Sediment-hosted Copper Deposits Research Articles

Metasomatism and depletion of the southern Gawler Craton from combined mantle xenocryst and AusLAMP magnetotelluric data

Metasomatised mantle is considered a prerequisite for the formation of many major ore deposits. Since magnetotellurics (MT) is strongly sensitive to mantle metasomatism, MT is a useful tool for analysis of mineral systems that incorporate a metasomatised mantle as a key ingredient. In this work, we combine recently reported kimberlite-hosted mantle xenocryst data from the southern Gawler Craton and Adelaide Superbasin with AusLAMP MT models. We find good correlations between mantle MT conductors and geochemical indicators of mantle metasomatism from clinopyroxene xenocrysts, with the most metasomatically enriched lithospheric mantle beneath the Adelaide Superbasin and more depleted mantle beneath the Gawler Craton. There is a significant step in lithospheric thickness across the Adelaide Superbasin, and particularly around the Terowie kimberlite cluster. Combined with the fertile mantle, this helps explain this region’s prospectivity for sediment-hosted copper deposits. High mantle resistivities and depleted geochemical compositions towards the central Gawler Craton on and north of the Eyre Peninsula are consistent with melting of previously metasomatised mantle, including during production of the Gawler Range Volcanics and Hiltaba Suite Large Igneous Province. Most of the major iron oxide copper gold (IOCG) and gold deposits in the region lie on the edge of this zone of mantle melting, consistent with mineral systems models that require melting of previously metasomatised mantle in the generation of these deposits.

Age of provenance for the Palaeoproterozoic Kemen Group, Udokan Complex: Newly recognised Palaeoproterozoic crust-forming event in the western Aldan Shield, Siberian Craton

In this study, new geological, geochronological, and Hf isotopic data are presented for the metaterrigenous deposits of the Kemen Group of the Udokan Complex in the Chara-Olekma terrane of the Aldan Shield, Siberian Craton. Their age of deposition and possible provenances are discussed, along with crust-forming events in the Aldan Shield. The Palaeoproterozoic carbonate-terrigenous deposits of the Udokan Complex in the Kodar-Udokan basin are the hypostratotype of the Lower Proterozoic deposits of the Eastern Siberia and the Far East, and host one of the largest and oldest sediment-hosted copper deposits. Concordia ages of detrital zircons demonstrate age peaks of ca. 2.02, 2.15, 2.38, 2.54, 2.73, 2.82, 2.93, 2.96, 3.00, 3.04 and 3.14 Ga on the probability plot. The morphology, internal texture, and Hf isotopic composition of the Meso- and Neoarchean detrital zircons indicate reworked Paleo- to Mesoarchean crustal sources in provenance areas. No rocks with the ages of ca. 2.02 Ga have been previously recognised in the Chara-Olekma terrane. Characteristics of the ca. 2.02 detrital zircons indicate their primary magmatic origin and proximal sedimentary transport. Hf isotopic data imply that the Palaeoproterozoic rocks in provenance area originated mainly from juvenile sources in a subduction-related setting. The Palaeoproterozoic island arc or an active continental margin probably existed within the western Aldan Shield or its framing and were later completely eroded or partially overlain by younger sediments. Erosion of the Palaeoproterozoic orogen led to deposition of the Chinei and Kemen groups of the Udokan Complex over a short time interval of ca. 1.90–1.88 Ga. Detrital zircons from the Kemen Group deposits reveal for previously unrecognised and lost from geological record Palaeoproterozoic crust-forming event on the western Aldan Shield. Available data show that significant part of the Siberian Craton was formed during ca. 2.07–1.98 Ga crust-forming events that indicate the discrete episodic nature of the continental crust formation and must be considered in models of its growth. The differences in isotope structure and geological history of the Siberia and the Laurentia are in agreement with palaeogeographic reconstructions suggesting that Siberia and Laurentia were not joined together in the Columbia/Nuna supercontinent.

Fluid Flow, Alteration, and Timing of Cu-Ag Mineralization at the White Pine Sediment-Hosted Copper Deposit, Michigan, USA

Abstract White Pine, located in Michigan’s Upper Peninsula, is an archetypal sediment-hosted stratiform copper deposit. The Midcontinent rift system is one of only seven basins globally that host a giant sediment-hosted stratiform copper deposit. Despite many similarities with other deposits of this type, White Pine displays some important differences, including the late Mesoproterozoic age, a thick basalt sequence, an apparent lack of evaporites, and a lacustrine depositional setting. This study analyzes paleofluid flow related to the formation of White Pine and places a particular emphasis on structural and diagenetic fluid pathways. Most of the ore is located in a 30-m-wide zone spanning the Copper Harbor Formation red beds and the overlying Nonesuch Formation shales. Sedimentation of these units was accompanied by subtle synsedimentary faulting. Premineralization phases include calcite concretions and nodules, illite and hematite grain coatings, isopachous chlorite rims, emplacement of liquid petroleum (now pyrobitumen), and bleaching. Mineralization introduced native copper into the footwall sandstones and a zoned suite of native copper and sulfur-poor copper sulfide minerals across a migrating redox front in the overlying shales where copper minerals nucleated on authigenic and detrital chlorite grains. Postmineralization phases include quartz cement, calcite cement, and calcite veins that partially overlapped inversion of synsedimentary faults. Contrary to previous studies, we identified evidence for only one phase of mineralization. An Re-Os chalcocite age of 1067 ± 11 Ma places mineralization 11 to 17 m.y. after host-rock deposition. Sulfide δ34S values of –14.0 to 29.9‰ suggest an important contribution from sour gas and thermochemical sulfate reduction of seawater. Carbon (δ13C) and oxygen (δ18O) isotope compositions of five calcite generations range from –15.1 to –1.3‰ and 10.4 to 41.3‰, respectively, and record early meteoric pore water displaced by later seawater. White Pine is both a sediment-hosted stratiform copper deposit and a paleo-oil field. Synsedimentary faults controlled the sedimentological character of the upper Copper Harbor Formation, and together these imparted a strong control on fluid flow and later diagenetic processes. Early oxidized meteoric fluids were displaced by liquid petroleum and sour gas, which were in turn succeeded by metal-rich but sulfate-poor oxidized seawater. Burial compaction during deposition of the overlying Freda Formation drove fluids through White Pine due to its situation on a paleotopographic high near the basin margin. Mineralization occurred at ~125°C at depths of ~2.0 km and spanned incipient basin inversion related to the distal effects of Grenvillian orogenesis. The hightenor copper mineral assemblage is the product of an abundant supply of metal from basaltic volcanic detritus in the Copper Harbor Formation and low seawater sulfate concentrations in late Mesoproterozoic oceans. This demonstrates that viable sediment-hosted stratiform copper systems can form when a readily leachable metal source rock is present, even if hypersaline and sulfate-rich brines are not.

Constraints on the Genesis of Cobalt Deposits: Part II. Applications to Natural Systems

AbstractIn a companion paper in this issue, the authors reviewed the properties of cobalt, its mineralogy, and the processes that concentrate it to exploitable levels. Using this information and knowledge of the geology of the principal types of cobalt deposits, the present paper assesses the conditions and controls of cobalt transport and deposition and develops/refines plausible models for the genesis of these deposits. Economic cobalt deposits owe their origins to the compatible nature of Co2+, which causes it to concentrate in the mantle, mainly in olivine, and to be released to magmas only after high degrees of partial melting (i.e., to komatiitic and basaltic magmas). Thus, there is a very close association between cobalt deposits and mafic and ultramafic rocks. Magmatic deposits, in which Co is subordinate to Ni, develop through sulfide-silicate liquid immiscibility as a result of the very strong preference of these metals for the sulfide liquid. Predictably, these deposits reach their highest grades where hosted by olivine-rich ultramafic rocks. Approximately 60% of the world’s cobalt resource is of hydrothermal origin and is contained in sediment-hosted copper deposits in the Democratic Republic of the Congo. Using a combination of thermodynamic data and geologic information, we have refined a model in which Co is leached from mafic and ultramafic rocks by oxidized, chloride-rich hydrothermal fluids, derived from evaporation, and deposited in response to decreasing fO2 in carbonaceous sediments that accumulated in intracratonic rift basins. Economic Co deposits also develop as hydrothermal vein systems, in which Co is the primary ore metal. In the only deposits of this type that are currently being exploited (Bou Azzer, Morocco), the source of the Co was an adjacent serpentinized peridotite. The ore fluid was an oxidized, high-salinity brine derived from evaporites, and deposition occurred in response to pH neutralization by the felsic to intermediate igneous host. The final major class of Co deposits is laterite-hosted and develops on olivine-rich ultramafic rocks or their serpentinized equivalents. Our thermodynamic modeling shows that Co is leached from an ultramafic source by mildly acidic fluids as Co2+ and is transported down the laterite profile, eventually concentrating by a combination of adsorption on Mn oxides, incorporation in the structure of absolane (an Mn oxide), and precipitation as heterogenite (HCoO2). The dissolution of cobalt at the surface and its deposition at depth are controlled mainly by pH, which decreases downward; oxygen fugacity, which also decreases downward, has the opposite effect, inhibiting dissolution of cobalt at the surface and promoting it at depth. It is our hope that this introduction to the economic geology of cobalt and the processes responsible for the formation of cobalt-bearing ores will help guide future studies of cobalt ore genesis and strategies for the exploration of this critical metal.

Constraints on the Genesis of Cobalt Deposits: Part I. Theoretical Considerations

Abstract Cobalt is in high demand because of the key role that cobalt-lithium-ion batteries are playing in addressing the issue of global warming, particularly in facilitating the transition from the internal combustion engine to electrically driven vehicles. Here, we review the properties of cobalt and the history of its discovery, briefly describe its mineralogy, and explore the processes that concentrate it to potentially exploitable levels. Economic cobalt deposits owe their origin to the compatible nature of Co2+, its concentration in the mantle in olivine, and its release, after high degrees of partial melting, to komatiitic and (to a lesser extent) basaltic magmas. Primary magmatic deposits, in which Co is subordinate to Ni, develop through the separation of immiscible sulfide liquids from mafic and ultramafic magmas and the very strong partitioning of these metals into the sulfide liquid. We evaluate the factors that concentrate cobalt to economic levels by these processes. Cobalt is also concentrated by aqueous fluids, either at ambient temperature in laterites developed over ultramafic rocks or hydrothermally in sediment-hosted copper deposits and in cobalt-rich vein deposits, where it crystallizes mainly as sulfide and arsenic-bearing minerals, respectively. Using the available thermodynamic data for aqueous Co species, we evaluate cobalt speciation as a function of temperature and show that, whereas it is transported at ambient temperature in most environments as the simple ion (Co2+), it is most mobile in hydrothermal systems as chloride species. Based on thermodynamic data compiled from a variety of sources, we evaluate stability relationships among some of the principal cobalt sulfide and oxide minerals as a function of temperature, pH, fO2, and αH2S and, in conjunction with the aqueous speciation data, determine their solubility. This information is used, in turn, to predict the physicochemical conditions most favorable for cobalt transport and ore formation by hydrothermal fluids. As thermodynamic data are not available for the cobalt arsenide and sulfarsenide minerals that form the vein-type ore deposits, we use chemographic analysis to qualitatively evaluate their stability relationships and predict the physicochemical controls of ore formation. The data and interpretations of processes presented in this paper provide the theoretical basis for a companion paper in this issue in which we develop plausible models for the genesis of the principal cobalt deposit types.

Geometallurgical Characterisation with Portable FTIR: Application to Sediment-Hosted Cu-Co Ores

Cobalt (Co) mine production primarily originates from the sediment-hosted copper (Cu) deposits of the Democratic Republic of Congo (DRC). These deposits usually consist of three ore zones with a supergene oxide ore blanket overlying a transition zone which grades into a sulphide zone at depth. Each of these zones display a mineral assemblage with varying gangue mineralogy and, most importantly, a distinct state of oxidation of the mineralisation. This has direct implications for Cu and Co extraction during mineral processing as it dictates which processing method is to be used (i.e., leaching vs. flotation) and affects the performance of these. To optimise resource efficiency, reduce technical risks and environmental impacts, comprehensive understanding of variation of ore mineralogy and texture in the deposit is essential. By defining geometallurgical ore types according to their inferred metallurgical behaviour, this information can serve to classify the resources and improve resource management. To obtain insight into the spatial distribution of mineral grades, it is necessary to develop techniques that have the potential to measure rapidly and, preferably, within the mine at relatively low-cost. In this study, the application of portable Fourier transformed infrared (FTIR) spectroscopy is investigated to measure the mineralogy of drill core samples. A set of samples from a sediment-hosted Cu-Co deposit in DRC was selected to test this approach. Results were validated using automated mineralogy (QEMSCAN). Prediction of gangue and target mineral grades from the FTIR spectra was achieved through partial least squares regression (PLS-R) combined with competitive adaptive reweighted sampling (CARS). It is shown that the modal mineralogy obtained from FTIR can be used to classify the ore according to type of mineralisation and gangue mineralogy into geometallurgical ore types. This classification supports selection of a suitable processing route and is likely to affect the overall process performance.

A Rapid Cu Enrichment Mechanism from Cu-Bearing Brine in Kuqa Basin, Xinjiang, China: Controlled by Crystallized Sequence of Saline Minerals

Sediment-hosted copper deposit is usually related to arid climate, ancient saline lake basin, and brine. The Kuqa Basin filled with giant-thickness evaporite units is located in the northern Tarim Basin, Xinjiang, China. It is famous for sandstone-hosted Cu deposits formed by synsedimentary processes. However, our recent studies reveal that Cu enrichment is closely related to brine on the surface of clastic rocks in the basin. It is shown that green Cu mineral coexisting with halite and gypsum occurred in the fractured fault belts of sandstones or was precipitated with halite on the surface of maroon clay in the scallops of sandstone. By SEM, EDS, and geochemical analysis methods on Cu-mineralized solid samples and brines, respectively, combined with previous geological evidence, our studies demonstrate that green Cu mineral is paratacamite, and it occurred with gypsum, halite, secondary glauberite, natural copper, and probably lead chloride on the fractured fault belts of sandstones or surface of clay. Meanwhile, the precipitation of paratacamite is controlled by a crystallized sequence of saline minerals accompanying with evaporated-concentrated course of brine in which gypsum, secondary glauberite, paratacamite, and halite are crystallized in turn. The Cu-bearing brine derived from meteoric waters and ancient seawater has a powerful capacity to leach metallic ions from its surrounding rocks and can be formed in a very short time (10 days is OK) in normal pressure and temperature conditions; also, the cycle of surface-Cu enrichment (mineralization) is only a few months (no more than 5). These indicate that a rapid Cu enrichment mechanism from Cu-bearing brine occurs on the earth’s surface of the evaporite basin. The mechanism might be supposed to make an enormous amount of metal mineralization in a short time if considered from a large-scale spatial viewpoint. By contrast with the lengthy geological period, the short evolutionary cycle of Cu enrichment (mineralization) is obviously different from the previous cognition.

Cobalt resources in Europe and the potential for new discoveries

Global demand for cobalt is increasing rapidly as we transition to a low-carbon economy. In order to ensure secure and sustainable supplies of this critical metal there is considerable interest in Europe in understanding the availability of cobalt from indigenous resources. This study reviews information on cobalt resources in Europe and evaluates the potential for additional discoveries.Based on published information and a survey of national mineral resource agencies, 509 cobalt-bearing deposits and occurrences have been identified in 25 countries in Europe. Harmonised cobalt resources, classified using the United Nations Framework Classification (UNFC), have been estimated for 151 deposits in 12 countries where data are available. The calculated total resource comprises 1342649 tonnes of contained cobalt metal. This includes: 114638 tonnes in commercial projects with current cobalt extraction; 370409 tonnes in potentially commercial projects; 111107 tonnes in historic estimates compliant with modern reporting; and 746495 tonnes in non-compliant historic estimates. Analysis of these data reveals that cobalt resources are widely distributed across Europe in deposits of several different types.Global mine production of cobalt is dominated by stratiform sediment-hosted copper deposits, magmatic nickel-copper deposits and nickel laterite deposits, but other deposit types may also be significantly enriched in cobalt. In Europe, current cobalt production is derived from three mines in Finland: the magmatic sulfide deposit at Kevitsa; the Kylylahti deposit of volcanogenic massive sulfide (VMS) affinity; and the black shale-hosted deposit at Sotkamo (Talvivaara).This study has identified 104 deposits in Europe that are currently being explored for cobalt, of which 79 are located in Finland, Norway and Sweden. The Fennoscandian Shield and the Caledonian Belt in these countries are high priority exploration terrains for a variety of cobalt-bearing deposits, notably magmatic Ni-Cu-Co deposits. The Svecofennian, Sveconorwegian and the Caledonian orogenies in Fennoscandia also resulted in the formation of several other cobalt-enriched deposit types. These include chiefly metasediment- and metavolcanic-hosted Co-Cu-Au, VMS, skarn and polymetallic vein deposits.The Kupferschiefer deposits in Poland and Germany are stratiform sediment-hosted Cu deposits with some similarities to the Central African Copperbelt, which is the predominant global producer. However, the cobalt grade in the Kupferschiefer deposits is relatively low (0.005–0.008% Co) and not currently economic to exploit without significant improvement in extraction technology.In the Balkans and Turkey cobalt grades and tonnages are known in 27 nickel laterite deposits, with several containing more than 10000 tonnes of cobalt metal. Only nickel is currently recovered from these deposits, but new processing technologies such as high-pressure acid leaching could enable cobalt recovery in the future.Small polymetallic cobalt-bearing vein deposits in several European countries have been historic producers of cobalt. Today most are uneconomic, but new technologies and the drive towards locally-sourced raw materials could make them viable future sources of cobalt.Our analysis suggests that geological availability in Europe is not a problem. However, many economic, technological, environmental and social challenges will have to be overcome for exploration projects to become commercial.

Base metal mineralization of the Kolyma terrain in Northeast Russia: Overview and genetic classification

Research subject. The Prikolyma terrain located in the Northeastern part ofRussia constitutes a long-lived Precambrian thrust-faulted structure hosting numerous Cu, Pb and Zn deposits of different types.Materials and methods. The mineralization of the terrain was examined during a course of research and exploration works over the 2007–2012. The rock geochemistry was studied using ICP-OES analysis at the Stuart Geochemistry and Essay laboratory (Moscow). The microprobe analysis of minerals was carried out at the facilities of the Far Eastern Branch of the Russian Academy of Sciences (Magadan) using a Camebax X-ray microanalyzer. The isotopic ratios of sulphur in sulphides were measured using a Finnigan MAT 253 isotope mass spectrometer.Results. The porphyry-copper deposit Nevidimka is represented by skarns and sulphide-quartz stockworks embedded in porphyry granites. The vein deposits Opyt and Glukhoye constitute sulphide-carbonate-quartz veins, the composition of which corresponds to copper-polymetallic ores of the peripheral parts of the copper-porphyry formation. These deposits feature a similar geochemistry and composition of sulphides and sulphur isotopes, which is characteristic of the Riphean complexes of the Prikolyma terrain. The stratiform Pb-Zn veins Nadezhda-3 and Khaya enclosed in Proterozoic dolomites represent parallel-bedding disseminated sulphides. The composition of these ores indicates their diagenetic origin. Tne stratiform copper deposit Oroyok is embedded in Proterozoic shales and can be referred to sediment-hosted copper deposits of a transgressive type.Conclusions. The diversity of Cu-Pb-Zn mineralization types in the Prikolyma terrain is established to have resulted from multiple cyclic changes of the geodynamic ore formation regime. During each such cycle, syngenetic mineralization was followed first by epigenetic and then by vein mineralization. The mobile, thrust-faulted structure caused repeated rejuvenation of ores, which inherited the geochemical features of hosting rocks.

Fluid geochemistry of the Serra Pelada Au-Pd-Pt deposit, Carajás, Brazil: Exceptional metal enrichment caused by deep reaching hydrothermal oxidation

Serra Pelada is a high-grade hydrothermal Au-Pd-Pt deposit within the Carajás mineral province, eastern Amazon craton, which shows an exceptional metal enrichment at carbon-enriched hosted ores (>1000’s ppm Au + Pt + Pd). The main orebody is structurally hosted at the hinge of a recumbent syncline, consisting of dolomitic metasandstones at the outer part of the fold, a layer of carbonaceous metasiltstone in which most orebodies are located, and red siltstone in the core of the fold. Distal hydrothermal alteration comprises spatially separated chlorite – carbon (reduced) and hematite (oxidized) alteration zones. The mineralized zones include silicification and argillic (carbon- kaolinite-, and hematite-rich) alteration zones. Fluid inclusions hosted by quartz and dolomite crystals from distal alteration zones and silicified portions within the mineralized zone record a wide range of salinity (5–22 wt% NaCleqv.) but relatively constant homogenization temperatures (170 ± 25 °C). Pressure and temperature estimations based in the fluid inclusion microthermometry and selenide thermometry constrain the formation of the deposit at 250–270 °C and 1.2–1.7 kbar. Element concentrations of alkali metals, Pb, Cs and to a lesser extent Ba correlate with salinity, whereas redox-sensitive elements including U and Ce vary widely. Gold concentrations from 50 to 500 ppb detected in some inclusions are consistent with the highly oxidizing conditions defined by selenide mineralogy. The presence of uranium and gold within fluid inclusions of the distal hematite alteration zone confirms the oxidizing, metal carrier fluids. The occurrence of hydrothermally precipitated carbon implies that a reducing CH4-bearing fluid was also present, and the structural relationships suggest that mixing between this reducing fluid (and interaction with carbon-upgraded rocks) with an acidic, oxidizing and metal-carrying fluids was the main process driving ore metal precipitation. The genesis of the Serra Pelada Au–Pd-Pt deposit shows similarities with sediment-hosted copper deposits and unconformity-related U ± Au ± PGE deposits, having in common the downflow of highly oxidizing fluids into the hydrothermal domain of the Earth's upper crust. Major differences in metal proportions of these broad classes of ore deposits and other sediment-hosted systems in different ore provinces are primarily caused by differences in source rocks available for oxidative leaching and variations in the geometry of the hydrothermal system.

Geophysics for Sediment Hosted Copper and Gold Mineralisation, The Role of 3DIP

Sediment hosted copper mineralisation involves redox precipitation of copper sulphides where oxidised basinal fluids interact with in situ organic material or migrated hydrocarbons. This is a common process in sedimentary basins so it is important to find fast and cost-efficient methods for their exploration. Airborne magnetic/ electromagnetic and ground gravity and electrical resistivity-induced polarisation (IP) methods are commonly used to explore for these types of deposits. The application of IP methods can be utilised as a direct targeting tool in the sediment hosted environment.Multichannel receivers, large transmitters, improvements in processing capacity has led to more confidence in inversion results and the recent popularity of the 3D IP technique. Examples of the application of large 3D IP surveys for sediment hosted copper deposits from Zambia and Alaska show that high grade copper mineralisation is associated with an IP response. Sedimentary textures associated with mineralisation compromise the inductive conductivity and resistivity response (anisotropy). An integrated exploration approach using geology, geochemistry and geophysics helps alleviate pursuing responses from digenetic pyrite, graphitic shales and specular haematite.

Geology and Metallogenesis of the Sediment-Hosted Cu-Ag Deposit of Tizert (Igherm Inlier, Anti-Atlas Copperbelt, Morocco)

The Tizert Cu-Ag deposit is the largest of a series of sediment-hosted copper deposits of the Anti-Atlas copper province in Morocco. Mineralized rocks in the deposit contain disseminated sulphides within a Late Ediacaran, dominantly siliciclastic sedimentary formation named the Basal Series. Isopach map of the Basal Series thickness shows that during the Late Ediacaran the area was composed of large subsiding zones separated by paleohighs. The ore-grade zones are well developed along basin margins adjacent to the basement paleohighs. These mineralized zones display a lateral sulphide zoning with central bornite-chalcocite zones grading outward to intermediate chalcopyrite and external pyrite zones. There is also a vertical sulphide zoning with evolution from bornite and chalcocite dominant mineralized rocks at the bottom to chalcopyrite and pyrite dominant mineralized rocks at the top of the lithostratigraphic succession. A second style of mineralization is represented by sulphide filled fractures and veins present in the Basal Series, as well as in the basement and the overlying dolomites. The similarity of the paragenetic sequences between the disseminated and the vein-hosted mineralization suggests that they may be related to the same mineralizing event, the disseminated style of mineralization being rapidly followed by the onset of the vein-style mineralization.

Future copper resources

Concerns about future supplies of raw materials demand careful examination of underlying assumptions and data. Flawed deposit information, ignored undiscovered resources and questionable assumptions about future consumption require a new look at copper resources.A careful compilation of 1978 copper-bearing mineral deposits totals 2700 million metric tons of copper including past production—considerably more than reported in previous studies. About 69% of the copper is in porphyry copper deposits and 12% in sediment-hosted copper, Magmatic sulfide (mostly intrusive Ni) deposits account for 5.1%, and IOGC adds about 4.7%. VMS deposits represent 45% of the 1978 deposits but only 4.9% of the copper.The largest 20% of the deposits account for over 92% of the total copper metal. In other words, total Cu content in the smaller 1600 deposits is only about 8% of all Cu known in all deposits. This is a consequence of highly skewed frequency distributions of deposit tonnages and contained metals in all kinds of mineral deposits. This relationship is critical if one is concerned about long-term supply of copper. Typically, distributions of contained metal can be modeled well by the lognormal distribution for individual types of deposits.Information used here and in many other studies on copper includes past production. Total past production through 2015 is about 667 million tons Cu. After subtracting past production from the total copper in known deposits, the remaining unproduced copper from known deposits is 2030 million tons. Known deposits inform us about undiscovered copper resources.Over 80% of known copper is in porphyry copper and sediment-hosted copper deposits. A reliable and robust USGS managed global assessment of 225 tracts for porphyry Cu and sediment-hosted Cu produced an expected value estimate of 3500 million tons Cu in undiscovered deposits. Deposit types not assessed such as IOGC are likely to have significant amounts of undiscovered copper. If the proportion of total Cu accounted for by the two major deposit types assessed is the same proportion in all undiscovered deposits, total Cu expected in these other deposit types would add an additional 850 million tons. The reasonable estimate of copper in undiscovered mineral deposits of 4350 million tons when added to the unmined 2030 million tons in known deposits provides an estimate of 6380 million of tons Cu, which far exceeds estimates published by other researchers.Growth in copper production appears to be exponential over time but appears to be linear with respect to population. Demand for copper is not driven by time, but rather by population and per capita income. Rates of population increases are slowing and incomes in many countries are increasing. Per capita consumption of copper will increase over the coming years as populous nations such as China and India develop increasing per capita incomes, but the demand will likely level off as their economies improve. The large estimated copper resources along with evidence of slowing demand for copper over the long term considerably extend the time of “peak copper” and the long mine life of large deposits means the decline in production after will not be rapid. The focus of copper supply concerns should be on important problems such as improving recovery rates, careful consideration of the benefits and costs of mining very large deposits, technologies to increase exploration success in covered areas and reducing costs of underground mining.

An Example of Synorogenic Sediment-Hosted Copper Mineralization: Geologic and Geochronologic Evidence from the Paleoproterozoic Nussir Deposit, Finnmark, Arctic Norway

Sediment-hosted copper-silver mineralization in the Raipas Supergroup of the Repparfjord tectonic window of Finnmark, northernmost Norway, is present in two main stratigraphic horizons at Nussir and Ulveryggen. The stratigraphically lower Ulveryggen deposit is hosted by irregular lenses of dominantly fluviatile sandstone and conglomerate, whereas the Nussir deposit, with a strike length of ~9 km, is associated with dolomitic siltstone and dolomite. Both deposits display intense structural control, and apart from the classic stratiform geometry of the disseminated cupriferous sulfides, high-grade mineralization includes abundant foliation parallel and transgressive veinlets, fissures, and irregular lenses and aggregates, with or without quartz, carbonate, chlorite, and biotite gangue. A close association with ductile deformation is apparent. Although scarce, molybdenite occurs intimately associated with the cupriferous sulfides at Nussir, in a paragenetic sequence comprising chalcopyrite-bornite-molybdenite-chalcocite-neodigenite in both the stratiform disseminated and veinlet mineralization. U-Pb zircon dating of a tuffaceous horizon from the dominantly volcanic Nussir Group, collected 60 m above the ore horizon at Nussir, yielded an age of 2073.1 +23.2/−12.4 Ma that confirms accumulation in an intercontinental rift or island-arc environment during construction of the Paleoproterozoic Columbia supercontinent. Re-Os geochronology on Nussir molybdenite returned ages of 1761 ± 8 and 1768 ± 7 Ma, which represent the timing of the copper-silver mineralization in the area. This age, the oldest direct, unambiguous determination reported for a sediment-hosted copper deposit, implies that the copper mineralization took place ~300 m.y. after the sedimentation and volcanism responsible for the host sequence, and syntectonically with the Svecofennian (Svecokarelian) orogeny in the Fennoscandian Shield.

Geology, Fluid Inclusions, and Isotope Geochemistry of the Jinman Sediment‐hosted Copper Deposit in the Lanping Basin, China

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 1200-1201 Meeting Abstracts Geology, Fluid Inclusions, and Isotope Geochemistry of the Jinman Sediment-hosted Copper Deposit in the Lanping Basin, China Jinrang ZHANG, Corresponding Author Jinrang ZHANG Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu, 610081 ChinaCorresponding author. E-mail: zhangjinrang123@163.comSearch for more papers by this authorHanjie WEN, Hanjie WEN State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002 ChinaSearch for more papers by this authorYuzhuo QIU, Yuzhuo QIU State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002 China Key Laboratory for Metallogenic, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 ChinaSearch for more papers by this authorZhichao ZOU, Zhichao ZOU Chengdu University of Technology, Chengdu 610059 ChinaSearch for more papers by this author Jinrang ZHANG, Corresponding Author Jinrang ZHANG Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu, 610081 ChinaCorresponding author. E-mail: zhangjinrang123@163.comSearch for more papers by this authorHanjie WEN, Hanjie WEN State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002 ChinaSearch for more papers by this authorYuzhuo QIU, Yuzhuo QIU State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002 China Key Laboratory for Metallogenic, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 ChinaSearch for more papers by this authorZhichao ZOU, Zhichao ZOU Chengdu University of Technology, Chengdu 610059 ChinaSearch for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12379_67Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 1200-1201 RelatedInformation

Dating of U-rich heterogenite: New insights into U deposit genesis and U cycling in the Katanga Copperbelt

The Katanga Copperbelt region of the Democratic Republic of Congo hosts world-class cobalt deposits accounting for ∼50% of the world reserves. Heterogenite (CoOOH) is the most abundant Co-bearing secondary mineral in the region. Its occurrence is the result of oxidation of Cu–Co-sulfides and associated Co reprecipitation in the uppermost part of the deposits, during the Pliocene. In addition to sediment-hosted copper and cobalt ore deposits, the Katanga Copperbelt also hosts numerous uraniferous mineral occurrences and deposits, which can be associated with heterogenite. Within these deposits, heterogenite can have high concentrations of U (up to 3.5%) and Pb (up to ∼4%).In situ SIMS U–Pb ages were obtained for heterogenite samples from the U deposits of Shinkolobwe, Kalongwe and Kambove. These analyses yield distinct Neoproterozoic ages, at ∼876Ma, ∼823Ma and in the ∼720 to ∼670Ma age range. As the geological context prevailing at those times was not favorable for heterogenite formation, these ages most probably record geological events that are not the formation of the mineral itself. For instance, the heterogenites could have inherited the U–Pb signature of a U-rich mineral, most likely uraninite, formed and/or yet reworked at ∼876Ma, ∼823Ma and in the ∼720 to ∼670Ma time interval and spatially associated with primary Co-sulfides. In this hypothesis, the ages obtained in this paper are significant for understanding the cycling and re-deposition of U at given moments in the regional geological history.In such context, the ∼876Ma and the ∼823Ma age are consistent with syn-early diagenetic concentration of uranium in sediments of the Katanga basin. The ∼720 to ∼670Ma ages are interpreted as a phase of U remobilization related to hydrothermal fluid circulation induced by late Nguba proto-oceanic rifting or by early stages of Congo-Kalahari craton convergence, and associated hydrothermal circulation.

Equilibrium isotopic fractionation of copper during oxidation/reduction, aqueous complexation and ore-forming processes: Predictions from hybrid density functional theory

Copper exists as two isotopes: 65Cu (∼30.85%) and 63Cu (∼69.15%). The isotopic composition of copper in secondary minerals, surface waters and oxic groundwaters is 1–12‰ heavier than that of copper in primary sulfides. Changes in oxidation state and complexation should yield substantial isotopic fractionation between copper species but it is unclear to what extent the observed Cu isotopic variations reflect equilibrium fractionation. Here, I calculate the reduced partition function ratios for chalcopyrite (CuFeS2), cuprite (Cu2O), tenorite (CuO) and aqueous Cu+, Cu+2 complexes using periodic and molecular hybrid density functional theory to predict the equilibrium isotopic fractionation of Cu resulting from oxidation of Cu+ to Cu+2 and by complexation of dissolved Cu. Among the various copper(II) complexes in aqueous environments, there is a significant (1.3‰) range in the reduced partition function ratios. Oxidation and congruent dissolution of chalcopyrite (CuFeS2) to dissolved Cu+2 (as Cu(H2O)5+2) yields 65–63δ(Cu+2–CuFeS2)=3.1‰ at 25°C; however, chalcopyrite oxidation/dissolution is incongruent so that the observed isotopic fractionation will be less. Secondary precipitation of cuprite (Cu2O) would yield further enrichment of dissolved 65Cu since 65–63δ(Cu+2–Cu2O) is 1.2‰ at 25°C. However, precipitation of tenorite (CuO) will favor the heavy isotope by +1.0‰ making dissolved Cu isotopically lighter. These are upper-limit estimates for equilibrium fractionation. Therefore, the extremely large (9‰) fractionations between dissolved Cu+2 (or Cu+2 minerals) and primary Cu+ sulfides observed in supergene environments must reflect Rayleigh (open-system) or kinetic fractionation. Finally the previously proposed (Asael et al., 2009) use of δ65Cu in chalcopyrite to estimate the oxidation state of fluids that transported Cu in stratiform sediment-hosted copper deposits is refined.

Gold-bearing ferroselite (FeSe2) from Trogtal, Harz, Germany, and significance of its Co/Ni ratio

Ferroselite from Trogtal, the type locality of the cobalt selenide trogtalite, in the Harz Mountains, Germany, forms a trogtalite–ferroselite assemblage in pockets of massive clausthalite in which specular hematite is dispersed. The pockets occur in hematite-impregnated carbonate veins, emplaced in a reddened greywacke of Lower Carboniferous age. Ferroselite contains ~0.2–5.0 ppm Au; trogtalite has even higher Au contents. Ferroselite has Co/Ni ratios mostly above unity. These characteristics likely reflect oxidizing brines with Co/Ni > 1, such as those involved in the formation of sediment-hosted copper deposits.

SIMS U–Pb dating of uranium mineralization in the Katanga Copperbelt: Constraints for the geodynamic context

The Katanga Copperbelt, in the southeastern part of the Democratic Republic of the Congo (DRC), occurs within the Pan-African Lufilian fold-and-thrust belt and hosts numerous uraniferous mineral occurrences in addition to the world-class sediment-hosted copper and cobalt ore deposits. In the 1950s and 1960s, Cahen et al. gave a relatively wide range of U mineralization ages, using U–Pb dating on whole-rock samples. Although these ages nowadays appear as inaccurate because of large error ranges, they were frequently used to discuss the regional geodynamic events. This paper offers a reappraisal of the age range previously published, using in-situ SIMS U–Pb analyses. Based on these analyses, two ages are regarded as analytically reliable and significant (652.3 ± 7.3 Ma and 530.1 ± 5.9 Ma), and hence as having implications for the understanding of geological and geodynamic context in the study area. In the Katanga Copperbelt, the siliciclastic rocks of the Lower Roan Group are slightly enriched in uranium. A major U mineralization/(re-)mobilization episode took place at ~ 652 Ma, during proto-oceanic rift basin development. This phase took place in an extensional tectonic regime and led to the (re-)mobilization of U within fractures and voids. Such deposits are observed along the ~ 250 km-long Kalongwe–Luishia tectonic lineament. This metal concentration was reworked at ~ 530 Ma, at the occasion of the climax of Lufilian deformation and metamorphism. This event gave rise to the U deposits in the southern border of the Katanga Copperbelt (and in Northern Zambia). The Kolwezi deposit is a deposit located further to the North. Notwithstanding its initial position further to the south, the deposit is heavily faulted and the thrusts and faults could have focused the fluids associated with the deformation, at ~ 530 Ma.

The Cretaceous sediment-hosted copper deposits of San Marcos (Coahuila, Northeastern Mexico): An approach to ore-forming processes

Abstract In the San Marcos ranges of Cuatrocienegas, NE Mexico, several sediment-hosted copper deposits occur within the boundary between the Coahuila Block, a basement high mostly granitic in composition and Late Paleozoic to Triassic in age, and the Mesozoic Sabinas rift basin. This boundary is outlined by the regional-scale synsedimentary San Marcos Fault. At the basin scale, the copper mineralization occurs at the top of a ∼1000 m thick red-bed succession (San Marcos Formation, Berrisian), a few meters below a conformable, transitional contact with micritic limestones (Cupido Formation, Hauterivian to Aptian). It consists of successive decimeter-thick roughly stratiform copper-rich horizons placed just above the red-beds, in a transitional unit of carbonaceous grey-beds grading to micritic limestones. The host rocks are fine- to medium-grained arkoses, with poorly sorted and subangular to subrounded grains. The detrital grains are cemented by quartz and minor calcite; besides, late iron oxide grain-coating cement occurs at the footwall unmineralized red-beds. The source area of the sediments, indicated by their modal composition, is an uplifted basement. The contents of SiO 2 (40.70–87.50 wt.%), Al 2 O 3 (5.91–22.00 wt.%), K 2 O (3.68–12.50 wt.%), Na 2 O (0.03–2.03 wt.%) and CaO (0.09–3.78 wt.%) are within the ranges expected for arkoses. Major oxide ratios indicate that the sedimentary-tectonic setting was a passive margin. The outcropping copper mineralization essentially consists in a supergene assemblage of chrysocolla, malachite and azurite. All that remains of the primary mineralization are micron-sized chalcocite grains shielded by quartz cement. In addition, pyrite subhedral grains occur scattered throughout the copper-mineralized horizons. In these weathered orebodies copper contents range between 4.24 and 7.72 wt.%, silver between 5 and 92 ppm, and cobalt from 8 to 91 ppm. Microthermometric measurements of fluid inclusions in quartz and calcite crystals from footwall barren veinlets gave temperatures of homogenization between 98 °C and 165 °C, and ice-melting temperatures between −42.5 °C and −26.1 °C. The primary copper mineralization formed during the early diagenesis, contemporary with the active life of the Sabinas Basin. The mineralizing fluids were dense, near neutral, moderately oxidized brines that originally formed from seawater that, driven by gravity, infiltrated to the deepest parts of the basin and dissolved evaporites. As a result, they became hydrothermal fluids of moderate temperature capable of leaching high amounts of copper. The source of this metal could be mafic detrital grains and iron oxides of the underlying Jurassic and Lower Cretaceous red-beds. Copper precipitation took place when the brines passed through the redox boundary marked by the transition from red- to grey-beds. The upward movement of the brines was promoted by a high heat flow that allowed their convective circulation and their ascent along the synsedimentary San Marcos Fault.