Analysis Of Platinum Group Elements Research Articles

Circum-cratonic mantle archives the cumulative effects of plume and convergence events

The cumulative effects of heating, various melts/fluids, and tectonic stress from plume and convergent events can produce complex geochemical signatures in circum-cratonic mantle domains. The lithospheric mantle beneath the northwestern Tarim Craton witnessed the Tarim plume and multi-stage convergent events, thus providing a good opportunity to investigate the depletion and enrichment of circum-craton mantle driven by their cumulative effects. Here, we present the in-situ mineral major/trace elements, clinopyroxene Sr isotopic and whole-rock analyses of platinum group elements and Re-Os isotopes for peridotite xenoliths from Piqiang in the northwestern Tarim Craton. Combined with peridotite xenoliths from Tuoyun (South Tianshan Belt) and Xikeer (inner Tarim), we established a lithospheric mantle profile to constrain the formation and subsequent evolution of the circum-Tarim mantle in response to the subduction of the archipelagic ocean and the impingement of the Tarim plume. The Piqiang peridotites have moderately refractory compositions (Mg# in Ol: 90.1–90.9; average values) and can be divided into Group A lherzolites (subgroups A1, A2 and A3) and Group B wehrlite. Group A1 lherzolites contain copper-poor sulfides and clinopyroxenes depleted in incompatible elements, and are interpreted as melting residua that experienced negligible metasomatism. Group A2 lherzolites have disequilibrium textures and are depleted in Nb and Ta with high Ti/Eu but low (La/Yb)N ratios in clinopyroxene, demonstrating recent volatile-rich melt metasomatism. Carbonatitic metasomatism from a mixed crust-mantle source is recorded in the Group A3 lherzolites, as their clinopyroxenes have highly variable 87Sr/86Sr ratios (0.7028–0.7057) with low Ti/Eu and high (La/Yb)N. Overall, Group A lherzolites display high initial 187Os/188Os ratios (0.1198–0.1271, excluding suprachondritic values), yielding the Neoproterozoic peak (∼650 Ma) TRD eruption model ages and the minimum estimate for the age of lithospheric mantle formation of 1.1 Ga. Their high-Na clinopyroxenes, low-Ca orthopyroxenes, and low melting pressures (<3 GPa) suggest that the initial melt extraction of these peridotites was the result of lateral mantle accretion triggered by multi-stage subduction of the Neoproterozoic Pan-Rodina Ocean. In this case, the greater fertility of the Tuoyun peridotites compared to those from Piqiang defines a trend of lateral accretion, while the low whole-rock Al2O3 but high 187Os/188Os ratios of the Xikeer peridotites point to a second melt extraction event. This melt extraction event is interpreted as reflecting low-flux plume melts that heated and melted the overlying lithospheric mantle at the edge of the early Permian Tarim plume. Meanwhile, the Piqiang peridotites, further from the center of the Tarim plume, underwent carbonatitic metasomatism originating from the lower-flux plume melts that involved the high-density components from recycled oceanic crustal materials. The mantle melt activity and faulting related to the India-Eurasia collision provided the reactive melts to form the Group B wehrlite and prepared migration pathways for volatile-rich melts to metasomatize Group A2 lherzolites. Collectively, the accretion, re-extraction, and metasomatic modification of circum-craton mantle reflected a response to the cumulative effects of the plume and convergence events. Our study reveals that the mechanical, thermal, and chemical effects from different dynamic events interacted with each another and worked together to affect the circum-craton mantle evolution.

High grade ores of the Onverwacht platinum pipe, eastern Bushveld, South Africa

ABSTRACT The platiniferous dunite pipes are discordant orebodies in the Bushveld Complex. The Onverwacht pipe is a large body (&amp;gt;300 m in diameter) of magnesian dunite (Fo80–83) that crosscuts a sequence of cumulates in the Lower Critical Zone of the Bushveld Complex. In a pipe-in-pipe configuration, the main dunite pipe at Onverwacht hosts a carrot-shaped inner pipe of Fe-rich dunite pegmatite (Fo46–62) which comprises the platinum-bearing orebody. The latter was ca. 18 m in diameter and a mining depth of about 320 m was reached. In the present work, a variety of ore samples were studied by whole-rock geochemistry, including analyses of platinum group elements, ore microscopy, and electron probe microanalysis. Olivine of the ore zone displays considerable chemical variation (range 46–62 mol.% Fo) and may represent either a continuum, or different batches of magma, or vertical or horizontal zonation within the ore zone. Chromite is principally regarded to be a consanguineous component of the pipe magma that crystallized in situ and simultaneously with olivine. The Onverwacht mineralization is Pt-dominated (&amp;gt;95% of the platinum group elements) and the ore is virtually devoid of sulfides. Platinum-dominated platinum group minerals predominate, followed by Rh-, Pd-, and Ru-species. Pt-Fe alloys are most frequent, followed by Pt-Rh-Ru-arsenides and -sulfarsenides, platinum group element antimonides, and platinum group element sulfides. Our hypothesis on the genesis of the Onverwacht pipe and its mineralization is as follows: After near-consolidation of the layered series of the Critical Zone, the magnesian dunite pipe of Onverwacht was formed by upward penetration of magmas that replaced the existing cumulates initially by infiltration, followed by the development of a central channel where large volumes of magma flowed through. Fractional crystallization of olivine within the deeper magma chamber and/or during ascent of the melt resulted in the formation of a consanguineous, residual, more iron-rich melt. This melt also contained highly mobile, supercritical, water-bearing fluids and was continuously enriched in platinum group elements and other incompatible elements. In several closing pulses, the platinum group element-enriched residual melts crystallized and sealed the inner ore pipe. Crystallization of the melt resulted in the coeval formation of Fe-rich olivine, chromite, and platinum group minerals. The non-sulfide platinum group element mineralization was introduced in the form of nanoparticles and small droplets of platinum group minerals, which coagulated to form larger grains during evolution of the mineralizing system. The suspended platinum group minerals acted as collectors of other platinum group elements and incompatible elements during generation and ascent of the melt. With decreasing temperature, the platinum group mineral grains annealed and recrystallized, leading to the formation of composite platinum group mineral grains, complex intergrowths, or lamellar exsolution bodies. On further cooling, platinum group minerals overgrowing Pt-Fe alloys formed by reaction of leached elements and ligands like Sb, As, and S mobilized by supercritical magmatic/hydrothermal fluids. Redistribution of platinum group elements/platinum group minerals apparently only occurred on the scale of millimeters to centimeters. Finally, surface weathering led to the local formation of platinum group element oxides/hydroxides by oxidation of reactive precursor platinum group minerals.

Platinum-group and trace elements in Cu-sulfides from the Loolekop pipe, Phalaborwa: implications for ore-forming processes

Although Cu-sulfide mineralization within the Loolekop pipe of the Phalaborwa Igneous Complex has been extensively studied, certain aspects of the sulfide metallogenesis remain unclear. This research aims to constrain the relative timing and processes involved in Cu-sulfide mineralization within the Loolekop pipe through textural analysis and trace element composition of the three different types of sulfide assemblages in this intrusion. The first primary magmatic mineralization phase contains dispersed bornite with chalcopyrite exsolution and local traces of chalcocite and covellite related to fluid alteration, whereas the second primary phase is characterized by veins of chalcopyrite with cubanite exsolution. The third mineralization phase relates to leaching of primary sulfide assemblages by oxidizing fluids, resulting in desulfurization and the formation of valleriite [(Fe2+,Cu)4(Mg,Al)3S4(OH,O)6] and magnetite. Whole-rock ICP-MS analyses of platinum-group elements (PGE) indicate a mantle origin of the primary Cu-sulfides (bornite-chalcopyrite assemblages). In situ trace element analyses of sulfide assemblages also show evidence of external material input, most likely of crustal origin, during magma and sulfide liquid ascent, before decoupling of the sulfide liquid and the melt, although the exact source is unclear. The enrichment of Pd-group PGE (PPGE: Pd, Pt) over Ir-group PGE (IPGE: Os, Ir, Ru) in Cu-sulfide phases suggests the presence of an intermediate solid solution (iss)-monosulfide solid solution (mss) system. It is proposed that a Cu- and PPGE-enriched sulfide liquid fractionated from an IPGE-enriched mss, followed by the formation of an iss, and finally the extraction of a PPGE-rich Cu-liquid from the iss forming the bornite-chalcopyrite assemblages. Sulfide textures and the presence of chalcopyrite veins suggest that the iss was leached by high-temperature hydrothermal fluids at depth that remobilized and precipitated Cu along the fractures within the intrusion. Subsequently, all the primary magmatic phases were affected by late-stage fluids, which triggered their alteration into valleriite, also precipitating along fractures within the Loolekop pipe.

Determination of platinum group elements in catalysts recycling products by SEM with energy dispersive spectrometer

Analysis of platinum group elements (PGE) extracted from various catalysts used in the car, petroleum and chemical industries requires use of microanalytical methods. PGE content in the platinum powder concentrates K176 and K177 was studied by SEM-EDS. The content of main elements was determined using analytical lines Fe Kα1, Si Kα1, Sn Lα1, Pt Lα1, Re Lα1. The obtained data for the chemical composition are in good agreement with the result obtained by X-ray fluorescence analysis and ICP-MS method. Powdered platinum concentrates are considered to be ferrosilicide (FeSi), where PGE are localized at the phase boundaries and in separate patches of the K176 sample, or distributed over the volume of particles in the K177 sample.

In situ analysis of platinum group elements in equilibrated ordinary chondrite kamacite and taenite

AbstractPlatinum group element (PGE) concentrations have been determined in situ in ordinary chondrite kamacite and taenite grains via laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). Results demonstrate that PGE concentrations in ordinary chondrite metal (kamacite and taenite) are similar among the three ordinary chondrite groups, in contrast to previous bulk metal studies in which PGE concentrations vary in the order H &lt; L &lt; LL. PGE concentrations are higher in taenite than kamacite, consistent with preferential PGE partitioning into taenite. PGE concentrations vary between and within metal grains, although average concentrations in kamacite broadly agree with results from bulk studies. The variability of PGE concentrations in metal decreases with increasing petrologic type; however, variability is still evident in most type six ordinary chondrites, suggesting that equilibration of PGEs does not occur between metal grains, but rather within individual metal grains via self‐diffusion during metamorphism. The constant average PGE concentrations within metal grains across different ordinary chondrite groups are consistent with the formation of metal via nebular condensation prior to the accretion of ordinary chondrite parent bodies. Post‐condensation effects, including heating during chondrule‐formation events, may have affected some element ratios, but have not significantly affected average metal PGE concentrations.

Preservation of an Archaean whole rock Re-Os isochron for the Venetia lithospheric mantle: Evidence for rapid crustal recycling and lithosphere stabilisation at 3.3 Ga

Re-Os and platinum group element analyses are reported for peridotite xenoliths from the 533Ma Venetia kimberlite cluster situated in the Limpopo Mobile Belt, the Neoarchaean collision zone between the Kaapvaal and Zimbabwe Cratons. The Venetian xenoliths provide a rare opportunity to examine the state of the cratonic lithosphere prior to major regional metasomatic disturbance of Re-Os systematics throughout the Phanerozoic. The 32 studied xenoliths record Si-enrichment that is characteristic of the Kaapvaal lithospheric mantle and can be subdivided into five groups based on Re-Os analyses. The most pristine group I samples (n=13) display an approximately isochronous relationship and fall on a 3.28±0.17Ga (95 % conf. int.) reference line that is based on their mean TMA age. This age overlaps with the formation age of the Limpopo crust at 3.35–3.28Ga. The group I samples derive from ∼50 to ∼170km depth, suggesting coeval melt depletion of the majority of the Venetia lithospheric mantle column. Group II and III samples have elevated Re/Os due to Re addition during kimberlite magmatism. Group II has otherwise undergone a similar evolution as the group I samples with overlapping 187Os/188Os at eruption age: 187Os/188OsEA, while group III samples have low Os concentrations, unradiogenic 187Os/188OsEA and were effectively Re-free prior to kimberlite magmatism. The other sample groups (IV and V) have disturbed Re-Os systematics and provide no reliable age information. A strong positive correlation is recorded between Os and Re concentrations for group I samples, which is extended to groups II and III after correction for kimberlite addition. This positive correlation precludes a single stage melt depletion history and indicates coupled remobilisation of Re and Os. The combination of Re-Os mobility, preservation of the isochronous relationship, correlation of 187Os/188Os with degree of melt depletion and lack of radiogenic Os addition puts tight constraints on the formation and subsequent evolution of Venetia lithosphere. First, melt depletion and remobilisation of Re and Os must have occurred within error of the 3.28Ga mean TMA age. Second, the refractory peridotites contain significant Re despite recording >40 % melt extraction. Third, assuming that Si-enrichment and Re-Os mobility in the Venetia lithospheric mantle were linked, this process must have occurred within ∼100Myr of initial melt depletion in order to preserve the isochronous relationship. Based on the regional geological evolution, we propose a rapid recycling model with initial melt depletion at ∼3.35Ga to form a tholeiitic mafic crust that is recycled at ∼3.28Ga, resulting in the intrusion of a TTG suite and Si-enrichment of the lithospheric mantle. The non-zero primary Re contents of the Venetia xenoliths imply that TRD model ages significantly underestimate the true depletion age even for highly depleted peridotites. The overlap of the ∼2.6Ga TRD ages with the time of the Kaapvaal-Limpopo collision is purely fortuitous and has no geological significance. Hence, this study underlines the importance of scrutiny if age information is to be derived from whole rock Re-Os analyses.

Analysis of platinum-group elements in drill core samples from the Meishan Permian-Triassic boundary section, China

There is a long-standing controversy of what triggered the extinction at the Permian-Triassic boundary, the most severe mass extinction in the geologic record, including flood basaltic volcanism and/or bolide impact hypothesis. In order to clarify various pieces of evidence for the mass extinction event at the Permian-Triassic boundary, some researchers from some laboratories throughout the world have made a comprehensive study on a group of samples from the Meishan area of China. Some fresh core samples from the Permian-Triassic boundary in the Meishan area were analyzed in this study. The results showed that there is no Ir anomaly. Moreover, the PGEs patterns of those samples show obvious differentiation characteristics, that is different from the case encountered in meteorites. So no evidence supports the hypothesis of extraterrestrial impact. In contrast, the PGEs patterns are similar to those of Siberian and Emeishan basalts, which indicates that those PGEs are derived mainly from the basalts, lending a support to the correlation between mass extinction at the Permian-Triassic boundary and flood basaltic volcanism. This study has also confirmed the results for samples from section C prior to the analysis of the samples.

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%.

REPLY TO: “NANOMETER-SIZED PLATINUM-GROUP MINERALS (PGM) IN BASE METAL SULFIDES: NEW EVIDENCE FOR AN ORTHOMAGMATIC ORIGIN OF THE MERENSKY REEF PGE ORE DEPOSIT, BUSHVELD COMPLEX, SOUTH AFRICA: DISCUSSION” by Louis J. Cabri: Fig. 1

First of all, I would like to thank L. Cabri for uncovering errors in our paper. This gives us the opportunity to correct them. Cabri critically discussed the energy-dispersive X-ray (EDX) analyses of platinum-group elements (PGE) presented in our paper and questioned the “relatively” high

Determination of Pt, Pd and Rh in Brassica Napus using solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry

Conventional approaches for the analysis of platinum group elements (PGEs) in plant material suffer from sample digestion which results in sample dilution and therefore requires high sample intakes to maintain the sensitivity. The presented solid-sampling method avoids sample digestion while improving sensitivity when compared to digestion-based inductively coupled plasma optical emission spectrometry (ICP-OES) methods and allows the analysis of sample masses of 5mg or less. Detection limits of 0.38μgg−1, 0.14μgg−1 and 0.13μgg−1 were obtained for Pt, Pd and Rh, respectively using a sample intake of 5mg. The reproducibility of the procedure ranged between 4.7% (Pd) relative standard deviation (RSD, n=7) and 7.1% (Rh) RSD for 25ng analytes. For quantification, aqueous standards were applied on paper filter strips and dried. Only the dried filters were introduced into the electrothermal vaporization unit. This approach successfully removed memory-effects observed during analysis of platinum which occurred only if liquid standards came into contact with the graphite material of the furnace. The presented method for overcoming the Pt-memory-effects may be of further interest for the analysis of other carbide-forming analytes as it does not require any technical modification of the graphite furnace (e.g., metal inlays, pyrolytic coating). Owing to lack of suitable certified reference materials, the proposed method was compared with conventional ICP-OES analysis of digested samples and a good agreement was obtained. As a result of the low sample consumption, it was possible to determine the spatial distribution of PGEs within a single plant. Significant differences in PGE concentrations were observed between the shoots (stem, leaves) and the roots. Pd was mainly found in the roots, whereas Pt and Rh were also found in higher concentrations in the shoots.

Concentrations of Platinum Group Elements (Pt, Pd, Rh) in Airborne Particulate Matter (PM2.5and PM10-2.5) Collected at Selected Canadian Urban Sites: a Case Study

Increasing environmental concentrations of platinum group elements (PGEs), in particular platinum (Pt), palladium (Pd) and rhodium (Rh), from catalytic converters has been reported worldwide. Initially it was believed that the emitted PGEs remain in the roadside environment, but recent studies have shown that fine PGE-containing particles can be transported and distributed at regional and long-range levels. Therefore, the monitoring of PGEs in airborne particulate matter (PM) is important for the estimation of potential risks to human health and to the ecosystem. The aim of this study is to present the first results from an analysis on the concentration and distribution of Pt, Pd and Rh in PM collected on Teflon filters at two selected urban sites (Toronto, Ontario; Edmonton, Alberta) collected within the Canadian National Air Pollution Surveillance (NAPS) network. In this work, a quadruple inductively coupled plasma mass spectrometry (ICP-MS), combined with microwave assisted acid digestion using aqua regia was used. A cation exchange separation was used to alleviate the matrix-induced spectral and nonspectral interferences prior to ICP-MS analysis. To obtain sufficient material needed for PGEs analysis, fine PM (particles with aerodynamic diameter less than 2.5 mm; PM2.5 ) and coarse PM (with aerodynamic diameter between 2.5 and 10 mm; PM10-2.5 ) samples were combined into composite samples on a seasonal basis. The obtained results will be discussed and compared with literature data.

Enrichment of Rh, Ru, Ir and Os in Cr spinels from oxidized magmas: Evidence from the Ambae volcano, Vanuatu

Experimental studies, performed under oxidized conditions ( fO 2 > QFM + 2, where QFM is quartz–fayalite–magnetite oxygen buffer), have shown that Rh, Ru, Ir and Os are strongly compatible with Cr spinel, whereas empirical studies of Cr spinels from ultramafic–mafic rocks suggest that the experimental results may overestimate the partition coefficients. We report laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of platinum-group elements (PGE), Au and Re abundances in Cr spinels from the Ambae volcano, Vanuatu ( fO 2 = QFM + 2.5), the Jimberlana layered intrusion, western Australia, and the Bushveld complex, South Africa ( fO 2 ∼ QFM). The results show that Rh and IPGEs (Iridium-group PGE; Ru, Ir, Os) partition strongly into the Cr spinels that crystallized from the oxidized Ambae lavas whereas most of the Cr spinels from the more reduced Jimberlana layered intrusion and the Bushveld complex contain no detectable PGE, Au or Re, with exception of ∼10 ppb of Ir in some Jimberlana Cr spinels. In the Ambae Cr spinels, Rh, Ru and, to lesser extent Os, are positively correlated with Fe 3+, Ni and V. The homogeneous distribution of Rh and IPGEs in LA-ICP-MS time-resolved spectra indicates that these elements are in solid solution in Cr spinels. Pt–Fe alloys occur as inclusions within the Ambae Cr spinels, which indicate that the Ambae melt was saturated with Pt. Our results show that partitioning of Rh, Ru and Ir into Cr spinels increases with increasing oxygen fugacity, which suggests that the high concentrations of these elements in the Ambae Cr spinels are due to the high oxygen fugacity of the host magma. Therefore, Cr spinels may play an important role in controlling the concentrations of Rh and IPGEs during fractional crystallization of oxidized ultramafic–mafic magmas and during partial melting of oxidized arc mantle.

F-1 Analysis of Platinum Group Elements (PGE) by Means of Total Reflection X-ray Fluorescence (TXRF) Spectrometry

F-1 Analysis of Platinum Group Elements (PGE) by Means of Total Reflection X-ray Fluorescence (TXRF) Spectrometry

Towards the analysis of platinum group elements at low levels in insulating materials

The operating parameters for a high current caesium sputter source have been modified so that stable beams of anions can be obtained from natural non-conducting samples. This technique has been applied to the analysis of gold and platinum group elements in silicate matrices, particularly olivines. The handling of interferences resulting from the large number of molecular ions produced in such a target, and the effect of differences in the matrices of reference materials are discussed.

Changes in Palladium, Platinum, and Rhodium Concentrations, and Their Spatial Distribution in Soils Along a Major Highway in Germany from 1994 to 2004

Soil samples were collected along the highway A5 from the major junctions Frankfurter Kreuz to Darmstäder Kreuz from July to September, 2004 and analyzed for palladium (Pd), platinum (Pt), and rhodium (Rh). The results were compared to analyses of platinum group elements (PGE) in soils collected along this same stretch of highway in 1994. The goal of this study is to detect any changes that may have occurred in the concentration and environmental distribution patterns of these metals over this 10 year period. The concentrations of Pd in soils along the highway were found to be about 15 times higher on average than those measured in 1994. Pt and Rh concentrations increased 2 and 1.6 times, respectively, during this time period. The significant rise in Pd concentrations in soils observed for the time period of analysis is likely due to its use in automobile catalytic converters in Germany since 1993. The results also show a strong positive relationship between PGE emissions and traffic density and speed. The results indicate that increases in the concentrations of Pd, Pt, and Rh in soils along the highway are not limited to the soil surface. Pt was measured as deep as 12 cm. Pd was determined at even greater depths of 12-16 cm. The presence of Pd at lower depths compared to Pt suggests that this element has a higher solubility. Pd, Pt, and Rh concentrations display a strong inverse relationship with distance from the road, with decreasing levels with increasing distance from the highway. Nonetheless, Pd and Pt were detected in a meadow as far as 50 m from the highway, a much greater distance compared to that measured for these metals in 1994. Pt concentrations were also found to significantly correlate with levels of Rh and Pd. The ratios between the PGE analyzed (Pt/Rh and Pd/Rh) display a shift toward Pt and Pd. The results clearly show that PGE concentrations have increased over time. Observed increases in Pd concentrations are particularly a cause of concern.

Analyses of platinum group elements in mosses as indicators of road traffic emissions in Austria

The concentrations of platinum group elements (PGE; platinum, palladium, rhodium) and 17 other elements in mosses growing at 32 sampling sites along 12 roads in Austria were analysed. The study included passive monitoring of naturally growing mosses with an experimental design using mosses samples exposed in a tunnel experiment. PGEs (Pt, Pd, Rh) were analysed by ICP-MS (ELAN DRC II, Perkin Elmer SCIEX) according to EN ISO 17294-2 Tl.29. Mean concentrations of PGEs in five moss species were: Pt 7.07±9.97, Pd 2.8±5.2 und Rh 0.6±0.8 ng g −1 dry weight. This is comparable to data derived from measurements of gasoline autocatalyst emissions or airborne particles (<10 μm). Compared to soils and road dust along highways, concentrations in mosses were lower by a factor of ten, compared to grasses they were comparable or somewhat higher. The ratios between the various PGEs were calculated as follows (mean values): Pt/Pd 7.9±10.2, Pt/Rh 12.6±8.3 and Pd/Rh 3.7±2.2. The number of light duty vehicles (<3.5 t) and the distance from the road were the main influential factors for PGE concentrations. Especially strong correlations could be found between Pt and Sb, Cu, Zn, and Cd (in decreasing order), which are all elements derived mainly from road traffic emissions. Cluster analysis (Partioning Around Medoids Method) separated elements derived mainly from soil dust (Ca, Al). An analysis of spatial deposition patterns of PGEs showed a reciprocal decrease of concentrations with increasing distance from the road, reaching background values at distances between 10 and 200 m, sometimes even more, but outside the spatial range of our investigation.

Laser Ablation ICP-MS Developments and Trends for 2003

This annual review of laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) covers the year 2003. Significant advances were made in understanding laser-sample interactions. In particular, research defined the distribution of particle sizes produced by the interplay of laser wavelength, laser pulse width and the gas environment of ablation. A link between particle sizes and elemental and isotopic fractionation at both the ablation site and in the ICP was established. Experimental 15 7 nm and femtosecond laser systems were tested with promising results. The number of applications of LA-ICP-MS in geology and environmental Earth science continued to grow with particular interest in element concentration and isotope ratio profiling of materials, linking composition to time scales. In situ isotopic ratio measurements were increasingly made using multicollector magnetic sector ICP-MS instruments. Other applications of wide interest included bulk sampling of rocks and ores prepared as lithium borate glasses; low level analysis of platinum-group elements, rhenium and gold in sulfides, metal and silicates; in situ uranium-lead zircon geochronology; and melt and fluid inclusion analysis.

Comet or asteroid shower in the late Eocene?

The passage of a comet shower approximately 35 million years ago is generally advocated to explain the coincidence during Earth's late Eocene of an unusually high flux of interplanetary dust particles and the formation of the two largest craters in the Cenozoic, Popigai and the Chesapeake Bay. However, new platinum-group element analyses indicate that Popigai was formed by the impact of an L-chondrite meteorite. Such an asteroidal projectile is difficult to reconcile with a cometary origin. Perhaps instead the higher delivery rate of extraterrestrial matter, dust, and large objects was caused by a major collision in the asteroid belt.

LA-ICP-MS analysis of platinum-group elements and other elements of interest in ancient gold

One of the most promising methods for ancient gold analysis is laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS). It is a quasi-non-destructive multi-elemental analytical method with detection limits in the range of ppm or below, depending on the element. Internal and external standardizations are used. Different types of standards are necessary to measure major (required for the internal standardization), minor and trace elements. High-purity gold standards doped with trace elements as well as ancient gold coins were found suitable for that purpose. The reproducibility and the accuracy of the results obtained are good enough to consider LA-ICP-MS as reliable to determine trace-element concentrations in ancient gold.

Reference materials for geochemical PGE analysis: new analytical data for Ru, Rh, Pd, Os, Ir, Pt and Re by isotope dilution ICP-MS in 11 geological reference materials

Abundances of Ru, Rh, Pd, Re, Os, Ir and Pt are reported in 11 high- and low-abundance reference materials (RMs) that are currently in use for platinum group element (PGE) analysis. Analytical data was obtained by isotope dilution ICP-MS using a simple on-line chromatographic column for analyte–matrix separation after high-pressure asher (HPA-S) digestion. It is demonstrated that certified concentrations of platinum group element RMs are not sufficiently precise to detect bias. Most provisional and information values of the CANMET-CCRMP RM concentrations below 1 ng g −1 are biased toward higher concentrations. Currently, high-abundance RMs, often with matrices that do not match those of the samples, are used inappropriately for validation of analytical procedures for peridotites and basalts with low to moderate PGE concentrations. To improve this situation, several mafic and ultramafic RMs were included in this study to evaluate their usefulness for geochemical analysis of platinum group elements and rhenium. Peridotites UB-N and GP13 as well as basalt TDB-1 are sufficiently homogeneous at a 2-g test sample portions level to be used as RMs for method validation.