Nickel Sulfide Fire Assay Research Articles

Precious metal mobility during serpentinization and breakdown of base metal sulphide

Serpentinization of ultramafic rocks drives geochemical exchange between the hydrosphere, biosphere and lithosphere in surficial environments and at depth. Precious metals are implicated in these hydration reactions because of the well-known association between peridotite-hosted Au and placer platinum-group mineral (PGM) deposits sourced from serpentinized ophiolite complexes at surface. However, the distribution of precious metals in mantle rocks and their mode of occurrence at the onset of serpentinization are not well understood because early-stage features are typically obliterated with progressive hydration. Herein we report electron probe microanalysis (EPMA) and laser ablation inductively coupled mass spectrometry (LA-ICPMS) spot and mapping results for a suite of base metal sulphide (pentlandite, pyrrhotite, chalcopyrite), native metal (Cu and Fe) and Ni-Fe alloy (awaruite) from variably serpentinized peridotite and pyroxenite (Late Permian to Early Triassic Nahlin ophiolite, Cache Creek terrane; Atlin, British Columbia, Canada). Pentlandite and pyrrhotite occur with magmatic clinopyroxene and Cr-spinel as ultrafine inclusions (few μm) and as coarser interstitial base metal sulphides (≤200 μm) that are enveloped by native metal (Cu and Fe) and Ni-Fe alloy. Because native Fe- and awaruite-bearing mineral assemblages require reduced and/or low-fS2 conditions, we suggest that these replacement textures document destabilization of base metal sulphide phases during the conversion of olivine to serpentine and magnetite. Desulphurization reactions decoupled precious metals from relict pentlandite at the microscale, with Ag, Pd, Pt and Au partitioning from sulphides into both awaruite and native metal (Cu and Fe) at concentrations up to 100s of ppm. New high-resolution LA-ICPMS maps also point to clusters of ultrafine PGM, tellurides, bismuthides and metal alloys that were either remobilized within the serpentinized mesh and/or represent the completely desulphidized product of ultrafine, intergranular base metal sulphide. Other PGE (Os and Ir) are mostly hosted within relict pentlandite and/or pyrrhotite that were preserved during incomplete desulphurization, along with lesser microscale remobilization of these elements into ultrafine veins. New whole-rock PGE (nickel-sulphide fire-assay; NiS-FA) results demonstrate that precious metal remobilization was limited to the microscale during the earliest stages of serpentinization, which, in the case of Au, is consistent with its low solubility within such reduced, low fS2 fluids. Precious metal mobility during the early stages of serpentinization may therefore depend on the stability of Ni-Fe alloy, native metal (Cu and Fe) and PGM. Progressive serpentinization, complete replacement of olivine and destabilization of the reduced, low-fS2 mineral assemblage likely represents an important process to liberate, transport and concentrate precious metals within more oxidized and/or sulphur-bearing fluids in surficial and deep subduction environments.

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.

A rapid and practical strategy for the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in large amounts of ultrabasic rock by inductively coupled plasma optical emission spectrometry combined with ultrasound extraction

This proposed method regulated the determination of platinum, palladium, ruthenium, rhodium, iridium and gold in platinum-group ores by nickel sulfide fire assay—inductively coupled plasma optical emission spectrometry (ICP-OES) combined with ultrasound extraction for the first time. The quantitative limits were 0.013–0.023μg/g. The samples were fused to separate the platinum-group elements from matrix. The nickel sulfide button was then dissolved with hydrochloric acid and the insoluble platinum-group sulfide residue was dissolved with aqua regia by ultrasound bath and finally determined by ICP-OES. The proposed method has been applied into the determination of platinum-group element and gold in large amounts of ultrabasic rocks from the Great Dyke of Zimbabwe.

Determination of the Optimum NiS Fire Assay Parameters for Pt, Pd, and Rh in Automotive Exhaust Catalytic Converters

This work investigates the performance of the nickel sulfide fire assay (NiS-FA) for the pyrometallurgical analysis of platinum group elements (PGEs) from mixtures of automotive exhaust catalytic converters (e.g., gasoline, diesel, and diesel particular filter) by assessing the effects of various flux materials and reaction parameters on platinum, palladium, and rhodium recovery. Inductively coupled plasma mass spectrometry and atomic absorption spectroscopy (AAS) are used for the analysis of the NiS-FA beads. We found that the optimum recovery (at least 99.0%) was achieved with reaction of 11.5 g of flux (0.53 w/w ratio, sodium tetraborate:sodium carbonate), 1 g nickel, and 0.84 g sulfur (1.2 w/w ratio, Ni:S) per gram of sample for 90 min at 975°C. Reference standards (NIST SRM 2557) were used to compare efficiencies and identify the optimum conditions. The results are consistent with certified values and PGEs could be recovered within the 95% confidence level. The precision (<4.0% RSD) of all measurements, expressed as percentage relative standard deviation (SD), ranged up to 3.0%.

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.

Determination of iridium and gold in rock samples by using pre-concentration neutron activation analysis

Nickel sulfide (NiS) fire assay was used for the pre-concentration of Ir and Au in rock samples. The beads obtained after fire assay were irradiated directly with neutrons to determine Ir and Au. To suppress the reaction of 58Ni(n,p)58Co, the fire assay was carried out by using a small amount of Ni (0.0625 g) and the NiS bead samples were irradiated by neutrons with high Cd ratios. Analytical results of Ir and Au for rock samples were close to literature values, confirming that our procedure of INAA with pre-concentration can be applied to rock samples for the determination of ppb to sub-ppb level of Ir and Au.

A non-magmatic iron projectile for the Gardnos impact event

The goal of this study is to identify the type of projectile responsible for the formation of the late Precambrian Gardnos impact structure in Norway. Fifteen impactite samples, predominantly impact breccias and suevites from the central and northeastern part of the structure, were analyzed for platinum group elements (PGE) and Au using nickel-sulfide fire assay combined with inductively coupled plasma mass spectrometry (ICP-MS). Major and trace elements were measured in the same samples using X-ray fluorescence (XRF). In addition, the concentrations of siderophile elements Ni, Cr, and Co were determined by ICP-MS after acid digestion. The samples collected at the contact between suevite and the sedimentary infill yielded the highest PGE concentrations (Ir = 1.926 ng/g, Ru = 3.494 ng/g, Pt = 4.716 ng/g, Rh = 0.766 ng/g, Pd = 2.842 ng/g for GC6). The CI-normalized PGE patterns are characterized by Ru and Rh enrichments suggesting a non-chondritic impactor. Concentration plots of the different PGE display an excellent correlation ( R > 0.99), indicative of a single source for the PGE enrichment. The Ni/Cr ratio of the Gardnos impactor (2.56 ± 0.20) agrees with that of chondrites (2 to 7), whereas Ir is depleted relative to Ni in this projectile (Ni/Ir ratio of 92 000 ± 8000 compared to an average Ni/Ir ratio of 23 150 ± 4250 for chondrites). There is no clear indication of selective post-depositional remobilization of the characteristic highly siderophile elements. The Ni/Ir and Cr/Ir data combined with the non-chondritic PGE ratios probably indicate a differentiated projectile. Based on (1) the similarity of the inter-element ratios of the impactor with the iron phase of non-magmatic iron meteorites and (2) the presence of characteristics of both chondrites and iron meteorites (Ni/Cr and Ni/Ir ratios), an IA or IIIC non-magmatic iron meteorite is a very plausible impactor.

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%.

Increase of platinum group element concentrations in soils and airborne dust in an urban area in Germany

Since 1993, all new cars sold in the European Union had to be fitted with catalytic converters. Undoubtedly, these measures brought about a great progress concerning traffic emission controls. However, this technology also led to new emissions. A rapid accumulation of the catalytic active noble metals Pt, Pd, and Rh in the environment was observed and concern arose about potential environmental and health risks. This work aimed at a contribution to a monitoring of platinum group element (PGE) emission and accumulation by comparing analytical data, all generated in 1999 and in 2005 in an urban area in Germany. Oriented at the 1999 sampling strategy, soil and airborne dust samples were taken in 2005 at the same sampling sites located mainly close to heavily used roads in the region of Braunschweig. For the enrichment of the analytes, conditioned soil samples as well as loaded glass fiber filters from air sampling were transferred to the nickel sulphide fire assay. For analyses, the ICP-MS technique was applied. High Pt, Pd, and Rh concentrations were detected especially in top soil layers (0–2 cm) directly at the roadsides or on center strips. At one road outside the city, where traffic moved with a constant speed of about 80 km/h, maximum concentrations in soil were found to be 50.4 μg/kg for Pt, 43.3 μg/kg for Pd, and 10.7 μg/kg for Rh. PGE concentrations were the highest close to that road and exponentially declined with growing distance. At a second road, where vehicles run with a constant speed of 50 km/h, the highest concentrations were detected in the center strip soil: 88.9 μg/kg (Pt), 77.8 μg/kg (Pd), and 17.6 μg/kg (Rh). At a third crowded street in the centre of Braunschweig with stop and go traffic, the highest soil concentrations were determined, namely 261 μg/kg for Pt, 124 μg/kg for Pd and 38.9 μg/kg for Rh. The sampling of airborne dust at this roadside revealed for Pt 159 pg/m 3 air or 1730 μg/kg dust, for Pd 37.8 pg/m 3 air or 410 μg/kg dust, and for Rh 10.0 pg/m 3 air or 110 μg/kg dust. A comparison of analytical results of 2005 with those of 1999 revealed a distinct increase of PGE concentrations in soils closely along heavy traffic roads by a factor of 2.1 to 8.9; once even a factor of 15 was determined. The findings also document, that especially Pt and Rh concentrations were elevated in airborne dust.

Platinum-group elements of the Meishan Permian–Triassic boundary section: Evidence for flood basaltic volcanism

Permian–Triassic boundary sections record the most severe mass extinction event in geological history. However, there is a long-standing controversy of whether bolide impact and/or basaltic flood volcanism triggered the mass extinction. Platinum-group elements (PGEs) are enriched in most extraterrestrial materials, but highly depleted in the terrestrial crust materials. We analyzed Ir, Ru, Rh, Pt and Pd in a set of samples from the global stratotype section and point (GSSP) of the Permian–Triassic boundary at Meishan, China, using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) and nickel sulfide fire assay (NiS-FA) combined with Te coprecipitation. The samples have no Ir anomaly (5–53 pg/g), and their PGE patterns normalized to chondrites are highly fractionated with Ir/Pd ratios of 0.02–0.03 × CI, distinct from most extraterrestrial materials. In contrast, these patterns are closely parallel to those of the Siberian and probably Emeishan flood basalts, suggestive of possible sources of PGEs from the basalts. The abundances of PGEs increase in order of the pyrite lamina on the top of bed 24, bed 25 and bed 26, and then decrease to bed 28, probably indicative of a maximum eruption of the flood basalts during deposition of bed 26. The new data favor massive volcanism, rather than extraterrestrial impact, as a major cause of the Permian–Triassic boundary mass extinction.

Platinum group elements provide no indication of a meteoritic component in ICDP cores from the Bosumtwi crater, Ghana

Abstract— In an attempt to identify the type of projectile, 14 samples from the Bosumtwi crater in Ghana were analyzed for platinum group element (PGE) concentrations by nickel sulfide fire assay inductively coupled plasma—mass spectrometry (ICP‐MS). The majority of the samples come from the impactite material recovered by cores LB‐07A and LB‐08A, which were drilled by the International Continental Scientific Drilling program (ICDP). One sample originates from the fallback material found at the contact between the impactite and the overlying lake sediment in core LB‐05B. No clear signature of a meteoritic contamination was identified in the 13 impactite samples. The target rock apparently dominates the PGE contribution in the impactites. These results agree with the PGE concentrations reported for the suevites collected at the crater rim and in other parts of the Bosumtwi ICDP cores. However, based on Cr and Os isotopic signatures, a meteoritic component could be present in the sample of fallback material, supporting the reports of the existence of meteoritic material in the Ivory Coast tektites. Further analyses of the fallback material from the Bosumtwi drill cores should confirm (or not) this first result.

Evaluation of a technique for determining Re and PGEs in geological samples by ICP-MS coupled with a modified Carius tube digestion

In the determination of Re and platinum group elements in geological samples, various techniques have been employed for digesting samples, including Carius tube, high-pressure asher (HPA-S), alkali fusion and nickel sulfide fire assay. The normal Carius tube technique is able to digest relatively small amount of sample and has a possible safety problem caused by a high internal pressure. This paper reports a modified Carius tube method which utilizes a sealed stainless steel high-pressure autoclave filled with water to prevent explosion of the tube. During heating, the external and internal pressures of the Carius tube increase simultaneously, such that the possible explosion of Carius tube can be avoided. Consequently, this technique allows a higher temperature (up to 330°C), a greater volume of aqua regia (up to 2/3 of the total volume of the Carius tube) and thus larger sample mass (12 g) relative to the normal Carius tube technique. Fairly good agreement were obtained for PGE poor mafic rocks (IPGE < 0.03 ng/g). The efficiency to dissolve ultramafic rocks and chromites at different temperatures was investigated. We demonstrate that this technique is more effective than normal Carius tube technique for ultramafic rocks and chromites containing refractory minerals and the detection limits and precision can be improved for PGE poor mafic samples. The total procedural blanks are lower than 0.003 ng for Os, 0.03 ng for Re, Ir, Ru and Rh and 0.4 ng for Pd and Pt.

Nickel sulfide fire assay improved for pre-concentration of platinum group elements in geological samples: a practical means of ultra-trace analysis combined with inductively coupled plasma-mass spectrometry

A method was developed for ultra-trace determination of all six platinum group elements (PGE) by inductively coupled plasma-mass spectrometry (ICP-MS). With involvement of Fe to the fusion charge compositions of the conventional NiS fire assay, a whole assay button in water may disintegrate into powder and then be dissolved with HCl. The insoluble residue was collected, and dissolved with HCl + H(2)O(2) in a sealed Teflon beaker. After the HCl + H(2)O(2) treatment the Os signal response is at least 10 times as high as that in HCl medium. With isotopic dilution method for determination of Os, all six PGE were analyzed in one sample preparation. This method was applied to a series of Chinese PGE certified reference materials, GBW 07288 to GBW 07294, and the results were found to be in reasonable agreement with the certified values. Limits of detection were assessed from the whole chemical procedure and they are 0.17 ng g(-1) for Ru, 0.01 ng g(-1) for Rh, 0.16 ng g(-1) for Pd, 0.03 ng g(-1) for Os, 0.07 ng g(-1) for Ir and 0.11 ng g(-1) for Pt. This method of precision (RSD%) was evaluated using two reference materials of GBW 07291 and GBW 07294, and it is within the range from 4.2% to 10.3%.

Determination of Platinum‐Group Elements in Geological Reference Materials by High Resolution‐ICP‐MS after Nickel Sulfide Fire‐Assay Collection and Te Co‐Precipitation

Inductively coupled plasma‐mass spectrometry (ICP‐MS) after NiS fire assay‐Te co‐precipitation was employed in the determination of Ru, Rh, Pd, Os, Ir and Pt at ng g‐1 levels in six platinum‐group element (PGE) geological reference materials. In general, the average of several results was in good agreement with the certified values taking into account respective uncertainties. High relative standard deviations were observed for the reference materials GPt‐3 and GPt‐4. Problems associated with the NiS fire assay procedure and PGE determination at the sub‐10 ng g‐1 level are reviewed and discussed.

Platinum group elements in impactites of the ICDP Chicxulub drill core Yaxcopoil‐1: Are there traces of the projectile?

Abstract— This study presents results of platinum group element (PGE) analyses of impactites from the Yaxcopoil‐1 (Yax‐1) and Yucatán 6 drill cores of the 180 km‐diameter Chicxulub crater. These are the main elements used for projectile identification. They were determined by nickel sulfide fire assay combined with inductively coupled plasma mass spectrometry. The concentration of PGE in the samples are low. The concentration patterns of the suevite samples resemble the pattern of the continental crust. We conclude that any meteoritic fraction in these samples is below 0.05%. A syn‐ and post‐impact modification of the PGE pattern from meteoritic toward a continental crust pattern is very unlikely. The globally distributed fallout at the Cretaceous‐Tertiary (K/T) boundary, however, has high PGE concentrations. Therefore, the lack of a significant meteoritic PGE signature in the crater is not an argument for a PGE‐poor impactor. Taking the results of three‐dimensional numerical simulations of the Chicxulub event into account, the following conclusions are drawn: 1) The main fraction of the impactor was ejected into and beyond the stratosphere, distributed globally, and deposited in the K/T boundary clay; and 2) the low amount of projectile contamination in the Yax‐1 lithologies may reflect an oblique impact. However, the role of volatiles in the mixing process between projectile and target is not well‐understood and may also have played a fundamental role.

Comparison of Recoveries by Lead Fire Assay and Nickel Sulfide Fire Assay in the Determination of Gold/ Platinum/ Palladium and Rhenium in Sulfide Ore Samples

We compared the recovery of gold, palladium and platinum by two fire assaying procedures, using nickel sulfide and lead as collectors. The presence of appreciable amounts of sulfide minerals in the sample caused interferences in both procedures. An in‐house reference sample, a reference sample of high‐grade sulfide ore and samples of high sulfide content from the Recsk porphyry copper ore in Hungary were analysed by both methods. The elements were determined by inductively coupled plasma‐atomic emission (ICP‐AES) and/or inductively coupled plasma‐mass spectrometry (ICP‐MS). It was found that for the sulfide ore samples, the recoveries of Au and Pd are sometimes lower by nickel sulfide fire assay than by lead fire assay. Recovery of Re by nickel sulfide fire assay was found to be low: the average recovery of five repeated analyses of the reference sample NIST SRM 330 was 9% with a relative standard deviation of 48%. Increasing the amount of S in the fusion flux gave better recovery.

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.