.J. and Paradis, S. (2009): Carbonate-hosted, nonsulphide, zinc-lead deposits in the Southern Kootenay Arc, British Columbia (NTS 082F/03); in Geological Fieldwork 2008, British Columbia Ministry of Energy, Mines and Petroleum Resources, Paper 2009-1, pages 205-218.

Paradis, S. and Simandl, G.J. (2011): Carbonate-hosted, Nonsulphide Zn-Pb (supergene) Mineral Deposit Profile B09; in Geological Fieldwork 2010, BC Ministry of Energy, Mines and Petroleum Resources, Paper 2011-1, pages 189-193.


 

Sand and Gravel

B12
by Z.D. Hora
Retired, British Columbia Geological Survey, Victoria, B.C., Canada

 

IDENTIFICATION

 

SYNONYMS: Aggregate, granular deposits, fluvial and glaciofluvial sediments, ice-contact deposits, outwash, alluvial sand and gravel, beach sand and gravel.

 

COMMODITIES (BYPRODUCTS): All-purpose construction aggregate, special fill, railroad ballast (sometimes gold, platinum group elements, garnet, ilmenite, cassiterite, gemstones – diamond, emerald, ruby and sapphire, spinel).

 

EXAMPLES (British Columbia (MINFILE #) - Canada/International): Colwood Delta, Coquitlam Valley, Sechelt, Stuart River esker complex, small deposits almost everywhere.

 

GEOLOGICAL CHARACTERISTICS

 

CAPSULE DESCRIPTION:  Surficial sediment of sand and gravel deposited as a stream channel fill, fan or delta, usually in late-glacial or post-glacial period. Deposition may have occurred in contact with glacier ice (e.g., esker, kame complexes, crevasse fillings), or beyond the ice margin (e.g., outwash plain, raised delta).

 

TECTONIC SETTINGS: Generally unimportant. Sand and gravel deposits occur in high-energy stream sediments in all tectonic belts. In coastal areas, isostatic or tectonic uplift produces raised landforms that are readily mined.

 

DEPOSITIONAL ENVIRONMENT/GEOLOGICAL SETTING: Advancing glaciers incorporate significant quantities of bedrock and surficial materials that are freed during glacial melting and transported by meltwater downstream. Sand and gravel deposits can be divided into glaciofluvial sediments: mainly eskers, crevasse fill and kame complexes and outwash, and fluvial/alluvial sediments that form stream channel deposits, terraces, alluvial fans and deltas. In the early stages of deglaciation, meltwater streams deposited deltaic accumulations where high-energy water flow suddenly entered low-energy lacustrine or marine environments. Those deposits were lifted up during isostatic rebound and can be found along the BC coastline up to 200 metres above present sea level. In the BC interior, raised deltaic gravels and sands are granular facies of glaciolacustrine silts in basins (e.g. the Okanagan Valley, Rocky Mountain Trench, or Kamloops and Prince George areas). Alluvial fills in present drainage channels are usually reworked products of earlier glaciofluvial sediments.

 

AGE OF MINERALIZATION: Mainly Holocene and Pleistocene in glaciated areas, Holocene to Tertiary in unglaciated regions. Pre-Holocene sand and gravel deposits in glaciated terrain in Canada are not usually preserved. In BC, older sand and gravel sediments occur locally (e.g., in the lower part of the sequence in the Coquitlam Valley and in most gravel pits on Saanich Peninsula).

 

HOST/ASSOCIATED ROCK TYPES: Usually poorly to moderately well-sorted pebble, cobble and/or boulder gravel with variable proportions of fine- to coarse-grained sand; deltaic deposits locally interbedded with glaciomarine or glaciolacustrine silts and clays; ice–proximal glaciofluvial deposits commonly interbedded with till or glaciogenic debris flow deposits; fluvial sands and gravels often overlain by floodplain silts and organic deposits.

 

DEPOSIT FORM: Depending on their origin, sand and gravel deposits may exhibit a variety of shapes and geomorphic forms including: floodplains, terraces (raised valley-side benches), fans (cone-shaped) and deltas (triangular in plane view) and glaciofluvial kames (irregular hills or hummocks), eskers (ridges up to tens of kilometres long), outwash plains and raised deltas.

 

TEXTURE/STRUCTURE: Particle size decreases as stream energy decreases and with distance of transport. Particle roundness also decreases with transport distance. In high-energy environments, the deposits are generally more poorly sorted. Internal structure varies with the type of deposit as follows:

 

Channel and terrace deposits: mainly trough cross-bedded sand and/or gravel sequences; cut-and-fill structures common; capped by floodplain silts, fine sands and organics.

 

Alluvial delta: usually sand-dominated, grading out into silts and clays; interbedded organic silts and peats common in the topset.

 

Alluvial fan: poorly sorted sands and gravels, often with diamicton interbeds; crude bedding dips toward the valley centre, generally fining down-dip and from the fan centre to the sides.

 

Glaciofluvial delta: coarse-grained, steeply dipping, foreset beds; underlain by fine-grained bottomset beds; often capped by fining-up channel-fill (topset) sequences.

 

Kames and eskers: poorly sorted sands to boulder gravels; commonly with collapse features and kettle holes.

 

ORE MINERALOGY [Principal and subordinate]: Composition of aggregate particles depends on the source areas. Provenance is also a major factor in determining the quality of the resulting aggregate product. Bedded and schistose rocks usually provide lower quality products, while massive igneous rocks and metamorphic rocks, such as gneisses and quartzites, produce better quality aggregate. In sedimentary source areas, limestones and cemented sandstones are better than shales, siltstones or weak sandstones.

 

GANGUE MINERALOGY [Principal]: Clay and silt particles and organic pockets must be separated by screening and washing the final product. Also, cobbles and boulders have to be removed or separated and processed by crushing.

 

ALTERATION MINERALOGY: Soft and weak rocks are a deleterious component of every type of construction aggregate. Prolonged weathering may weaken some otherwise competent rock types. This is particularly true for older Pleistocene and Tertiary deposits in glaciated areas, and for all deposits in non-glaciated areas. Percolating groundwater may result in coating of gravel particles with calcium carbonate, clay or iron hydroxides. Such coatings may negatively affect the strength and durability of bonding with cement in concrete structures.

 

WEATHERING: Soft and weak rocks and those with high porosity are sensitive to increased physical weathering and deterioration.

 

ORE CONTROLS: The composition of the bedrock in the source area has a major impact on aggregate quality. A variety of factors influence the usability of granular sediment for individual products, which frequently have distinct quality requirements. Quality of construction aggregate for particular end uses is controlled by a number of physical and chemical parameters specified in ASTM and CSA Standards. The main factors influencing suitability for different end uses are the relative proportions of competent rock types, components reactive with cement like chert, other amorphous silica varieties, volcanic glass, sulphides and organics like peat. Other important criteria include the absence of clay and silt; clean clast surfaces; isometric shapes and granulometric composition. Sometimes in the absence of a quality aggregate, some granular deposits can be improved by more sophisticated processing. Use of a different type or higher proportion of cement in a concrete mix may be another solution.

 

GENETIC MODEL: Sand and gravel deposits are deposited by high-energy streams draining continental areas, mainly during deglaciation. The main source of the granular material is melting glacier ice containing large quantities of eroded bedrock and sediment. This outwash material is transported by flowing water and deposited in a variety of landforms with granular material as a main component.

 

ASSOCIATED DEPOSIT TYPES: Placer deposits of gold, PGE, gemstones and garnet (C01, C02, C03).

 

COMMENTS: Quarried crushed aggregate is an alternative to sand and gravel. Dredging of off-shore sand and gravel or deposits in river channels is taking place locally in B.C.

 

EXPLORATION GUIDES

 

GEOCHEMICAL SIGNATURE: None.

GEOPHYSICAL SIGNATURE: Ground penetrating radar can delineate the geometry, structure and thickness of granular deposits provided they are not overlain by clay or clay-rich till. Shallow seismic and resistivity surveys can help outline the thickness and homogeneity of a granular deposit, particularly the presence of clay layers or till, and depth of the groundwater level.

 

OTHER EXPLORATION GUIDES: Remote sensing and air photo interpretation are used to identify the granular landforms.

 

ECONOMIC FACTORS

 

TYPICAL GRADE AND TONNAGE: Grade is determined by ASTM or CSA specifications and can be highly variable, depending on location and intended use. Tonnage also can vary widely. For example, even a small deposit of a few hundred thousand tonnes may be an important source for local use in populated areas. Such a deposit, however, must contain aggregate that does not require complicated processing. Similar examples are borrow pits used in road construction and maintenance. Large, sophisticated operations, like BC tidewater pits (e.g., Colwood, Port Mellone, Sechelt, Jervis Inlet) that produce a variety of special products and supply more distant markets, can have tens of millions of tonnes of resource.

 

ECONOMIC LIMITATIONS: In populated areas, the main limiting factors for developing aggregate resource are availability of land and support of the local community. Transportation costs are often the main economic factor controlling deposit development and may favour the development of hard rock crushing operation closer to the market.

 

END USES: A broad variety of construction products including ‘pit run’ for general uses and fill, natural stone for buildings and roads, crushed rock for landscaping, road bases, asphalt, gravel driveways and parking lots, concrete aggregate, drainage gravel, and specialty sands, such as those used for sandblasting and masonry sand for mortar and stucco.

 

IMPORTANCE: Sand and gravel are the main, basic construction materials for building cities and infrastructure. British Columbia uses between 40 and 50 million tonnes of aggregate annually in construction. Building an average family home requires about 100 tonnes of aggregate; for a school it takes approximately 15 000 tonnes; for 1 kilometre of 4-lane highway, between 40 and 60 thousand tonnes of aggregate are needed.

 

REFERENCES

 

Bobrowsky, P.T., Massey, N.W.D. and Matysek, P.F. (1996): Aggregate Forum. Developing an Inventory That Works for You. BC Ministry of Energy, Mines and Petroleum Resources, Information Circular 1996-6, 61 pages.

Bobrowsky, P.T., editor (1998): Aggregate Resources: A global perspective. A.A. Balkema, Rotterdam, 637 pages.

Barksdale, R.D., editor (1991): The Aggregate Handbook. National Stone Association, Washington, D.C., 640 pages.

Bolen, W.P. (2000): Construction Sand and Gravel; in Mineral Industry Surveys, U.S. Geological Survey, pages 66.1–66.19.

Hora, Z.D. (1988): Sand and Gravel Study 1985. Transportation Corridors and Populated Areas. B.C. Ministry of Energy, Mines and Petroleum Resources, Open File 1988-27, 41 pages.

Hora, Z.D. and Basham, F.C. (1980): Sand and Gravel Study 1980. B.C. Lower Mainland. BC Ministry of Energy, Mines and Petroleum Resources, Paper 1980-10, 74 pages.

Langer, W.H. (1988): Natural Aggregates of the Conterminous United States, US Geological Survey Bulletin 1594, US Geological Survey, Washington, D.C., 33 pages

McCarl, H.N. (1994): Aggregates: Markets and Uses; in Industrial Minerals and Rocks, D.D. Carr, senior editor , Society for Mining, Metallurgy, and Exploration, Inc. Littleton, Colorado, pages 287–293.

Vagt, O.(2002): Mineral Aggregates; in Canadian Minerals Yearbook, Minerals and Metals Sector, Natural Resources Canada, pages 34.1–34.8

 

 

*  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 Residual/Surficial Deposits

 
BC Profile # Global Examples B.C. Examples
B01* Glenravel (Ireland) - -
B02* Riddle (Oregon), Mt. Vernon (Washington) - -
B03* Mt. Gibson (Australia), Akaiwang (Guyana) - -
B04* Queensland, Pocos de Caldas (Brazil), Salem Hills (Oregon) Florence (Sooke)
B05 Germany, North Carolina, Idaho Lang Bay, Sumas Mountain
B07* Trois Riviéres (Québec) Whipsaw Creek, Limonite Creek, Iron King
B08 Flodelle Creek (Washington) Prairie Flats
B09 Transvaal (Pb-Zn, South Africa), Sardinia (Pb-Zn), Jamaica (Al) Villalta (Fe)
B10 Rio Tinto (Spain) Villalta
B11* - - Cheam Lake (Chiliwack)
B12 - - - -