Study Of Trace Elements Research Articles

R/V Isabu-Based First Ultraclean Seawater Sampling for Ocean Trace Elements in Korea

Trace elements (Mn, Fe, Co, Ni, Cu, Zn, etc.) are essential micronutrients for marine organisms and are thus related to major issues in the ocean, such as climate change, ecosystem change, and pollution. However, given their extremely low concentrations in seawater, contamination-free clean seawater sampling for trace elements onboard is the most crucial factor in this study. Because of the absence of both clean seawater sampling techniques and related infrastructure (e.g., a research vessel equipped with a nonmetal sampling system), the trace element community in Korea has not contributed to the global community studying trace elements in the ocean, although the associated global joint study program “GEOTRACES” has been operating for 10 years. With the newly launched research vessel (R/V) Isabu of the Korea Institute of Ocean Science and Technology (KIOST), Korea is now equipped with a large comprehensive R/V complete with a contamination-free PRISTINE ultraclean seawater sampling system for trace elements. We conducted clean seawater sampling 2 research cruises in the Indian Ocean during 2017–2018 aboard the R/V Isabu, and we successfully obtained reliable data, which agree well with previously reported trace element data at these locations. Here, we present the procedure and preliminary results of clean water sampling for trace elements based on the R/V Isabu, as the first Korean open ocean trace element study. From this study, we expect that R/V Isabu will play an important role in research on oceanic trace elements and isotopes in the future.

The ancient quarrying areas of the sandstones used in the UNESCO historical centre of Urbino (Marche, Italy) as inferred from geological, petro-chemical and physical-mechanical investigations

Many buildings of the historical centre of Urbino (Marche, Central Italy), included in the UNESCO World Heritage List, are characterized by portals consisting of sedimentary rocks such as limestones or sandstones. In order to identify the possible quarries of provenance of sandstones used for architecture, we addressed our research to the Sant'Ippolito area (20 km ESE of Urbino), where historical stonemasons have been extensively documented since the 14th century. Few traces of ancient exploitation indicate some extraction sites. All the investigated rocks (both from monumental portals of Urbino and geological outcrops) consist of fine- to medium- grained sandstones with a variable content of bioclasts. Two different groups were recognized (using the petrographic Q-F-R classification diagram): (i) lithic arenites belonging to the Colombacci Formation; and (ii) feldspathic lithic arenites referable to the Tripoli Unit. In particular, petrographic data indicate that the sandstones used in the historical buildings of Urbino, come from the arenitic lithofacies of the Messinian p.p. Colombacci Formation of the Sant'Ippolito area. In addition, comparative geochemical studies of whole rock major and trace elements point out three outcrops of the above formation, as possible sites of ancient extraction. Sandstones of the Tripoli Unit and the Marnoso-Arenacea Formation, widespread in the study area and near Urbino respectively, are ruled out as source rocks, based on both petrographic and geochemical data.Anomalously high values of some heavy elements such as Pb, Zn and As, recognized in some of the portals, likely derive from a combination of various anthropogenic sources of pollution close to the investigated monuments, such as domestic heating and emissions from road traffic in the past.From a mechanical point of view, the uniaxial compressive strength tests, carried out on a representative number of selected samples of the Colombacci Formation lithic arenites, yelded low values and high variability. Other investigated physical parameters also indicate that the stones used for the portals did not represent a good choice as building material. This implies that the stonemasons of Sant’Ippolito chose local raw materials for their availability, aesthetic qualities and good workability, rather than structural properties.

The effects of amphibolite facies metamorphism on the trace element composition of pyrite and pyrrhotite in the Cambrian Nairne Pyrite Member, Kanmantoo Group, South Australia

The trace element composition of pyrite has been used to explore for hydrothermal ore deposits and to understand ore-forming processes. However, the effects of metamorphism on the trace element distribution in pyrite have received relatively limited attention. In this study, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of pyrite and pyrrhotite, along with minor amounts of sphalerite, chalcopyrite, and galena, are used to evaluate the effects of amphibolite facies metamorphism on the trace element distribution and remobilization of metals in iron sulfides in the clastic sediment-hosted Cambrian Nairne Pyrite Member (NPM), South Australia. The NPM and the Mt. Torrens Pb-Zn-Ag prospect, which occur near the base of the Kanmantoo Group, preserve irregularly zoned subhedral to euhedral metamorphic pyrite (Py1) and anhedral pyrrhotite (Po1), along with relatively minor quantities of remobilized anhedral pitted and cataclastic pyrite (Py2a) in quartzofeldspathic rocks and anhedral inclusion-poor pyrite (Py2b) in calc-silicate rocks that armor or cross-cut earlier formed Py1. Rare anhedral secondary melnikovite pyrite (Py3) locally formed on the margins of Py1 and Py2a. Trace element studies show that Py1 in the NPM at Brukunga and Ironstone Ridge contains mean values of 1254 ppm Co, 123 ppm Ni, 2167 ppm As, 16 ppm Se, 10 ppm Cu, 25 ppm Zn, and 15 ppm Pb, whereas Py1 in the Mt. Torrens prospect contains mean values of 2312 ppm Co, 263 ppm Ni, 1835 ppm As, 95 ppm Se, 9 ppm Cu, 6 ppm Zn, and 9 ppm Pb. Rare inclusion-rich cores of Py1 show higher concentrations of trace elements than inclusion-free rims with minor amounts of chalcopyrite, galena, and sphalerite forming along grain boundaries or in fractures within pyrite. This is interpreted to be the result of the release of Cu, Pb, and Zn from pyrite as it recrystallized. Remobilization of these elements then formed discrete sulfides at the millimeter to centimeter scale, with some exceptions at the meter scale where chalcopyrite, sphalerite, and galena, along with other sulfides and sulfosalts, formed in veins and tension gashes. These observations suggest that remobilization of trace metals, including Cu, Pb, and Zn, did not migrate more than a few meters at most. Moreover, despite the recrystallization of pyrite and pyrrhotite and subsequent remobilization of some trace elements (i.e., Co, Ni, As), which were structurally bound in these Fe sulfides, still retain elevated concentrations at amphibolite facies conditions.Remobilization of metals from the NPM during metamorphism to form Cu-Au (e.g., Kanmantoo) and Pb-Zn-Ag-(Cu-Au) (e.g., Angas, Wheal Ellen) deposits in the Tapanappa Formation stratigraphically higher in the Kanmantoo Group seems unlikely. However, it is possible that one source of metals for these deposits could have been leached from the NPM and carried in large hydrothermal cells prior to metamorphism. Such a scenario is consistent with previously published sulfur isotope data for sulfides from the NPM, and Cu-Au and Pb-Zn-Ag-(Cu-Au) deposits, which indicate that sulfur derived from the NPM and pyritic schists in the Kanmantoo Group was a likely source of sulfur for the base and precious metal deposits.

A comparison study of Singareni and Talcher coal samples through elemental analysis using PIXE technique

A comparative study of trace elements in Singareni and Talcher coals was carried out using Particle Induced X-ray Emission technique with a 3 MeV proton beam. Concentrations of sixteen elements, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr and Pb were obtained and compared with Clarke’s values to ascertain the enrichment factor for each. Pearson correlation and hierarchical cluster analyses were used to understand the relationship between the inorganic constituents of coal. It is anticipated that this study of trace elements in coals will be useful to protect environment and to regulate the emission of toxic elements during coal combustion and utilization.

Pre-Mesozoic Crimea as a continuation of the Dobrogea platform: insights from detrital zircons in Upper Jurassic conglomerates, Mountainous Crimea

U–Pb dating, Hf-isotope, and trace-element studies on two detrital zircon samples from sandstone interlayers in the Upper Jurassic conglomerates of the Southern coast of the Mountainous Crimea provide new information on the primary crystalline complexes from which those conglomerates were sourced. The U–Pb age spectra of studied zircons suggest that they were most likely sourced from the (meta)sedimentary complexes of the Eastern and Western Pontides blocks and the Dobrogea platform. In particular, a close similarity of the Precambrian age spectra with the detrital zircons from Late Neoproterozoic–Late Paleozoic (meta)sedimentary complexes of the Dobrogea block provides strong supporting evidence for the affinity between the Pre-Mesozoic basement of the Crimea and the Dobrogea platform. The zircons in the first sample were recycled through Dobrogea sedimentary complexes and originated from terranes with Amazonia affinities, while zircons in the second sample were recycled through the Taurides and originated from terranes related to northeastern Africa and Arabia. The strong similarity of the Precambrian parts of the age spectra of the Dobrogea complexes and the sample K15-007 suggests a resemblance of the Crimea’s Pre-Mesozoic foundation and the Dobrogea platform. Initial analytical data are provided in Electronic Supplementary Materials A (ESM A). Descriptions of measurement parameters, methodologies, and constants used to process primary analytical data and some processing results are reported in ESM B (Figs. B1–B8). Schemes of locations within Balkans–Anatolia–Black Sea–Caucasus region the crystalline complexes with Jurassic, Triassic, Permian–Carboniferous, as well as Late Neoproterozoic–Cambrian and Ordovician–Devonian ages are in ESM C (Figs. C1, C3–C5).

The lawsonite-glaucophane blueschists of Elba Island (Italy)

Evidence for high-P blueschist-facies metamorphism was found in metabasites embedded in calcschists of Eastern Elba Island (Northern Apennines, Italy). Study of immobile trace elements (REEs and HFSEs) in the metabasites indicates an affinity with T- and E-MORBs, and they are interpreted as sill or dykes intruded in the western margin of the Adria continental plate. The minerals are heterogeneously distributed in the rock, constituting mafic and Ca-Al-rich microdomains inherited respectively from the magmatic pyroxene- and plagioclase-rich zones of the original doleritic rock. The peak pressure paragenesis consisted of lawsonite, aegirine-omphacite, glaucophane and chlorite. Former rhombic prisms of lawsonite have been replaced by pseudomorphic clinozoisite (0.1 mm in size) with inclusions of Ms. ± Ab ± Qz. The inclusions are preferentially oriented parallel to one of the diagonals of the basal rhombic sections, indicating that the two diagonals were not crystallographically equivalent. This implies that the protocrystals were orthorhombic prisms with {110} faces, which is the case of lawsonite. The different compositions shown by white mica and epidote in the pseudomorphs (muscovite and Fe3+-poor clinozoisite) and in the matrix (phengite and Fe3+-rich epidote) also suggest the former presence of Mg- and Fe-poor lawsonite in these rocks. Thermodynamic modelling, using the THERMOCALC software and dataset, suggests that metabasites experienced a clockwise P-T path from the lawsonite-blueschist to epidote-blueschist subfacies, down to greenschist facies. The estimated peak pressure conditions are P ≥ 1.6 GPa and 450 < T < 500 °C. Glaucophane grew mainly during the lawsonite-to-epidote transition and is dated at 19.8 ± 1.4 Ma by the 40Ar/39Ar method. This evolution is interpreted in terms: (i) intrusion of basic magmas in carbonatic and pelitic sediments (post-late Cretaceous, pre-Oligocene), (ii) subduction (Oligocene), (iii) collision (early Miocene: 19.8 ± 1.4 Ma), (iv) exhumation and granite intrusion (middle-late Miocene), favored by extensional tectonics. We underline that the eastern part of Elba Island belongs to a blueschist-facies belt that extends from Gorgona Island, in the northwest, to Argentario and Giglio Island in the southeast, so many of the conclusions of this study can be extended to the whole of this belt.

Comment on “Combined igneous and hydrothermal source for the Kiruna-type Bafq magnetite-apatite deposits in Central iran; trace element and oxygen isotope studies of magnetite” by Mehdipour Ghazi et al. (2019), (Ore Geology Reviews 105, 590–604)

The Ediacaran Bafq magnetite-apatite-pyrolusite-jaspilite ores (1.7Gt@50% Fe, 0.08–7.78% P, 0.01–5% Mn) occur in proximal zone of exhalative submarine altered rhyolites as well as in interdistal-distal zone of tuffaceous rhyolites, shale, dolomite and jaspilites. Mehdipour Ghazi et al. (2019) do not address adequate convincing evidences on the age and so-called magmatic immiscibility-hydrothermal model of El Laco-type Kiruna ores for the Bafq iron district. Firstly, the presence of Spriggina, Dickinsonia and Medusites and 207Pb/206Pb ratios in zircon attest to an Ediacaran rather than Cambrian age of iron mineralization. Secondly, there are no pahoehoe-aa flow structures and spherulitic-dendritic textures in magnetite to classify the deposits as magmatic or igneous ores. Thirdly, the presence of syngenetic submarine Ediacaran rhyolite-hosted magnetite ores has no similarity to the Pliocene subaerial andesitic eruption of El Laco-type Kiruna ores whatsoever. In fact, there are no global examples of immiscibility magnetite ores reported to be associated with submarine rhyolitic eruption in current studies. Importantly, the occurrence of dropstone-bearing jaspilites and geochemical discrimination diagrams are not in favor of El Laco-type Kiruna ores, but support the Ediacaran-type banded iron formations (BIFs).

A Case-Control Study of Essential and Toxic Trace Elements and Minerals in Hair of 0–4-Year-Old Children with Cerebral Palsy

The objective of the present study was to assess hair essential and toxic trace elements and minerals in children with cerebral palsy in relation to age of the examinees. A total of 70 children with cerebral palsy and 70 healthy controls aged 0-4years old were enrolled in the present study. The examined children were also divided into two age groups of those younger and older than 2years old. Hair trace element content was assessed using ICP-MS at NexION 300D (PerkinElmer, USA). The obtained data demonstrate that hair boron was more than 2-fold lower in CP children as compared with the control group. At the same time, hair Na, Se, and V levels were 21%, 12%, and 20% lower when compared with healthy controls, respectively. It is also notable that a 9% and 28% decrease in hair Fe and Li levels respectively were nearly significant. The observed alterations were more profound in a younger group of patients. No significant group difference in hair toxic metal and metalloid levels was observed between the general cohorts of children with and without CP. In regression models, only hair Al and Ca contents were significantly associated with the presence of cerebral palsy, whereas hair Mg, Na, Ni, and Se levels were characterized as significant negative predictors. The observed alteration in trace element metabolism may also provide an additional link between cerebral palsy, psychomotor delay, and certain diseases, including diabetes, epilepsy, and osteoporosis. However, further studies using other substrates (blood, urine) or biomarkers are required.

Fine scale study of major and trace elements in the Fe-Mn nodules from the South China Sea and their metallogenic constraints

Many marine Fe-Mn polymetallic nodules may contain high concentrations of Mn, Cu, Ni, Zn, Co and rare earth elements plus yttrium (REY). To determine the occurrence and enrichment processes of these metals in the Fe-Mn nodules, we conducted high resolution mineralogical and geochemical studies on the Fe-Mn nodules collected from the South China Sea. In-situ EPMA and LA-ICP-MS analyses and elemental imaging were performed on individual microlayers of the nodules to reveal the major and trace element distributions.The whole-rock mineralogical and chemical compositions of the Fe-Mn nodules indicate a hydrogenetic origin. The Mn mineral phases are mainly composed of nanocrystalline vernadite with interlayered 10 Å and 7 Å phyllomanganates, such as todorokite, birnessite, and buserite. Fe(-Ti) oxides/hydroxides are intergrown and essentially X-ray amorphous feroxyhyte and goethite. We recognize two main types of microlayers: Type-A layer (suboxic diagenetic precipitates) containing a high Mn/Fe ratio and high concentrations of Cu, Ni, Zn, Ba, Li and Mg, and Type-B layer (oxic hydrogenetic accretions) with low fractionation of Mn and Fe and high contents of Co, REY, Ti, Sr and Pb. Furthermore, elemental mapping indicates that the enrichments of Co and REY are mainly associated with Fe mineral phases rather than Mn ones, which are enriched in Mg, Cu, Ni, Zn, Li and Ba. Two mineralization processes and metal distributions in the individual microlayers are identified in the Fe or Mn mineral phases. The occurrence of 10 Å and 7 Å phyllomanganates in Type-A layers are commonly enriched in trace metals such as Ni, Cu, Zn, Li, Ba, and Mg, whereas the metals for the Type-B layers include Co, Ti, Pb, Sr, REY, which may be carried by the intergrowing Fe(-Ti) oxyhydroxides and vernadite. Thus, hydrogenesis and diagenesis facilitate the enrichment of Fe-Co-Ti-Sr-Pb-REY and Mn-Ni-Zn-Cu-Li-Ba-Mg, respectively, during the mineralization of the South China Sea nodules.

Elemental distribution by synchrotron X‐ray microfluorescence of prostate 3D cell culture

Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X‐ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X‐ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE‐1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X‐ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X‐ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease.

Links between iron supply from Asian dust and marine productivity in the Japan Sea since four million years ago

AbstractAeolian dust input exerts significant influence on oceanic biogeochemical cycles and further potentially controls atmospheric CO2 concentrations. However, the possible link between long-term aeolian dust supply and primary productivity in the western North Pacific remains poorly understood. Here, we present a comprehensive study of major and trace elements and total organic carbon (TOC) concentrations of sediments from Integrated Ocean Drilling Program (IODP) Site U1430 in the southern Japan Sea, in order to reconstruct oceanic palaeoproductivity evolution and test its possible link to Asian dust input since 4 Ma. Palaeoproductivity proxies indicate remarkable increases in productivity at ∼3–2 Ma followed by high-frequency oscillations in productivity since 1.2 Ma. We suggest that higher dust-derived iron supply from Central Asia at 3–2 Ma, which was likely driven by the growth of the Northern Hemisphere ice sheets, could account for enhanced primary productivity and export production in the Japan Sea. Such increased oceanic palaeoproductivity could enhance organic carbon burial, which might contribute to the decrease in atmospheric CO2 concentrations, and provide a positive feedback to the global cooling. However, the Tsushima Warm Current (TSWC) intrusion via the southern Tsushima Strait, which was controlled by glacioeustatic sea level changes, has been the principal cause of the rapid changes in primary productivity and benthic redox condition since 1.2 Ma, regardless of continuously increased Asian dust input.

Bulk trace elements of Mg-rich cryptocrystalline and ferrous radiating pyroxene chondrules from Acfer 182: Their evolution paths

A trace element study of Mg-rich cryptocrystalline (CC) and ferrous radiating pyroxene (RP) chondrules, covering from the ultra-refractory Zr to the volatile K, was performed to better understand the processes involved in chondrule formation and their subsequent evolution. The shape, textures and bulk chemical compositions (CC and RP) of the studied chondrules indicate that they once must have been hypersthene-olivine normative liquids that were quenched. Their chondritic Ca/Al ratio and the positive Yb vs. La correlation around primordial values point to a cosmochemical process as responsible of chondrules formation. Based on their REE patterns, and regardless of their mineralogy, chondrules are divided in two populations: Fractioned-REE (F-REE) and Unfractionated-REE (U-REE). Both populations show different evolution paths, while cooling of the nebula gas and give new hints about chondrule-forming reservoirs.

Study of trace elements in fruits of dates at Turbat-Punjgur region of Balochistan with reference to medicinal and environmental pollution

Study of trace elements in fruits of dates at Turbat-Punjgur region of Balochistan with reference to medicinal and environmental pollution

The Sidi El Hemissi Triassic “ophites” (Souk Ahras, NE Algeria): petrology, geochemistry, and petrogenesis

The Sidi El Hemissi region, Souk-Ahras, is part of the Tellian Atlas where the Triassic sediments tectonically outcrop under the Tellian nappes of the Maghrebide chain. Mafic rocks, mainly gabbros and dolerites, called “ophites,” are interbedded as a ~ 200 × 30-m lenticular body within the Triassic gypsum-rich formation. These rocks show granular, microgranular, and microlithic textures and are composed of plagioclase, amphibole, pyroxene, and scarce olivine crystals. Albitization is the main alteration process, though chloritization, calcitization, and epidotization of ferromagnesian minerals can also be occasionally observed. The major, trace, and rare earth element studies show that these mafic rocks display relatively low P2O5 (less than 0.2 wt%) and moderate to low TiO2 contents (less than 2 wt%) and exhibit low-Ti continental tholeiitic basalt affinity. They are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) compared with high field strength elements (HFSE) and heavy rare earth elements (HREE). This, along with the observed weak Nb and Ce anomalies and the low-Ti contents, suggests an enriched mantle source for the generation of the magma, which likely underwent crustal contamination before emplacement within the Triassic sediments. The petrological and geochemical features of the Sidi El Hemissi ophites show many similarities with the basaltic rocks emplaced during the Late Triassic–Early Jurassic times, now cropping out in north-western Africa, south-western Europe, north-eastern, and south-eastern America. This large magmatic activity is believed to be related to the continental rifting associated with the early stages of the Pangea breakup.

Fluid–rock interaction and its effects on the Upper Triassic tight sandstones in the Sichuan Basin, China: Insights from petrographic and geochemical study of carbonate cements

Tight sandstone gas is an important unconventional hydrocarbon resource, but its exploration is made difficult by the compactness and heterogeneity of the sandstone. Fluid–rock interaction and subsequent cementation play key roles in developing this heterogeneity. We conducted a petrographic, trace element, and isotopic study of the Upper Triassic Xujiahe sandstones from the Sichuan Basin, to investigate fluid–rock interactions and associated diagenetic effects. Carbonate fragments and cements are widespread in these sandstones, and are the primary control on the nature of the Xujiahe sandstone reservoirs. The carbonate cements primarily comprise of calcite and are typically distributed around the margins of sandstone bodies and along fine-grained beds. Carbonate minerals in the centre or at the margin of sandstone units have heavy δ13Ccarb values of ca. 0‰, whereas δ13Ccarb is markedly depleted in the transition zone with values as low as −10‰, reflecting a contribution from organic carbon. Manganese, Strontium and Barium generally become enriched in the carbonate cements with diagenesis, and their concentrations correlate with porosity and δ13Ccarb. Redox sensitive Mn, and fluid-mobile Sr and Ba were analysed to reveal the diagenetic processes and environment of carbonate precipitation. We propose that fluids flowed preferentially along the central parts of sandstone units, associated with mineral dissolution, whereas cementations took place near the margins of the units. Fluid–rock interaction, especially that involving late hydrocarbon-related fluids, greatly enhances the heterogeneity of sandstones and can potentially create high-quality reservoirs in the central parts of tight sandstone units.

Microbial assemblage and palaeoenvironmental reconstruction of the 1.38Ga Velkerri Formation, McArthur Basin, northern Australia.

The ca. 1.38 billion years (Ga) old Roper Group of the McArthur Basin, northern Australia, is one of the most extensive Proterozoic hydrocarbon‐bearing units. Organic‐rich black siltstones from the Velkerri Formation were deposited in a deep‐water sequence and were analysed to determine their organic geochemical (biomarker) signatures, which were used to interpret the microbial diversity and palaeoenvironment of the Roper Seaway. The indigenous hydrocarbon biomarker assemblages describe a water column dominated by bacteria with large‐scale heterotrophic reworking of the organic matter in the water column or bottom sediment. Possible evidence for microbial reworking includes a large unresolved complex mixture (UCM), high ratios of mid‐chained and terminally branched monomethyl alkanes relative to n‐alkanes—features characteristic of indigenous Proterozoic bitumen. Steranes, biomarkers for single‐celled and multicellular eukaryotes, were below detection limits in all extracts analysed, despite eukaryotic microfossils having been previously identified in the Roper Group, albeit largely in organically lean shallower water facies. These data suggest that eukaryotes, while present in the Roper Seaway, were ecologically restricted and contributed little to export production. The 2,3,4‐ and 2,3,6‐trimethyl aryl isoprenoids (TMAI) were absent or in very low concentration in the Velkerri Formation. The low abundance is primary and not caused by thermal destruction. The combination of increased dibenzothiophene in the Amungee Member of the Velkerri Formation and trace metal redox geochemistry suggests that degradation of carotenoids occurred during intermittent oxygen exposure at the sediment–water interface and/or the water column was rarely euxinic in the photic zone and likely only transiently euxinic at depth. A comparison of this work with recently published biomarker and trace elemental studies from other mid‐Proterozoic basins demonstrates that microbial environments, water column geochemistry and basin redox were heterogeneous.

Trace element systematics and ore-forming processes in mafic VMS deposits: Evidence from the Troodos ophiolite, Cyprus

The volcanogenic massive sulfide (VMS) deposits in the Troodos ophiolite (Cyprus) are ancient analogues for modern day seafloor massive sulfide mineralisation formed in a supra-subduction zone environment. In this study we present the first detailed in situ study of trace elements in sulfides from twenty VMS deposits hosted in the Troodos ophiolite to better understand factors that influence the distribution, enrichment and incorporation of trace elements in different sulfide minerals.On a mineral scale, trace elements exhibit systematic variations between pyrite, chalcopyrite and sphalerite. Pyrite preferentially incorporates As, Sb, Au and Te, whilst chalcopyrite is enriched in Co and Se. Sphalerite is trace element poor with the exception of Ag and Cd. Selenium averages 278 ppm (n = 150) in chalcopyrite but only 42 ppm (n = 1322) in pyrite. Bismuth and Te in pyrite show a weak positive correlation (R2 = 0.35) in some VMS deposits possibly linked with the occurrence of Bi-telluride inclusions. Trace element concentrations also vary between colloform and euhedral pyrite, with an enrichment of Au, As, Sb, Cu and Zn in colloform compared to euhedral pyrite.Time resolved laser ablation profiles reveal that the trace element distribution on a mineral scale is not uniform and varies with crystallographic effects, fluctuating physicochemical fluid conditions such as temperature, pH, fS2, fO2 and ligand availability during sulfide precipitation. Incorporation mechanisms in sulfides differ between elements in pyrite, Ag, As, Se and Pb are hosted in solid solution or as nanoscale inclusions, whilst Au, Sb and Te may form micro-scale inclusions.On a regional scale (20 km) the distribution of trace elements exhibits systematic variations between three major structural domains; namely the Solea, Mitsero and Larnaca grabens. The VMS deposits of the magmatic-tectonic Solea graben are enriched in Se, Co, Te, Au and Cu relative to Mitsero, which is a purely extensional feature. Therefore, we hypothesise that a variable magmatic volatile influx related to a) ‘magma’ volume, b) migration of the magmatic-hydrothermal crack front and associated brine liberation or c) a variation in protolith metal concentration are responsible for regional scale variations in VMS geochemistry. This is suggested to be intrinsically linked to the spreading architecture of Troodos.

Low to moderate toenail arsenic levels in young adulthood and incidence of diabetes later in life: findings from the CARDIA Trace Element study

Some studies suggest a positive association between arsenic exposure and risk of diabetes. However, the findings are inconsistent and inconclusive, particularly at a low to moderate arsenic exposure level, and longitudinal data are lacking. We examined toenail arsenic at low to moderate level in young adulthood in relation to incidence of diabetes later in life. This study included 4102 black and white participants aged 20–32 at baseline (1987–88) who completed up to 7 follow-up exams through 2015–16. Toenail arsenic was measured by collision-cell inductively-coupled-plasma mass-spectrometry. Incident diabetes was defined as fasting glucose ≥ 126 mg/dL, non-fasting glucose ≥ 200 mg/dL, 2-h postchallenge glucose ≥ 200 mg/dL, hemoglobin A1c ≥ 6.5%, or use of glucose-lowering medications. Cox proportional hazards model and generalized estimating equations (GEEs) were used to determine the associations of quintiles of toenail arsenic with incident diabetes and other metabolic parameters. The median (inter-quartile range) toenail arsenic level was 0.097 (0.065–0.150) ppm in this study. During the follow-up period, 599 incident cases of diabetes were identified. After adjustment for potential confounders, the hazards ratio (95% confidence interval) was 0.96 (0.73, 1.27) (P for linear trend= 0.85) comparing the highest to the lowest quintile of toenail arsenic levels. No significant association was observed between toenail arsenic and levels of fasting glucose, insulin, homeostatic model assessment of insulin resistance, homeostatic model assessment of beta cell function, or C-reactive protein. The null associations persisted across subgroups of age, sex, race, and body mass index. Findings from this longitudinal study do not support the hypothesis that low to moderate toenail arsenic levels in young adulthood is associated with diabetes risk later in life.

Distribution of nutrients and trace elements in forest soils of Singapore

Information on chemical fertility status and on trace element concentrations for Singapore soils is sparse. In this study, concentration and distribution of nutrients and trace elements in forest soils of Singapore, and the effect of geology on the current conditions of soils, were evaluated. Litter and mineral soil samples (0–10 cm, 10–20 cm, 20–50 cm) were divided into three groups according to geology (sedimentary rocks, Neogene-Quaternary sediments and igneous rocks). Basic soil properties, exchangeable cations including cation exchange capacity (CEC), and pseudototal concentrations of 17 elements including nutrients and potentially toxic elements (PTE; As, Cd, Cu, Cr, Ni, Pb, Zn) were determined. Results showed that the soils of Singapore were acidic (pH 3.7–6.2) and characterised by a low CEC (maximum mean value: 100 mmolc kg−1) and low P concentrations (mean values of 0.28 g kg−1 or less) irrespective of geology. Pseudototal concentrations of PTE were also low, except for As. However, significantly (p < 0.05) higher concentrations of soil organic carbon, total P, base forming elements, exchangeable base cations and PTE (except As and Cd) were found in soils developed on sedimentary rocks and Neogene-Quaternary sediments compared to those developed on igneous rocks. Although total N and S concentrations did not differ significantly between the three geological groups, the differences in nutrient status were more pronounced than in trace element levels across geology. The properties of forest soils, which are mainly unaffected by anthropogenic activities, vary depending on the parent material, i.e. igneous or sedimentary rocks and Neogene-Quaternary sediments.

Combined igneous and hydrothermal source for the Kiruna-type Bafq magnetite-apatite deposit in Central Iran; trace element and oxygen isotope studies of magnetite

The main deposits of the Bafq district (Choghart, Se Chahun and Chadormalou deposits) are magnetite-apatite ore bodies with Early Cambrian age, hosted by Early Cambrian volcano-sedimentary rocks, showing lava flow structure with miarolitic cavities and occasional brecciation. The texture and geochemistry (trace elements and O-isotope) of the studied magnetite crystals show three types of magnetite with different proportions in different parts of the district and the deposits. These are primary ignious magnetite and high-temperature hydrothermal magnetite in the massive parts of the deposits and foam-like magnetite in the veins or in the fractures of the massive part. The lack of zonation, high Ti/Fe ratios and δ18O values (2‰<) indicate that massive magnetites formed at high temperature condition, while foam-like magnetite recrystallized at lower temperature. Textures and Co, V, Ti, Al, and Pb contents are used to distinguish ignious magnetites from the high-temperature hydrothermal magnetites. Foam-like magnetites contain lower REE and has lower δ18O values (2‰>) than the massive magnetites.The magmatic origin for the main part of the ores in the Bafq is more plausible. Contamination of the primary magmas of the Bafq magmatic rocks with crustal phosphorus and evaporate units was the major agent for triggering iron-rich melt immiscibility from the original magma. Concentration of volatiles in the iron-rich melt involving in crystallization of the primary magnetite and nucleation of the aqueous fluid bubbles on magnetite surfaces led to ascending the buoyant fluid bubble-magnetite aggregates. This caused continuation of the magmatic magnetite microlites growth from the iron-rich magmatic-hydrothermal fluid and formed high-temperature hydrothermal magnetite. Formation of hypersaline fluid due to crystallization of iron-rich melt at shallow depth led to crystallization of titanite (and Th-U-REE-bearing minerals) and sodic-calcic alteration related to magnetite mineralization. Microscopic evidence (replacement of magnetite by hematite and filling of fractures of thorite by magnetite) show that degassing continued at shallow depth, which led to re-crystallization of the primary magnetites and formation of the foam-like magnetites.