Nickel Sulphide Fire Assay Preconcentration Research Articles

Determination of ultra-trace osmium and ruthenium in geological samples by ICP-MS combined with nickel sulfide fire assay pre-concentration and microwave digestion

A new method for the detection of ultra-trace Os and Ru in geological samples by inductively coupled plasma mass spectrometry (ICP-MS) combined with nickel sulfide fire assay and microwave-assisted digestion was proposed. Os and Ru were separated from the sample matrix in nickel sulfide fire assay stage and concentrated into FeNi sulfide button. After dissolution and filtration of FeNi sulfide button, a new microwave digestion method was carried out in this work for the complete dissolution of platinum group sulfide precipitation. The volatile behaviors of Os and Ru with concentrations ranged from 0.500 to 100.0 ng mL−1 under the proposed microwave digestion conditions were studied. Fixed volatile proportion of Os was first discovered and the average volatile proportion was 14.0% with RSD of 1.1%. The analytical performance of the proposed method was studied and the detection limits were 0.012 ng g−1 for Os and 0.014 ng g−1 for Ru. The precisions that were evaluated within five replicate results of GBW07290 were 5.2% for Os and 4.4% for Ru. Further, applied this method for the detection of Os and Ru in several reference materials including chromite, the detection results were all well agreement with the certified values, which demonstrated its' practicability for the detection of ultra-trace Os and Ru in geological samples. This method is stable and reliable. More importantly, it shows a practical method for the accurate determination of ultra-trace Os and Ru for survey large number of geological samples.

Determination of Ultra-Trace Platinum, Palladium, Ruthenium, Rhodium, and Iridium in Rocks and Minerals by Inductively Coupled–Plasma Mass Spectrometry Following Nickel Sulfide Fire Assay Preconcentration and Open Mixed Acid Digestion

Platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), and osmiun (Os) are platinum-group elements with similar physic-chemical properties, and have important applications in geochemistry and environmental chemistry. However, due to their low abundance and inhomogeneous distribution in natural ores as well as the nugget effect, the accurate determination of the platinum-group elements has been a challenge for geological analysis. In this work, self-prepared and purified sodium carbonate (NiCO3) instead of commercial nickel oxide (NiO) was used as the fire assay collector in order to greatly reduce the reagent blank and method detection limits. In addition, the fuming time of HClO4 was strictly controlled at 10 min and a high sensitive method was developed for the simultaneous determination of ultra-trace Pt, Pd, Ru, Rh, and Ir in minerals by inductively coupled plasma-mass spectrometry (ICP-MS) following preconcentration with the nickel sulfide fire assay. Under the optimized conditions, the linear ranges of Pt, Pd, Ru, Rh, and Ir were between 0 and 100 ng mL−1, with correlation coefficients exceeding 0.9997. The detection limits were 0.015, 0.056, 0.014, 0.004, 0.012 ng mL−1 (for 10 g sample) for Pt, Pd, Ru, Rh and Ir, respectively. The developed method was successfully applied to analyze Chinese Certified Reference Materials (CRMs) GBW07288, GBW07289, GBW07290, GBW07291, GBW07292, GBW07293, GBW07294, GBW07101, GBW07102 and GBW07201 and the determined values were in good agreement with the certified values. The relative standard deviations (n = 5) of Pt, Pd, Ru, Rh and Ir were between 3.42% and 6.87% for the determination of GBW07291.

Reevaluation of siderophile element abundances and ratios across the Cretaceous–Paleogene (K–Pg) boundary: Implications for the nature of the projectile

The discovery over 30years ago at Gubbio (Italy) and Caravaca (Spain) of an enrichment in the concentrations of iridium (Ir) and the other platinum group elements (PGE) by up to four orders of magnitude (Irmax=0.10–87ng/g) compared to average continental crustal background levels remains one of the most important discoveries in the Earth sciences. Since then, similar anomalies have been detected in more than 120 Cretaceous–Paleogene (K–Pg) boundary sites worldwide. Highly elevated Ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact-related lithologies (melt rocks, impact ejecta material, etc.), delivered when an extraterrestrial object strikes Earth. The presented work adds 113 unpublished PGE analyses of 38 K–Pg sections worldwide to the existing literature. The analytical protocol relied on for this purpose consisted of a combination of a nickel-sulfide fire assay pre-concentration technique and subsequent trace metal determination via inductively coupled plasma-mass spectrometry (ICP-MS). Through repeated determination of key siderophile elements (i.e., Cr, Co, Ni, and PGE), the importance of sampling, nugget effects, and analytical methodologies applied becomes more apparent. Even more critically, these analytical effects are superimposed by the local syn- and post-depositional conditions that have affected the pristine meteoritic signature of the K–Pg impactor, including potential fractionation during vaporization and condensation, dissimilar PGE carrier phases, terrestrial PGE input, sedimentation rate, reworking, diagenesis, bioturbation, and chemical diffusion. While chondrite-normalized PGE patterns of individual sites appear relatively flat (i.e., chondritic), strong variations in siderophile element content and inter-element ratios exist between K–Pg locations, inter-laboratory measurements, and replicate analyses, hampering a precise projectile identification using (highly) siderophile elements. Only when considering improved databases of siderophile element concentrations in meteorites, in combination with linear regression analysis to calculate inter-element ratios from a large suite of ejecta deposit sites, the nature of the K–Pg projectile can be resolved. Application of this methodology to an extensive data set of continental and marine sites, very proximal to distal to the Chicxulub impact structure, supports a carbonaceous chondritic impactor (type CM or CO).

Geochemical characteristics of the platinum-group elements in the Abulangdang ultramafic intrusion, Sichuan Province, China

The contents of the platinum-group elements (PGEs: Os, Ir, Ru, Rh, Pt, Pd) in the Abulangdang ultramafic intrusion have been determined using ICP-MS after nickel sulfide fire assay preconcentration. Different samples show significant differences in absolute PGE abundance. They display a pronounced negative incline in mantle-normalized patterns which are characterized by strong enrichment in IPGEs (Os, Ir, Ru) and depleting to slight enrichment in PPGEs (Rh, Pt, Pd). The characteristics of PGE distribution in the Abulangdang rocks are due to the combined action of sulfide and non-sulfide (spinel/chromite or alloy or micro-granular aggregation of metals). In comparison with the mafic-ultramafic rocks which host Ni-Cu-PGE deposits in the Emeishan Large Igneous Province (ELIP), it is assumed that the Abulangdang ultramafic intrusion may be the product of early-stage magma activity in the ELIP.

Accumulating characteristics of platinum group elements (PGE) in urban environments, China

The three-way catalytic converters [mainly using platinum, palladium and rhodium of platinum group elements (PGE)] have been widely used to reduce the pollution arising from vehicular traffic. Since the late 1990s, the Chinese government has implemented measures for new vehicles, equipped with the three-way catalytic converters in metropolitan cities. However, the PGE spreading on environments has not been strongly concerned in developing countries. This study investigated the accumulation characteristics of PGE in urban environments in China. A few samples from India were also analyzed and compared with those from China. The collected soil, aerosol and plant samples were determined for PGE by inductively coupled plasma–mass spectrometry (ICP-MS) after nickel sulphide fire assay preconcentration. The results have shown higher PGE contents in the samples from the cities where vehicles were fitted with autocatalysts for longer time periods. The highest values are 160 ng/g for Pt, 107 ng/g for Pd and 34.5 ng/g for Rh in Hong Kong soils, whereas the lowest values are 2.59 ng/g for Pt, 1.31 ng/g for Pd and 0.40 ng/g for Rh in Kolkata soils. In Beijing and Guangzhou aerosol samples, the PGE concentrations are 6.22 to 24.3 pg/m 3 for Pt and 1.16 to 8.60 pg/m 3 for Rh and 7.68 to 12.2 pg/m 3 for Pt and 2.15 to 5.15 pg/m 3 for Rh, respectively. The levels of PGE abundances in the urban environments of China have been significantly elevated with increasing number of vehicles equipped with autocatalysts.

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%.

Precise determination of PGE in a GSJ reference sample JP-1 by ID-ICPMS after nickel sulfide fire assay preconcentration

All platinum group element (PGE) abundances of a standard rock JP-1 are determined by isotope dilution method (for Ru, Pd, Os, Ir and Pt) and external calibration method (only for Rh) using ICP-MS combined with a fire assay preconcentration technique. The errors range 13–25% (2σ; n = 5), which are comparable with those by the similar methods combined with chemical separation of PGE (Pearson and Woodland, 2000; Meisel et al., 2001). Large deviations between our data and preferable values proposed by the Geological Survey of Japan (GSJ) are observed for Os and Ir. The scattered Os data might be indicative of heterogeneity of Os in JP-1. From various viewpoints, it seems likely that our Ir data are much more reliable than the preferable values proposed by GSJ.

Determination of Platinum‐Group Elements and Forty Two Other Elements in Two Candidate Danish Cretaceous‐Tertiary Boundary Clay Reference Materials by INAA, ENAA and RNAA

Ruthenium, rhodium, palladium, osmium, iridium and platinum (PGEs) and forty two other elements in two candidate geological Cretaceous‐Tertiary boundary clay reference materials taken from the Fish Clay, Stevns Klint, Denmark, were determined by a combination of neutron activation analysis (NAA) consisting of instrumental, epithermal and radiochemical NAA with or without nickel sulfide fire assay preconcentration. The accuracy of the experimental values was assessed by the comparative analysis of the certified reference materials.

EXTREME FRACTIONATION OF PLATINUM GROUP ELEMENTS IN VOLCANOGENIC MASSIVE SULFIDE DEPOSITS

Platinum group elements (PGE) and gold in selected ore samples and associated lithologies from four well-known volcanogenic massive sulfide (VMS) districts (i.e., the kuroko Zn-Pb-Cu deposits of Hokuroku, Japan; the Besshi Cu-Zn deposit of Shikoku, Japan; the Cu-Zn-Au-Ag deposits of Manitouwadge, Ontario, Canada; and the Cu-Zn-Co deposits of Outokumpu, Finland) have been determined by nickel sulfide fire assay preconcentration, tellurium coprecipitation, and inductively coupled plasma mass spectrometry analysis. The chalcopyrite-rich samples associated with mafic-ultramafic rocks from Besshi, Manitouwadge, and Outokumpu locally contain elevated contents of Pd (up to 1.8 ppm), Rh (up to 0.8 ppm), and Au (up to 14 ppm), whereas those of the kuroko deposits hosted by felsic volcanic rocks are poor in PGE. Moreover, the chalcopyrite-rich samples and cordierite-orthoamphibole gneisses show extreme fractionation of Au, Ir, Pd, and Pt (Au/Ir values up to 108,000; Pd/Ir, up to 29,500; and Pd/Pt, up to 2,100), which are somewhat similar to previously reported Au/Ir and Pd/Ir values in modern sea-floor hydrothermal sulfides but are significantly higher than those in magmatic Ni-Cu sulfides. The extreme fractionation of Au, Ir, Pd, and Pt in these volcanogenic massive sulfide deposits cannot be explained by the relative metal solubilities in sea-floor hydrothermal fluids but may be related to local remobilization of PGE and Au during late hydrothermal alteration and/or metamorphism.

Determination of Platinum‐Group Elements and Gold in Two Russian Candidate Reference Materials SCHS‐1 and SLg‐1 by ICP‐MS after Nickel Sulfide Fire Assay Preconcentration

Ruthenium, rhodium, palladium, iridium, platinum and gold in two Russian geological candidate reference materials SCHS‐1 and SLg‐1 were determined using inductively coupled plasma‐mass spectrometry after nickel sulfide fire assay preconcentration. Platinum‐group elements have very low concentrations in the samples, the range being from 0.01 ng g‐1 to 1.57 ng g‐1. Analytical results are presented along with a brief description of the analytical procedure. Accuracy of the results was assessed by the comparative analysis of the certified reference material.

Chemical speciation study of platinum group elements in geological samples by stepwise dissolution and inductively coupled plasma mass spectrometry

A chemical speciation study method for platinum group elements in geological samples was developed, including stepwise dissolution, nickel sulphide fire assay preconcentration and inductively coupled plasma mass spectrometry (ICP-MS) determination. Samples were firstly separated into eight components (water-soluble phase, exchangeable phase, carbonate phase, Fe/Ni metal phase, sulfide phase, oxide phase, silicate phase and HF-insoluble residue) by a newly-revised selective chemical dissolution procedure. The separated components were pretreated and subjected to nickel sulphide fire assay to preconcentrate platinuim group elements, which were determined by ICP-MS. The chemical speciation of platinum group elements in a Danish Cretaceous/Tertiary (K/T) boundary sample was studied as a demonstration.

DETERMINATION OF PLATINUM GROUP ELEMENTS IN FOUR NEW REFERENCE SAMPLES OF MARINE SEDIMENTS AND NODULES BY NEUTRON ACTIVATION ANALYSIS AFTER NICKEL SULPHIDE FIRE ASSAY PRECONCENTRATION

Platinum group elements were determined in two new reference samples of marine sediments (GSMS‐2 and GSMS‐3) and in two new reference samples of manganese nodules (GSPN‐2 and GSPN‐3) by neutron activation analysis after nickel sulphide fire assay preconcentration. Analytical data obtained are presented along with a brief description of the analytical procedure.

Interference by neutron induced second order nuclear reaction in activation analysis of platinum group elements after a nickel sulphide fire assay preconcentration

In determining the trace platinum group elements and gold in rocks and ores by the neutron activation analysis after a nickel sulphide fire assay preconcentration, there are interferences due to nuclides produced from second order nuclear reactions. This paper presents the degree of interference calculated over the ranges of long irradiation times and of reactor neutron flux from 1·1013 to 1·1015 n·cm−2·s−1. According to the results of these calculations, every one of the second order interfering reactions on the PGE+Au, except the197Au(n, γ)198Au(n, γ)199Au reaction, can be neglected under the long irradiation time or high reactor neutron flux. Special attention is given to the interference from gold in the determining platinum.

Neutron activation analysis after a nickel sulphide fire assay preconcentration for determination of all platinum group elements in rocks

Neutron activation analysis after a nickel sulphide fire assay preconcentration for platinum group elements (PGE) has been established in our laboratory. In this work, the all PGE in DZ∑-2, a Chinese certified ultramafic rock standard reference material, are determined for testing the accuracy and precision of the method. The experimental conditions and the blank values from reagents and detection limits for the method are also presented.

DETERMINATION OF ALL PLATINUM GROUP ELEMENTS IN SIX NEW CHINESE PGE GEOCHEMICAL STANDARD REFERENCE SAMPLES USING NEUTRON ACTIVATION ANALYSIS AFTER A NICKEL SULPHIDE FIRE ASSAY PRECONCENTRATION

Six new Chinese PGE geochemical standard reference samples, GPt‐1 to GPt‐6, were analyzed by neutron activation analysis after nickel sulphide fire assay preconcentration. Analytical data on all platinum group elements are presented along with a brief description of the analytical procedure.

Determination of the platinum-group elements in South African kimberlites by nickel sulphide fire-assay and neutron activation analysis

Ten kimberlites from various localities in South Africa have been analysed for all of the platinum-group elements (PGEs) and gold using a nickel sulphide fire-assay preconcentration followed by neutron activation analysis (NAA). Problems encountered during the analysis of these samples prompted a radio tracer study to test the recovery of the precious metals during firing, and then the subsequent dissolution of the assay button. The results of this study suggest solutions to the potential problems of incomplete melting of MgO-rich and CO 2-rich during fire-assay, and minimising losses of Pt, Pd and Au during dissolution. Furthermore, this improved procedure offers lower limits of detection than previous methods which combined fire-assay and NAA. The concentrations of PGEs determined in this study of South African kimberlites are compared with previous partial analyses from the literature, indicating that earlier analyses may have seriously overestimated the concentrations of the some PGEs in kimberlites.