Suite Of Trace Elements Research Articles

Hydrologic and biogeochemical controls on trace element export from northern Wisconsin wetlands

Wetlands play an important role in determining the water quality of streams and are generally considered to act as a sink for many reactive species. However, retention of chemical constituents varies seasonally and is affected by hydrologic and biogeochemical processes including water source, mineral weathering, DOC and SPM cycling, redox status, precipitation/dissolution/adsorption, and seasonal events. Relatively little is known about the influence of these factors on trace element cycling in wetland-influenced streams. To explore the role of wetlands with respect to the retention/release of trace elements to streams, we examined temporal and spatial patterns of concentrations of a large suite of trace elements (via ICP-MS) and geochemical drivers in five streams and wetland rivulets draining natural wetlands in a northern Wisconsin watershed as well as in their groundwater sources (terrestrial recharge, lake recharge, and older lake recharge). We performed principal components analyses of the concentrations of elements and their geochemical drivers in both the streams and rivulets to assist in the identification of factors regulating trace element concentrations. Variation in trace and major element concentrations among the streams was strongly related to the proportion of terrestrial recharge contributing to the stream. A dominant influence of water source on rivulet chemistry was supported by association of groundwater-sourced elements (Ba, Ca, Cs, Mg, Na, Si, Sr) with the primary statistical factor. DOC appeared in the first principal component factor for the streams and in the second factor for the rivulets. Strong correlations of Al, Cd, Ce, Cu, La, Pb, Ti, and Zn with DOC supported the important influence of DOC on trace metal cycling. A number of elements in the rivulets (Al, La, Pb, Ti) and streams (Al, Ce, Cr, Cu, La, Pb, Ti, Zn) had a significant particulate cycle. Redox cycling and precipitation/dissolution reactions involving Fe and Mn likely impacted Cu and Mo as evidenced by the low levels in the rivulets. Variance in Fe, Mn and the metal oxy-anions was associated with factors related to redox cycling and adsorption reactions in the wetland sediments. In streams, DOC and metals with a high affinity for DOC were associated with a factor which also included negative loadings for groundwater-sourced elements, reflecting the importance of seasonal hydrologic events which flush DOC and metals from wetland sediments and dilute groundwater sourced metals. Redox processes were of secondary importance in the streams but of primary significance in the rivulets, documenting the importance of anoxic conditions in wetland sediments on groundwater en route to the stream.

Multistage Sedimentary and Metamorphic Origin of Pyrite and Gold in the Giant Sukhoi Log Deposit, Lena Gold Province, Russia

Gold mineralization at Sukhoi Log in eastern Siberia is hosted in a deformed Neoproterozoic organic-bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline. The deposit contains about 30 million ounces of gold at an average grade of 2.0 g/t Au and is one of the largest known undeveloped gold resources. The high-grade gold zone forms a gently dipping tabular body in the core of the anticline. The best gold grades occur in narrow, bedding-parallel pyrite-quartz veinlets that have been folded during the main deformation event. Lower grade gold is associated with disseminated pyrite developed in and around the high-grade core of the deposit. Detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments. The two earliest forms of pyrite, termed py1 and py2, are commonly developed in stratiform layers of micron-sized crystals, framboids and fine euhedra, which are interpreted as synsedimentary to early diagenetic in origin. Coarser grained, bedding-parallel aggregates of inclusion-rich pyrite, termed py3, contain inclusions of arsenopyrite, native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation. Coarse euhedral pyrite, py4, overgrows the earlier pyrite (py1, py2, and py3), and the slaty cleavage developed in the host rocks, indicating a syndeformation timing. Late- stage, inclusion-free pyrite, py5, overgrows and replaces earlier sulfides and is considered to be syn- to late deformation. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold, varying from 0.4 to 12.1 ppm, with a mean of 3.22 ppm Au, and 1,900 ppm As. Py1 is also enriched in a suite of trace elements (Mo, Sb, Ni, Co, Se, Te, Ag, Cu, Pb, Zn, Mn, Ba, Cr, U, V), which are similar to those concentrated by organic processes in euxinic sedimentary environments. Later generations of pyrite, from py2 to py5, including pyrite in bedding- parallel pyrite-quartz veinlets, contain progressively lower contents of invisible gold and most other trace elements. However, this metamorphic and postmetamorphic pyrite contains microinclusions of free gold, arsenopyrite, pyrrhotite, sphalerite, and chalcopyrite. The paragenetic, textural, and chemical relationships at Sukhoi Log suggest that gold was clearly initially introduced prior to cleavage development, accompanying sedimentation of the organic-rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite. Subsequently, accompanying deformation, gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding-parallel pyrite-quartz veinlets. Two key processes are considered vital to the formation of the Sukhoi Log deposit: original synsedimentary and early diagenetic concentration of gold, dissolved within arsenian pyrite in organic-rich black shales, and metamorphic processes that liberated gold from the early forms of arsenian pyrite, to be concentrated as free gold, and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite-quartz veinlets in the core of an overturned anticline. These ore-forming processes are unlikely to be unique to Sukhoi Log; other black-shale and turbidite-hosted deposits that occur in rifted continental margin environments, which have undergone collision and basin inversion, may form by similar processes.

Partitioning of U and Th during garnet pyroxenite partial melting: Constraints on the source of alkaline ocean island basalts

Uranium series disequilibria in ocean island basalts (OIB) provide evidence for the presence of garnet in their source region. It has been suggested that enriched OIB signatures derive from mantle lithologies other than peridotite, such as eclogite or pyroxenite, and, in particular, that silica-poor garnet pyroxenite is the source lithology for alkali basalts. To test the ability of such a source to produce the U–Th disequilibria observed in alkali OIB, we determined experimentally clinopyroxene-melt and garnet-melt partition coefficients for a suite of trace elements, including U and Th, at 2.5 GPa and 1420–1450 °C. The starting composition for the experiments was a 21% partial melt of a silica-poor garnet pyroxenite. Experimentally determined clinopyroxene-melt partition coefficients range from 0.0083 ± 0.0006 to 0.020 ± 0.002 for Th and from 0.0094 ± 0.0006 to 0.024 ±0.002 for U, and garnet-melt partition coefficients are 0.0032 ± 0.0004 for Th and 0.013 ± 0.002 for U. Comparison of our experimental results with partition coefficients from previous experimental studies shows that the relative compatibilities of U and Th in both garnet and clinopyroxene are different for different mineral compositions, leading to varying degrees of U/Th fractionation with changing lithology. For a given melting rate and extent of partial melting, mafic lithologies tend to produce larger 230Th excesses than peridotite. However, this effect is minimized by the greater overall extents of melting experienced by eclogites and pyroxenites relative to peridotite. Results from chromatographic, batch, and fractional melting calculations with binary mixing between partial melts of pyroxenite and peridotite, carried out using our new partitioning data for the pyroxenite component and taking into account variable productivities and different solidus depths for the two lithologies, suggest that OIB are not the product of progressive melting of a source containing a fixed quantity of garnet pyroxenite. Melting a peridotite with enriched signatures, and mixing those melts with melts of a depleted, “normal” peridotite, is an alternative explanation for the trends seen in Hawaiian, Azores and Samoan lavas.

Variability in the Yield of Benzophenanthridine Alkaloids in Wildcrafted vs Cultivated Bloodroot (Sanguinaria canadensis L.)

Populations of bloodroot [Sanguinaria canadensis L. (Papaveraceae)] are found throughout the eastern forests of North America, with particular abundance in the southern Appalachian Mountains. Increasingly, it is finding use in Europe as a nonantibiotic animal feed supplement to promote weight gain. As efforts to cultivate this herb are underway, there is a need to understand the effect of agronomic permutations on both the dry mass rhizome yield and the yield of benzophenanthridine alkaloids. Month-to-month variability of the concentration of the alkaloids sanguinarine and chelerythrine in both cultivated and wildcrafted bloodroot was examined. The alkaloid yield was consistently higher, but more variable, in wildcrafted plants. On average, cultivated rhizomes were both larger and more consistently sized than those that were wildcrafted. The concentration of a suite of trace elements was measured in soil that was collected concomitantly with each plant accession. Differences in element profiles were compared against alkaloid yields.

Cycling of B, Li, and LILE (K, Cs, Rb, Ba, Sr) into subduction zones: SIMS evidence from micas in high- P/ T metasedimentary rocks

The Catalina Schist (California) affords a unique opportunity to evaluate the effects of varying prograde P– T paths on the magnitudes of devolatilization and chemical/isotopic alteration of subducting sediments. Analysis of a suite of trace elements (Li, B, Rb, Sr, Cs, Ba) in micas obtained by secondary ion mass spectrometry (SIMS) complements previously published whole-rock data for metasedimentary rocks in the Catalina Schist and circumvents problems associated with chemical/isotopic overprinting during retrogression, further elucidating trace element redistribution during devolatilization along prograde P– T paths. SIMS mineral analyses confirm the inference from the whole-rock data that white mica (and in a few higher-grade samples, also biotite) is the dominant reservoir for B, Rb, Ba, and Cs. The mineral residency of Li and Sr is more complex, as Li is also highly concentrated in chlorite (where present) and in some amphiboles, and Sr whole-rock budgets are strongly influenced by the presence or absence of Ca-rich phases (e.g., lawsonite, clinozoisite, minor carbonate and titanite). Changes of concentrations of B and Cs, in white micas, with increasing metamorphic grade parallel the whole-rock trends, further demonstrating the loss of these elements from recrystallizing white micas during prograde devolatilization reactions. Trace element data for other minerals in the metasedimentary samples (Ca–Al silicates, plagioclase, chlorite, biotite, garnet, kyanite) confirm expected concentrations as related to ionic radius and charge and demonstrate element redistribution during prograde (and retrograde) reactions. For amphibolite-facies metasedimentary rocks, multiple generations of white mica, including a finer-grained, higher-Si generation related to retrogradation, have distinct trace element compositions. In pegmatites produced by partial melting at amphibolite-facies conditions, B, Li, and the LILE are similarly concentrated in coarse-grained muscovite, indicating inheritance of trace element compositions from their metasedimentary sources. These SIMS data, combined with the whole-rock data for the same samples, demonstrate that the deep transfer of relatively “fluid-mobile” trace elements is strongly dependent upon the prograde P– T path experienced by the subducting sediments. Efficient retention of B, Cs, and N in micas, to depths of > 40 km, is evident from study of these and other forearc metasedimentary suites that experienced low- T prograde paths representative of most modern subduction zones, and is consistent with models invoking additions of these elements from the slab into arc source regions, perhaps to contribute to the across-arc chemical trends (Be/Be, B/La, Cs/Th, Ba/Th) observed in some margins.

GEOCHEMICAL- MINERALOGICAL AND METALLOGENETICAL ASPECTS CONCERNING THE ORIGIN OF SEDIMENTS FROM LEG. 22 D.S.D.P DRILLED SITES 212 AND 213 IN EASTERN INDIAN OCEAN

Basic mineralogical and geochemical data, are presented for sediment core samples from Deep Sea Drilling Project(D.S.D.P) boreholes .Sites 212 and 213 respectively, from the eastern Indian Ocean. In both Sites the Fe-Mn oxides are abundant controlling a numerous suite of trace elements. In Site 212 the Fe-Mn oxides are more abundant in the upper part of the borehole having mainly a diagenetic or hydrogenous origin, whilst in Site 213 these oxides are more abundant in the lower part having mainly a hydrothermal origin. In both Sites clay minerals are consisting mostly of the expandable mixed layered smectite/illite. The geochemical data shows that in both Sites the majority of the sediments have the characteristics of typical deep sea clay being both of detrital and authigenic origin. In Site 212 these clays with considerable amount of palygorskite and the zeolite clinoptilolite, both of authigenic origin, opaline silica, biogenous CaCOj ,the Fe-Mn oxides and some other detrital minerals together control the bulk chemical composition of the sediments. In Site 213 the clays with large amounts of Fe-Mn oxides and considerable amounts of the zeolite Phillipsite and Palygorskite in small amounts and some other detrital minerals, control the chemical composition of the sediments. The increase in the Ti/Al and Mg/Al ratios with depth in both Sites implies a volcanoclastic input in the bottom sediments probably from the underlying basaltic basement

Effects of competition and coal-combustion wastes on recruitment and life history characteristics of salamanders in temporary wetlands

Amphibians in natural systems must cope with a number of biotic and abiotic stressors that can potentially interact with pollutants to influence toxicity. Although interactive effects of short-lived pesticides with various environmental stressors have been studied, how persistent and bioaccumulative compounds such as metals interact with natural stressors to influence amphibians remains unexplored. We exposed the salamander Ambystoma talpoideum to coal-combustion wastes (a complex mixture of metals and metalloids, hereafter referred to as CCW) at low and high larval density throughout aquatic development in mesocosms simulating temporary wetlands. CCW and high density reduced survival to metamorphosis by 57–77% and 85–92%, respectively, and the effects of these two factors together were additive. Reduced metamorphosis was due in part to larval mortality prior to initiation of pond drying, but CCW and high density also extended the larval period, causing mortality of larvae that were not ready to metamorphose before the pond dried. To our knowledge, this is the first demonstration of a pollutant-induced extension of larval period leading to reduction in amphibian recruitment. Metamorphs were smaller in high density compared to low in reference ponds, but those from CCW emerged at similar sizes irrespective of density, suggesting less-than-additive effects of density and CCW on metamorph size. The adverse responses of salamanders to CCW were likely due to direct toxicity, as A. talpoideum metamorphs accumulated high concentrations of a suite of trace elements (As, Se, Sr, and V), and also to indirect effects on the community food web. We conclude that in no case did the addition of a natural stressor (high density) exacerbate CCW-related effects, but that the effects of CCW alone can be detrimental to larvae of salamanders that breed in temporary ponds.

Non-river flood barium signals in the skeletons of corals from coastal Queensland, Australia

Two corals from coastal Queensland (Cow and Calf Islands, and Orpheus Island) have been analysed for a suite of trace elements by laser-ablation ICP-MS (LA-ICP-MS). Barium signals in these two corals are ‘anomalous’ in comparison with Ba behaviour seen in other near-shore corals from this region. The two corals display large sharp peaks in spring which do not correlate with markers of river discharge (Y/Ca and fluorescence). This Ba pattern contrasts with ‘normal’ behaviour—characterised here by the patterns previously published for two other coastal Queensland corals (King Reef and Pandora Reef), which display Ba peaks in summer associated with flooding of nearby rivers [1] [D.J. Sinclair, M.T. McCulloch, Corals record low mobile barium concentrations in the Burdekin River during the 1974 flood: evidence for limited Ba supply to rivers?, Palaeogeogr. Palaeoclimatol. Palaeoecol. 214 (1–2) (2004) 155–174]. Similarities are observed between the anomalous Ba in the Queensland corals and other published patterns of Ba behaviour in corals from South Africa and the Arabian Sea. This non-river flood Ba behaviour is characterized by large sharp spikes of Ba which are resistant to oxidative cleaning and form a continuous horizon within the coral. Curiously, not all corals from a region display anomalous Ba behaviour despite being in similar environments. The timing of anomalous Ba is consistent within a coral, but may vary from one location to the next. Anomalous Ba spikes are too large to be caused by Ba-rich upwelling, and no single environmental forcing function seems to be able to account for their timing. This combination of observations argues against an exogenous abiotic source for the anomalous Ba signal; instead, it may result from a biological event triggered by a combination of environmental parameters. Three hypotheses are presented, and critically tested against the observations: barite inclusion following phytoplankton blooms, decaying blooms of the blue-green algae Trichodesmium, and physiological perturbations associated coral mass spawning. None of the three hypotheses are fully consistent with all of the observations and it is concluded that no satisfactory explanation currently exists for the anomalous Ba spikes.

Platinum-group elements in Deccan mafic rocks: a comparison of suites differentiated by Ir content

A suite of 18 Deccan mafic rocks including 14 basalts and four dolerite dykes from seven different localities in the Maharashtra region of the western Deccan volcanic province were analyzed for Ir, Pt, Pd and Au by radiochemical neutron activation analysis (Ir, Pd and Au) and lead fire assay (Pt, Pd and Au) with ICP–MS finish. To provide additional petrogenetic insight, major elements, a suite of trace elements including rare earth elements (REEs), and Sr and Nd isotopic compositions were also determined. Based on the distribution of Ir values, two subsets of samples were distinguished. One includes 14 samples with average Ir concentration of 0.024 ppb, and the other, a much smaller group of four samples, averages 0.21 ppb Ir or some 10 times the average concentration of the larger group. These two subsets are differentiated by other compositional properties in addition to noble metal contents. These include lower REE, higher transition element (Ni, Cr) and S contents, large negative Nb–Ta anomalies in mantle normalized profiles, more radiogenic Sr and very negative ε Nd isotopic compositions in the Ir-rich group. In addition, Pd, Pt and Au averages are lower in the Ir-rich group. These geochemical features are interpreted to reflect processes of magma generation in a mantle environment and magma contamination in a crustal or lithospheric mantle setting. The critical mantle variable is percentage partial melting of source peridotite. Relatively higher percentage partial melting is required to generate the Ir-rich magmas. Based mainly on Sr and Nd isotopic evidence and Nb–Ta abundances, the Ir-rich group is considered more strongly modified by crustal and/or lithospheric mantle assimilation than the main group of melts. Fractional crystallization appears to have increased Pd, Au and Cu contents of the main group of magmas relative to the Ir-rich magmas, and is probably a significant factor distinguishing these Deccan rocks as having higher concentrations of these elements than other continental flood basalts (CFBs).

Fingerprinting of South African cement clinkers and gypsum as a tool for cement identification purposes

The final composition of cement is of great importance for both the manufacturer and the consumer, since the behaviour of the cement and its application depend largely on it's composition. The composition of cement in turn, depends heavily on the raw materials, the geological origin thereof and the manufacturing process. In previous research, the major element composition of cement has been well-characterised, but the minor and trace element composition in many cases has not. This investigation is an attempt to analyse some of the materials comprising cement, cement clinker and gypsum, for a suite of trace elements that will provide a unique fingerprint of the final product. It was found that for both the clinker and the gypsum a suite of trace elements can be successfully employed to uniquely characterise the materials. The contribution of such a fingerprint is that it can provide valuable information in the case of a forensic analysis for discrimination purposes and also predict the behaviour of these species with regard to their immobilisation in a cementitious matrix.

The interrelationships among trace element cycling, nutrient loading, and system complexity in estuaries: A mesocosm study

Biogeochemical interactions between a suite of trace elements and nutrients were examined in a series of experimental mesocosm experiments to understand how multiple stressors affect estuarine environments and how these effects are modified by the complexity of the system used to examine them. Experimental treatment included additions of nutrients and trace elements separately and combined, along with a gradient in experimental system complexity. Eight mesocosm experiments were carried out from 1996 through 1998. Increased nutrients generally decreased dissolved trace element concentrations, in large part through an increase in phytoplankton biomass, but also by increasing the concentration of metals in the particles. Trace element additions increased dissolved nutrients by decreasing phytoplankton biomass. The presence of sediments reduced both dissolved trace element and nutrient concentrations. Other complexity treatments had weaker effects on both dissolved nutrients and trace elements. Many of the observed effects appeared to be seasonal, occurring only in spring, or their magnitude was greater in spring. This may be linked to a change from phosphorus to nitrogen limitation that often occurs in the Patuxent River estuary in the late spring or early summer period.

Geochemical evolution of the Dras–Kohistan Arc during collision with Eurasia: Evidence from the Ladakh Himalaya, India

Abstract The Dras 1 Volcanic Formation of the Ladakh Himalaya, India, represents the eastern, upper crustal equivalent of the lower crustal gabbros and mantle peridotites of the Kohistan Arc exposed in Pakistan. Together these form a Cretaceous intraoceanic arc now located within the Indus Suture zone between India and Eurasia. During the Late Cretaceous, the Dras–Kohistan Arc, which was located above a north‐dipping subduction zone, collided with the south‐facing active margin of Eurasia, resulting in a switch from oceanic to continental arc volcanism. In the present study we analyzed samples from the pre‐collisional Dras 1 Volcanic Formation and the postcollisional Kardung Volcanic Formation for a suite of trace elements and Nd isotopes. The Kardung Volcanic Formation shows more pronounced light rare earth element enrichment, higher Th/La and lower ɛNd values compared with the Dras 1 Volcanic Formation. These differences are consistent with an increase in the reworking of the continental crust by sediment subduction through the arc after collision. As little as 20% of the Nd in the Dras 1 Volcanic Formation might be provided by sources such as the Karakoram, while approximately 45% of the Nd in the Kardung Volcanic Formation is from this source. However, even before collision, the Dras–Kohistan Arc shows geochemical evidence for more continental sediment contamination than is seen in modern western Pacific arcs, implying its relative proximity to the Eurasian landmass. Comparison of the lava chemistry in the Dras–Kohistan Arc with that in the forearc turbidites suggests that these sediments are partially postcollisional, Jurutze Formation and not all pre‐collisional Nindam Formation. Thus, the Dras–Eurasia collision can be dated as Turonian–Santonian (83.5–93.5 Ma), older than it was previously considered to be, but consistent with radiometric ages from Kohistan.

Partial melting in Archean subduction zones: constraints from experimentally determined trace element partition coefficients between eclogitic minerals and tonalitic melts under upper mantle conditions

The partitioning of an extensive suite of trace elements between garnet, clinopyroxene, and hydrous tonalitic melts has been studied experimentally at 1.8 GPa and 1000–1040 °C. The knowledge of trace element partitioning between minerals and coexisting tonalitic melts is essential for geochemical models in order to explain the genesis of Archean tonalite-trondhjemite-granodiorite suites (TTGs). Our experiments were performed on a natural tonalite doped with two different trace element mixtures and with TiO 2 to stabilize titanates. Trace element concentrations of crystals and coexisting melts were measured by laser ablation microprobe. The partition coefficients ( D's) are independent of the trace element concentration over the concentration ranges used. The partition coefficients reported in this paper are a considerable extension of the few available data sets in intermediate to silicic systems. The D-values mostly agree well with previously published data and with predictive models. The garnet partition coefficients show steeper patterns with higher D's for heavy REE, lower D's for highly incompatible elements and lower La/Yb-ratios than previously published data for basaltic systems, whereas clinopyroxene partition coefficients show similar patterns but higher values than for basaltic systems. A set of calculated partition coefficients based on best-fit parabolas was used to model trace element fractionation in melts in equilibrium with rutile-bearing eclogitic residues. The calculated melts reproduce the overall trace element patterns of Archean TTGs, i.e. the melts show strongly fractionated REE patterns, depletions in Nb and heavy REE, and high Zr and Hf concentrations relative to Sm on normalized plots. The calculated residues have depleted trace element patterns with positive Nb anomalies and flat heavy rare earth element patterns similar to rutile-bearing xenolithic eclogites reported from Siberia and West Africa. Restites from eclogite melting are complementary to Archean TTGs and may be an important reservoir of Nb and Ta.

Dry deposition and foliar leaching of mercury and selected trace elements in deciduous forest throughfall

The estimated annual throughfall deposition flux of Hg in a northern mixed-hardwood forest in the Lake Huron Watershed was 10.5±1.0 μg m −2 compared to an annual precipitation Hg flux of 8.7±0.5 μg m −2 (June 1996–June 1997). The source of this additional Hg in throughfall is often attributed to wash-off of dry deposition, but foliar leaching of Hg may also be important. To determine the influence of both dry deposition and foliar leaching of Hg and other elements in throughfall, we measured a suite of trace elements (Hg, Al, Mg, V, Mn, Cu, Zn, As, Rb, Sr, Cd, Ba, La, Ce, and Pb) in throughfall, precipitation, and ambient air samples from a northern mixed-hardwood forest. Based on a multiple linear regression model, dry deposition had the most important influence on Hg, Al, La, Ce, V, As, Cu, Zn, Cd, and Pb fluxes while foliar leaching strongly influenced Mg, Mn, Rb, Sr, and Ba fluxes in net throughfall. The Hg dry deposition flux was estimated using gaseous and aerosol Hg measurements and modeled deposition velocities. The calculated dry deposition flux (∼12–14 μg m −2) of Hg to the canopy indicated that atmospheric deposition of Hg could easily account for all of the Hg deposited in net throughfall (1.9±0.1 μg m −2). Although there is a large uncertainty associated with these techniques, the modeling estimates indicate that atmospheric Hg may account for all of the Hg deposited in litterfall (11.4±2.8 μg m −2).

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.

Trace elements in aerosol and precipitation at New Castle, NH, USA

Concentrations of a suite of trace elements (Al, Ag, As, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sr, V, Zn) were measured in aerosol and precipitation samples collected at a coastal site in New Castle, NH, from August 1996, through July 1997. Metal concentrations in aerosol and precipitation exhibit a high degree of temporal variability over the annual cycle, varying by approximately one order of magnitude or less for aerosol metals and by ∼2–3 orders of magnitude in precipitation. Estimates of the total annual atmospheric deposition of metals to the Gulf of Maine range from ∼10 3 kg yr −1 for Ag, ∼10 4–10 5 kg yr −1 for the majority of metals, and ∼10 6 kg yr −1 for the crustal elements Al and Fe.

The effect of Ca-Tschermaks component on trace element partitioning between clinopyroxene and silicate melt

We have studied the influence of Ca-Tschermaks (Calcium Tschermaks or CaTs) content of clinopyroxene on the partitioning of trace elements between this phase and silicate melt at fixed temperature and pressure. Ion probe analyses of experiments carried out in the system Na 2O–CaO–MgO–Al 2O 3–SiO 2, at 0.1 MPa and 1218°C, produced crystal-melt partition coefficients ( D) of 36 trace elements (Li, Cl, Sc, Ti, V, Cr, Fe, Co, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Sb, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta and W), for clinopyroxene compositions between 10 and 32 mol% CaTs. Partition coefficients for 2+ to 5+ cations show, for each charge, a near parabolic dependence of log D on ionic radius of the substituting cation, for partitioning into both the M1 and M2 sites of clinopyroxene. Fitting the results to the elastic strain model of Blundy and Wood [Blundy, J.D., Wood, B.J., 1994. Prediction of crystal-melt partition coefficients from elastic moduli. Nature 372, 452–454] we obtain results for the strain-free partition coefficients of theoretical cations ( D 0), with site radius r 0, and for the site's Young's Modulus ( E). In agreement with earlier data our results show that increasing ivAl concentration in cpx is matched by increasing D, E M1, E M2 and D 0 for tri-, tetra- and pentavalent cations. The degree of fractionation between chemically similar elements (i.e. Ta/Nb, Zr/Hf) also increases. In contrast, D values for mono-, di- and hexavalent cations decrease with increasing ivAl in the cpx. The large suite of trace elements used has allowed us to study the effects of cation charge on D 0, r 0 and E. We have found that D 0 and r 0 decrease with increasing cation charge, e.g. r 0=0.66 Å for 4+ cations and 0.59 Å for 5+ cations substituting into M1. Values of E M1 and E M2 increase with cation charge as well as with increasing ivAl content. The increase in E M2 is linear and close to the trend set by Hazen and Finger [Hazen, R.M., Finger, L.W., 1979. Bulk modulus-volume relationship for cation–anion polyhedra. J. Geophys. Res. 84 (10) 6723–6728] for oxides. E M1 values are much higher and do not fit the trend predicted by the Hazen and Finger relationship.

The application of laser ablation ICP-MS to the analysis of volcanic glass shards from tephra deposits: bulk glass and single shard analysis

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been applied to the chemical analysis of fine-grained (125–250 μm) volcanic glass shards separated from tephra deposits. This has been used both for bulk sample analysis and for the analysis of individual shards. Initial work concentrated on the use of an infra-red (IR) laser operating at 1064 nm, which gave craters of the order of 200 μm and was suitable for the analysis of bulk samples. This technique requires of the order of 80 μg of sample to determine a full suite of trace elements. Modification of the laser optics to enable operation in the ultra-violet (UV, at 266 nm) enables craters between 5 and 50 μm diameter to be produced, and the UV laser couples better with glass than the IR laser. We have applied this UV laser system to the analysis of single shards from Miocene tephra deposits from the Ruby Range in south-west Montana. Detection limits are below 1 ppm for a wide range of petrogenetically significant elements, but are critically dependent upon operating conditions. Calibration is achieved using synthetic multi-element glasses, with internal standardisation provided from electron probe analyses. Analysis of single shards provides a wide range of data from a single sample, enabling (i) magmatic evolution to be discerned within one eruption and (ii) the identification of separate populations of shards within one deposit which may not be apparent from the electron probe data. In this paper we will present a summary of the techniques used for both bulk sample and single shard analysis and compare some new bulk analyses with analyses of glass derived from other analytical methods.

Crystal-chemical controls on trace element partitioning between garnet and anhydrous silicate melt

We performed experiments at 3.0 GPa and 1530‐1565 °C to investigate the effects of crystal composition on trace element partitioning between garnet and anhydrous silicate melt. Bulk compositions along the pyrope (Py: Mg 3Al2Si3O12)-grossular (Gr: Ca 3Al2Si3O12) join, doped with a suite of trace elements (Li, B, K, Sc, Ti, Sr, Y, Zr, Nb, Cd, In, REE, Hf, Ta, Th, and U) produced homogeneous garnets, ranging in composition from Py 84Gr16 to Py 9Gr91, in equilibrium with melt. Trace element partition coefficients ( D-values), measured by SIMS, depend greatly on the Mg/ (Mg + Ca) of garnet. For example, from Py84 to Py9, DLa increases from 0.004 to 0.2, whereas DU increases from 0.029 to 0.42. These variations can be explained by the lattice strain model of Blundy and Wood (1994), which describes trace element partitioning of an element i in terms of the ionic radius of i (ri), the size of the lattice site on which i partitions (r0), the Young’s modulus of the site (), and the (theoretical) partition coefficient D0 for an ion of radius r0. For trivalent cations substituting in the garnet X-site (Y, REE, Sc, and In), apparent values of r0 fitted to our data vary systematically from 0.935 ± 0.004 A (Py 84) to 0.99 ± 0.01 A (Py 9), a trend consistent with variations in the size of the X-site. Values of D0 show an increase from Py9 (D0 = 2.8 ± 0.1) to Py 84 (4.8 ± 0.1) and Young’s modulus E varies from 257 ± 20 GPa for Py 60 to 590 ± 40 GPa for Py 84. These results allow a quantitative assessment of the influence of crystal chemistry on garnet-melt D-values, thereby forming the basis for a predictive model similar to that recently developed for clinopyroxene-melt partitioning by Wood and Blundy (1997). Our new data emphasize the importance of taking into account crystal composition when modeling trace element behavior in natural systems.

Nd-Sr isotopic and trace element geochemistry of river sediments and soils in a fertilized catchment, New South Wales, Australia

Neodymium and strontium isotopes and a suite of trace elements have been used to distinguish between the various sources of particulate loads and soils in a major catchment of the Murray-Darling drainage system, the largest river in Australia. One of the goals was to estimate additions of Sr and rare earth elements of anthropogenic (fertilizer) origin to the natural catchment sources to the soils and streams. Among possible sediment sources, Tertiary basalts and Paleozoic metagraywackes have the lowest 87Sr/ 86Sr and highest ϵ Nd, whereas Paleozoic metapelitic rocks have negative ϵ Nd and the highest 87Sr/ 86Sr. Phosphate fertilizers have strongly negative ϵ Nd and 87Sr/ 86Sr similar to Tertiary seawater. Soils formed on basalt and metagraywacke have compositions that are shifted toward higher 87Sr/ 86Sr and lower ϵ Nd than their parent rocks. REE patterns and elemental ratios such as Nd/P are also distinctive between fertilizer and natural catchment sources. Reservoir sediment from the upper catchment have isotopic and trace element compositions that confirm that the dominant source of stream particulates is from basalt soils in the steep upland part of the catchment. Mixing calculations based on isotopic and elemental compositions for reservoir sediment in the upper catchment are consistent with less than 0.2% bulk addition by mass of fertilizer to the natural sediment source. The isotopic compositions of soils in less easily eroded portions of the upper catchment reflect the addition of a component to the soil which is interpreted to be wind-blown dust, derived either from Paleozoic granitoids that dominate the lower regions of the catchment or from more distal westerly sources. Sediment from the lower catchment requires that the dominant source below the reservoir is derived from Paleozoic granitoid and metapelitic rocks of the New England fold belt. The lower catchment sediments show no definitive evidence of either basalt or fertilizer input. Natural sources dominate the particulate loads in these streams.