Thomas Meisel

Osmium isotopic compositions of mantle xenoliths: A global perspective

0.0008 (level of confidence 95%) was defined on the basis of 117 spinel-bearing xenoliths from this work and data from the literature, including data for massif peridotites. The 187 Os/ 188 Os ratio of the PUM is similar to the range of compositions defined by ordinary and enstatite chondrites, not carbonaceous chondrites. Spinel-bearing mantle peridotites sampled by volcanism and peridotite massifs appear to have been extracted from a common fertile source (PUM) between 1 and 2 Ga ago. These peridotites now form part of the subcontinental lithospheric mantle underlying continental crust of similar or greater formation age. Copyright

A simple procedure for the determination of platinum group elements and rhenium (Ru, Rh, Pd, Re, Os, Ir and Pt) using ID-ICP-MS with an inexpensive on-line matrix separation in geological and environmental materials

A simple and highly selective analytical procedure is presented here for the concentration determination of Ru, Rh, Pd, Re, Os, Ir and Pt via isotope dilution, which is suitable for the investigation of geological and environmental materials. Sample preparation consists of a sample digestion step in a high pressure asher (HPA-S) with concentrated HNO3 and HCl and drying down of the sample solution after the Os concentration was determined via sparging OsO4 into an ICP-MS. After drying and redissolution of the remaining solution the other PGEs are separated on-line from their matrix in a simple cation-exchange column that is coupled to a quadrupole ICP-MS. Through this technique it is possible to monitor in every sample the isotopes of the analytes as well as of those elements that cause isobaric interferences or that potentially cause interferences through molecular species. Concentrations of the two or more isotopic elements can be calculated through isotope ratios, whereas Rh is calculated via the peak area. Data for ultramafic reference materials UB-N and GP13 with concentrations lower than 8 ng g−1 show excellent reproducibilities (n = 9) for Re, Pd and Pt (2.5–3.9% RSD) and Pt, Ru, Rh, Os and Ir (4.5–7% RSD). It can be demonstrated that a large portion of the higher standard deviations is caused by sample heterogeneity. Road dust (BCR-723) was included to demonstrate the strength of this procedure for the determination of environmental samples. Reproducibilities (n = 5) for Re, Pt and Os were between 1.2 and 2.3% RSD, 5.2% RSD for Pd and 11% RSD for Rh. Data for Ru and Ir are presented for the first time.

Simplified method for the determination of Ru, Pd, Re, Os, Ir and Pt in chromitites and other geological materials by isotope dilution ICP-MS and acid digestion

A method for the determination of low Ru, Pd, Re, Os, Ir and Pt abundances in geological reference materials by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion in a high pressure asher (HPA-S) is presented. The digestion technique is similar to that using Carius tubes but easier to handle and reaches higher temperatures. Osmium can be determined as OsO4 with ICP-MS directly after digestion through a sparging technique. The remaining elements are preconcentrated by means of anion column chromatography. The resin is digested directly without elution leading to high yields but this causes problems if Zr is present at higher levels in the silicate rich materials. The analytical results for international platinum group element (PGE) reference materials, chromitite CHR-Bkg, basalt TDB-1 and gabbro WGB-1, are presented and compared with literature data, demonstrating the validity of the described method. Although higher in concentration, PGEs determined for reference material WGB-1 were worse than for TDB-1 indicating a more inhomogeneous distribution of the platinum group mineral phases. The low PGE abundance chromitite standard, CHR-Bkg, is likely to be homogeneous for Ru, Re, Os and Ir and is recommended as a reference material for the study of chromitites. Detection limits (3s x total procedure blank) range from 0.012 ng (Re and Os) to 0.77 ng (Pt), which could be further improved by applying higher quality acids.

Re–Os systematics of UB-N, a serpentinized peridotite reference material

The reference material (RM) UB-N is a typical representative of earths upper mantle. It is a serpentinized garnet and spinel-bearing peridotite (a metamorphosed lherzolite) from the Vosges mountains, France, that is well characterized for major and many trace elements. In order to test whether UB-N is a suitable Re–Os reference material, 32 digestions in three different laboratories (CRPG/CNRS, MPI (Mainz) and University of Leoben) with four different digestion techniques (low-temperature acid attack, Carius tube dissolution, high-pressure asher (HPA-S) acid attack and alkali fusion) were performed. The results show that the low-temperature acid attack is unsuitable for the study of the Re–Os systematics of UB-N. Surprisingly, the well-established Carius tube acid digestion technique also fails to completely digest all Os-bearing mineral phases. Only alkali fusion and HPA-S acid attack yield the highest Os concentrations. Though sample inhomogeneity has been recognized (approximately 6% RSD for 2-g sample aliquots), it is possible to determine a well-defined average Os concentration of 3.85±0.13 ng g−1 (95% confidence; 19 digestions, fusion and HPA-S only). Rhenium-bearing minerals are very homogeneously distributed and replicates within each laboratory yield highly reproducible results independent of the digestion technique. A value of 0.2095±0.0040 ng g−1 (95% confidence; n=24) is assigned to the Re concentration. The best estimate for the whole-rock 187Os/188Os is 0.1278±0.0002 (95% confidence; n=12). The UB-N reference material now has well-understood Re–Os systematics that are typical of fertile upper mantle rocks. Analysis of this standard is, thus, highly recommended for the validation of Re–Os analytical procedures.

Geochemistry and tectonomagmatic affinity of the Yungbwa ophiolite, SW Tibet

The Yungbwa ophiolite is a thrust sheet of about 800 km2 tectonically overlying an Upper Cretaceous melange south of the Indus–Tsangpo Suture Zone in SW Tibet. Both units have been thrust over the sedimentary series of the Tibetan Tethys zone in the course of the India–Eurasia collision. Harzburgite and clinopyroxene-poor lherzolite are the dominant lithologies. Occasional gabbronoritic and basaltic dikes crosscut the mantle tectonites, but plutonic and volcanic sections are notably absent. The majority of basaltic dikes are tholeiitic and similar to N-MORB with respect to LREE depletion, ratios of diagnostic trace elements and Sr and Nd isotope systematics. Sm–Nd isotope data of three tholeiitic samples yielded an isochron age of 147±25 Ma (MSWD=0.59), and an initial e(t)Nd value of +8.8. In addition, magnesio-hornblende in a tholeiitic basaltic dike yielded a 40Ar/39Ar age of 152±33 Ma. The mineral chemistry of the spinel–peridotites is consistent with an origin in a tectonic setting similar to abyssal peridotites. The nearly chondritic initial 187Os/188Os value of a Re-poor orthopyroxene concentrate matches the composition of abyssal peridotites. The strongly LREE depleted trace element signature of the peridotite clinopyroxenes resembles that of clinopyroxenes from ocean floor peridotites. The Nd isotopic composition of a clinopyroxene concentrate is extremely depleted (143Nd/144Nd=0.514420), indicating an early Jurassic time of depletion (TDM=187 Ma) and suggesting that this clinopyroxene represents residual mantle material. In contrast, the bulk peridotites are characterized by convex-downward REE patterns, coupled with low 143Nd/144Nd ratios and elevated 87Sr/86Sr ratios. We suggest that these geochemical signatures resulted from secondary processes during or after emplacement of the ophiolite complex.

Petrogenesis and geotectonic setting of ultramafic rocks in the Eastern Alps: constraints from geochemistry

In the Eastern Alps, a heterogeneous pile of Pre-Mesozoic and Mesozoic nappes was emplaced during several distinct orogenic events. Ultramafic rocks are preserved in: (1) Pre-Mesozoic basement units of the Penninic Tauern Window and in Austroalpine basement complexes, and (2) in Mesozoic units within Penninic windows and in overlying Austroalpine segments. Geochemical data (major, trace and rare earth elements, REE, of bulk rock samples) of ultramafic rocks from 18 regions covering all the major tectonic units are presented. Metamorphic olivine-rich and clinopyroxene-rich ultramafic rocks and serpentinites from the Cambro-Ordovician Lower Schist cover units of the Tauern Window (Stubach Group, “Greiner Series”) are grouped into peridotites (#Mg values=molecular 100×Mg/(Mg+Fetot), 87–92; <2 wt.% Al2O3) and clinopyroxene-rich pyroxenites (#Mg=80–92; 1–3 wt.% Al2O3). Major and trace element characteristics indicate a residual origin of most peridotites as restites after 10–20% partial melting. Most probably, the pyroxenites are crystal segregates from a basaltic melt in a mantle transition zone. Small lenses of completely serpentinised ultramafic rocks in the Cambrian Habach Group (#Mg=90–92) also have residual character, although they are strongly metasomatised. The Stubach and Habach Groups developed in a back arc and volcanic arc setting, respectively, along the northern margin of Gondwana. Metamorphic harzburgite and dunite (#Mg=89–90; 0.5–2.4 wt.% Al2O3) veined by metagabbroic dikes were sampled in the Austroalpine Silvretta nappe (Hochnorderer). The harzburgites represent restites after 12% partial melting in suboceanic mantle, most probably during the Cambrian. In the Austroalpine basement east of the Tauern Window, metamorphosed ultramafic rocks occur in association with amphibolite and eclogite in the Proterozoic (about 750 Ma) Speik Complex. Harzburgite and dunite (#Mg=89–92; 0.1–0.8 wt.% Al2O3) are highly depleted in incompatible elements (2.6–35 ppb Yb) and are interlayered with small amounts of more fertile peridotite (amphibole-rich harzburgite and lherzolite, #Mg=89; up to 3.0 wt.% Al2O3), metaclinopyroxenite (#Mg∼85) and hornblendite. Coarse-grained orthopyroxenite (#Mg=89–92; 0.5–0.7 wt.% Al2O3; 19–36 ppb Yb) is present as veins and stocks in the harzburgite–dunite sequence. Chondrite-normalised rare earth element patterns of harzburgite–dunite and orthopyroxenite are characteristically U-shaped. The geochemical data indicate that harzburgites and some dunites are products of multiple melting events. They can be modelled as restites after 20–30% partial melting from already depleted mantle in a suprasubduction zone geotectonic setting. Orthopyroxenites crystallised from high-(Si, Mg) melts with a significant crustal component, probably during a Cambrian subduction event. In Mesozoic units of the Penninic windows (Lower Engadine, Tauern and Rechnitz windows), serpentinised ultramafic rocks of harzburgitic composition (#Mg=90–92; 1.1–2.0 wt.% Al2O3) are associated with metagabbro, metabasalt, radiolarite and ophicarbonate. Furthermore, serpentinised lherzolites (#Mg=88–90; 2.9–4.6 wt.% Al2O3) are exposed in the Matrei Zone (a tectonic melange zone between Penninic and Austroalpine nappes), in the Lower Austroalpine Reckner Complex and in a body of unclear tectonic affiliation at the southern margin of the Lower Engadine Window at Nauders. The harzburgites are residual mantle left behind after 10–15% partial melting of a fertile source, and form part of the Mesozoic (Jurassic) incomplete ophiolite sequences of the Ligurian–Piemontais ocean. The lherzolites, having experienced less than 10% partial melting, are either attributable to an early (Permian) rifting episode during break-up of Pangaea, or represent subcontinental mantle from the Adria plate tectonically incorporated into the Neo-Tethys.

The Jurassic South Albanian ophiolites: MOR- vs. SSZ-type ophiolites

Abstract Within the western belt of the southern Albanian ophiolites, the Voskopoja ophiolite consists of three subunits: Voskopoja, Morava and Rehove. These are predominantly lherzolites with minor harzburgites and dunites in the mantle section. Above come ultramafic and mafic cumulates including wehrlites, troctolites and olivine gabbros. Gabbronorites are restricted to the Morava subunit. Isotropic clinopyroxene gabbros, extrusives and sediments are present only in Rehove and Voskopoja. The volcanic section is dominated by basaltic breccias, including megablocks with sheeted dykes, pillow lavas and isolated dykes. The basaltic breccias grade upwards into sandstones, in turn, interlayered with argillites and cherts of Jurassic age. The basalts are predominantly clinopyroxene–plagioclase basalts, either aphyric or plagioclase phyric. Geochemically, they are divided into four groups: (1) an intermediate Ti and Zr group with low Ni (hereafter called low-Ni group), (2) an intermediate Ti–Zr group with high Ni (hereafter called high-Ni group), (3) a high-Ti–Zr group and (4) a low-Ti–Zr group. The high-Ni content in group 2 is interpreted as originating from olivine and spinel xenocrysts. Apart from the high-Ni content, groups 1 and 2 are comparable with the volcanics of the “low- to high-Ti intermediate ophiolites.” By contrast, group 3 is more comparable to the high-Ti ophiolitic extrusives in the western ophiolite belt of northern Albania. Group 4 consists SSZ-type basalts and is widespread in the volcanics of the eastern ophiolite belt. Comparison of the ultramafic–mafic cumulates and the basaltic volcanics with those in the northern part of the western belt in Albania and the Pindos ophiolite indicates that there is a systematic variation in petrography and geochemistry from north to south in the western belt, with an increasingly distinct SSZ signature towards the south. Ultramafic and mafic cumulates, as well as basalts from the Shebenik massif in the eastern belt, are similar to those of Voskopoja, implying a genetic relationship.

Antimony speciation in soil samples along two Austrian motorways by HPLC-ID-ICP-MS

Distribution of antimony and its inorganic species in soil samples along two traffic routes (A14, Rankweil and S36, Knittelfeld) in Austria was determined, since vehicle emissions are an important anthropogenic source of Sb in soil. The samples were taken along three parallel lines at about 0.2, 2 and 10 m distances from the edge of the road and in two depths range (0-5 and 5-10 cm from the soil surface). The optimized extraction was carried out using 100 mmol L(-1) citric acid at pH 2.08 applying an ultrasonic bath for 45 min at room temperature. Speciation analyses were done using on-line isotope dilution after a chromatographic separation of Sb species. Results of the two traffic routes confirmed significant accumulations of Sb at surface (0-5 cm depth) exceeding the natural background values by more than ten times at the S36 or four times at the A14. Concentrations of the extractable inorganic species decreased to natural background levels within a few meters from the edge of the traffic lane. The predominant Sb species was Sb(V). The Sb(III) concentrations at 5-10 cm depths range are nearly constant with distance from the edges of the two roads. Magnetic susceptibility data of all soil samples show the same distribution pattern as Sb and Sb(V) concentrations along the two traffic roads with an excellent correlation. This is an evidence for an anthropogenic source of Sb such as abrasions of motor vehicles surfaces or braking linings. The input of Sb and its inorganic species at one of the sampling sites (Knittelfeld) in samples taken in 2002 and in those taken recently (2005) was monitored. An increase in Sb (>or=30%), Sb(v)(>or=51%) and Sb(iii)(>or=10%) concentrations was only observed near the edge (<or=2 m) of the road.

The rare earth elements in municipal solid waste incinerators ash and promising tools for their prospecting

Bottom and fly ashes from Municipal Solid Waste Incinerators (MSWI) are hazardous products that present concern for their safe management. An attractive option to reduce their impact both on the environment and the financial commitment is turning MSWI ashes into secondary raw materials. In this study we present the REE content and distribution of bottom and fly ashes from MSWI after a highly effective digestion method and samples analysis by ICP-MS. The chondrite-normalised REE patterns of MSWI bottom and fly ash are comparable with that of crustal averages, suggesting a main geogenic source. Deviations from typical crustal pattern (e.g., Eu, Tb) disclose a contribution of likely anthropogenic provenance. The correlation with major elements indicates possible sources for REE and facilitates a preliminary resource assessment. Moreover, magnetic susceptibility measurements can be a useful prospecting method in urban ores made of MSWI ashes. The relationship between REE and some influencing parameters (e.g., Pricing Influence Factor) emphasises the importance of MSWI ash as alternative source of REE and the need of further efforts for REE recovery and purification from low concentrations but high flows waste.

Suitability of elemental fingerprinting for assessing the geographic origin of pumpkin (Cucurbita pepo var. styriaca) seed oil

An analytical method was developed and validated for the classification of the geographical origin of pumpkin seeds and oil from Austria, China and Russia. The distribution of element traces in pumpkin seed and pumpkin seed oils in relation to the geographical origin of soils of several agricultural farms in Austria was studied in detail. Samples from several geographic origins were taken from parts of the pumpkin, pumpkin flesh, seeds, the oil extracted from the seeds and the oil-extraction cake as well as the topsoil on which the plants were grown. Plants from different geographical origin show variations of the elemental patterns that are significantly large, reproducible over the years and ripeness period and show no significant influence of oil production procedure, to allow to a discrimination of geographical origin. A successful differentiation of oils from different regions in Austria, China and Russia classified with multivariate data analysis is demonstrated.