Determination of Ge, As, Se and Te in Silicate Samples Using Isotope Dilution-Internal Standardisation Octopole Reaction Cell ICP-QMS by Normal Sample Nebulisation

A method for the determination of Ge, As, Se and Te in silicate samples using isotope dilution-internal standardisation (ID-IS) octopole reaction cell (ORC) ICP-QMS by normal sample nebulisation was developed. The method does not involve either hydride generation or ion exchange. Germanium, Se and Te were determined by isotope dilution (ID), and As was determined by ID-IS. A silicate sample with an added Ge-Se-Te spike was digested with an HF-HNO₃-HBr mixture, dried, re-dissolved with HF and the supernatant liquid was directly aspirated into an ORC-ICP-QMS instrument with He or H₂ gas. No matrix effects were observed down to a dilution factor (DF) of ∼ 70 for Ge, Se and Te and DF of ∼ 1000 for As, which resulted in 3s detection limits in silicates of 2, 1, 0.1 and 4 ng g⁻¹, respectively. Advantages of the method are the simple sample introduction as well as a capability of determining S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ID-IS-ICP-QMS/SFMS from the same solution. Furthermore, the total sample solution consumption was only 0.253 ml with DF = 2000. Therefore, only a 0.13 mg test portion was required. To demonstrate the applicability of this technique, Ge, As, Se and Te in eight silicate reference materials were determined, as well as S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta in four carbonaceous chondrites.     

Concentration and distribution of elements in Late Permian coals from western Guizhou Province,China

With the aim of better understanding geochemistry of coal, 71 Late Permian whole-seam coal channel samples from western Guizhou Province, Southwest China were studied and 57 elements in them were determined. The contents of Al, Ca, Co, Cr, Cu, Fe, Ga, Hf, K, Li, Mn, Mo, Nb, Ni, Sn, Ta, Ti, Th, U, V, Zr, and REEs in the Late Permian coals from western Guizhou Province are higher than the arithmetic means for the corresponding elements in the US coals, whereas As, Ba, Br, F, Hg, P, Se, and Tl are lower. Compared to common Chinese coals, the contents of Co, Cr, Cu, Ga, Hf, Li, Mn, Mo, Ni, Sc, Sn, Ti, U, V, Zn, and Zr in western Guizhou coals are higher, and As, F, Hg, Rb, Sb, Tl, and W are lower. Five groups of elements may be classified according to their mode of occurrence in coal: The first two, Group A, Tm–Yb–Lu–Y–Er–Ho–Dy–Tb–Ce–La–Nd–Pr–Gd–Sm, and Group B, As–Sr–K–Rb–Ba–F–Ash–Si–Sn–Ga–Hf–Al–Ta–Zr–Be–Th–Na, have high positive correlation coefficients with ash yield and they show mainly inorganic affinity. Some elements from Group B, such as Ba, Be, Ga, Hf, and Th, are also characterized by significant aluminosilicate affinity. In addition, arsenic also exhibits high sulfide affinity (r_S–Fe>0.5). The elements, which have negative or lower positive correlation coefficients with ash yield (with exceptions of Bi, Cs, Nb, Mn, Se, and Ti), are grouped in other four associations: Group C, Cr–V–Mo–U–Cd–Tl; Group D, Hg–Li–Sc–Ti–Eu–Nb–Cs–W; Group E, Bi–Sb; and Group F, Co–Ni–Cu–Pb–Zn–Mg–Se–Ca–Mn–S–Fe. The correlation coefficients of some elements, including Co, Cr, Cu, Fe, Hg, Li, Mo, Ni, P, S, Sc, U, V, and Zn, with ash yield are below the statistically significant value. Only Cr and Cu are negatively correlated to ash yield (−0.07 and −0.01, respectively), showing intermediate (organic and inorganic) affinity. Manganese and Fe are characterized by carbonate affinity probably due to high content of epigenetic veined ankerite in some coals. Phosphorus has low correlation coefficients with any other elements and is not included in these six associations. There are five possible genetic types of enrichment of elements in coal from western Guizhou Province: source rock, volcanic ash, low-temperature hydrothermal fluid, groundwater, and magmatic hydrothermal inputs.     

Bottled drinking water: Water contamination from bottle materials (glass,hard PET,soft PET), the influence of colour and acidification

A test comparing concentrations of 57 chemical elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, I, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sm, Sn, Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn and Zr) determined by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 294 samples of the same bottled water (predominantly mineral water) sold in the European Union in glass and PET bottles demonstrates significant (Wilcoxon rank sum test, α = 0.05) differences in median concentrations for Sb, Ce, Pb, Al, Zr, Ti, Th, La, Pr, Fe, Zn, Nd, Sn, Cr, Tb, Er, Gd, Bi, Sm, Y, Lu, Dy, Yb, Tm, Nb and Cu. Antimony has a 21× higher median value in bottled water when sold in PET bottles (0.33 vs. 0.016 μg/L). Glass contaminates the water with Ce (19× higher than in PET bottles), Pb (14×), Al (7×), Zr (7×), Ti, Th (5×), La (5×), Pr, Fe, Zn, Nd, Sn, Cr, Tb (2×), Er, Gd, Bi, Sm, Y, Lu, Yb, Tm, Nb and Cu (1.4×). Testing an additional 136 bottles of the same water sold in green and clear glass bottles demonstrates an important influence of colour, the water sold in green glass shows significantly higher concentrations in Cr (7.3×, 1.0 vs. 0.14 μg/L), Th (1.9×), La, Zr, Nd, Ce (1.6×), Pr, Nb, Ti, Fe (1.3×), Co (1.3×) and Er (1.1×).     

Validation of a field filtration technique for characterization of suspended particulate matter from freshwater. Part II. Minor, trace and ultra trace elements

A field filtration method for the concentration and separation of suspended particulate matter (SPM) from freshwater systems and the subsequent determination of minor, trace and ultra trace elements (As, Ba, Be, Cd, Co, Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Zn and Zr) is validated with respect to detection limits, precision and bias. The validation comprises the whole procedure including filtration, sample digestion and instrumental analysis. The method includes two digestion procedures (microwave acid digestion and alkali fusion) in combination with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Total concentrations of these 27 trace and minor elements have been determined in suspended particulate matter (SPM) from lake and river water with low levels of suspended solids (<2 mg L⁻¹ DW), and a wide range of element concentrations. The precision of the method including filtration, digestion and instrumental determination ranges between 8% and 18% RSD for most elements on a dry weight basis. Higher recovery after acid digestion is found for some elements, probably because of volatilization or retention losses in the fusion procedure. Other elements show higher recovery after fusion, which is explained by more efficient decomposition of refractory mineral phases relative to the non-total acid digestion. Non-detectable concentrations of some elements are reported due to small differences between blank filter levels and the amounts of elements present on the filters after sampling. The method limits of detection range between 0.7 ng and 2.65 μg, as estimated from the blank filter samples. These detection limits are 10–550 times higher compared to the corresponding instrumental limits of detection. The accuracy and bias of the overall analytical procedure was assessed from replicate analysis of certified reference materials. A critical evaluation of the instrumental capabilities of the ICP-QMS instrumentation in comparison with a double focusing sector field plasma mass spectrometry technique (ICP-SFMS) is also included. It was found that a modified microwave acid digestion procedure in combination with ICP-SFMS could replace ICP-AES determinations and fusion digestions for most of the investigated elements. Guidelines and limitations for this time- and labour- efficient procedure, offering accurate results for the majority of elements studied are discussed.     

Geochemistry of trace metals and Pb isotopes of sediments from the lowermost Xiangjiang River, Hunan Province (P. R. China): implications on sources of trace metals

This paper reports a geochemical study of trace metals and Pb isotopes of sediments from the lowermost Xiangjiang River, Hunan province (P. R. China). Trace metals Ba, Bi, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Cd, Sn, Sb, Pb, Tl, Th, U, Zr, Hf, Nb and Ta were analyzed using ICP-MS, and Pb isotopes of the bulk sediments were measured by MC-ICP-MS. The results show that trace metals Cd, Bi, Sn, Sc, Cr, Mn, Co, Ni, Cu, Zn, Sb, Pb and Tl are enriched in the sediments. Among these metals, Cd, Bi and Sn are extremely highly enriched (EF values >40), metals Zn, Sn, Sb and Pb significantly highly (5 < EF < 20), and metals Sc, Cr, Mn, Co, Ni, Cu and Tl moderately highly (2 < EF < 5) enriched in the river sediments. All these metals, however, are moderately enriched in the lake sediments. Geochemical results of trace metals Th, Sc, Co, Cr, Zr, Hf and La, and Pb isotopes suggest that metals in the river sediments are of multi-sources, including both natural and anthropogenic sources. Metals of the natural sources might be contributed mostly from weathering of the Indosinian granites (GR) and Palaeozoic sandstones (PL), and metals of anthropogenic sources were contributed from Pb–Zn ore deposits distributed in upper river areas. Metals in the lake sediments consist of the anthropogenic proportions, which were contributed from automobile exhausts and coal dusts. Thus, heavy-metal contamination for the river sediments is attributed to the exploitation and utilization (e.g., mining, smelting, and refining) of Pb–Zn ore mineral resources in the upper river areas, and this for the lake sediments was caused by automobile exhausts and coal combustion. Metals Bi, Cd, Pb, Sn and Sb have anthropogenic proportion of higher than 90%, with natural contribution less than 10%. Metals Mn and Zn consist of anthropogenic proportion of 60–85%, with natural proportion higher than 15%. Metals Sc, Cr, Co, Cu, Tl, Th, U and Ta have anthropogenic proportion of 30–70%, with natural contribution higher than 30%. Metals Ba, V and Mo might be contributed mostly from natural process.     

Extreme enrichment of Sb, Tl and other trace elements in altered MORB

We have analyzed 25 trace elements (e.g., Sb, Tl, Sn, rare earth elements (REE), Th, U, Nb, Pb, Zr, Hf, and Y) in altered mid-ocean ridge basalts (MORB) from locations near the mouth of the Gulf of California. Our results imply that the heavy REE and Y are not seriously affected by seawater alteration, in agreement with previous studies. The elements Zr, Hf, Nb, light REE and Sr are enriched up to a factor of 2 in some extremely altered samples. However, element ratios between Zr, Hf, and Nb (e.g., Zr/Hf, and Zr/Nb) are not greatly affected, presumably due to the chemical similarity of these elements during any exchange process. The enrichment of Th and Sn is even higher. Antimony, Tl, Cs, Rb, Rb, and Ba are most easily altered by water-rock interaction and are therefore the best indicators for seawater alteration. The enrichment factor of the most mobile element Sb is up to 2000.

There is a weak correlation between the concentration in seawater and the enrichment factors. On the other hand, the worldwide pelagic clay pattern matches the enrichment pattern much more closely, and the limited data available for local oceanic sediments give an even better correlation. A plausible model to explain the enrichment pattern may be an elemental exchange between basalt and seawater that had interacted earlier with overlying sediments.     

Statistical assessment of geochemical pattern in overbank sediments of the river Sava,Croatia

Four overbank profiles from the three terraces of different age were sampled in 10 to 20 cm intervals for the bulk content of major and minor (Ca, Mg, Fe, Ti, Al, Na, K and P) and trace (Mo, Cu, Pb, Zn, Ni, Co, Mn, As, U, Th, Sr, Cd, Sb, V, La, Cr, Ba, W, Zr, Ce, Sn, Y, Nb, Ta, Sc, Li, Rb and Hf) elements in the minus 0.125 mm fraction. Univariate statistics together with analysis of variance discriminated between the lower-lying carbonate (CA) population dominantly composed of carbonates and the overlying silicate (SI) population being dominantly of silicate mineralogy. This stratified pattern resulted from the intensive erosive action of melting glaciers exerted on limestones and dolomites in the alpine region, followed by local inputs mainly of silicate composition. Elements exhibiting the greatest between-population variability are Ca and Mg being enriched in the CA population and Fe, Mn, P, Sr, Al, Na, K, Li, Rb, Y, Zr, Ni, Cr and Ti being enriched in the SI population. Anomalously high Hg, Pb and Ba concentrations (maximum values: 6,500±2,860 ppb, 225±13 ppm and 1,519±91 ppm, respectively) in the lowermost part of the profile S7, which is nearest to the Croatian-Slovenian border, derive from the mineralized Slovenian catchment area. This profile also contains trimodal frequency distributions of Fe, Mn and P whose highest concentrations coincide with increased values of Zn and Cu which are bimodally distributed. Geochemical patterns of majority of elements in all four profiles consistently reflect the average compositions of the upstream drainage basins.     

Pedo-geochemical baseline content levels and soil quality reference values of trace elements in soils from the Mediterranean (Castilla La Mancha, Spain)

To evaluate trace element soil contamination, geochemical baseline contents and reference values need to be established. Pedo-geochemical baseline levels of trace elements in 72 soil samples of 24 soil profiles from the Mediterranean, Castilla La Mancha, are assessed and soil quality reference values are calculated. Reference value contents (in mg kg^?1) were: Sc 50.8; V 123.2; Cr 113.4; Co 20.8; Ni 42.6; Cu 27.0; Zn 86.5; Ga 26.7; Ge 1.3; As 16.7; Se 1.4; Br 20.1; Rb 234.7; Sr 1868.4; Y 38.3; Zr 413.1; Nb 18.7; Mo 2.0; Ag 7.8; Cd 4.4; Sn 8.7; Sb 5.7; I 25.4; Cs 14.2; Ba 1049.3; La 348.4; Ce 97.9; Nd 40.1; Sm 10.7; Yb 4.2; Hf 10.0; Ta 4.0; W 5.5; Tl 2.3; Pb 44.2; Bi 2.2; Th 21.6; U 10.3. The contents obtained for some elements are below or close to the detection limit: Co, Ge, Se, Mo, Ag, Cd, Sb, Yb, Hf, Ta, W, Tl and Bi. The element content ranges (the maximum value minus the minimum value) are: Sc 55.0, V 196.0, Cr 346.0, Co 64.4, Ni 188.7, Cu 49.5, Zn 102.3, Ga 28.7, Ge 1.5, As 26.4, Se 0.9, Br 33.0 Rb 432.7, Sr 3372.6, Y 39.8, Zr 523.2, Nb 59.7, Mo 3.9, Ag 10.1, Cd 1.8, Sn 75.2, Sb 9.9, I 68.0, Cs 17.6, Ba 1394.9, La 51.3, Ce 93.5, Nd 52.5, Sm 11.2, Yb 4.2, Hf 11.3, Ta 6.3, W 5.2, Tl 2.1, Pb 96.4, Bi 3.0, Th 24.4, U 16.4 (in mg kg^?1). The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination.     

The Zr/Hf ratio as a fractionation indicator of rare-metal granites

The Zr-Hf geochemical indicator, i.e., the Zr/Hf ratio (in wt %) in granitic rocks is proposed to be used as the most reliable indicator of the fractionation and ore potential of rare-metal granites. It was empirically determined that the fractional crystallization of granitic magma according to the scheme granodiorite → biotite granite → leucogranite → Li-F granite is associated with a decrease in the Zr/Hf ratio of the granites. The reason for this is the stronger affinity of Hf than Zr to granitic melt. This was confirmed by experiments on Zr and Hf distribution between granitic melt and crystals of Hf-bearing zircon (T = 800°C, P= 1 kbar). The application of the Zr/Hf indicator was tested at three classic territories of rare-metal granites: eastern Transbaikalia, central Kazakhstan, and the Erzgebirge in the Czech Republic and Germany. The reference Kukul’bei complex of rare-metal granites in eastern Transbaikalia (J₃) is characterized by a uniquely high degree of fractionation of the parental granitic melt, with the granites and their vein derivatives forming three intrusive phases. The biotite granites of phase 1 are barren, the leucogranites of phase 2 are accompanied by greisen Sn-W mineral deposits (Spokoininskoe and others), and the final dome-shaped stocks of amazonite Li-F granites of phase 3 host (in their upper parts) Ta deposits of the “apogranite” type: Orlovka, Etyka, and Achikan. The Kukul’bei Complex includes also dikes of ongonites, elvanes, amazonite granites, and miarolitic pegmatites. All granitic rocks of the complex are roughly coeval and have an age of 142±0.6 Ma. The Zr/Hf ratio of the rocks systematically decreases from intrusive phase 1 (40–25) to phases 2 (20–30) and 3 (10–2). Compared to other granite series, the granites of the Kukul’bei Complex are enriched in Rb, Li, Cs, Be, Sn, W, Mo, Ta, Nb, Bi, and F but are depleted in Mg, Ca, Fe, Ti, P, Sr, Ba, V, Co, Ni, Cr, Zr, REE, and Y. From earlier to later intrusive phases, the rocks become progressively more strongly enriched or depleted in these elements, and their Zr/Hf ratio systematically decreases from 40 to 2. This ratio serves as a reliable indicator of genetic links, degree of fractionation, and rare-metal potential of granites. Greisen Sn, W, Mo, and Be deposits are expected to accompany granites with Zr/Hf < 25, whereas granites related to Ta deposits should have Zr/Hf < 5.     

THE GEOCHEMISTRY OF TANTALUM AND NIOBIUM

Ta and Nb are associated in nature. Both are oxyphile and are related geochemically to Fe, Mn, Ti, rare earths U, Th, Zr, W, Sn, Bi, and Sb. Both accompany the alkali metals,especially Na and Li. Their close relationship explains their isomorphism in mineral-forming processes. Zr, W, and Sn entrain Ta and Nb in the crystal lattices of their minerals in limited amounts. The concentration of Ta and Nb increases in the course of magma evolution from ultrabasic to alkalic. Nb predominates over Ta in the main kinds of rocks by from 5:1 to 17:1. Only in granite pegmatites is Ta dominant. In granitic rocks Ta and Nb are associated with Fe, Mn, Bi, Sb, W, and Sn. In granosyenitic complexes they form complex minerals with Ti, rare earths of the Y subgroup, U, and Th. Concentrations of Ta and Nb in granitic and granosyenitic complexes increase toward the end of the magmatic and pegmatitic processes, and afterward diminish toward the end of the pneumatolytic-hydrothermal processes. In alkalic complexes Ta and Nb are associated with Ti, rare earths of the Ce group, and Th. Concentrations of Ta and Ni in alkalic massifs are caused by magmatic differentiation. In alkalic ultrabasic complexes, in magmatic and pegmatitic processes, Ta and Nb do not form independent minerals but enter into minerals of Ti and Fe, i. e. perovskite, titanomagnitite, and pyroxenes. --M. Russell.     

流域上游基岩与下游冲积平原土壤化学组成的对比

对海河水系流域、鄱阳湖水系流域上游的基岩与下游的冲积平原土壤之间化学组成的对比研究显示,下游冲积物土壤的化学组成明显地受源岩成分、形成过程和形成环境的影响。流域上游基岩的一些特征元素在冲积物土壤中被明显地继承,如海河流域基岩和土壤中的CO2、CaO、MgO、FeO、Sr,鄱阳湖流域基岩和土壤中的W、Sn、Bi、U、Th、Pb、Rb、Tl、As、Sb、Se、Hg、Nb、Ta、Hf、B、Be、Ge、Pt、Pd、Y。受形成过程和形成环境的影响,处于暖温带半湿润季风气候下的海河流域冲积平原土壤以极富集CO2、CaO、Na2O、Cl,显著富集MgO、FeO、Sr,富集P、S为特征;而处于亚热带湿润季风气候下的鄱阳湖流域冲积平原土壤则以显著富集Hg、Se和富集Al2O3、Fe2O3H2O^＋、W、Sn、Bi、Mo、U、Th、Pb、Rb、Cs、Tl、Li、Be、B、Ga、Ge、Nb、Ta、Zr、Hf、As、Sb、Co、Cr、Ti、V、Zn、Pt、Pd、REE、Y为特征。无论是海河流域还是鄱阳湖流域的冲积平原土壤,均富集As、Sb、Hg、B、Cl、W、Sn、Bi、Pb、Se、Ge、Li、Cs、Cu、Au、Fe2O3、V、Cr、Ni、Zr、Hf、Y。     

四川省癌死亡率与土壤环境中化学元素的关系

利用中国癌死亡率与土壤坏境中化学元素的相关性成果，研究了四川省癌死亡率与土壤环境中化学元素：As、Cd、Co、Cu、Hg、Mn、Ni、Pb、Se、V、Li、Na、K、Rb、Cs、Mg、Ca、Sr、Ba、B、Al、Ga、In、Tl、Sc、Y、La、Ce、Pr、Nd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Th、U、Sn、Ti、Zr、Hf、Sb、Bi、Ta、Te、Mo、W、Br、I、Fe等52个元素含量的关系     

Characterisation of Memory Effects and Development of an Effective Wash Protocol for the Measurement of Petrogenetically Critical Trace Elements in Geological Samples by ICP-MS

High sensitivity and low detection limits would seem to make inductively coupled plasma-mass spectrometry (ICP-MS) an ideal analytical tool for determining low (sub-μg g^-1) concentrations of the rare earth elements (REE), Y, Zr, Nb, Hf, Ta, Sn, W, Mo, Th, and U in most mafic materials (e.g. Hall and Plant 1992). However, the generally "sticky" nature exhibited by most of the high field strength elements (HFSEs: Zr, Nb, Hf, Ta, Th and U) as well as Sn, W and Mo can result in spurious results due to memory effects transmitted between unknowns and calibration samples. This, in turn, can seriously compromise the sensitivity, accuracy, and precision of ICP-MS analyses for these elements in geological materials. Data resulting from analyses with poor accuracy and precision can lead to erroneous interpretation and misleading petrogenetic modelling. To resolve this problem, we propose an effective wash protocol for these critical trace elements.     

Determination of High Field Strength Elements, Rb, Sr, Mo, Sb, Cs, Tl and Bi at ng g−1 Levels in Geological Reference Materials by Magnetic Sector ICP-MS after HF/HClO4 High Pressure Digestion

Six low abundance rock reference materials (basalt BIR-1, dunite DTS-1, dolerite DNC-1, peridotite PCC-1, serpentine UB-N and basalt TAFAHI) have been analysed for high field strength elements (Zr, Nb, Hf, Ta, Th and U), Rb, Sr, Mo, Sb, Cs, Tl and Bi at ng g⁻¹ levels (in rock) by magnetic sector inductively coupled plasma-mass spectrometry after HF/HClO₄ high pressure decomposition. The adopted method uses only indium as an internal standard. Detection limits were found to be in the range of 0.08 to 16.2 pg ml⁻¹ in solution (equivalent to 0.08 to 16.2 ng g⁻¹ in rock). Our data for high field strength elements, Rb, Sr, Mo, Sb, Cs, Tl and Bi for the six selected low abundance geological reference materials show general agreement with previously published data. Our Ta values in DTS-1 and PCC-1 (1.3 and 0.5 ng g⁻¹) are lower than in previously published studies, providing smooth primitive mantle distribution patterns. Lower values were also found for Tl in BIR-1, DTS-1 and PCC-1 (2, 0.4 and 0.8 ng g⁻¹). Compared with quadrupole ICP-MS studies, the proposed magnetic sector ICP-MS method can generally provide better detection limits, so that the measurement of high field strength elements, Rb, Sr, Mo, Sb, Cs, Tl and Bi at ng g⁻¹ levels can be achieved without pre-concentration, ion exchange separation or other specialised techniques.     

Determination of Zirconium, Niobium, Hafnium and Tantalum at ng g-1 Levels in Geological Materials by Direct Nebulisation of Sample HF Solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble M and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were > 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.     

Effects of alteration on element distributions in archean tholeiites from the Barberton greenstone belt,South Africa

Major and trace element and modal analyses are presented for unaltered, epidotized, and carbonated tholeiite flows from the Barberton greenstone belt. Au, As, Sb, Sr, Fe⁺³, Ca, Br, Ga, and U are enriched and H₂O, Na, Mg, Fe⁺², K, Rb, Ba, Si, Ti, P, Ni, Cs, Zn, Nb, Cu, Zr, and Co are depleted during epidotization. CO₂, H₂O, Fe⁺², Ti, Zn, Y, Nb, Ga, Ta, and light REE are enriched and Na, Sr, Cr, Ba, Fe⁺³, Ca, Cs, Sb, Au, Mn, and U are depleted during carbonization-chloritization. The elements least affected by epidotization are Hf, Ta, Sc, Cr, Th, and REE; those least affected by carbonization-chloritization are Hf, Ni, Co, Zr, Th, and heavy REE. Both alteration processes can significantly change major element concentrations (and ratios) and hence caution should be used in distinguishing tholeiites from komatiites based on major elements alone. The amount of variation of many of the least mobile trace elements in the altered flows is approximately the same as allowed by magma model calculations. Hence, up to about 10% carbonization and 60% epidotization of tholeiite do not appreciably affect the interpretation of trace-element models for magma generation.     

Constraints from eclogite and MARID xenoliths on origins of mantle Zr/Hf–Nb/Ta variability

New trace-element data of rutile in kimberlite-borne ~1.85 Ga eclogite and pyroxenite xenoliths from the central Slave craton, as well as ~110 Ma MARID xenoliths from the Kaapvaal craton, provide constraints on the origins of lithospheric and sublithospheric mantle variability in high field strength element ratios. Rutiles in eclogites and pyroxenites have Zr/Hf ranging from 20 to 62 and Nb/Ta ranging from 10 to 40. Rutiles in MARID xenoliths have Zr/Hf from 24 to 33 and Nb/Ta from 10 to 41. Calculated whole-rock Zr/Hf is suprachondritic for eclogites with suggested gabbroic protoliths and subchondritic for boninite-like eclogites; the latter is consistent with cpx-controlled depletion in the protolith source. Within each eclogite type, positive correlations of Zr/Hf with La/Lu and negative correlations with Lu/Hf likely reflect fractionation of cpx and/or plagioclase during crystallisation of the protoliths. Zr/Hf–Nb/Ta relationships of some MARID-type rocks, which are products of lithospheric mantle metasomatism, and eclogite xenoliths plot on a silicate differentiation trend, whereas other samples have higher Nb/Ta at a given Zr/Hf. Fractionation of a few percent rutile from an HFSE-rich mafic melt can generate a trend towards strongly increased Nb/Ta at minimally changed Zr/Hf in the residual melt. Superposition of rutile fractionation on the effects of silicate differentiation, which fractionates Zr/Hf more strongly than Nb/Ta, can explain the Zr/Hf–Nb/Ta relationships of most eclogites from the central Slave craton as well as those of MARID rocks, metasomatised peridotites and group II kimberlites. By contrast, Zr/Hf–Nb/Ta relationships suggest that Group I kimberlites are mixtures between depleted peridotite and carbonatite. Thus, high Nb/Ta is a signature of lithospheric processes and may not be important in deeply subducted eclogites that bypass extended residence in the lithosphere. Conversely, considerable primary Zr/Hf variability was inherited by the eclogites, which is indicative of the compositional diversity of ancient subducted oceanic crust, which is expected to have generated substantial heterogeneity in sublithospheric basalt sources.     

Multi-Elemental Analysis of ATHO-G Rhyolitic Glass (MPI-DING Reference Material) by Femtosecond and Nanosecond LA-ICP-MS: Evidence for Significant Heterogeneity of B,V, Zn,Mo, Sn,Sb, Cs,W, Pt and Pb at the Millimetre Scale

This paper reports on the application of variants of LA-ICP-MS – including infrared femtosecond laser ablation (fs-LA) inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) and nanosecond laser ablation (ns-LA) coupled with single-collector sector-field (SF-) ICP-MS – to the in situ determination of trace elements in different splits of the reference material (RM) ATHO-G (MPI-DING). Analyses of the materials performed by fs- and ns-LA-ICP-MS demonstrated the efficiency of the techniques with typical accuracy at a level of ≤ ± 20%. One ‘anomalous’ split, however, displayed a significant discrepancy from the reference concentrations for B, V, Zn, Mo, Sn, Sb, Cs, W and Pb. Three- to six-fold enrichment of V, Mo, Cs and Pt relative to the reference contents in this split is likely to have been due to direct contact of the silicate melt with Pt crucible walls and ceramics. Boron, Zn, Sn, Sb, W and Pb depletion relative to the reference concentrations is probably due to siderophile element adsorption by the Pt walls and/or related to the formation of volatile-depleted compositional cords during the preparation process. Our results imply that additional precautions should be taken against volatile/siderophile element heterogeneity in marginal/surface layers (≤ 10 mm) during the preparation of RMs by the fusion technique.     

5-Br-PADAP二波长联合分光光度法同时测定矿石中铌和钽

铌、钽的显色剂很多,但由于两元素性质相近,常互相干扰,特效的光度测定方法却不多,能同时测定的更少。 5—Br—PADAP近年已成功地用于测定铌,测钽时则无法消除铌的干扰,有人     

Trace element abundances in andesites

Abundance data for Cs, Rb, Tl, Ba, Pb, Sr, the rare earths, Th, U, Zr, Hf, Sn, Nb, Mo, Mn, Cu, Co, Ni, Sc, V, Cr, Ag, Sb and the major elements are reported for two andesites and a dacite from Saipan, nine andesites and a dacite from Bougainville and two andesites from Fiji. The Saipan rocks are low-K varieties and contain notably low abundances of Rb, Ba, Th and U and have rare earth patterns subparallel to chondritic patterns. The Bougainville andesites include low-Si and high-K varieties which have higher concentrations of the large cations. The Fijian samples are close to the average circum-Pacific andesite and have rareearth patterns sub-parallel to those of sedimentary rocks.All the andesites contain characteristically low (< 20 ppm) values for Ni and have Ni/Co ratios < 1, and V/Ni ratios > 10.These data preclude derivation of calc-alkaline rocks by mixing of upper crustal material or by fractional crystallisation from basaltic parents. A two stage model is proposed involving sea-floor spreading and transportation of the oceanic crust down the dipping seismic plane into the mantle where it is remelted to form andesites.