Ni Ores Research Articles

Nickel distribution and speciation in rapidly dehydroxylated goethite in oxide-type lateritic nickel ores: XAS and TEM spectroscopic (EELS and EFTEM) investigation

The distribution of Ni in four lateritic Ni-goethites that were rapidly dehydroxylated to form hematite by shock heating at 340/400°C and 800°C for 30 min was investigated using synchrotron X-ray diffraction (SXRD), TEM spectroscopy (EELS and EFTEM) and synchrotron X-ray absorption spectroscopy (XAS). The Ni K-edge EXAFS results for non-heated samples showed three distinct Ni–Fe shells, including two edge-sharing (R Ni–Fe ∼ 3.01 and R Ni–Fe ∼ 3.22 Å) and a double corner-sharing (R Ni–Fe ∼ 3.52 Å) complex for most of the samples. These interatomic distances are indicative of Ni substituting for Fe in goethite, which has resulted in an expansion in the goethite structure along the a-axis direction and a contraction along the b-axis direction. Ravensthorpe Ni goethite was considerably different from the other goethites, with two Ni–O interatomic lengths (R Ni–O ∼ 2.04 and 2.46 Å), an edge-sharing (R Ni–Fe ∼3.04 Å) and a corner-sharing (R Ni–Fe ∼ 3.56 Å) complex. The R Ni–O ∼ 2.46 Å bond length is not indicative of Ni substituting for Fe in goethite, nor is it associated with single or multiple scattering events in NiO, Ni(OH)2 or Ni substituting for Fe in Fe oxides. The corresponding Ni K-edge EXAFS results for 340/400°C and 800°C heated samples (i.e. hematite) were very similar. Four distinct metal neighbours correspond to Fe/Ni in face-sharing (R Ni–Fe ∼ 2.87–2.91 Å) and three different corner-sharing complexes (R Ni–Fe ∼ 3.37– 3.41 Å, R Ni–Fe ∼ 3.62– 3.64 Å and R Ni–Fe ∼ 3.92– 4.09 Å) represent Ni substituting for Fe in hematite. The fourth shell is indicative of an inner sphere surface complex. EFTEM maps for Ni in goethite are consistent with the formation of a surface complex as they provide evidence for clustering of Ni on the surface of neoformed hematite crystals. There was no evidence from EXAFS or SXRD supporting the formation of discrete Ni phases (e.g. NiO) as a result of shock heating. Therefore, for Ni-goethites subjected to shock heating at 800°C (i.e. high-temperature dehydroxylation to hematite), most of the Ni is retained in the structures of the neoformed hematites, whereas some of the Ni migrates to the surface of the neoformed hematite where it forms a surface complex. During acid dissolution (e.g. heap leaching) of oxide-type lateritic Ni ores, Ni on the hematite surface is more accessible to acid solutions; therefore, these results may provide a basis for more efficient extraction methods for Ni in oxide-type lateritic Ni ores, as well as providing information on the possible redistribution of Ni in heated goethite-rich soils.

A study on the recovery of Pt−Pd and MgO from Yunnan Cu–Ni ore in China

The combination of flotation and hydrometallurgy had been introduced to dressing the ore in Yunnan, which involves Pt and Pd metallic minerals and serpentines containing high MgO, for recovering both simultaneously, which may be a new try in China. Based on experiments of leaching of Mg2+ and Fen+ and flotation of copper minerals and nickel minerals, two processing flowsheets are reported. One flowsheet is flotation leaching with sulphuric, and the other is leaching flotation of the residue. Generally, the first flowsheet is better in which recoveries of Cu, Ni, Pt and Pd are all over 80%, and MgO ratio of leaching is 98·81%, while the second is better in commercial and practical consideration.

Mobility of metals in nickel mine spoil materials

Abstract An understanding of the biogeochemical behaviour of metals in mine spoil materials is a prerequisite to rehabilitate Ni mining sites. The objective of this study was to characterize the fate of metals in different Ni ore spoil materials as influenced by hydrological conditions and fertilisation practices. In tropical ultramafic complexes, the different stages of lateritic weathering lead to two types of ores, and therefore, to two spoil types. They are mainly either a clay-rich saprolite, so-called “garnierite”, enriched in phyllosilicates, or a limonitic material, enriched in Fe oxides. Lysimeter columns were designed to monitor leaching waters through both spoil materials. The garnieritic spoil released higher concentrations of Mg (mean = 2.25 mg L −1 ), Ni (0.39 mg L −1 ) and Cr (1.19 mg L −1 ) than the limonitic spoil (Mg = 0.5 mg L −1 ; Ni = 0.03 mg L −1 and Cr = 0.25 mg L −1 ). Chromium was mainly in an anionic form in leaching solutions. As exchangeable pools of Cr(VI) in limonite (980 mg kg −1 of KH 2 PO 4 -extractable Cr) are considerable its release in water may still occur in the case of a pH increase. In mixed spoil, metal concentrations were almost as low as in the limonitic one. The effect of mineral-N fertilisation was a strong release of cations (Ni, Mg) into the leachate. Phosphate amendment did not affect the soil solution composition under experimental conditions.

Natural radioactivities in iron and nickel ores imported into Japan and the dose assessmentfor workers handling them

Japan imports Fe and Ni ores from abroad for use as industrial raw materials inthe manufacture of industrial products like stainless steel. Some of these oresmight contain high levels of radioactivity, and then workers handling them wouldbe exposed to radiation without being aware of it. Activity concentrations inthese ores should be measured to evaluate the radiation exposure of workers.In this study, Fe and Ni ores used as industrial raw materials were collectedfrom iron and steel companies, and the activity concentrations of the 238U series, the 232Th seriesand 40K in these ores were determined using inductively coupled plasma mass spectrometry(ICP-MS) and gamma ray spectrometry. The activity concentrations of the 238U series, the 232Th seriesand 40K in these ores samples were lower than the International Atomic Energy Agency (IAEA)values. The doses to workers handling these ores were estimated using methods for doseassessment given in a report by the European Commission. In each scenario, amaximum value of the annual effective dose to workers was estimated to be about6.8 × 10−6 Sv, which was lower than intervention exemption levels (annual dose1.0 × 10−3 Sv) given in International Commission on Radiological Protection (ICRP) Publication82.

Laser-induced breakdown spectroscopy for on-line sulfur analyses of minerals in ambient conditions

Different options of laser-induced breakdown spectroscopy arrangements for on-line analyses of sulfur in minerals in ambient conditions have been investigated. Depending on the sulfur concentration and the sample type, the following conditions appear as optimal: for concentration values of 20–30% (for example Cu and Ni ores, gypsum, anhydrite, and barite) it is the single-pulse option with emission in near infra-red; for concentration values of 5–10% it is the double-pulse option with emission in the green; for concentration values down to 0.2% (for example in coal) it is the single-pulse option in near VUV with a N 2 filled spectrometer.

Petrogenetic modeling of three mafic–ultramafic layered intrusions in the Emeishan large igneous province, SW China, based on isotopic and bulk chemical constraints

Mafic–ultramafic layered intrusions align along a N–S trending fault zone in the central part of the late Permian Emeishan large igneous province, SW China. We present major and trace element and clinopyroxene Sr, Nd, Pb and O isotopic compositions of three representative mafic–ultramafic layered intrusions, the Panzhihua gabbro intrusion that hosts V–Ti–Fe ores, the Limahe peridotite intrusion that hosts Cu–Ni ores, and the Xinjie peridotite and pyroxenite intrusion that hosts both V–Ti–Fe and Cu–Ni–PGE ores. The Panzhihua intrusion is more evolved, and rich in Fe and Ti, whereas the Limahe ore-bearing rocks are rich in Mg, and the unmineralized gabbro-diorites are rich in Ca and Al. Both the petrology and geochemistry of the Xinjie intrusion are transitional between those of the two other intrusions. Petrography and geochemistry indicate that there is a large amount of cumulus magnetite and ilmenite in the Panzhihua and Xinjie intrusions. This has changed the ratios of elements normally considered incompatible in basaltic systems (e.g., La/Zr and La/Nb), because high field strength elements (Zr, Hf, Nb and Ta) show significant partitioning into the magnetite structure [Klemme, S., Günthe, D., Hametner, K., Prowatke, S., Zack, T., 2006. The partitioning of trace elements between ilmenite, ulvospinel, armalcolite and silicate melts with implications for the early differentiation of the moon. Chemical Geology 234, 251–263]. The parental magma of the Panzhihua intrusion is estimated to be ferropicrite. Thus, in combination with their low δ18O values (<6‰), we infer that the generation of the Panzhihua intrusion could be ascribed to ascending plume-derived magma contaminated by a Fe- and Ti-rich lithospheric mantle source. In contrast, negative εNd(t) values (−0.6 to −4.13), high δ18O values (>6‰), radiogenic Pb isotopic compositions, and high La/Nb and La/Ta ratios imply that the Limahe intrusion was derived from mantle-plume magmas contaminated by granitic crustal materials. The δ18O values (4.8–8.0‰) and Pb isotope ratios suggest that the Xinjie intrusion may result from plume-derived magmas variably contaminated by basic crustal materials in situ. The formation of the different types of the magmatic-ore deposits within the Emeishan LIP may be mainly attributed to their different sources.

Composition and origin of the Çaldağ oxide nickel laterite, W. Turkey

The Caldag nickel laterite deposit located in the Aegean region of W. Turkey contains a reserve of 33 million tons of Ni ore with an average grade of 1.14% Ni. The deposit is developed on an ophiolitic serpentinite body which was obducted onto Triassic dolomites in the Late Cretaceous. The deposit weathering profile is both laterally and vertically variable. A limonite zone, which is the main ore horizon, is located at the base of the profile. A hematite horizon is located above the limonite, which in the south of the deposit is capped by Eocene freshwater limestones and in the north by a siliceous horizon. The deposit is unusual in lacking a significant saprolite zone with little development of Ni-silicates. The boundary between the limonite zone and serpentinite below is sharp with a marked decrease in concentrations of MgO from 13 to 1 wt.% over a distance of 2 mm representing the ‘Mg discontinuity’. Ni concentrations within goethite, the main ore mineral, reach a maximum of ~3 wt.% near the base of the limonite zone. Silica concentrations are high throughout most of the laterite with up to 80 wt.% silica in the upper portion of some profiles. The combination of a serpentinite protolith and a high water table at Caldag, in association with an aggressive weathering environment in a tropical climate, resulted in the formation of an oxide-dominated deposit. The precipitation of silica may coincide with a change in climate with silica precipitation linked to an increase in seasonality. Additional variations within profile morphology are attributed to transportation during and after laterite development as a result of faulting, pocket type laterite formation and slumping, each of which produces a contrasting set of textural and geochemical features.

Trace metal and As solid-phase speciation in sulphide mine tailings – Indicators of spatial distribution of sulphide oxidation in active tailings impoundments

Abstract Redistribution of potentially harmful metals and As was studied based on selective extractions in two active sulphide mine tailings impoundments in Finland. The Hitura tailings area contains residue from Ni ore processing, while the Luikonlahti site includes tailings from the processing of Cu–Co–Zn–Ni and talc ores. To characterize the element solid-phase speciation with respect to sulphide oxidation intensity and the water saturation level of the tailings, drill cores were collected from border zones and mid-impoundment locations. The mobility and solid-phase fractionation of Ni, Cu, Co, Zn, Cr, Fe, Ca, Al, As, and S were analysed using a 5-step non-sequential (parallel) selective extraction procedure. The results indicated that metal redistribution and sulphide oxidation intensity were largely controlled by the disposal history and strategy of the tailings (sorting, exposure of sulphides due to delayed burial), impoundment structure and water table, and reactivity of the tailings. Metal redistribution suggested sulphide weathering in the tailings surface, but also in unsaturated proximal areas beside the earthen dams, and in water-saturated bottom layers, where O 2 -rich infiltration is possible. Sulphide oxidation released trace metals from sulphide minerals at both locations. In the Hitura tailings, with sufficient buffering capacity, pH remained neutral and the mobilized metals were retained by secondary Fe precipitates deeper in the oxidized zone. In contrast, sulphide oxidation-induced acidity and rise in the water table after oxidation apparently remobilized the previously retained metals in Luikonlahti. In general, continuous disposal of tailings decreased the sulphide oxidation intensity in active tailings, unless there was a delay in burial and the reactive tailings were unsaturated after deposition.

Comparative bioaccumulation of trace elements between Nautilus pompilius and Nautilus macromphalus (Cephalopoda: Nautiloidea) from Vanuatu and New Caledonia

The concentrations of 16 trace elements were investigated and compared for the first time in the digestive and excreting tissues of two Nautilus species (Cephalopoda: Nautiloidea) from two geologically contrasted areas: (1) N. macromphalus from New Caledonia, a region characterized by its richness in nickel ores and its lack of tectonic activities and (2) N. pompilius from the Vanuatu archipelago showing high volcanic and tectonic activities. In both Nautilus species, results clearly highlighted that the digestive gland played a key role in the bioaccumulation and storage of Ag, Cd, Ce, Co, Cu, Fe, La, Nd, V, and Zn whereas As, Cr, Mn, Ni, Pb, and Se were accumulated in a greater extent in the excreting tissues (i.e. pericardial and renal appendages). Despite contrasting environments, no significant difference ( p<0.05) was found between the two Nautilus species in the concentrations of most of the essential and non-essential elements, including Ni and associated metals in Ni ores (i.e. Co and Mn). As nautilus lives on the outer shelf of barrier reefs, these results strongly support the hypothesis that the New Caledonian lagoon traps the major amount of the trace elements derived from natural erosion and the intense mining activities conducted on land. In contrast, the concentrations of the rare earth elements (Ce, La, and Nd) were significantly higher in N. pompilius than in N. macromphalus, probably as a result of the local enrichment of Vanuatu waters by specific environmental processes, such as volcanism or upwelling.

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.

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.

Geology, petrology and geochemistry of the Baishiquan Ni–Cu-bearing mafic–ultramafic intrusions in Xinjiang, NW China: Implications for tectonics and genesis of ores

The Baishiquan mafic–ultramafic intrusions associated with magmatic Ni–Cu–(PGE) sulfide deposit are located in the northern margin of the Central Tianshan Block in northern Xinjiang, NW China. The intrusions consist of olivine pyroxenite, pyroxene peridotite, troctolite, hornblendite, gabbro and diorite. The peridotite and pyroxenite are the main host rock for the Cu–Ni ores. The crystallization sequence of the intrusions is generally as follows: olivine – plagioclase – orthopyroxene – clinopyroxene – amphibole – biotite. The chemical compositions of the rocks have SiO 2 (38–51%), MgO (7–32%) and Al 2O 3(4.2–18%), and relatively low TiO 2(0.32–0.96%) and K 2O+Na 2O (0.06–3.4%). In general, they are characterized by enrichment in large ion lithophile elements (LILE, e.g., Rb, Sr, K, U, Pb and Th) and light rare earth elements (LREE), depletion in high field strength elements (HFSE, e.g., Nb, Ta, Ti and P) relative to primitive mantle and MORB. The absolute PGE abundances are low. Sr–Nd–Pb isotope data suggest a mixture of multi-components of mantle sources, including depleted asthenospheric mantle end-member with MORB-like isotopic signature and EMIIend-member related to subducted oceanic crust. These geochemical characteristics indicate that the parental magma was high-magnesium tholeiitic. Sulfur had reached saturation and immiscible sulfides droplets segregated from silicate magmas before their emplacement. Contamination by a small amount of subducted-related components combined with crystal fractionation resulted in the Ni–Cu-(PGE) mineralization.

Geochemical and hydrodynamic constraints on the distribution of trace metal concentrations in the lagoon of Nouméa, New Caledonia

Seawater samples were collected in the lagoon of Nouméa (southwest New Caledonia) along two transects from eutrophic coastal bays to the oligotrophic barrier reef. Land-based emissions to the lagoon were measured with dissolved and particulate concentrations of chromium (Cr) and nickel (Ni), used as tracers of both terrigenous and industrial (Ni ore treatment) activities, as well as dissolved and particulate concentrations of zinc (Zn), used as a tracer of urban effluents. The spatial variability of metal concentrations was related to geochemical and hydrodynamic conditions, i.e., respectively: (1) natural and anthropogenic emission sources, and chemical processes occurring in the water column; and (2) water residence times. The parameter used to describe the residence time of water masses was the local e-flushing time, i.e. the time required for a tracer mass contained within a given station to be reduced by a factor 1/ e. High metal concentrations were found in coastal areas (up to 9000 ng dissolved Ni L −1), and steeply decreased with distance from the coast (down to 101 ng dissolved Ni L −1 near the barrier reef) to reach levels similar to those found in remote Pacific waters, suggesting a rapid renewal of waters close to the barrier. Distributions of metals in the lagoon are controlled upstream by land-based emission sources and later chemical processes. Then hydrodynamics constrain metal distributions, as shown by the observed relationship between local e-flushing times and the spatial variability of metal concentrations. In addition, a change in the direction of prevailing winds yielded a decrease of dissolved metal concentrations at the same site by a factor of 2.5 (Cr and Ni) and 2.9 (Zn). It is suggested that the residence time is a key parameter in the control of elemental concentrations in the lagoon waters, as much as land-based emission sources.

40Ar– 39Ar age, geochemistry and Sr–Nd–Pb isotopes of the Neoproterozoic Lengshuiqing Cu–Ni sulfide-bearing mafic–ultramafic complex, SW China

The Lengshuiqing Cu–Ni sulfide deposit of the Yanbian area in Sichuan Province, SW China, is hosted by relatively small mafic–ultramafic bodies that intruded Mesoproterozoic metavolcanic rocks and schists. The mafic–ultramafic complex is mainly composed of the olivine-hornblende pyroxenite and hornblende gabbro units. 40Ar/ 39Ar age, elemental and Sr–Nd–Pb isotopic results of the complex are reported in this paper. 40Ar/ 39Ar dating of hornblende yielded an age of 821 ± 1 Ma for the mafic–ultramafic complex. This age is similar to the SHRIMP U–Pb zircon age of 825 ± 12 Ma for the adjacent Gaojiacun mafic–ultramafic complex. This suggests that the Lengshuiqing mafic–ultramafic complex originated from Neoproterozoic mafic magma. The olivine-hornblende pyroxenite unit is characterized by high MgO contents (24.25–28.08%), Mg # values (74.5–78.0) and compatible elements (Cr = 1179–2336 ppm, Ni = 732–1303 ppm), low ΣREE (19.5–44.6 ppm) and other incompatible element contents. The hornblende gabbro unit has MgO = 7.32–12.51%, Mg # = 55.0–69.3, Cr = 37.7–1131 ppm, Ni = 50.0–243 ppm and ΣREE = 37.2–75.4 ppm. Most of the rocks are moderately enriched in LREE ((La/Yb) N = 2.28–7.67), and significantly depleted in Nb–Ta ((Nb/La) PM = 0.17–0.47; (Ta/La) PM = 0.19–0.58), with slightly moderately positive Eu anomalies ( δ Eu = 0.95–1.65). The trace element feature of the ore-bearing samples is similar to that of the rocks in the complex. The variations in major and trace elements can be well explained by magma crystal fractionation. Isotopically, the rocks in Lengshuiqing mafic–ultramafic complex are characterized by low 87Sr/ 86Sr(i) (0.7039–0.7044), positive ɛ Nd(i) (+2.2 − +4.3) and low radiogenic Pb values ( 206Pb/ 204Pb(i) = 17.382–17.913, 207Pb/ 204Pb(i) = 15.518–15.578, 208Pb/ 204Pb(i) = 37.227–38.019). The ores also have positive ɛ Nd(i) (+2.4 − +5.4), and low radiogenic Pb values ( 206Pb/ 204Pb(i) = 17.256–17.733, 207Pb/ 204Pb(i) = 15.484–15.555, 208Pb/ 204Pb(i) = 36.924–37.665). All the samples exhibit positive ɛ Nd(i) values, suggesting that their parental magmas were derived from a long-term depleted asthenospheric mantle. The relatively large variations in 87Sr/ 86Sr(i) of the ores (0.7012–0.7046) could be ascribed to the interaction between magma and country rocks. A good positive correlation between Nb/La and Nb/Th reveals that crustal assimilation was involved in their genesis. This contamination resulted in the observed depletion of Nb and Ta in rocks and ores. The crustal contamination and fractional crystallization, similar to the process of magmatic assimilation and fractional crystallization (AFC), are thus critical for the formation of the Lengshuiqing Cu–Ni ore deposit. The Neoproterozoic Lengshuiqing Cu–Ni sulfide-bearing mafic–ultramafic intrusions formed in an intraplate continental rift, which was most likely related to a mantle plume underneath the supercontinent Rodinia.

Dehydroxylation and dissolution of nickeliferous goethite in New Caledonian lateritic Ni ore

Goethite is a major constituent in ferruginous soils in a lateritic nickel deposit on the Koniambo massif in New Caledonia, and dehydroxylation of nickeliferous goethite may occur naturally due to fire and during the processing of lateritic Ni ore. Goethite started to alter to hematite in 2 h of heating at 230–250 °C and had completely altered to hematite at 340 °C and higher temperatures. For most heated samples the rate of dissolution of Fe in 1 M HCl followed the cube root equation with a single straight line describing the data, however for samples where both goethite and hematite were present the data did not conform to this equation. There was an approximately 7 fold increase in the rate of dissolution for samples heated to 340 °C which can be accounted for by the increase in surface area (2-fold) due to the development of micropores and the increase of structural defects in poorly ordered hematite structures (protohematite and hydrohematite) (3.5-fold) formed by partial dehydroxylation of goethite. For heated samples Ni, Cr, Al, Co and Mn showed congruent dissolution with iron indicating uniform incorporation of these metals in the structures of the iron oxides and complete retention of these metals in crystals during the goethite to hematite transition. V and Cu showed only partial dissolution (i.e. noncongruent dissolution) indicating that some V and Cu may be associated with another less soluble mineral (e.g. ilmenite).

Sub-microscopic phases in the bon accord Ni ore body, Barberton, South Africa

Sub-microscopic phases in the bon accord Ni ore body, Barberton, South Africa

Studies concerning nickel electrowinning from acidic and alkaline electrolytes

High-purity nickel is mainly produced by electrowinning from sulphate and chloride solutions in the presence of high concentrations of boric acid as a buffer. The generally used pH is in the range 3–4 if Ni concentration in the electrolyte is higher than 10 g/l. Lower Ni concentration, as in the case of either industrial liquid effluents and in situ low grade Ni ore leaching, needs pH values ranging from 10 to 11 in order to hinder the evolution of hydrogen. Ni electrowinning from acidic and alkaline solutions is studied to determine in both cases the best operative conditions. Particularly Ni concentration, additive presence, pH values, temperatures, cathode material, current density and voltage, to be used in the case of low Ni concentration, have been considered to obtain low energy requirements together with pure nickel having a good morphology.

Acid drainage reassessment of mining tailings, Black Swan Nickel Mine, Kalgoorlie, Western Australia

This paper describes the geochemical testing of mine tailings sourced from the Black Swan Ni Mine located near Kalgoorlie, Western Australia. Acid–base accounting was used to provide an indication of the acid generating capacity of two kinds of mining tailings: disseminated-ore tailings from the Cygnet Tailings Dam Storage Facility (CTDSF) and massive-ore tailings from the Silver Swan Tailings Dam Storage Facility (SSTDSF). All of the tailings in SSTDSF have acid generating potential which is consistent with previous research reports. New findings in this paper reveal that approximately 16% of the tailings in CTDSF have the potential to be acid generating. In contrast, previous reports state that the disseminated-ore tailings are classified as non-acid forming. Most of the potential acid generating tailings in the CTDSF are found in the upper-middle sections of the tailings profile, but some are located at the bottom of the tailings dam. The upper-middle section of the tailings is oxidized because these tailings have interacted with atmospheric O 2 and rain and surface water. Oxidation of the bottom tailings in the CTDSF may be due to infiltration of ground water into hidden fractures under the east bank of CTDSF, which caused these tailings to oxidize under closed and reduced conditions. The acid drainage in the tailings dam storage facility was observed 3 a, after the development of the Black Swan Nickel project. This delayed production of acid drainage was likely due to the slow rates of acid neutralization provided by alteration gouge minerals such as Mg/Fe-carbonates (magnesite–siderite series) associated with the Ni ores. The acid drainage leaking from the tailings dams has contaminated neighboring ground water via increased acidity and heavy metals. Because of the potential acid generation in some of the disseminated ore tailings, it is inadvisable to use disseminated ore tailings as cover materials in the storage facility to isolate the underlying potentially-acid-forming tailings from O 2 and water, as proposed by previous research reports.

Chemical Evolution and Origin of Nickel Sulfide Mineralizationin the Sudbury Igneous Complex, Ontario, Canada

Chemical Evolution and Origin of Nickel Sulfide Mineralizationin the Sudbury Igneous Complex, Ontario, Canada