Combined Trace Element Research Articles

From birth to death: The role of upper-crustal thermal maturation and volcanism in porphyry ore formation revealed in the Yerington district

The current race towards greener energy and its intertwined increase in Cu demand imposes the need to find mineralized centers that are economic despite greater depths. To this end, a better understanding of the processes controlling the metal tonnage of porphyry Cu deposits, the main source of Cu, is needed and the focus of current research and debate. This study provides a comprehensive view of the duration of upper-crustal magmatism and its significance in the degree of metal endowment in porphyry Cu deposits using the Yerington batholith, Nevada, USA, as a case study. The Yerington district constitutes an exceptional example of an exposed porphyry Cu system where the plutonic environment that fed the porphyritic dikes is accessible. Combining trace element geochemistry and high-precision geochronology of zircon from all exposed units, we propose that the thermal maturation of the upper crust by a continuum in magmatic activity without significant hiatuses is a key factor in enabling the formation of large porphyry Cu style mineralization. The Yerington magmatic system transitioned from a volcanically active environment with coeval plutonism to a growing upper-crustal magmatic reservoir that fed the porphyritic dikes and associated mineralized centers to then resume its volcanic activity terminating the ore-forming episode. A relatively high volcanic/plutonic ratio characterized the first expressions of Jurassic magmatism in the district from ∼170 Ma with the coeval eruption of the Artesia Lake volcanics and the protracted emplacement of the McLeod Hill pluton. Geochemically, this period recorded distinctive negative Eu anomalies and a gentle increase in Yb/Dy ratios in zircon with decreasing Ti contents over a large range of zircon crystallization temperatures. This persistent magmatism over ∼2 Myr thermally matured the upper crust, enabling the growth of magmatic reservoirs that formed the Bear and Luhr Hill plutons without known volcanic activity for ∼1.3 Myr. Zircon trace element compositions indicate that this transition occurred as a continuum in decreasing negative Eu anomalies and increasing Yb/Dy with decreasing Ti contents and age across the plutonic units, reaching the more evolved signatures and lowest crystallization temperatures in the zircon from porphyry dikes. An increase in the volcanic/plutonic ratio with the eruption of the Fulstone Spring sequence likely terminated the ore-forming potential of the district. Although many other studies have provided important views on the timing and duration of porphyry Cu deposit formation, the link to their plutonic roots has been limited due to their inaccessibility. Therefore, this study offers the first complete picture into the temporal and chemical evolution of an upper-crustal magmatic system and the roles that factors like prolonged magmatism and volcanism play before and after ore formation. We argue that without the thermal maturation of the upper crust, the construction of a long-lived magmatic reservoir would not have been possible, precluding the formation of porphyry Cu deposits. Under this premise, not only the duration of ore-related magmatic activity, but the occurrence of long-lived precursor magmatism might exercise crucial control on the final tonnage of the deposit and should be considered during exploration for new porphyry deposits.

Zircon double-dating, trace element and O isotope analysis to decipher late Pleistocene explosive-effusive eruptions from a zoned ocean-island magma system, Ascension Island

In this first detailed study of zircon from Ascension Island, South Atlantic, we take a novel approach combining trace element and O isotope compositional data with double-dating (disequilibrium 238U–230Th and (U–Th)/He) to decipher timescales and dynamics of magmatic processes. The Echo Canyon (EC) sequence comprises small-volume explosive-effusive eruptions of trachyte that tapped a compositionally zoned magma system. Associated volcanic hazards may be constrained from the age of volcanism, duration of magma storage, and magma source and plumbing system character. Zircon U–Th–Pb dating of lithic lava clasts has revealed recurrent evolved volcanism at 1.34 and 0.6 Ma, and 95 ka. The (U–Th)/He zircon cooling ages indicate that most of the EC explosive-effusive sequence erupted in a brief episode at ca. 95 ka. Additionally, uniform 238U–230Th zircon crystallisation ages suggest moderately protracted magma storage with melt present at depth for at most 103–104 years before eruption. The enriched character of zircon trace element compositions, relative to MORB, in the absence of a continental crustal signature in the oxygen isotope values (δ18O range 2.67–5.63‰), suggests the presence of an enriched component in the EC magma source. Furthermore, low δ18O zircon compositions imply assimilation of high temperature hydrothermally altered country rock by the source magma. The mineral assemblage in crystal-poor pumices indicates equilibrium storage conditions: zircon saturation and Ti-in-zircon crystallisation temperatures are consistent with alkali feldspar-melt temperatures. Significantly, zircon crystals were preserved both as macrocryst inclusions and in the groundmass of EC explosive and effusive deposits. These rocks preserve evidence of magma evolution by fractional crystallisation. This process led to pre-eruptive compositional stratification, which is evidenced in the range of whole-rock major and trace element compositions and zircon Zr/Hf values. Notably, zircon crystallisation and cooling ages derived from pumice, lava, and accidental lithic lava clasts in highly explosive pyroclastic deposits, have revealed episodes of evolved magmatism that would otherwise have gone undetected. In addition, the zircon trace element and isotope compositions, in combination with the range of crystallisation ages, evidence progressively deeper tapping of less evolved magma stored in discrete lenses. Thus, a combined zircon geochronological-geochemical approach can place constraints on the ca. 0.6 Ma recurrence of past explosive-effusive pulses of millennial to decamillennial duration and their enriched magma sources. This information is relevant for assessing hazards and informing monitoring and forecasting efforts to assist in managing associated risks for small ocean island volcanoes with particularly vulnerable populations and infrastructure.

Quality of life in patients with novel coronavirus infection: association with disease severity and change depending on rehabilitation regimens after inpatient treatment

Objective. Imbalance of vitamin and mineral substances is considered as one of the leading functional conditions in patients with post-COVID syndrome.Materials and Methods. Тotal of 195 consecutively recruited patients were examined. The average age of the surveyed was 54 (12.1) years. After discharge from the hospital, patients were randomly recommended four rehabilitation regimens: Group A - standard rehabilitation, mainly including anticoagulant therapy (n = 47); Group B - where, in addition to standard methods, vitamin preparations were administered (n = 49); Group C - where, in addition to standard methods, mineral preparations were administered (n = 48); Group D - where, in addition to standard methods, vitamins and mineral preparations were administered (n = 51). The quality of life was assessed using the scales of the SF-36 questionnaire.Results. Patients with severe COVID-19 had a lower quality of life on admission and discharge from the hospital than those with moderate disease. Rehabilitation activities within 6 months after an acute coronavirus infection, the quality of life was increased by 10-20%. The most pronounced result was observed in patients of group D, who used trace elements in combination with vitamins.Conclusion. Intake of vitamin-mineral complexes into rehabilitation regimens improves the quality of life of patients with post-COVID syndrome.

Methodology for Evaluating the North Atlantic Igneous Province Reveals Multiple Hotspots at Breakup

AbstractThe North Atlantic Igneous Province (NAIP) has been the focus of numerous studies. However, a systematic integrated methodology to assess the NAIP, has so far been lacking. For this purpose, a synclinal oceanic rift approach is developed from the stratigraphic record. Mechanisms are addressed combining trace element and seismic velocity data as a proxy for excess mantle potential temperature (ΔTp), using simple mantle melting models. Unconformities play a major role in this assessment, providing evidence for a drop in ΔTp to ambient levels (≤50°C). Three phases can be delineated in the stratigraphic record: a (a) Pre‐; (b) Syn‐; and (c) Post‐breakup phase. The Syn‐breakup phase is bound at the base by the Breakup Unconformity and at the top by the Magmatic Unconformity. At breakup, magmatic crustal thickness (H) can be estimated from addition of basalt‐ and Lower Igneous Crust isopachs. These seismic estimations can be further constrained by observations on volcanic transport directions. This allows differentiation between hotspots and Volcanic Passive Margins (VPMs), where hotspots are characterized by continuous ΔTp amplitude variations, whereas VPMs only display declining or absent fluctuations post breakup. On Iceland and the Greenland‐Iceland‐Faroe Ridge, H is primary controlled by ΔTp fluctuations promoting ridge jumps and second, associated fluctuating active upwelling ratio (χ ∼ 2–4). Results suggest that there were at least three hotspots active at breakup. The West Greenland and proto‐Jan Mayen hotspots lost importance in the Oligocene, while Iceland remained and is currently the main hotspot in the North Atlantic.

Lipid biomarkers and metal pollution in the Holocene record of Cartagena Bay (SE Spain): Coupled natural and human induced environmental history in Punic and Roman times

We reconstructed the palaeoenvironmental conditions of Cartagena Bay during the Holocene after a multidisciplinary study to identify natural variations and the anthropic processes of this coastal area. A total of 119 samples were recovered for amino acid racemization dating, 3 for radiocarbon dating (14C), and four sets of 80 samples for sedimentological and palaeontological determination, mineralogical content, biomarker and trace elements quantification. Two natural scenarios were identified from the variations of n-alkane indices and palaeobiological content. The first period (6650–5750 yr cal BP) was marked by the development of euhaline marine conditions with strong inputs from aquatic macrophytes and high biodiversity. After a hiatus, the area underwent a profound change, becoming a paucispecific brackish marsh environment with increasing inputs from land plants, with possible episodes of emersion with a greater presence from terrestrial gastropods (3600–300 cal yr BP). By combining trace element abundance and stanol distributions, our study also provides a novel approach to identify the predominant influence of anthropogenic factors in the last three millennia in the coastal record of Cartagena Bay. Findings confirmed that Pb mining and metallurgy began during the Bronze Age, with considerable inputs of this heavy metal into the atmosphere during Phoenician, Punic and particularly Roman times compared to the Middle Ages. Pollution by Cu and Zn was also observed during Punic and Roman times, and was first documented in the Middle Ages. In addition, faecal stanols, such as coprostanol, derived mainly from humans, and 24-ethylcoprostanol from herbivores were present, thereby indicating for the first time a continuous presence of human populations and significant pollution input since 3600 yr cal BP, this being greater in the late Bronze Age and Phoenician, Punic and Roman times than during Late Antiquity and the Middle Ages, when the city was in decline.

Investigating the provenance of iron bars from Les Saintes‐Maries‐de‐la‐Mer Roman shipwrecks (south‐east France) with iron isotopes

AbstractFe isotopes were used to determine the origin of iron bars from Les Saintes‐Maries‐de‐la‐Mer Roman shipwrecks, which was a major archaeological finding at the end of the 20th century in France. Their Fe isotope composition was measured by multi collector‐inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS) after chemical Fe purification. The results allowed us to suggest provenances that were compared with those based on trace element analyses of slag inclusions. For most of the bars, we validate the provenance hypotheses previously proposed. Two bar groups originate from the Montagne Noire metallurgical district (south‐west France), whereas a third group comes from another source, not clearly identified so far. In this context of Roman iron production, we argue for a non‐spatially segmented production, where bars were manufactured close to smelting sites. Combined trace element and Fe isotope analyses on the same objects provide crucial information about the nature of their ore source. The elemental heterogeneity, positive Eu anomaly and Fe isotopic homogeneity of several bars were inherited from gossan‐type ores, whereas the negative Eu anomaly and variable Fe isotopes signature of others most likely correspond to sedimentary iron ores. This study demonstrates that combined trace element and Fe isotopes analyses in a well‐defined archaeological context is a promising approach for provenance studies of iron metals of archaeological interest.

Trace element and Pb and Sr isotope investigation of tooth enamel from archaeological remains at El-Kurru, Sudan: Evaluating the role of groundwater-related diagenetic alteration

This study reports new trace element and Pb and Sr isotope compositions of tooth enamel from archaeological remains at a Medieval (Christian) cemetery located adjacent to the Kushite royal cemetery of El-Kurru, Sudan. The archaeological site of El-Kurru is located along the Nile River on the southern edge of the Nubian Plateau; the bedrock geology consists of Neoproterozoic crystalline basement and is overlain by fluvial sandstones and mudstones of Cretaceous age. El-Kurru is situated between two well-developed drainage basins, and in the past has been subjected to periodic (wadi-related) flooding as a result of intense local precipitation events. Enamel samples were taken from 18 individuals of varying ages and both sexes. Trace element abundances for a significant number of samples record elevated concentrations relative to modern (“in-vivo”) enamel, including Pb and U; however, the abundances for both elements do not correlate significantly with the contents of the remaining trace elements (Ba, Fe, Mg, Mn, Nd, Sr) investigated here. The calculated enrichment factors for all trace elements studied here relative to average crustal values are not consistent with exposure to Pb ores for human purposes, which is corroborated by the Pb isotope results. The Sr isotope compositions define 2 main groups that yield 87Sr/86Sr ratios that are either higher or lower than 0.7072 with similar Sr abundances (range between ~100 and ~400 ppm). The Pb isotope compositions are extremely variable and correlate well with their corresponding U/Pb ratios; the former overlap Pb isotope ratios for proximal Neoproterozoic rocks belonging to the Saharan Metacraton and Arabian Nubian Shield tectonic provinces. The combined trace element abundances and Sr and Pb isotope compositions for the enamel samples located within the Christian cemetery at El-Kurru are best interpreted to record interaction with groundwater that occurred post-mortem during flooding events. As reported in previous anthropological studies of a similar nature, the Pb isotope results reported here are particularly sensitive to monitoring post mortem diagenetic alteration given their extremely low abundances in non-altered tooth enamel. In contrast, the 87Sr/86Sr ratios have been minimally perturbed by post mortem alteration, and therefore most likely represent individuals with distinct Sr isotopic signatures inherited from different geographic regions.

Improvement of sewage sludge anaerobic digestion through synergistic effect combined trace elements enhancer with enzyme pretreatment and microbial community response

In this study, a double E strategy (enzymes and enhancer) characterized by high efficiency for enhancing sewage sludge anaerobic digestion (AD) is proposed. This strategy combines addition of trace elements (TEs) enhancer and enzyme pretreatment, inducing a synergistic effect on AD, and it is more effective and economical compared with TEs addition or enzyme pretreatment in isolation. When adding 400 U/g cocktail enzymes and 1.24% trance elements enhancers, the cumulative methane production and the maximum daily methane increased yield by 45.29% and 84.7%, respectively. According to microbial community analysis, the double E strategy significantly motivate the growth of acetogens and protein fermenting bacterium. The relative abundance of Fermentimonas and Lutispora increased by 6.15% and 5.4%, respectively. Archaeal community analysis and changes in the mcrA gene abundance demonstrate enrichment of hydrogenotrophic methanogens, with the methanogens exhibiting high vitalities and stress resistance. The double E strategy could be a promising way to improve industrial sewage sludge AD efficiency.

A geochemical study of the Crown Formation and Bird Member lavas of the Mesoarchaean Witwatersrand Supergroup, South Africa

Abstract The ca. 2.97 to 2.80 Ga Witwatersrand Supergroup, South Africa, represents the oldest intracontinental sedimentary basin of the Kaapvaal craton. Two volcanic units occur in this supergroup: the widespread Crown Formation lavas in the marine shale-dominated West Rand Group and the more geographically restricted Bird Member lavas, intercalated with fluvial to fluvio-deltaic sandstone and conglomerate of the Central Rand Group. These units remain poorly studied as they are rarely exposed and generally deeply weathered when cropping out. We report whole-rock major and trace elements, Hf and Nd-isotope whole-rock analyses of the lavas from core samples drilled in the south of the Witwatersrand basin and underground samples from the Evander Goldfield in the northeast. In the studied areas, both the Crown Formation and Bird Member are composed of two units of lava separated by sandstone. Whereas all the Crown Formation samples show a similar geochemical composition, the upper and lower volcanic units of the Bird Member present clear differences. However, the primitive mantle-normalized incompatible trace element concentrations of all Crown Formation and Bird Member samples show variously enriched patterns and marked negative Nb and Ta anomalies relative to Th and La. Despite the convergent geodynamic setting of the Witwatersrand Supergroup suggested by the literature, the Crown Formation and Bird Member are probably not related to subduction-related magmatism but more to decompression melting. Overall, the combined trace element and Sm-Nd isotopic data indicate melts from slightly to moderately depleted sources that were variably contaminated with crustal material. Greater contamination, followed by differentiation in different magma chambers, can explain the difference between the two signatures of the Bird Member. Finally, despite previous proposals for stratigraphically correlating the Witwatersrand Supergroup to the Mozaan Group of the Pongola Supergroup, their volcanic units are overall geochemically distinct.

The clastic record of a Wilson Cycle: Evidence from detrital apatite petrochronology of the Grampian-Taconic fore-arc

Detrital apatite deposited before, during and after Grampian-Taconic arc accretion in western Ireland reveals dramatic changes in source provenance and provides a detailed detrital petrochronological record of a Wilson Cycle sited on the Laurentian margin. These determinations are made possible by recent improvements in source rock type diagnosis by apatite trace element analysis. In addition, by interrogating the proportion of apatite derived from peraluminous vs metaluminous melt and felsic vs mafic melt in detritus, temporal changes can be seen in the relative proportions of these magma compositions over time. We present combined trace element and U-Pb age data for detrital apatite in clastic formations from the South Mayo Trough, a uniquely well-preserved fore-arc basin accreted to the Laurentian margin during the Grampian-Taconic orogeny (∼ 475 – 460 Ma), which records the early phase of closing of the Iapetus Ocean. Apatite deposited before collision is derived from the Laurentian margin and mafic igneous rocks of the Central Iapetus Magmatic Province associated with the Neoproterozoic break-up of Rodinia / Pannotia leading to the birth of the Iapteus Ocean. Following the onset of ocean closure in the Cambrian, igneous apatite derived from the nascent Grampian-Taconic arc is detected. Apatite derived from felsic and peraluminous melts becomes progressively more dominant over apatite from more mafic and metaluminous sources as the arc evolves from an intra-oceanic to continental arc setting after collision. The subsequent Grampian-Taconic unroofing history recorded by detrital apatite records the transition from ancient Laurentian margin- and intra-oceanic arc-derived detritus, to the exhumation of the high-grade metamorphic core of the Grampian-Taconic orogen and the exposure of post-collisional continental-arc granitoids. Our results are in broad agreement with both the Grampian fore-arc provenance record (heavy mineral analysis, detrital zircon U-Pb and white mica Ar-Ar) and the Laurentian crustal reworking record derived from the geochemistry of volcaniclastic units in the South Mayo Trough. However, we also obtain novel provenance information undetected by detrital zircon in the South Mayo Trough, such as apatite derived from the Central Iapetus Magmatic Province. Critically this information is obtained from a single mineral system, which eliminates the need to consider differing mineral stabilities during weathering, transport and diagenesis. The high preservation potential for apatite in similar tectonic environments illustrates the potential to employ detrital apatite as a record of Earth's lithological composition in deep time.

Geodynamic Implications of Synchronous Norite and TTG Formation in the 3 Ga Maniitsoq Norite Belt, West Greenland

We present new data for the ~3.0 Ga Maniitsoq Norite Belt of the Akia Terrane, West Greenland, with the aim of understanding its petrogenesis. The Maniitsoq Norite Belt is hosted in regional TTG and dioritic orthogneisses, intruded by later sheets of TTG and granite pegmatites, and comprises two main rock types: plagioclase-rich ‘norites’ and pyroxene-rich ‘melanorites’. Both norites and melanorites have high SiO2 contents (52 – 60 wt% SiO2), high bulk rock Mg# (0.57 – 0.83), and low TiO2 contents (0.1 – 0.7 wt%). Their trace element patterns are defined by depleted HREEs, highly enriched LREEs, negative anomalies in Nb, Ta, and Ti, and variable anomalies in Zr, Hf, and Eu. New zircon U-Pb geochronology data and previously published ages establish an emplacement age of 3013 ± 1 Ma for the majority of the Maniitsoq Norite Belt, with magmatism continuing until 3001 ± 3 Ma. This ~12 Myr period of norite magmatism is coeval with an ongoing period of TTG production in the Akia Terrane. Norite Belt emplacement was closely followed by high temperature, low pressure granulite-facies metamorphism at ~800 °C and 900 °C/GPa) and that the norite magmas were emplaced into thin crust and lithosphere. Compositions of the norites and melanorites can be explained by derivation from a single mafic parental melt (~13 wt% MgO), with the norites predominantly accumulating plagioclase and the melanorites predominantly accumulating pyroxene. Evidence from field relationships, the presence of xenocrystic zircon, major element compositions and combined trace element and Hf-isotope modelling suggests the norites were contaminated by assimilation of ~20 – 30% continental TTG crust. Geochemical and Hf-Nd isotopic constraints indicate that the norite mantle source was depleted, and that this depletion occurred significantly before the emplacement of the norite magmas. Contemporaneous production of both TTGs and norite, their emplacement in thin crust, and the rapid transition to high temperature, low pressure granulite-facies metamorphism is best explained by their formation in an ultra-hot orogeny. Formation of norites in this setting may be restricted to > 2.7 Ga, when geothermal gradients were higher on Earth.

Content of Selected Macro- and Microelements in the Liver of Free-Living Wild Boars (Sus Scrofa L.) from Agricultural Areas and Health Risks Associated with Consumption of Liver.

Simple SummaryLiver is a traditional dish and a basic ingredient of traditional dishes consumed in many countries worldwide. The analysis of trace elements and macro- and microelements in the liver of wild boars is important due to the insufficient amount of available scientific information in this field. The material comprised liver samples taken from 70 wild boars (Sus scrofa L.). The animals represented the following ranges of age: Up to one year (group I), from one to three years (group II), and over three to five years (group III). It was shown that the wild boar liver is a rich source of mineral compounds. The age was found to exert an effect on the concentration of most minerals. The sex significantly determined the content of iron, calcium, and cadmium. The results obtained in our study indicate that children should avoid a frequent intake of wild boar liver. In turn, this type of liver can be a valuable source of such elements as Fe, Zn, and Cu for adults. The permissible concentration of Cd in the liver was exceeded in five samples. We suggest that regular control of the content of trace elements in wild boar liver is extremely important and advisable for assessment of the level of consumer exposure. The toxic metal content can be determined to assess the degree of environmental pollution and for biomonitoring of contamination. The information included in this article may be useful for environment protection agencies and policy makers that design strategies for environmental protection and human health and safety regulations.The aim of the study was to determine the levels of selected toxic and non-toxic elements in the liver of free-living wild boars from agricultural areas and to assess health risks associated with liver consumption. Samples were collected from 70 wild boars. The animals were divided into three age groups (group I up to one year, group II from one to three years, group III over three to five years). It was shown that wild boar liver is a rich source of mineral compounds (K, Fe, Mg, Ca, Zn, and Cu). The age was found to exert an effect on the concentration of most minerals. The sex significantly determined the content of Fe, Ca, and Cd. The maximum allowable level of Cd in the liver was exceeded in two and three samples from groups I and III, respectively. Therefore, regular monitoring of the content of this element in tissues of game animals is extremely important and advisable to assess the consumer exposure to this metal. From the point of view of human health, the estimation of the non-carcinogenic risk indicated that the intake of individual trace elements through the consumption of the liver was safe, whereas consumption of combined trace elements (only in the case of the consumption of the wild boar liver twice a week) suggested a potential health risk to children.

Trace elements and machine learning for Brazilian beef traceability

Brazilian livestock with a herd of more than 215 million animals is distributed over a vast area of 160 million hectares, leading the country to the first position in the world beef exports and second in beef production and consumption. Animals risen in the biomes Amazônia, Caatinga, Cerrado, Pampa and Pantanal were selected for this study. Beef samples were analyzed for their elemental content by neutron activation analysis and classified according to their origin by three machine learning algorithms (Multilayer Perceptron, Random Forest and Classification and Regression Tree). Significant differences (p < 0.0001) were observed between the beef elemental content from the different biomes for all multivariate contrasts using NPMANOVA. The highest classification performance was obtained for the biomes Amazônia and Caatinga using Multilayer Perceptron. Results showed the feasibility of combining trace element content and machine learning approaches for the Brazilian beef traceability.

Regional similarities in lead isotopes and trace elements in galena of the Cyclades Mineral District, Greece with implications for the underlying basement

Polymetallic ore deposits of the Aegean Sea, Greece, are temporally and spatially associated with the emplacement of Miocene granitoids and Pliocene to Quaternary volcanic units along the active volcanic arc and occur adjacent to the crustal-scale detachment systems. A variety of mineral deposits (e.g., carbonate-replacement, skarn, porphyry, vein-type, and low- to high-sulfidation epithermal deposits) formed during different stages of back-arc evolution and can be found in the footwall and hanging wall of the major detachment systems and all tectono-stratigraphic units. New galena Pb-isotope data collected by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis exhibit a range of isotopic ratios: 206Pb/204Pb: 18.68–18.91, 207Pb/204Pb: 15.67–15.75 and 208Pb/204Pb: 38.83–39.18, with a resolvable geographic pattern. Together with compiled Pb-isotope data of Cycladic galena, large-scale regional similarities in the Pb-isotope signatures are recognized, suggesting distinct sources of lead in the underlying basement. Base metal-rich deposits in the west Cyclades have a common lead source with a more radiogenic signature, whereas lead in the deposits in the north-central Cyclades was derived from a less radiogenic source. Similarities between the Pb-isotopic signature of galena and regional host rocks suggest, that the pre-Alpine Cycladic Basement was the main source of lead for the deposits in the north and central, and the metamorphosed volcano-sedimentary Lower Cycladic Blueschist Nappe was the source of lead for the deposits in the west. Moreover, there is a close spatial relationship of the 206Pb/204Pb 18.84 line and trace of the proposed Trans-Cycladic Thrust. Regional trends were also observed in the new LA-ICP-MS trace element analysis in galena. Galena in carbonate-replacement and skarn deposits in the west is enriched in base metals and silver, whereas galena in vein-type deposits in the north and low- to high-sulfidation epithermal deposits along the active volcanic arc is enriched in gold, tellurides and selenium. Combined trace element and isotopic data of galena indicate distinct metal sources in the Cyclades. Heterogenous rock assemblages of mixed provenance and age account for the differences in lead isotopes. Whereas the base metals and silver are ultimately sourced from the basement, the precious metals might be derived from the metasomatized lithospheric mantle.

The Mesoarchaean Dominion Group and the onset of intracontinental volcanism on the Kaapvaal craton – Geological, geochemical and temporal constraints

The ca. 3.07 Ga volcanic rocks of the Dominion Group, South Africa, represent the oldest example of intracontinental, rift-related volcanism on the Archaean Kaapvaal craton. The volcanic assemblage comprises a >2 km-thick succession of mafic-intermediate lavas interlayered with felsic lavas and pyroclastic rocks. Textural and geological features indicate emplacement in a subaerial environment probably in an incipient intracontinental rift. We report SHRIMP UPb zircon ages, elemental and Nd-isotope bulk-rock analyses of drill core samples and interpret their petrogenesis in the context of a Mesoarchaean continental setting. The UPb zircon ages of four felsic samples from different stratigraphic levels yielded the same dates, resulting in a pooled 207Pb/206Pb age of 3074 ± 5 Ma. Primitive mantle-normalised incompatible trace element concentrations show enriched patterns with fractionated rare earth elements over high field-strength elements and negative anomalies of Nb and Ta relative to La.Initial εNd values for mafic and felsic rocks from −1.0 to −0.2 indicate melting of sources comprising time-integrated incompatible element-enriched mantle. The combined trace element and SmNd isotopic data suggest that the enrichment of incompatible elements and the low εNd values in the most primitive basalt samples (Mg# of 65–67) can be explained with contamination of asthenosphere-derived melts with crustal material or melting of an incompatible element-enriched upper mantle. The chemical compositions of the Dominion Group and Pongola Supergroup represent a significant petrogenetic departure from earlier Archaean (>3.6–3.1 Ga) magmatism as recorded in the Kaapvaal craton, which was dominated by komatiite-basalt volcanism and tonalite-trondhjemite-granodiorite intrusions. This change reflects the transition from a “greenstone belt type” tectonic setting to a failed intracontinental rift setting shortly after stabilisation of the Kaapvaal craton.

Multiple soil element and pH interactions constrain plant performance on tropical soils with a long history of fire

Agriculture and forestry in savanna soils worldwide are often constrained by multiple soil limitations. We measured the effect of fertilisation on growth of Pinus caribaea var. hondurensis in order to improve savanna soil productivity in the Northern Territory, Australia. Growth responses to nitrogen, potassium, sulfur and a combined trace element treatment (abbreviated to N × K × S × T) with basal phosphorus (P) application on three soils, and N × P × K × S × T on another three soils, were examined in glasshouse factorial experiments. Without P, there was little response to N, S or T. Growth was usually greatest on N + P + S treatments. The P applications increased soil pH and growth, while N and S applications decreased pH. Growth was consistently poor at soil pH &amp;lt; ~5.2; a pH where exchangeable cations can be leached from the soil and aluminium can become more mobile. Responses to P, N, S and K, and likely also to zinc, were consistent with savanna soils with a long history of nutrient losses due to fire and weathering. Establishing productive plantations or agriculture will require detailed knowledge of soil properties, careful attention to soil pH and balanced fertiliser applications so as not to produce perverse outcomes. Long-term protection from fires could improve soil conditions, to be balanced against the risks of crop loss through unplanned fire.

Mineral status, metabolism and performance of dairy heifers receiving a combined trace element bolus and out-wintered on perennial ryegrass, kale or fodder beet

The effects of a cobalt (Co), copper (Cu), selenium (Se), and iodine (I) trace-mineral ruminal bolus on the mineral status and performance of out-wintered, pregnant dairy heifers was investigated. Nine commercial farms grazing pasture (G), kale (K), or fodder beet (F) were used (n = 3 per forage), with forty heifers on each farm randomly allocated to not receive (B-) or receive (B+) two combined mineral boluses. Mean plasma Co concentrations were 0.021 and 0.041 µmol/L in B- and B+ respectively (p < 0.001), with serum vitamin B12 also higher in heifers receiving B+ than B- (p < 0.001). Mean plasma Se concentration was 0.50 and 0.82 µmol/L in B- and B+ respectively, with heifers that received B+ also having a higher (p < 0.05) mean blood GSH-Px concentration (30 and 76 U/mL haematocrit in B- and B+ respectively). Providing a mineral bolus did not affect plasma Cu concentration in heifers receiving G or F (p < 0.05), but was higher in KB+ compared to KB- (p < 0.05) at the middle and end of the out-wintering period. Heifers receiving KB- also had a lower haemoglobin and red blood cell count, but a higher mean corpuscular volume than KB+ at the end of the out-wintering period. Animals receiving B- had a higher plasma thyroxine concentration (p < 0.05). Neither the bolus nor forage type affected body weight (p > 0.05), however condition score was higher (p < 0.05) in B+ at the end of the study. It is concluded that the provision of a trace mineral bolus increased plasma concentrations of the minerals supplied, with the greatest benefits in animals grazing kale, but these increases were not translated into improved performance.

The influence of seawater calcium ions on coral calcification mechanisms: Constraints from boron and carbon isotopes and B/Ca ratios in Pocillopora damicornis

In order to better understand the response of coral calcification to changes in seawater chemistry, fragments of the coral Pocillopora damicornis were grown in seawater with varying [Ca2+]. Using a combined trace element (B/Ca) and stable isotope (δ11B, δ13C) approach, this paper explores the effect of seawater calcium concentrations ([Ca2+]SW) on coral calcification mechanisms and describes the manipulation of the extracellular calcifying fluid (ECF) pH (pHECF), saturation state (ΩECF) and dissolved inorganic carbon (DIC) speciation of the ECF. In these experiments, increases in [Ca2+]SW did not significantly influence calcification rates but caused the skeletal B/Ca ratio to significantly increase. To explain these results we propose a mechanism by which [CO32−]ECF is influenced by [Ca2+]SW. This mechanism suggests that the pHECF will be lowest in our highest [Ca2+] treatment and using this relationship we can place constraints on the pHECF. The difference in pHECF in our treatments is supported in part by a slight, but insignificant decrease in skeletal δ11B and δ13C values. We propose a novel dual-proxy approach to estimate pHECF, where calcification occurs at a pHECF > 9. This work emphasizes the importance of multi-element proxy approaches in understanding pH up-regulation and CO32− concentrations during calcification of corals.

Benefits of a Multiproxy Approach to Detrital Mineral Provenance Analysis: An Example from the Merrimack River, New England, USA

AbstractThe advantages in provenance research of U‐Pb dating different detrital minerals along with simultaneously analyzing trace elements is demonstrated in a study of sand from the mouth of the Merrimack River in New England, USA. Zircon ages record episodes of magmatism in the Early Paleozoic, peaking in the Early Devonian, followed by quiescence through the remainder of the Paleozoic and additional magmatic episodes in the Jurassic and Cretaceous. Simultaneous measurement of trace elements in zircons reveals a shift from arc magmatism to crustal melting associated with terrane collision in the Early Devonian, while many Jurassic grains are clearly derived from A‐type granites. Detrital monazites and rutiles have Devonian and Permian ages. Many of the older monazites have trace element characteristics suggestive of igneous origin, while Permian monazites are clearly metamorphic and record orogenesis that is absent from the detrital zircon record. Rutile grains have trace element chemistry indicative of mostly metasedimentary source rocks, and Zr thermometry indicates growth under amphibolite facies conditions. Age offsets between monazite and rutile populations provide information about the region's cooling history. Titanite grains have trace element chemistry mostly consistent with igneous origin and U‐Pb ages lining up with minor zircon age populations in the Ordovician‐Silurian and the Middle Devonian, suggesting that these magmatic episodes produced metaluminous compositions. These results show that combining trace element fingerprinting with dating and analyzing multiple detrital mineral species provide a more complete portrait of the geologic history of the sediment source region than U‐Pb dating of zircon alone.

Role of ancient, ultra-depleted mantle in Mid-Ocean-Ridge magmatism

There is debate to what degree mid-ocean ridge basalts (MORB) can be used to infer the composition of the sub-ridge mantle and whether the upper mantle contains components that are difficult to recognize by observations on MORB alone. Here we report trace element and isotope data on a fossil mantle section exposed in the ophiolitic Lanzo South massif, Italy. Our findings show the existence of clinopyroxenes in geochemically depleted melt-infiltrated harzburgites with an extreme radiogenic Hf-isotopic composition but MORB-like Nd isotopic compositions. The simplest way of explaining the depleted trace elements in combination with the decoupled isotopic compositions is that the harzburgites were infiltrated by a melt with isotopic compositions inherited from an anciently (>1 Ga) depleted source. The existence of melts from ultra-depleted sectors of the asthenosphere allows constraining of the configuration of the heterogeneities in the sub-ridge mantle. The parallel arrays in Hf–Nd isotope composition space of different Mid-Ocean ridge segments imply the ubiquitous presence of anciently depleted residual mantle as the matrix in which more enriched components occur in pockets.