Ni Sulfide Research Articles

Magmatic evolution of the ultramafic–mafic Kharaelakh intrusion (Siberian Craton, Russia): insights from trace-element, U–Pb and Hf-isotope data on zircon

The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element (PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and 250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial 176Hf/177Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history than is commonly assumed.

Nature and genesis of Kalimantan diamonds

The origin of alluvial diamonds from the four main diamond mining districts in Kalimantan was studied through characterisation of their properties, and determination of PT and age of formation of representative collections of diamonds from four localities of the island. The diamonds are mostly colourless, yellow or pale brown, shiny surfaced, dodecahedroids, octahedron/dodecahedroids, and more rarely cube combination forms. They are intensively resorbed. They have surface radiation damage and show abrasion features indicative of fluvial transportation and crustal recycling. The diamonds were polished down to expose internal structures and mineral inclusions. The majority of the diamonds are internally homogeneous or have simple octahedral zonation and show plastic deformation. Analysis by Fourier transform infra red spectroscopy of their N content and aggregation characteristics shows that many diamonds are well-aggregated type IaB implying a long-term, mantle residence time and/or high temperatures of formation. Identified inclusion parageneses are 68% peridotitic and 32% eclogitic. The peridotitic inclusions are represented by olivine, chromite, garnet, orthopyroxene and pentlandite. Olivines (Fo 92–93) belong to the dunite–harzburgite paragenesis, with one at Fo 90 identified as lherzolitic. Chromite inclusions with 65–66 wt.% Cr 2O 3 and < 1 wt.% TiO 2 are typical of chromite diamond inclusions world-wide. Two garnet inclusions identified are a subcalcic high chrome harzburgite “G10” and a mildly subcalcic type transitional between “G9” and “G10”. The eclogitic inclusions are represented by omphacite, rutile, kyanite and coesite. Re/Os dating of a high Ni sulphide inclusion from one peridotitic diamond gave an Archean model age of 3.1 Ga ± 0.2 (2 sigma). In terms of their external and internal morphology, N aggregation characteristics and paragenesis the Kalimantan diamonds resemble those transported to surface by kimberlite or lamproite from sources in the subcontinental lithospheric mantle. Five distinctive genetic groups of diamond have been recognised but occur mixed in each of the four diamond mining districts due to a presumed long history of sedimentary recycling and alluvial transportation. Thermobarometry calculations from diamond inclusion chemistry (930 °C to 1250 °C; > 4.2 GPa) are consistent with a paleo-heat flow of 38 to 40 mW/m 2 and derivation from 120 to 160 km depth, i.e. subcontinental mantle lithosphere conditions similar to diamonds from African and Yakutian cratonic situations.

In-situ analysis of diamonds and their inclusions from the Diavik Mine, Northwest Territories, Canada: Mapping diamond growth

Results are presented here of an in-situ study of diamonds from the A154 South kimberlite pipe at the Diavik diamond mine, Northwest Territories, Canada. One hundred and ten diamonds were selected from run of mine production on the basis of morphology and visible inclusions. Diamonds that crystallized as cubes have a higher incidence of fluorescence in response to UV light than those that have crystallized in the octahedral primary form. Fifty-one diamonds were cut and polished to expose included mineral grains and to allow for imaging of internal structure. Mineral inclusions were analysed in-situ for major element composition using electron microbeam methods. Internal zonation of the diamonds was imaged using cathodoluminescence in thirteen P-type diamonds, two U-type diamonds, nine E-type diamonds, and two diamonds with only sulfide inclusions of indeterminate paragenesis. Inclusions of Fe ± Cu ± Ni sulfide, magnesian chromite, ferropericlase, chromian diopside, forsteritic olivine, omphacite, and enstatite occur in order from most to least abundant. The chromite inclusions are lower in Mg than the worldwide average. At least six of the sulfide inclusions are significantly heterogeneous. Equilibration temperature and pressure conditions for the diopside inclusions indicate that the diamonds equilibrated in a region of geothermal gradient with an equivalent surface heat flow of 42 mW/m 2 over a range from 51–57 kbar and 1170–1260 °C.

The Dovyren intrusive complex: Problems of petrology and Ni sulfide mineralization

This paper presents a review of petrological-geochemical studies at the Yoko-Dovyren Massif with an emphasis on relations between parameters of the parental magma, a model for the genesis of the lower con- tact zone, and the nature of Ni sulfide ore mineralization, including the evaluation of the possible ore potential. Arguments are presented in support of the conclusion that the Dovyren magma brought much intratelluric oli- vine of the composition Fo 85-87 into the chamber, and the composition of the initial melt corresponded to gab- bronorite or moderately magnesian basite with no more than 10 wt % MgO. The probable temperature of the parental magma was approximately 1200-1250°e , and the sulfur solubility did not exceed 0.10-0.12 wt % ( P = 1 kbar, WM buffer). The comparison of this estimate with the average S contents in the bottom plagioperi- dotites ( 0.12 ± 0.06 wt %) indicates that the initial magma was saturated with a sulfide phase. For the first time the problem of the composition of contaminated dunites was formulated (these rocks occur in the Layered Series and contain more magnesian olivine Fo 87-92 ). The reason for the increase in the mg# of olivine is thought to be the partial melting and compaction of the original cumulates due to the infiltration of intercumulus melt enriched in volatile components. The volatiles were presumably provided by the thermal decomposition of car- bonate xenoliths, a process that resulted in an increase in the CO 2 pressure and the transfer of calcite-magnesite components of carbonates into the melt. This follows from (1) the occurrence of magnesian skarn developing after carbonates, (2) high CaO contents in olivine form the contaminated dunite, (3) the appearance of olivine- bearing pyroxenites and wehrlites in the upper part of the dunite zone, (4) correlation between the olivine and chromite composition in the contaminated and uncontaminated dunites, (5) broad variations in the oxygen iso- topic composition of olivine and plagioclase from rocks of the Layered Series, (6) experimental data on the dis- solution of carbonates in alkali basalt melts, and (7) analogies with isotopic-geochemical characteristics of rocks from the Jinchuan ultramafic complex. Petrological implications of the interpretation of the Dovyren chamber are discussed with reference to closed and flow-through (during an initial stage) magmatic systems. A petrological-geological model is proposed for the genesis of the Synnyr-Dovyren volcanic-plutonic complex and related Ni sulfide ore mineralization. The potential resources of Cu-Ni sulfide ores in the plagioperidotites are evaluated with regard to the still-unexposed part of the massif.

Melilitolite intrusion and pelite digestion by high temperature kamafugitic magma at Colle Fabbri, Spoleto, Italy

A subvolcanic body in Colle Fabbri (Umbria, Central Italy) intrudes sedimentary rocks and the overlaying extrusive breccia. The intrusive rock is melilitolite with essential leucite, kalsilite, and wollastonite plus accessory Ti-garnet, Ti–Al–Fe 3+-clinopyroxene, magnetite, perovskite, rankinite, Si-bearing apatite, Fe–Ni sulphides, and carbonate/zeolite. Bulk chemistry of melilitolite indicates a strong SiO 2-undersaturation, extremely high CaO composition, and strong initial potassic character. Sr and Nd isotopic ratios support a link with the source of kamafugites and carbonatites found in the same region. The igneous contact rock contains variable amounts of quenched clinopyroxene, anorthite, sanidine ± wollastonite, plus spinel and glass. Extremely high temperature melilitolite magma digested pelite country-rock, thus leading to a unique mineral composition. The homogenisation temperatures of mineral inclusions in contact rock demonstrate that crystallisation occurred well above 1230 °C. A large thermal aureole formed in a local clinker-like breccia, characterised by the association of felsic glass + indialite + tridymite ± Ti-magnetite, confirms high-temperature emplacement. Metasomatic/thermometamorphic phenomena favoured zone-specific mineralisation of hydrated Ca-silicates, hydrated complex sulphates and zeolites in breccias and encasing rocks.

Phosphorus-bearing sulfides and their associations in CM chondrites

Phosphorus-bearing Fe and Ni sulfides represent a new type of phosphorus compounds and are characteristic accessory phases of CM chondrites. The proportions of atoms in the sulfides can be approximated by the equation (Fe + Ni)/P = 0.965 ± 0.003 (1σ) · S/P + 1.255 ± 0.036 (1σ). Sulfides with high S/P ratios are systematically richer in Fe and poorer in Ni compared with low-S/P sulfides. Their characteristic minor elements are Cr, Ca, Co, K, and Na. The contents of Cr and Ca may reach several weight percent, but their incorporation does not affect the relation between (Fe + Ni)/P and S/P. This is also true of light elements (O and H), which probably occur in the P-bearing sulfides in certain amounts. The sulfides are usually associated with schreibersite, barringerite, eskolaite, and daubreelite. A negative correlation was observed between the Fe/Ni ratios of coexisting P-bearing sulfides and phosphides. Metallic iron was never found in association with the sulfides. It can be suggested that P-bearing sulfide is a primary phase rather than a secondary alteration product formed under the conditions of the CM chondrite parent body. This phase had to be stable in the solar nebula after the formation of Ca-Al inclusions and before the condensation of Fe-Ni metal. At high temperatures, P-bearing sulfide with low Fe/Ni and S/P ratios coexists with schreibersite in the solar gas. During condensation schreibersite is replaced by barringerite, which is accompanied by a decrease in the Fe/Ni ratio of phosphides and an increase in the S/P and Fe/Ni ratios of P-bearing sulfides. Trace element data suggest that the P-bearing sulfides could be formed in the solar nebula by the sulfidization of a precursor phase of extrasolar origin.

CHROMIAN SPINEL IN THE TURNAGAIN ALASKAN-TYPE ULTRAMAFIC INTRUSION, NORTHERN BRITISH COLUMBIA, CANADA

The Early Jurassic Turnagain intrusion (24 km2) in northern British Columbia, Canada, is one of a number of Alaskan-type intrusions that occur within the Mesozoic Quesnel accreted arc terrane. It is distinguished by the presence of magmatic Ni sulfide mineralization hosted by ultramafic cumulate rocks. Chromian spinel is a common accessory mineral ( 0.85, Fe2+/(Fe2+ + Mg) < 0.4] are preserved in magnesiochromite grains from the chromitites, which were isolated from nearby olivine and interstitial melt and thus did not significantly re-equilibrate during cooling. Extensive re-equilibration with evolved interstitial melt, defined by broadly linear trends of increasing Al, Fe3+, Ti, V and Fe2+/(Fe2+ + Mg) with decreasing Cr content, is recorded in chromian spinel grains from dunite, wehrlite, and olivine clinopyroxenite. These trends converge toward the compositional field of grains from the chromitites. Rims of Fe3+-rich chromite and Cr-bearing magnetite, up to 30 μm thick, formed around chromian spinel grains during subsolidus infiltration of oxygenated fluids and serpentinization. Relative to the global database of spinel compositions from Alaskan-type intrusions, the majority of the chromian spinel compositions from the Turnagain intrusion are characterized by lower Fe3+/(Fe3+ + Cr + Al) and higher Cr/ (Cr + Al), which is consistent with a relatively low oxygen fugacity for the parental magmas to the ultramafic cumulates. The Turnagain parental magmas were likely reduced by assimilation of graphite- and pyrite-bearing phyllite host-rocks, which led to local saturation in a sulfide liquid.

Platinum‐group element signature of the primitive mantle rejuvenated by melt‐rock reactions: evidence from Sumail peridotites (Oman Ophiolite)

AbstractPlatinum‐group element (PGE) abundances in mantle rocks are generally considered to result from a late meteorite addition to the early Earth, post‐dating the core separation event. As such, PGEs are key tracers for the Earth accretion history. For decades, the PGEs systematics of undepleted mantle peridotites has been used to constrain the composition of meteorite impactors involved in the late veneer material. Despite multiple evidence of considerable modifications by partial melting, harzburgites from the Sumail ophiolite (Oman) display a mean PGE composition very akin to recently refined estimates for the Primitive Upper Mantle (PUM) of the Earth. These rocks document a resetting of the PUM signature by percolating basaltic melts, which precipitated Pd‐enriched Cu–Ni sulphides within a strongly Pd‐depleted residual harzburgitic protolith. Such a resetting casts doubt on both the reliability of any PUM estimates and relevance of the PUM concept itself, at least for PGEs.

Interaction of Ni/SiO 2 with thiophene

The interaction between Ni/SiO 2 (18 wt%) and thiophene was studied by thermal gravimetric analysis (TGA) and in a fixed-bed reactor. The samples were prepared by incipient wetness impregnation and reaction was realized in hydrogen flow at 280–360 °C in the presence of 10–40 mbar of thiophene. It is found that sulfidation of Ni is not complete in TGA experiments and the maximum achievable transformation degree depends not only on the temperature and thiophene pressure, but also on the sample weight and the gas flow rate. The maximum transformation degree is shown to vary reversibly when conditions are changed. Analysis of the reaction products during sulfidation in a fixed-bed reactor showed that H 2S is present in the gas phase from the beginning of the reaction and that catalytic activity of the solid decreases strongly when going from Ni 0 to Ni 3S 2. All these observations suggest that, except at the surface, the interaction between thiophene and Ni/SiO 2 is not direct: thiophene is first desulfurized and then H 2S reacts with Ni. As Ni sulfidation progresses the amount of produced H 2S decreases (because of a lowering catalytic activity of the solid) and after certain time H 2S partial pressure can drop to the equilibrium value for Ni/Ni 3S 2 system. In such conditions Ni sulfidation cannot be completed and the system achieves a steady state corresponding to the maximum transformation degree observed in TGA experiments. The present study shows that due to involvement of a catalytic reaction, the stability of metallic particles in the presence of complex sulfur-containing molecules can be determined by the desulfurization activity of the metal and operation conditions rather than by the thermodynamics of the metal-sulfur system.

Metasomatic interaction between disseminated nickel sulphides and reduced metamorphic fluids, Honeymoon Well komatiite complex, Western Australia

Within the Honeymoon Well komatiite complex located within the Archaean Agnew-Wiluna greenstone belt, Western Australia, disseminated Ni sulphide deposits are hosted by completely serpentinised olivine-rich cumulates. These are unusual deposits as they contain large tonnages of mineralisation that are devoid of Cu despite containing up to >2%Ni and having magmatic Co and PGE values. About 55% of the 43 Mt Hannibals deposit consists of this style of mineralisation. The Cu distribution is spatially and geochemically related to bulk-rock changes in S and Fe with the Cu-absent parts of the deposit being variably depleted in these elements. Mimicking these changes in bulk composition is a zonation in sulphide–oxide assemblages of Ni-poor pentlandite-magnetite±pyrrhotite±chalcopyrite, pentlandite-magnetite±chalcopyrite, Ni-rich pentlandite-heazlewoodite±magnetite, and heazlewoodite-only with the latter occurring in zones showing the strongest S and Fe depletion. The sulphide mineral assemblages and bulk compositions correspond to variations in the non-sulphide mineralogy with much of the heazlewoodite mineralisation hosted by lizardite-iowaite±brucite-(magnetite absent) assemblages. Formation of highly reduced fluids during serpentinisation of olivine adcumulate and mesocumulate host sequences resulted in dissolution of sulphides in parts of the disseminated deposits. Copper, Co and Fe, soluble as chloride species, and S in the form of H2S were variably leached and removed from parts of the deposits. Passage of these reduced fluids through barren ultramafic rocks caused partial leaching of Fe and resulted in the formation of lizardite-rich alteration assemblages devoid of magnetite. Metamorphic Fe-Cu±Zn±Ni±Co bearing sulphides are common in pyroaurite-brucite magnetite veins and in former pyroxene-rich lithologies indicating the presence and mobility of these elements in some of the metamorphic fluids at Honeymoon Well. The location of the sulphide deposits immediately adjacent to major shear zones that bound the ultramafic complex allowed the infiltration and passage of large volumes of metamorphic fluids. During the lowermost greenschist facies metamorphism this caused semi-regional scale metasomatism of the ultramafic complex.

Ni sulfide/Ti 50Ni 50 electrode with the superelasticity

Ni sulfides layers were formed on the surface of a Ti 50Ni 50 alloy by reacting sulfur with a Ni film deposited on the alloy, and then microstructures, transformation behavior, shape memory characteristics, superelasticity and electrochemical properties were investigated. When a Ni film deposited on a Ti 50Ni 50 alloy was annealed under the sulfur pressure of 100 kPa at 623 K, sulfides layers consisted of NiS and NiS 2 were formed. When annealing was made at 648 K with annealing time less than 0.9 ks, sulfides layers with a mixture of NiS and NiS 2 were formed, while only NiS 2 was formed when it was made for 1.8 ks. When annealing was made at 673 K with annealing time longer than 0.9 ks, only NiS 2 was formed. With raising annealing temperature and prolong annealing time, NiS changed into NiS 2 accompanied with a morphological change from a particulate-like to a dense film-like. A Ti 50Ni 50 alloy with surface NiS 2 layer showed the two-stage B2–R–B19′ transformation behavior, the shape memory effect and a partial superelasticity with a superelastic recovery ratio of 78%. NiS 2 cathode showed a clear discharge behavior with multivoltage plateaus induced by intermediate reaction products; NiS and Ni 3S 2. The initial discharge capacity was 743 mA h g −1 corresponding to 85% of theoretical capacity and 65% of capacity duration is obtained at 20th discharge.

The sulfide ore looping oxidation process: An alternative to current roasting and smelting practice

This novel method utilizes the reactions of metal sulfides and metal oxides. It is applicable to single-metal systems such as Mo, Cu, Co, Ni, Fe, and Zn individual sulfides and to mixed sulfides such as chalcopyrite and Mo/Fe. In addition to primary ores, waste stream products such as spent catalysts can be effectively processed. The benchmark work done on MoS2/MoO3 resulted in an MoO2 product with less than 0.095 wt.% sulfur. Other sulfide concentrate materials showed similar results. In the first stage of the looping process, a highly concentrated SO2 off-gas stream is produced that could be directed to an acid plant or converted to liquid. The products from the first process step can be directed down line for further processing or can be used as is. In the second step of looping oxidation, the product is oxidized back to its fully oxidized state and is mainly looped back to drive the oxidation process in the first reaction. There are also several opportunities for energy recovery and conversion, making looping oxidation an energy-efficient process.

MD//Mo and MD//W [MD=Mn, Fe, Co, Ni, Cu and Zn] promotion via spillover hydrogen in hydrodesulfurization

The promotion effect of Mn, Fe, Co, Ni, Cu and Zn sulfides on the hydrodesulfurization (HDS) activity of Mo and W sulfides, under experimental conditions like industrial ones, using staked beds, was studied. Synergism between staked beds in all the studied pairs, with a magnitude that leads a volcano curve with a maximum in Co and Ni sulfides was detected. Promotion was well explained by the formation of spillover hydrogen (Hso) in the first bed (in which Mn, Fe, Co, Ni, Cu or Zn sulfides supported on γ-Al2O3 were located) that migrate to the second bed (in which Mo or W sulfides supported on γ-Al2O3 were located), 5 mm below.

PGE geochemistry and Re–Os dating of massive sulfide ores from the Baimazhai Cu–Ni deposit, Yunnan province, China

The Baimazhai deposit in Yunnan Province is one of the largest Cu–Ni sulfide deposits hosted in mafic–ultramafic intrusions in China. Concentrations of platinum-group elements (PGE) in massive sulfide ores and host rocks from Baimazhai were determined by using inductively coupled plasma mass spectrometry (ICP-MS) following nickel sulfide fire assay pre-concentration. The results show that the total PGE (ΣPGE) are quite low, decreasing gradually from central massive ores (78.2–556 ppb) to olivine pyroxenite (0.472–67.0 ppb), gabbro (0.847 ppb) and, websterite (0.76–0.809). The intruded lamprophyre dykes also show low ΣPGE (2.98–4.07 ppb). The ΣPGE exhibit obvious positive correlations with Au, Ni and Cu contents. Primitive mantle normalized PGE patterns of the massive Cu–Ni ores are of the Pt–Pd type with relatively steep and trough-like patterns, which are similar to those of the host rocks. In addition, the Pt/Pd and Cu/Pd ratios of the massive sulfide ores are similar to those of olivine pyroxenite, gabbro and websterite. These characteristics suggest that sulfides in the massive ores are of magmatic origin, co-genetic with their host rocks. The relatively high Pt/Pd ratios of the Baimazhai massive sulfide ores (averaging 0.83) and their host rocks imply that the Baimazhai sulfides formed in a single sulfide saturation event, but not through multiple sulfide injections. High Ir contents (0.77–5.52 ppb, averaging 2.35 ppb) and dramatically variable Pd/Ir ratios (4.76–296, averaging 138) of the massive sulfide ores suggest that the Baimazhai sulfide ores might have suffered significant late stage hydrothermal alteration. The Baimazhai massive sulfide ores yield a Re–Os isochron age of 259 ± 20 Ma (MSWD = 0.025), which is the same as the major eruption stage of the Emeishan large igneous province and the Baimazhai intrusion, further supporting their magmatic origin. The initial 187Os/ 188Os value of 0.456 ± 0.026 indicates that crustal contamination has played an important role during mineralization. The proportion of crust-derived Os is calculated to be more than 30%.

Prediction of hidden Au and Cu–Ni ores from depleted mines in Northwestern China: four case studies of integrated geological and geophysical investigations

Integrated geological and geophysical investigations were carried out in 26 active mines in Northwestern China during the period 2001–2006 to explore for hidden extensions of known ore bodies and to search for new mineralization. This paper presents four case studies from northwest China: the Kuoerzhenkuoa volcanogenic hydrothermal gold deposit, the Nanjinshan breccia-associated gold deposit, the Duolanasayi deposit, associated with a ductile–shear zone, and the Hulu magmatic Cu–Ni sulfide deposit. In these studies, detailed mine-scale geological studies were carried out to determine the location and controls on ore formation. Based on these investigations and a review of previous exploration data, genetic models for the deposits were evaluated, and specific new targets were generated. These target areas were tested with surface geophysical surveys using the Stratagem EH4 system, a hybrid-source magnetotellurics (MT) method. Analysis of the data obtained in the surveys identified geophysical target anomalies that were subsequently drilled. Many of these test holes demonstrate the presence of Au and Cu–Ni mineralization. Evaluation of the geological models was crucial in developing conceptual targets as a basis for surface geophysical surveys. These models established the most likely target areas where Au and Cu–Ni mineralization could occur, but they did not define the limits or the geometries of the mineralized zones. Hybrid MT surveys played an important role in defining the location of buried mineralized systems and in testing the validity of the conceptual targets. The resistivity cross-sections obtained by imaging the MT data established the boundaries and geometries of the host rocks, including the distribution of lithology, structures, alteration, and mineralization. The four case studies in this paper show how this integrated geological and geophysical approach was used successfully to discover hidden mineral deposits.

An oceanic composition on early and today's Enceladus

The oceanic composition on Saturn's moon Enceladus is evaluated through calculations of thermochemical equilibria at hydrothermal and freezing settings. Conditions of rock alteration are constrained from assumptions and models for the moon's interior composition and thermal evolution, and from the composition of Enceladus' plume. Results show that an early ocean was an alkaline Na+‐Cl−‐HCO3− solution. Underlying altered rocks consisted of Mg‐phyllosilicates, magnetite, Fe and Ni sulfides, and carbonates. Subsequent freezing of oceanic water caused the deposition of a NaCl hydrate, Na, K and Ca carbonates, and the formation of a salt‐free ice shell. If an aqueous phase exists on today's Enceladus, it could consist of eutectic Na‐Cl‐HCO3− brine that at least locally decouples the ice shell and facilitates tidal heating. A lack of firm detection of Na and Cl at Enceladus is consistent with the accumulation of salts at the ice‐rock boundary and implies the plume formation via sublimation in the ice shell.

Palaeoproterozoic Ni–Cu–PGE mineralisation in the Shakespeare intrusion, Ontario, Canada: a new style of Nipissing gabbro-hosted mineralisation

The 2217 Ma Shakespeare intrusion is part of the extensive 2˙2 Ga Nipissing gabbro suite and is hosted within 2˙45–2˙2 Ga Huronian Supergroup metasediments in the Southern Province of the Canadian Shield, close to the border with the Superior Province. The Shakespeare intrusion is a complex differentiated sill approximately 14 km in strike length and approximately 300 to 430 in thickness. It comprises two distinct magmatic packages: (a) a Lower Group composed of unmineralised pyroxenite and gabbro, and (b) an Upper Group composed of Ni–Cu–PGE mineralised melagabbro, quartz gabbro, and biotite quartz gabbro-diorite. The Shakespeare intrusion formed from a tholeiitic parental magma. All of the rocks in the intrusion are enriched in highly incompatible lithophile elements (HILE: Cs, Rb, U, Th, Nb, Ta, LREE) relative to moderately incompatible lithophile elements (MILE: Zr, Ti, HREE) and are strongly depleted in Nb and Ti relative to elements of similar incompatibility. These geochemical characteristics suggest that the Shakespeare magma underwent extensive degrees of upper crustal contamination before emplacement. Although other parts of the Nipissing gabbro suite exhibit similar geochemical characteristics, the Shakespeare intrusion is more enriched in HILE and more strongly depleted in Nb–Ti, and therefore appears to have undergone greater degrees of crustal contamination. Heavily disseminated to patchy net-textured (10–15%) Fe–Cu–Ni sulphides (pyrrhotite–chalcopyrite–pentlandite) occur in the upper portion of the melagabbro of the Upper Group, near and at the contact with the overlying quartz gabbro, and in melagabbro dykes. This is a new style of magmatic Ni–Cu–PGE mineralisation in the Nipissing gabbro suite. The mineralised zone contains abundant inclusions of quartzite, blue quartz eyes and rare diorite. The ores have compositions consistent with having been derived from the Shakespeare magma and to have equilibrated at moderate magma/sulphide ratios (R=500–1000). The Ni–Cu–PGE mineralisation in the Shakespeare deposit appears to have resulted from the following processes: (a) generation of Nipissing magmas via partial melting of mantle peridotite, (b) contamination of Nipissing magmas by continental crust during ascent, (c) introduction and crystallisation of contaminated but sulphide–undersaturated magmas into the Shakespeare intrusion, forming the Lower Group, (d) additional, apparently relatively local, crustal contamination and sulphide saturation resulting in the incorporation of abundant xenoliths of country rocks and the generation of moderate amounts of Ni–Cu–(PGE) sulphide melt, and, (e) introduction of the xenoliths and sulphide-bearing magma into the Shakespeare intrusion, forming the Upper Group, with heavier sulphides settling at the base of the new crystallisation floor, resulting in low-moderate R factor values.

Fabrication of superelastic NiS/TiNi electrode/current collector materials

Ni sulfides were formed on a Ni-deposited Ti–50.0Ni(at) alloy by annealing under a sulfur pressure of 100 kPa at 673 K for 0.36 ks. Martensitic transformation, superelasticity and electrochemical properties were characterized using different techniques. Ni sulfides consisting of NiS and NiS2 of thickness 0.8 μ m were formed by a reaction between Ni and S. Some spherical particles and pores were found in the sulfides. A Ti–50.0Ni alloy with Ni sulfide surface layers showed a two-stage B2–R–B19′ transformation behavior. A partial superelasticity with a superelastic recovery ratio of 78% found in a current collector showed a clear discharge behavior with a voltage plateau between 1.3–1.6 V. Discharge capacities of the Ni sulfide cathode decreased largely from 700 to 510 mAh(g-NiS2)−1 with increasing number of cycles up to 3, above which it decreased gradually.

A review of the Cu–Ni sulphide deposits in the Chinese Tianshan and Altay orogens (Xinjiang Autonomous Region, NW China): Principal characteristics and ore-forming processes

Several Cu–Ni sulphide deposits and occurrences have recently been discovered along parallel deep faults in the Chinese Tianshan and Altay orogenic belts, Xinjiang Province, NW China. The Kalatongke and several other Cu–Ni mineralized intrusions are located along the Irtysh fault, which separates the Altay orogenic belt from the Junggar basin. The Huangshan, Huangshandong, Xiangshan, Tudun, Erhongwa, Tula’ergen, and Hongling deposits occur along the Kanggurtag suture, which separates the Jueluotage orogenic belt from the Turpan-Hami (Tuha) basin. The Baishiquan, Tianyu, and Tianxiang deposits are located along the Arqikekuduke fault, which separates the Jueluotage orogenic belt from the Central Tianshan Precambrian terrane. The Poyi, Poshi, and Luodong deposits are located along the Baidiwa fault, which separates the Central Tianshan Precambrian terrane from the Beishan Paleozoic rift. Re–Os dating of Cu–Ni sulphide ores reveals that these Cu–Ni ore belts formed in a narrow age range of 298–282 Ma. This age range is about the same as those of associated intrusions and dykes dated by the SHRIMP zircon U–Pb method. Tectonic and geochronological constraints suggest that the amalgamation of continental blocks mainly occurred during the Late Carboniferous in the Central Asian orogenic belt. Large-scale hydrothermal and magmatic metallogenesis in the region occurred during post-collisional stages of Latest Carboniferous to Early Permian age. The Cu–Ni sulphide deposits are part of this metallogenic event. The Cu–Ni orthomagmatic sulphide deposits in northern Xinjiang are represented by: (1) net-textured type deposits by segregation of a Cu–Ni metal sulphide melt and (2) magma conduit type. Some mafic–ultramafic suites exhibit lithological zoning caused by strong differentiation. Stratiform orebodies are hosted by ultramafic rocks at the base of the magma chamber. Good examples are the Kalatongke, Huangshandong, and Poshi deposits. Others, such as the Xiangshan, Baishiquan, Tianyu, and Tula’ergen deposits, are hosted by magma conduits, consisting of peridotite, troctolite, and pyroxenite. These ultramafic rocks either occur within faults or are surrounded by gabbroic and dioritic intrusions. These two types of orthomagmatic Cu–Ni sulphide deposits are also distributed along the same ore belts. For instance, the differentiated sill-related Huangshandong deposit co-exists with the magma conduit type Tula’ergen deposit in the Jueluotage orogenic belt. Orthomagmatic Cu–Ni sulphide deposits in northern Xinjiang formed during post-collisional extension and are possibly related to a Late Carboniferous–Early Permian mantle plume event. The mafic–ultramafic suites and associated Cu–Ni deposits are commonly accompanied by dyke swarms and are characterized by elongated outcrops occurring along parallel E–W-trending regional faults. These mafic–ultramafic suites and accompanying dyke swarms are generally fractionated, implying that they were feeders of presently eroded flood basalts.

Outokumpu revisited: New mineral deposit model for the mantle peridotite-associated Cu–Co–Zn–Ni–Ag–Au sulphide deposits

The metaturbidites of the Palaeoproterozoic Jormua–Outokumpu thrust belt in eastern Finland enclose m- to km-scale ultramafic massifs that are distributed over an area of more than 5000 km 2. These bodies, which almost entirely consist of highly depleted mantle peridotites (now metaserpentinites and metaperidotites), are intimately associated with massive to semimassive, polymetallic Cu–Co–Zn–Ni–Ag–Au sulphide deposits that sustained mining in the region between 1913 and 1988. Currently, one deposit (Kylylahti) is proceeding into a definitive feasibility study emphasising the renewed economic interest for Outokumpu-type deposits. The origin of these Outokumpu-type Cu–Co–Zn–Ni–Ag–Au deposits is now re-interpreted to be polygenetic. First, their formation requires deposition of a Cu-rich proto-ore within peridotitic sea floor at ∼ 1950 Ma. Close modern analogues to the proto-ore setting include, for example, the Logatchev and Rainbow fields at the Mid-Atlantic Ridge, where venting of high-T–low-pH hydrothermal fluid resulted in accumulations of Cu–Zn–Co–Ag–Au sulphides on serpentinised ultramafic seafloor. Second, the Ni-rich composition of Outokumpu sulphide ores calls for a separate source for nickel: Some 40 Ma after the deposition of the Cu-rich proto-ore – concomitant with the obduction of the ultramafic massifs – disseminated Ni sulphides formed through chemical interaction between obducting peridotite massifs and adjacent black schists. This process was related to listwaenite–birbirite type carbonate–silica alteration at margins of the ultramafic massifs. Due to this alteration, silicate nickel was released from the primary Fe–Mg silicates and redeposited as Ni sulphides in the alteration fringes of the massifs. We propose that syntectonic mixing of these two “end-member” sulphides, i.e., the primary Cu-rich proto-ore and the secondary Ni-sulphide disseminations, resulted in the uncommon metal combination of the Outokumpu-type sulphides. Late tectonic solid-state re-mobilisation, related to the duplexing of the ore by isoclinal folding, upgraded the sulphides into economic deposits.