Copper mineral deposit types: A review

 Economic Geology

Mineral deposit types

Major types of copper mineral deposits are:

Porphyry copper deposits are high volume, low grade, but are important sources of copper. They typically contain between 0.4 and 1 percent copper in concert with smaller amounts of other metals, such as molybdenum, silver and gold. Porphyry copper mineral deposits are usually massive, with extraction taking place by open-pit mining.

Copper-bearing sedimentary rocks,  sandstone and shales hosted, are the second most important type of copper deposit, accounting for approximately one-quarter of the world’s identified copper deposits.

Magmatic sulphide deposits containing copper in association with nickel and platinum group elements (PGE) hosted by mafic and ultramafic rocks.

Sedimentary exhalative deposits (SEDEX) with copper found associated with lead, zinc and silver.

Epithermal deposits dominated by gold which may contain significant quantities of copper and silver

Volcanogenic massive sulfide (VMS) ore deposits, a source of copper sulfide formed through hydrothermal events in submarine environments.

Iron oxide-copper-gold (IOCG) ore deposits are highly valuable concentrations of copper, gold and uranium ores.

Copper skarn deposits, which in a broad sense are formed through chemical and physical mineral alterations created when two separate lithologies make contact.

Polymetallic veins, related to mainly porphyry copper, VMS and IOCG systems.

Residual deposits related to supergene gossan-type mineralisation processes.

·       Mineral exploration potential belts in Europe

Porphyry copper type deposits, Cu, Mo, Au, (Re),  are typically related to the evolution of the western Tethyan suture in the late Cretaceous and Cenozoic, especially in Eastern Europe where there is high potential for additional deposits. In Eastern Europe, the Upper Cretaceous in  the Tethyan margin, contains large porphyry-type districts, of which most were subsequently reactivated and are associated with epithermal-type ores. The most important are Kremnica in Slovakia, Telkibanya in Hungary, the Apuseni Mountains in Romania, Bor in Serbia, Assarel in Bulgaria and Bucim in North Macedonia. Other domains also host porphyry-type mineralization, of older age, although their classification as belonging to this deposit type is still debated. In the Fennoscandian Shield, several Cu-(Au)- or Cu–Mo-bearing Palaeoproterozoic deposits are described as porphyry style. The most important are Aitik (Cu–Au) and Tallberg (Cu–Au, Skellefte district), both in Sweden, and Kopsa (Au–Cu) related to a tonalite stock in the Hitura belt (in Finland). In relation to the Caledonian volcanism, there are a few smaller porphyry-type deposits of Lower Palaeozoic age in Great Britain, such as Coedy Brenin (Wales) and Black Stockarton Moor (Scotland). Hercynian magmatism in the Upper Palaeozoic is associated, especially in France, with Cu–Mo–W porphyry deposits, although their geodynamic context is poorly described (e.g. Beauvain, Mo; Sibert, Cu; Auxelles-le-Haut, W). There is also porphyry Mo mineral of various ages in Europe. The most important of these is probably Nortli in Norway, a group of deposits related to Permian intrusions in the Oslo rift.

 

This IOCG type, Fe, Cu, Au, (P, REE, U, Co), of mineralization can be found essentially in two Paleoproterozoic districts in the Fennoscandian Shield. The most important is Kiruna (northern Sweden), which is a type locality for IOCG, and the other one is Bergslagen (central Sweden). These districts contain large world-class iron deposits, with a typical magnetite-apatite paragenesis and sodium alteration. These districts also contain copper sulphide deposits that are interpreted as VMS (Viscaria) or porphyry (Aitik). More limited IOCG style deposits are also known in other parts of Europe. Some Fe (Fe–Cu) IOCG style deposits are identified in the Ossa Morena Zone in southwestern Iberia. They are mesozonal albitite-related magnetite deposits and are interpreted as being related to either residual melts of rift-related juvenile magmas (Cambrian) or anatexis of earlier mineralization during high T/low P metamorphism along major shear zones of Variscan age.

 The distribution of deposits of this type clearly highlights the major known VMS type provinces, Cu, Zn, Pb, (Ag, Au, Te, Sn, In): The Palaeoproterozoic districts of Skellefte and Bergslagen, in Sweden, and Vihanti- Pyhäsalmi and Outokumpu, in Finland; The Upper Palaeozoic (Devonian, Carboniferous) district of the southern Iberian province (e.g. Rio Tinto in Spain, Neves Corvo in Portugal) in Spain and Portugal; The Upper Cretaceous VMS district in Cyprus (Skouriotissa, Mavrovouni, Limni), related to the Troodos ophiolite complex. In addition to these three major mineralized provinces, there are several other smaller deposits. In Scandinavia, copper-rich stratiform sulphides formed in the Palaeozoic along the Caledonian domain. They could be VMS deposits of various types (e.g. Röros VMS in back arc setting, Tverrfjellet and Joma VMS of Besshi type, Sulitjelma VMS of Cyprus type). These mineral deposits seem to extend southward into the Dalradian Caledonian domain of Scotland (e.g. Ben Collum, Auchtertyre). Other VMS mineralization, of Devono-Carboniferous age, can be found in the European Hercynian domain. In France(Châteaulin basin, Saint-Georges-sur-Loire and Chessy), several volcanic related deposits have ages similar to those in the southern Iberian Province (Upper Devonian and Tournaisian). Their tonnages, however, are much smaller. In other parts of the Hercynian domain, massive sulphide deposits are preferentially of SEDEX type (e.g. Rammelsberg and Meggen in Germany, Rhinish-Hercynian domain. In the Navandistrict (Ireland), they are hosted in a Carboniferous foreland sedimentary basin. In addition, there are also numerous mineral deposits or groups of mineral deposits (with various commodities) where the classification is still debated. This is the case, in particular, for iron deposits in the Alps and the Balkan-Carpathian domain that were classified as SEDEX. They could in fact be replacement deposits (e.g. Ljubija and Omarska in Bosnia and Herzegovina, Erzberg in Austria). Mercury and copper deposits (e.g. Idrija in Slovenia, Munella in Albania), classified as SEDEX could also be epithermal.

 

Igneous carbonate replacement (Fe, W, Pb, Zn, Cu, Au) or skarn deposits occur where carbonate rocks are cut by younger intrusions. In Europe, they are distributed in three major domains: (i) the Precambrian Fennoscandian Shield, (ii) the Hercynian domain in southern Europe, and (iii) the Cenozoic Carpathian-Balkan domain. The Fennoscandian Shield contains iron deposits in greenstones of the Lappland Palaeoproterozoic domain (e.g. Puoltsa, Sautusvaara and Stora Sahavaara in Sweden, Kolari district in Finland). These deposits are related to ‘magnetite-enriched formations and Ca–Mg calc-silicates’, spatially associated with BIFs or Kiruna type IOCG. Recent studies in the Kolari area in Finland (i.e. Laurinoja and Kuervitikko Rautuvaara) show that metasomatized replacements are preferentially IOCG type facies rather than typical ‘intrusion-related skarn deposits. In the Bergslagen district in Central Sweden skarn mineralization is hosted by Paleoproterozoic marbles intruded by post-tectonic granites (1.8 Ga). Examples of such deposits include the Yxsjöberg  “scheelite-skarn deposit”, skarn iron lenses and skarn iron-sulphides lenses of Stollberg (Fe–Pb– Zn–Mn (Ag)), and sulphide skarn of Garpenberg (Zn). The Arendal (Klodeborg) iron deposit in Norway comprises magnetite skarn in Mesoproterozoic sequences (1.2–1.5 Ga) cut by younger intrusions (0.9–1 Ga), and the Knaben deposit (same age) is located in gneisses, paragneisses and amphibolites. In the southern part of the Hercynian domain, well-developed Palaeozoic (Cambrian and Devonian, essentially) carbonate layers and Hercynian (Upper Carboniferous, 310 Ma) magmatism allowed the development of tungsten- (and/or magnetite-) bearing skarns in the Pyrenees, the southern Massif Central, in Sardinia and in the Alps. The northern parts of the Hercynian arc display only minor occurrences, essentially because of the lack of Palaeozoic carbonate units. In the Balkan-Carpathian domain, numerous carbonates, essentially of Mesozoic age, and Upper Cretaceous-Cenozoic magmatic episodes allowed development of numerous replacement deposits in the vicinity of epithermal and porphyry domains. Important examples include Kremsica, Baia Mare, Bor, Madan, Trepča and Olympias in northern Greece. Minor deposits of this group can also be found in the western Mediterranean, related to Tertiary and Quaternary magmatic episodes in Spain, Sardinia (e.g. Calabona skarn associated with a dacitic porphyry copper) and close to Elba.

 Magmatic sulphide deposits, Ni, Cr, Cu, PGE, (Co, Bi, U, Ag), hosted mafic-ultramafic rocks, are located in the Fennoscandian Shield mainly in the Karelian area. They are related to the main rifting pulse and plume activity of the early Palaeoproterozoic. These deposits are located in Finland (i) in the Kemi district (Kemi, Cr; Sompujarvi, Pt; Siika-Kama, Pd and Suhanko, Pd); (ii) in Kevitsa (Ni) and Koitelainen (Cr), (iii) in the Uutela district (talc), (iv) in Hitura (Ni), Kotalahti (Ni) and Laukunkangas (Ni), and (v) farther south in Vammala (Ni) and Petolahti (Ni). Other deposits can be found in the Sveconorwegian domain (*1000–900 Ma). They are related to Ni–Cu sulphur-bearing deformed noritic intrusions in Rana, Flat and Ertelien (Norway). They were probably emplaced during an early rifting stage of the Sveconorwegian orogeny (equivalent to Grenvillian in Canada). Several deposits in Norway are related to the Scandinavian Caledonian domain. These include: (i) Altermark (talc) in Norway, (ii) the nickel istrict of Stekenjokk (Njeretjakke), with Cu–Ni sulphur (and PGE + Au enrichment in Stormyrplutten and Lillefjellklumpen) in Lower Ordovician basalts and gabbros, and (iii) the Rana deposit (Cu–Ni sulphur) related to a mafic-ultramafic intrusion. This type of deposit is uncommon in Palaeozoic rocks. One exception is the Cu–Ni Sulphur deposit of Aguablanca located in a mafic breccia pipe intrusion (of Lower Carboniferous age) fed by a mid-crust mafic-ultra mafic stock. It contains pyrrhotite, pentlandite and chalcopyrite formed from the crystallization of an immiscible sulphide-rich liquid. In the ‘ultramafic’ type, other deposits which should be included are: (i) the Amaden mercury deposit, which formed from the activity of a Silurian mantle plume although the host-rock is sedimentary to volcano-sedimentary and (ii) the ‘five elements’ vein deposits (Bi, Co, Ni, Ag, U), such as Jachymov in Czech Republic, which have a mafic to ultramafic signature. Finally, in the Balkan domain and in Greece, various deposits in the Mesozoic ophiolites are associated with ultramafic bodies (talc, magnesite, lateritic nickel, chromite lenses).

 Sedimentary,  sandstone and shales hosted deposits, Cu, U, Pb,(Ni, Co, Zn, V, PGE, Re) include the major copper mineralization in the Kupferschiefer Permian sediments. This type of mineralization mainly occurs in southern Poland (Lubin district), but also in Germany (Mansfeld, Richelsdorf, Spremberg). It also includes the Palaeoproterozoic metamorphosed black shales of Talvivaara in Finland (Ni, Co, Cu). These deposits were the subject of specific studies in the ProMine project aimed at testing ore bioleaching processes. This type also includes uranium deposits hosted in sandstones and schists of various ages. The main of potential are related to (i) uranium deposits of Tåsjö, Myrviken and Ranstad (alum shales) in relation with Cambro-Ordovician schists and sandstones (Sweden); (ii) Late Hercynian (Permian) deposits (e.g. Lodève half-graben in France, and Bulgaria), (iii) Cretaceous limestones (Cenomanian) in the Hamr-Liberec district (Czech Republic), and (iv) the Coutras Eocene sandstones (France). In addition to these typical Cu- or U-bearing mineralization, numerous Pb, Ba and/or F mineral deposits are hosted in sandstones in a transgressional context (e.g. Triassic), along the margin of Hercynian basement.

 Minor epithermal Gold  (Au, Ag, Sb, Hg, Te, Cu, In) and volcanic group potential can be found in the Fennoscandian Shield and western Europe Hercynian domain. On the other hand, the potential is much higher along the Tethyan suture, in south-eastern Europe, especially between Slovakia and Greece. The Carpathian-Balkan region, with its various epithermal and porphyry districts, is well known and form a semi-continuous belt which includes Kremnica in Slovakia, Telkibanya in Hungary, Baia Mare and Apuseni Mountains in Romania, Bor in Serbia, Assarel in Bulgaria and the eastern Rhodopes (Madan group in Bulgaria and Perama in Greece). Farther south, in the Balkan domain, epithermal type mineral deposits are more scattered. Of particular note is the Trepča district, in Kosovo, that combines carbonate-related and epithermal types.

 Underground extraction in polymetallic veins, Pb, Zn, Cu, U, (Ba, F), is the oldest mining industry in Europe. It extends in time from the Middle Ages to the twentieth century, with the geographic distribution of mined deposits controlled not only by mining criteria but also by culture and history. This mining activity mainly took place in the Hercynian domain, from the Bohemian Massif (Czech Republic) to France. Potential mapping of these deposits shows a heterogeneous distribution with an over-representation of France relative to its neighboring countries (compare for instance the Vosges and Black Forest Mountains on both sides of the Rhine graben). These polymetallic vein deposits are related to the Hercynian orogeny. The main vein-types are (i) Pb–Zn–Cu– Ag veins extracted since the Middle Ages essentially for silver (famous districts, such as the Erzgebirge, the Vosges Mountains, the Black Forest), (ii) antimony veins in the Brioude-Massiac district (France), (iii) peripheral tin and tungsten veins near felsic intrusions (e.g. Portugal, France and Cornwall), (iv) fluorite and barite low temperature veins along the border of the Hercynian domain (e.g. France). There are also uranium veins in two Hercynian domains (French Massif Central and Czech Bohemian Massif). The high frequency of such uranium deposits in some countries (e.g. France, L’Escarpière district; Czech Republic, Pibram district) partly results from intense prospection work carried out to support specific government policies at various times.

 Residual Deposits, Fe, Al, Ni, Cu, (Mn, Au, P, REE), show a significant geographic control and is found essentially in southern Europe. The main types of deposits are bauxites, lateritic nickel, residual concentration in carbonated ores (Mn, Fe a.o.), or gossan-type concentration from sulphides ore (Cu, Au a.o.). Bauxites develop in emerged domains, in relation to the alteration (essentially from Upper Cretaceous to Palaeogene) of an older carbonate basement (essentially Triassic to Lower Cretaceous). They result from the palaeogeographic and climatic evolution of the Tethyan margin during this period. The main bauxitic domains are to the west, the northern Pyrenean and Provence domains (Villevayac, les Baux) and to the east, the Balkan domain (e.g. Niksic in Montenegro, Mostar in Bosnia and Herzegovina, and the Giona-Parnassus district in Greece) and Hungary (Fenyöfö, Nyirád district). In ophiolitic series of the Balkan domain, some nickel lateritic mineral deposits formed as a result of the alteration of silica. Examples of such deposits are Citakovo-Glavica in Serbia, Rzanovo in North Macedonia, Evia (or Madu di Limni) and Aghios Ioannis (or Larimna) in Greece. Nickel residual deposits (e.g. Szklary en Poland) also formed from older Variscan ophiolitic mafic or ultramafic rocks. Some deposits have residual concentrations significantly enriched, relative to primary ores. Examples include: Mn (e.g. Urkút in Hungary), Fe (Ljubija in Bosnia), Zn (Iglesiente district in Sardinia), Cu and/or Au (e.g. Las Cruces, southern Iberian Province; Rudno and Banska,porphyry and epithermal provinces of Slovakia; Rouez in France, etc.

Predictivity mapping

The idea of the predictive method used in the ProMine project was to assess the favorability for by-products of other commodities from deposits in the ProMine mineral database. The objective was not to discover new deposits but to evaluate know deposits for a new targeted commodity. When searching for ‘high-tech’ and critical commodities, which most of the time are by-products,  by addressing a specific type of deposit (e.g. Cu–Mo porphyries for Re, or Pb–Zn deposits for Ge), this does not mean it contains, or not, the searched by-product. For several reasons (e.g. commodity not explored or not analysed), ore deposits mined in ancient times may have an unknown potential.

 Copper is a common commodity in the ProMine mineral database with 22 % of the deposits containing copper either as main or associated commodity. Five mineral deposit types are show potentially feasible copper grades, namely, Igneous intermediate/Porphyry Copper, VMS, mafic-ultramafic, sandstone- and shale-hosted and IOCG. Geological formations in Europe favorable to copper are quite numerous and include essentially sedimentary and volcanic rocks. Ages are also widespread, with (i) Paleoproterozoic VMS, mafic-ultramafic type and IOCG in Scandinavia, (ii) Lower Palaeozoic Caledonian VMS and veins, (iii) Upper Palaeozoic VMS in the southern Iberian province and French Brittany, and (iv) Permian sandstone-hosted deposits and Cenozoic igneous intermediate porphyry deposits in the Balkan-Carpathian region. The distribution of favorable areas clearly highlights the major known copper districts. In addition,  a considerable amount of detail is present in the results and show favorable areas where copper mineralization has not been identified, especially in the Balkan-Carpathian region.

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