Range Of Trace Element Concentrations Research Articles

Evolution from magmatic to hydrothermal activity beneath the Cerro Escorial volcano (NW Argentina) as sampled by erupted quartz and brines

Large quartz pebbles erupted with the Escorial ignimbrite provide insight into the late-magmatic evolution of the shallow, cooling magmatic-hydrothermal system below the Cerro Escorial volcano of the Southern Central Volcanic Zone in the Argentine Andes. The ignimbrite is of relatively small volume, crystal-rich, dacitic in composition, and not particularly water-rich, as amphibole is absent. Eruption temperature was estimated to be close to 850 °C. The quartz pebbles provide insight into the magmatic-hydrothermal transition beneath the volcano. Based on textures, trace element composition (analyzed by laser-ablation inductively-coupled plasma mass spectrometry), and inclusion content, the pebbles can be separated into pegmatite-like megacrysts and lower-temperature, epithermal microcrystalline quartz. Both types are distinct from magmatic phenocrysts present in porphyritic clasts ejected by the ignimbrite.The megacrysts show a wide range of trace element concentrations, with elevated Al concentrations and Al/Ti and Ge/Ti ratios compared to quartz phenocrysts. Although some contamination by submicroscopic inclusions and cooling to near-solidus temperatures may perturb the signal in some cases, the range of trace element concentrations in quartz crystals from this system may reflect a change in crystallization conditions from initial precipitation from typical evolved silicate melt to fast growth from residual melt and/or fluid in pegmatitic pockets or coarse-grained hydrothermal “veins” at locally variable precipitation conditions.Abundant primary and secondary silicate melt inclusions and a variety of secondary fluid inclusions are present within the megacrysts. In particular, brine inclusions are densely packed with salt crystals, sometimes anhydrite and/or a silicate crystal, but no visible liquid at room temperature, and co-existing vapor inclusions are of very low density. Heating experiments of brine inclusions reveal last salt and vapor bubble dissolution temperatures around 600–700 °C, but an immiscible silicate melt surrounding the homogenized salt globule remains even at unreasonably high temperature. The co-existence of silicate melt and fluid inclusions reinforces the magmatic nature of the fluids, while boiling trails of brine (with Cu concentrations of several percent) and vapor point to relatively low pressures (<100 MPa).

The role of trace elements in controlling H incorporation in San Carlos olivine

We conducted a series of hydroxylation experiments using mm-sized cuboids cut from six different crystals of San Carlos olivine with a range of trace-element concentrations. The cuboids were pre-annealed and then hydroxylated under identical conditions, ensuring that variation in the amounts of H incorporated depended only on the compositional variables. The pre-anneal was at 1400 °C, atmospheric pressure and an oxygen fugacity equivalent to Δlog FMQ + 1, with the subsequent hydroxylation at 800 °C and 1.5 GPa, for 3 days. Hydrogen was incorporated into all six crystals by the four main substitution mechanisms [Si], [Mg], [Ti] and [triv], with homogeneous H contents in the cores of the crystals, indicating H diffusion rates faster than 10− 11 m2/s. Total H as H2O in the homogeneous cores calculated by summing all the infrared absorbance bands ranges from 13 to 27 wt. ppm. The total H2O in the six pre-annealed crystals is poorly correlated with any measured compositional variable. However, when the H2O associated with individual infrared bands is compared, clear trends emerge. The intensity of absorption bands at 3572 and 3525 cm− 1 are strongly correlated with Ti concentrations, whose range in the six crystals exceeds an order of magnitude. Bands between 3400 and 3300 cm− 1, correlate negatively with Na+, but are positively correlated with the difference between molar Cr3+ and Na+. This highlights a previously unrecognised role for Na in suppressing H incorporation in natural olivines. The results confirm the important role that the trace constituents of olivine play in H incorporation. Two of these trace elements, Na and Ti, tend to be similarly enriched or depleted by partial melting or metasomatism of the mantle, but have opposite effects on H incorporation, with Ti enhancing it but Na suppressing it. Models estimating the effect of H in olivine on mantle rheology must, therefore, consider carefully the availability of these trace elements.

Spatial variability of trace elements in allotment gardens of four European cities: assessments at city, garden, and plot scale

Urban allotment gardens (UAGs) are expanding worldwide, especially in large cities. Environmental pressures (direct and diffuse pollution, gardener practice, geogenic contamination) often result in the accumulation of potentially harmful trace elements in garden soils. The objectives of this study were to assess the spatial variability of trace element distribution in UAGs from city, garden, and plot scale in four European cities; to provide a baseline understanding and identify abnormal values under environmental pressures; and to evaluate the potential of portable X-ray fluorescence screening as a useful tool in soil management. The four cities (Ayr and Greenock (Scotland), Lisbon (Portugal), Nantes (France)) provided a wide range of environmental pressures on soils. The locations of the 14 allotment gardens were identified in consultation with the local municipality in each city to reflect various land uses or according to previous evaluation of soil quality. Soil sampling was carried out in 66 plots in total, from which 3 datasets were produced: (i) basic soil properties and trace element concentrations from a composite sample of topsoil for each plot (trace elements quantified by inductively coupled plasma–optical emission spectrometry/mass spectrometry (ICP-OES/MS) or using in-lab portable X-ray fluorescence (PXRF); (ii) in situ PXRF measurement on composite samples (263 plots in Nantes); and (iii) composite samples from 32 small areas within 4 plots in one garden of Nantes. The results were analyzed to assess the spatial variability of soil properties. At city and garden scale, the variability observed for basic soil properties and major elements is dominated by local geology/parent material (pH, CaCO3, Fe) and gardening practice (OM, CaCO3), which vary between each country. The range of trace element concentrations is similar between each city except for Greenock. Extreme values are observed for Cu, Pb, and Zn reflecting human disruption. In most situations, the trace element contamination was explained through the historical and environmental situations of the site. The PXRF screening method proved useful in providing detailed mapping for hot spot detection or delineation, providing support for soil management at plot and garden scale. As anticipated, basic soil properties appear to be controlled by the parent material. At plot and garden scale, the trace element variability shows the influence of land use history and background and strong inputs from external factors (e.g., by industrial activity or traffic emission). The PXRF screening method appears to be an efficient solution for soil management as it can be used to discriminate zones which may require restriction on cultivation.

Trace element characterization of USGS reference materials by HR-ICP-MS and Q-ICP-MS

A trace-element characterization of United States Geological Survey (USGS) reference materials has been carried out using three different inductively coupled plasma mass spectrometer instruments: Nu Instruments AttoM, Thermo Scientific Element 2, and Agilent 7700x. The six USGS reference materials (BHVO-2, BCR-2, AGV-2, STM-2, RGM-2, and G-3) include both extrusive and intrusive rocks with compositions ranging from mafic to felsic that encompass a wide range of trace element concentrations and mineral phases. The prevalence of these 2nd (and 3rd) generation reference materials among geochemical laboratories and the added care that was taken during sample preparation make this generation of reference materials more suitable for characterization and use by the geochemical community.The mafic-intermediate reference materials (BHVO-2, BCR-2, and AGV-2) had the most abundant published characterization prior to this study, which allowed for thorough and direct comparison with previous studies (and USGS certificates). Published data for these reference materials are relatively well constrained for most elements (i.e., not highly variable) and the results of this study generally correspond well with the literature. This can, at least partially, be attributed to the relatively simple matrices of these reference materials together with their overall smaller range of trace element concentrations.Unlike the mafic-intermediate reference materials, STM-2 lacked any published trace element concentrations prior to this study and data for RGM-2 and G-3 were relatively sparse. Data for STM-2 and RGM-2 from this study are compared to preliminary USGS certificates, while data for G-3 are compared to the G-2 certificate values; for comparison with published data, RGM-1 and G-2 are included. Overall, the published data for RGM and G are variable across the entire suite of trace elements and display poorer agreement with the data from this study. This can be explained by the fact that, in addition to the comparison between generations that may add heterogeneity, the felsic reference materials have relatively complex matrices and larger ranges in trace element concentration. Given the new data that this study provides, the felsic reference materials can now be used by the geochemical community to produce more accurate trace element concentration analyses of felsic materials.By using three instruments with different configurations, this study also serves as a comparison of the performance of each instrument in response to an array of geologic matrices. The data reveal that the tested instruments are all capable of producing accurate and precise trace element concentration data over a range of geologic matrices, provided that each instrument is carefully operated within its dynamic range. In many cases, this could be accomplished simply by ensuring proper dilution of samples; however, when matrices are more complex, the use of medium and high resolutions can be useful in reducing the amount of preparative chemistry that is required to manage highly variable trace element concentrations within a single sample as well as any potential isobaric interferences.

Geochemical Trends of Trace Elements Concentration in Saline Lakes of Central Asia

The investigated Mongolian lakes are marked by a large range of trace element concentrations even in very small geographical areas. This work includes the data on major and trace element concentrations along of a series of samples collected in 2009 and 2012. Three geochemical types of lakes have been distinguished within the study area: (1) alkaline soda lakes, (2) chloride lakes with pH &lt; 9.0 and Na-Cl-dominated composition, and (3) sulfate ones with pH &lt; 8. The soda lakes show high concentrations of As, U, F and relatively low salinity. The chloride lakes have higher salinities and one of them was the most saline of all the lakes (Davsan Nuur). These lakes have higher concentrations of Li (up to 82.1 mg/L), Rb (up to 1350 mg/L), Br and Sr. Sulfate rich lakes are far less common in the area. Characteristic trace elements are Mo, Al and Sr. Thermodynamic modeling at 25°C and 1 bar total pressure was performed with the “HCh” code. We considered mineral and solution equilibria in soda lake waters and calculated the main uranium and arsenic species in solutions and bottom sediments of Shaazgay-Nuur lake to offer a possible way of As removal as an undesirable impurity in commercial products.

Chemical composition of bottled mineral waters in Estonia

Five commercially available in Estonia brands of bottled water have been analysed for 59 chemical elements by ICP-QMS and ICP-AES techniques to assess the quality of domestic mineral waters in scope of the European Groundwater Geochemistry Project initiated by the Geochemistry Expert Group of EuroGeoSurveys. Contents of 9 cations and anions, pH and electrical conductivity (EC) were measured in the bottled mineral waters by IC, titration and photometric methods. The data showed a significant difference between natural undiluted mineral water (Värska Originaal) characterised by the highest values of pH, EC and majority of trace elements studied, and other domestic waters sold in Estonia. The results obtained were compared with the drinking water standards (US EPA, EU and Estonian Permitted Limits). Despite of the wide range of trace element concentrations in all Estonian brands of commercially sold waters the estimated values are generally within defined maximum concentrations allowed for drinking water. The B concentration assessed in the Värska Originaal water above the maximal permitted values defined as 1 mg/L is a result of long residence time of water due to slow water exchange in the water-bearing Ordovician–Cambrian rocks. Differences in chemical composition of the bottled waters are linked to host rocks geology in the studied area.

Stream sediment, soil and forage chemistry as indicators of cattle mineral status in northeast Zimbabwe

Abstract Results of previous studies investigating the use of soil and forage chemistry as indicators of cattle mineral status have been somewhat equivocal, possibly due to the limited range of trace element concentrations in the areas investigated. This paper describes an investigation of the relationship between trace element concentrations in stream sediments, soils, forage (grass and leaves) and cattle blood (serum) in northeast Zimbabwe in order to identify which, if any, of the sample media provide a reliable guide to cattle mineral status. Soil, forage and cattle serum were collected from an area characterized by a wide range of Zn in stream sediments. The area was subdivided into three regions of relatively low, medium and high Zn concentration on the basis of stream sediment data and variations in the chemistry of cattle serum, forage, soil and stream sediment samples were examined. Significant correlations exist between element concentrations in stream sediments, soils and forage but there are no significant correlations with cattle serum. Although this lack of direct correlation may, in part, be due to a range of biological factors, it is suggested that high concentrations of Fe in soil and forage inhibit (i) the availability of P to plants and (ii) the absorption of Cu and Zn in cattle. This may have wide ranging implications due to the predominance of ferrallitic soils in many countries in tropical regions.

Surface titrations and electrokinetic measurements on australian cassiterites

Fragments of crystals of cassiterite from four Australian ore deposits were cleaned and finely ground. Their points of zero charge were measured by potentiometric titration of the surfaces in aqueous solutions of KNO 3. Isoelectric points were obtained from microelectrophoresis measurements. The values were compared with those for synthetic stannic oxide. It was found that, despite a range of trace element concentrations in the natural samples, the points of zero charge and isoelectric points were similar to each other and to stannic oxide.

Rare-earth element mobility in alteration pipes below massive CuZn-sulfide deposits

A convincing demonstration of trace-element mobility should satisfy two criteria: (1) the range of trace-element concentrations in the rock before and after alteration must be known with confidence; and (2) the absolute abundances and the ratios of the mobile trace elements should vary between altered and unaltered rocks. These criteria have been applied to the host felsic volcanics and alteration pipes associated with several Canadian massive CuZn-sulfide deposits. Although there is no evidence of rare-earth element (REE) mobility in the pervasive low-grade alteration envelopes adjacent to the deposits, the light and middle REE (LREE and MREE) plus Y have been systematically mobilized relative to the heavy REE (HREE) and other trace elements in the alteration pipes beneath the ore zones. There is evidence of minor LREE and MREE depletion in the most altered rocks at the South Bay Mine (Uchi Lake) and of significant LREE depletion in the alteration pipe beneath the Mattabi Mine (Sturgeon Lake). However, the strongest mobility is found at the Kidd Creek Mine where the LREE were leached from the rocks in the footwall stringer zone and redeposited in a metasomatic chlorite zone directly beneath the massive ore horizon, and the MREE and Y were preferentially lost from the system producing distinctive chondrite-normalized REE patterns with ( Tb Yb ) n ratios less than unity. Eu 2+ was found to be more mobile than the trivalent REE, especially at Kidd Creek where there is a marked increase in the magnitude of the Eu anomaly in the most altered samples. High-field-strength elements such as U, Th, Hf and Zr have not decoupled and apparently remained relatively immobile during all but the most intense alteration (i.e. Kidd Creek). Preliminary data suggest that the degree of REE mobility increases with the size of the deposit. Thus, REE mobility is a potentially useful method of distinguishing between small and large massive sulfide deposits at an early stage in exploration, however, this hypothesis requires further testing.