Trace Element Variations Research Articles

Columbite-Tantalite Group Mineral U-Pb Geochronology of Chaqiabeishan Li-Rich Granitic Pegmatites in the Quanji Massif, NW China: Implications for the Genesis and Emplacement Ages of Pegmatites

The Chaqiabeishan area is characterized by small Li-rich granitic pegmatites in the Quanji Massif (QM), northwest China. In this study, the columbite-tantalite group minerals (CGMs) from a typical Li-rich pegmatite dike were analyzed for major element contents using an EMPA (electron microprobe analyzer), for trace element contents using LA-ICP-MS (laser ablation-inductively coupled plasma mass spectrometry), and for ages using LA-ICP-MS U-Pb dating, respectively. The CGMs from the sample can be divided into two types, i.e., magmatic Type 1 and metasomatic Type 2. Although these two types of CGMs do not exhibit distinct major and trace element variations from core to rim within an individual grain, the Ta# values, Mn# values, and some trace element contents (such as Zr, Hf, W, and Sr) of Type 1 CGMs are distinct from those of Type 2 CGMs. The overall compositional changes from Type 1 CGMs to Type 2 CGMs are consistent with the typical evolutionary trend described for many lithium-cesium-tantalum (LCT) pegmatites and the complex spodumene trend described by Černý and Ercit (Bull. Mineral., 1989, 108, 499–532). The Type 2 CGMs have formed later and must be a metasomatic product of Type 1 CGMs. Eighteen Type 1 CGMs yielded a weighted mean 206Pb/238U age of 240.6 ± 1.5 Ma. The slight oscillatory zoning and/or sector zoning suggest that the dated Type 1 columbites have a magmatic origin. Thus, the crystallization ages of Type 1 columbites represent the emplacement ages of Li-rich pegmatites. One of the Type 2 CGMs yielded a 206Pb/238U age of 211.0 ± 4.7 Ma, which is hardly interpreted to be an age representing the later hydrothermal metasomatism, because one dataset has no apparent statistical significance. Therefore, our dating results can only indicate that the Li-rich pegmatite-forming melts were emplaced at approximately 240.6 Ma. Based on these results and previous studies of the 240–254 Ma granitoids in the QM, we conclude that the 240.6 Ma Li-rich granitic pegmatites, as well as 240–254 Ma granitoids in the QM, were both emplaced during the southward subduction of the Zongwulong Ocean Plate in the Late Permian to Middle Triassic.

Genetic relationship between greisenization and Sn–W mineralization in vein and greisen deposits: Insights from the Panasqueira deposit (Portugal)

The W–Sn Panasqueira ore deposit is a magmatic-hydrothermal system, which includes a high-grade quartz-vein type mineralization and a disseminated greisen-type mineralization occurring in the upper part of the Panasqueira two-mica granite. We investigated the genetic and chronological relationships between the greisenization of the Panasqueira granite and the formation of ore-bearing quartz veins by monitoring major and trace elements variations in quartz-white mica assemblages composing the two-mica granite, greisen and W–Sn-bearing quartz veins. The greisen is characterized by an overall depletion in Mg, Ti, Ca, Na, Ba, Sr, REE and enrichment in Fe, Li, Rb, Cs, Sn, W which reflect the breakdown of feldspars and fluid-rock interactions with W–Sn-bearing fluids. White-mica from greisen and mineralized quartz veins are enriched in granophile elements (F, Rb, Cs, Li, Sn, W and Zn) compared to magmatic muscovite from the two-mica granite. Trace elements contents in quartz depict trends which show the progressive enrichment in Ge and B and depletion in Al, Ti and Li from magmatic to hydrothermal quartz that emphasize the progressive evolution and cooling of the magmatic-hydrothermal system of Panasqueira. Geochemical similarities between quartz-white mica assemblages from greisen and wolframite-bearing veins suggest that greisenization and the formation of mineralized veins result from the same hydrothermal event and derived from the same source of hydrothermal fluids. Apatite from greisen and quartz vein yielded U–Pb ages of 292 ± 10 Ma and 295 ± 5 Ma respectively confirming that greisenization and the formation of mineralized veins occurred roughly at the same time. These ages also overlap with the emplacement age of the Panasqueira granite (296 ± 4 Ma), indicating a temporal link between greisenization, W–Sn mineralization and granite crystallization. Temperatures of the magmatic-hydrothermal system constrained by Ti-in quartz thermometry depicts a cooling trend from magmatic quartz of granite (700–600 °C) to hydrothermal quartz of greisen (500–400 °C) and veins (450–350 °C). These results suggest that greisenization and the formation of W–Sn bearing quartz veins occurred at the magmatic-hydrothermal transition, during which orthomagmatic fluids rich in volatils, incompatible elements and W–Sn were exsolved during the final solidification stage of the Panasqueira two-mica granite.

Variation of macroand trace elements in organs of the blue honeysuckle subspecies of various environmental and geographic provenance when grown in the Near-Ob foreststeppe (West Siberia, Russia)

The variation limits and organ distribution of macroand trace elements were determined in plants of the three subspecies of Lonicera caerulea L. The leaves, as compared with the stems, were found to accumulate more of B, Са, Mg, Mo, P and Sr and less of Al, Mn, Ti and Zn. The plants of different subspecies, grown on soils of the similar chemical element composition, showed statistically significant differences in contents and organ distribution patterns of Al, Cr, Cu, Fe, Mg, Mo, Na, Ni, Pb, Si, Ti and Zn. The stems of the subspecies of the Far East provenance (L. сaerulea subsp. kamtschatica and L. сaerulea subsp. venulosa) had abnormally high contents of Al, Cr, Fe, Na, Si and Ti.

Intraspecific variation of trace elements in the kelp gull (Larus dominicanus): influence of age, sex and location

Hepatic tissue of Larus dominicanus sampled on the coastline of the state of Santa Catarina in Brazil between October 2016 and May 2018 was used to evaluate intraspecific trends and spatial distribution of essential trace elements (Mn, Co, Cu, Zn, Mo and Cr) and non-essential trace elements (As, Pb, Cd, Hg, Ba and V). Principal Component Analysis (PCA) indicated differences in the bioaccumulation of trace elements between female adults and male adults, differences to sex and age were indicated by Kruskal-Wallis test. Heat maps suggest hot spots in locals with high concentration of trace elements in liver of Larus dominicanus. In general, the concentration of trace elements were comparable with values reported in other studies carried out for this species in South America and other regions of the world. The heat maps showed to be a promising tool to identify influences of the locality on bioaccumulation of trace elements in Larus dominicanus.

Characteristics of Trace Elements in Molybdenite and Its Application in Mineral Deposits

Previous studies on molybdenite are mainly focused on Re-Os dating for a deposit, by contrast there have relatively little on trace elements in molybdenite. On the basis of statistical summarizing the previous research results, this paper discusses the variation of trace elements of molybdenite in various deposits and the combination of the different trace elements in molybdenite of different deposits, which is expected to expand its application in mineral deposit science. The results show that Re and W contents in molybdenite have the potential to be used as tracer to trace its sources. Molybdenite in different types of deposits has different trace elements composition and content, which mainly depends on the ore-forming fluids. Trace elements exist in various states in molybdenite, including isomorphic substitution, inclusion, adsorption and so on. Elements such as Re, W, Se, Te and Nb can enter the molybdenite lattice by replacing Mo or S, while Pb, Zr, Fe and REE those elements mainly appear as mineral inclusions. Most trace elements (for Fe, Cu, Te, etc.) are positively correlated, which may indicate that their sources are in similiar among each other. A few trace elements were negatively correlated with each other, which may reflect the different in their sources.

Sedimentological and Geochemical Charectesization of Manaveli and Cuddalore Formations, Puducherry Basin, India

Sedimentological and Geochemical Charectesization of Manaveli and Cuddalore Formations, Puducherry Basin, India 
 
 Shyam N. Mude, Shyam Yawale and Vishal Choudhari 
 
 Department of Geology, Fergusson College (Autonomous), Pune- 411004, India
 Email: shyam.mude@fergusson.edu; shyammude25@yahoo.co.in
 
 Abstract: The lithostratigraphically rocks of Puducherry basin (Sub-basin of Cauvery Basin) have been classified as Valudavur, Mettuveli, Karasur, Manaveli, Cuddalore formations in ascending order of deposition. The sedimentological and geochemical studies of sediments from Manavali (Paleocene) and Cuddalore (Mio-Pliocene) formations were carried out to understand grain size variation and distribution of major oxides and trace elements. 
 The sieve analysis was used to study grain size variation and on the basis of grain sizes various geo-statistical parameters were calculated to understand depositional environment. The discriminant function analysis of the sediments from the Cuddalore Formation infers that mostly the sedimentation was occurred in fluvio-deltaic environment with incursions of shallow marine environment whereas bivariate plots suggests that the deposition was occurred in riverine to deltaic environment.
 The major element geochemistry of the Manaveli and Cuddalore formations have been carried out to understand the provenance, paleoclimate and source area weathering conditions. The values of CIA (Chemical Index of Alteration), CIW (Chemical Index of Weathering), ICV (Index of Compositional Variability) and PIA (Plagioclase Index of Alteration) of the sediments infer high weathering was occurred in source area of sediments for Manaveli and Cuddalore formations. The ratio (Al2O3+K2O+Na2O)/SiO2 indicate semi-humid climatic conditions during deposition of Cuddalore Formation whereas Manaveli Formation was deposited in semi-arid climatic conditions. The discriminant function diagram (A-CN-K Plot), suggest Quartzose sedimentary provenance for Cuddalore and Mafic igneous provenance for Manaveli Formation. 
 
 Keywords: Grain Size, Geochemistry, Manaveli, Cuddalore, Puducherry Basin

Variability of essential and non-essential trace elements in the follicular fluid of women undergoing in vitro fertilization (IVF)

Both essential and non-essential elements have been associated with female reproductive function in epidemiologic investigations, including among IVF populations. To date, most investigators have used blood or urine to assess biomarkers of exposure, with few employing ovarian follicular fluid (FF). FF may offer a more direct “snapshot” of the oocyte microenvironment than blood or urine, however previous studies report follicle-to-follicle variability in FF constituents that may contribute to exposure misclassification. Our objectives were to investigate sources of trace element variability, to estimate FF biomarker reliability among women undergoing IVF (n = 34), and to determine the minimum number of follicles required to estimate subject-specific mean concentrations. We measured As, Hg, Cd, Pb, Cu, Mn, Se, and Zn in FF samples using inductively coupled plasma tandem mass spectrometry. Inter-subject (between-women) variability contributed most of the variability in FF element concentrations, with ovarian, follicular, and analytical as smaller sources of variability. The proportion of variability attributable to sources between-follicles differed by age, body mass index (BMI), race, and cigarette smoking for Cu, Se, and Zn, by BMI and cigarette smoking for As, by primary infertility diagnosis for Hg, Cu, Se, and Zn, and by ovarian stimulation protocol for Mn and Se. Four to five individual follicles were sufficient to estimate subject-specific mean Cu, Se, and Zn concentrations, while >14 were necessary for As, Hg, Cd, Pb, and Mn. Overall, our results suggest that FF is a suitable source of biomarkers of As and Hg exposure in ovarian follicles. Although limited in size, our study offers the most comprehensive exploration of biological variation in FF trace elements to date and may provide guidance for future studies of ovarian trace element exposures.

Sex-related and spatial variation in trace elements in feathers of the Kentish plover (Charadrius alexandrinus) from different coastal areas of the Iberian Peninsula

This study investigated the sex-related and spatial variation in trace elements concentrations in feathers of the Kentish plover (Charadrius alexandrinus) inhabiting different coastal locations in the Iberian Peninsula. Feathers were sampled in a total of 50 breeding birds from 7 different locations: 3 on the Mediterranean coast (n=18), 1 on the Atlantic coast of Andalusia (n=9) and 3 on the NW Atlantic coast (n=23). The feathers were analyzed to determine the concentrations of Al, Cr, Mn, Cu, Zn, As, Se, Cd, Hg and Pb. All of the trace elements were present at detectable concentrations, and the mean concentrations of Al, Zn and Cu were highest of those considered. The coastal section had a significant effect on 5 elements (Mn, Cu, As, Cd and Pb). The mean concentrations of almost all of the trace elements were highest in the birds from Andalusia, intermediate in the birds from the Mediterranean area and, in general, lowest in the birds from the NW Atlantic coast. Females showed significant higher Mn concentrations and high levels of exogenous elements (Al and As) in contrast with males. Less preening activity during the day of female birds, when they are occupied in incubating eggs, could favour higher concentrations of exogenous trace elements. The high levels of several trace elements observed in the samples from Mediterranean and Atlantic coast of Andalusia may pose a serious threat to these populations.

Spatiotemporal variations, sources, water quality and health risk assessment of trace elements in the Fen River

As the largest river in Shanxi Province, the Fen River is the main water source for regional economic and ecological development. Water deficiency and industrialization have led to serious water pollution in the Fen River. The major and trace elements of seasonal river waters were measured to determine the spatiotemporal variations and assess the water quality as well as its controlling factors in the Fen River. Trace elements are divided into high abundance elements (B, Ba, Li, and Mn) and low abundance elements (As, Cu, Fe, Ni, Rb, Se, U, and V). The spatial variation of trace elements is obvious, with low values upstream, intermediate values downstream, and very high values midstream. The average values of the trace elements showed different seasonal variations, with high values of As, B, Ba, Mn, and Rb in the wet season, high Cu, V, and Li values in the dry season, and minor seasonal variations of Fe, Ni, Se, and U concentrations. Principal component analysis (PCA) and correlation analysis (CA) showed natural origins of Ba, Mn, Ni, and U, anthropogenic input of As, B, Cu, Li, Rb, Se, and V. According to the results of absolute principal component sore-multivariate linear regression (APCS-MLR), the major pollution sources in the Fen River basin were related to human activities. The land use type significantly influenced the concentrations of trace elements, with high values in the cropland and low values in the forest. The water quality index (WQI) values were higher in the midstream and wet season. In comparison with other rivers in the world, the pollution of the Fen River is at a moderate level. Health risk assessment showed that As, Ba, Mn, Ni, V, and Se were the potential pollutants damaging in the Fen River, especially for children. This study highlights the importance of seasonal sample analysis and can provide vital data for water quality conservation in the Fen River basin.

Concentration and variability of soil trace elements in an agricultural area in a semiarid region of the Irecê Plateau, Bahia, Brazil

In a previous study, a high concentration of Pb, Zn, Cr, and Mn in soil profiles located in the semiarid region of Brazil were found in areas used for decades by small family farmers for the production of the crops and raising small animals. This question motivated the current study to evaluate the soil variability spatial dependence on trace elements to quantify and map its occurrence in this area, comparing their concentration with reference values set by the Brazilian environmental agencies. Soil samples were collected at 0-0.20 and 0.20-0.40 m depths and 25, 50, 100, 200, and 400 m from the center and to both sides of five transects spaced from 1,000 m, forming a grid. The concentration of the trace elements As, Cd, Pb, Cu, Cr, Fe, Mn, Ni, Ti, and Zn was obtained in SW-846 3050B USEPA soil extract by ICP-OES. Spatial dependence for all evaluated elements allowed the elaboration of dispersion maps in the area, except for Cd. Trace elements concentrations were below the investigation values (limit value of a trace element in the soil with risk potential to humans and the environment) of the Brazilian environmental legislation (Conama). Pb and As concentrations were above the prevention values (limit value of a trace element in the soil that can sustain its primary functions), but, still, they presented low dispersion in the area. Zn concentration was above the prevention value, and dispersion was higher, regardless sampling point, which requires a major concern. Cr, Cu, Ni, Fe, Mn, and Ti concentrations were below the Conama reference values, and the dispersion was also low. Fortunately, except for Fe, it was observed that trace elements were concentrated around the central point of the "gossan", instead of distributed throughout in the agricultural area around it.

First year after the Brumadinho tailings’ dam collapse: Spatial and seasonal variation of trace elements in sediments, fishes and macrophytes from the Paraopeba River, Brazil

On January 2019, the B1 iron ore tailings' dam collapsed in Brumadinho, Brazil, being one of the worst mining-related disasters, with 270 human deaths (11 of them still missing) and 12.106 m3 of tailings released to the environment. The tailings devastated the Córrego do Feijão brook and reached the adjacent Paraopeba River, the region's main watercourse and a major tributary of the São Francisco basin. Although physicochemical parameters of the river were strongly impacted, and acute toxicological effects have been reported from exposure experiments, contamination of aquatic biota had not yet been assessed. Therefore, the aim of this study was to evaluate contamination by trace elements (As, Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn) in sediment, fish and macrophytes along the Paraopeba River, upstream and downstream from the dam failure site, during the dry and wet season. With the exception of Cd and Hg, all elements in sediment samples had lower median concentrations downstream. An inverse pattern was observed for the aquatic biota, with significant higher concentrations of Fe, Mn, Ni and Zn in fishes, and increased concentrations of most elements in macrophytes, indicating an increase in element bioavailability. A significant seasonal variation was observed with increased concentrations of As (dry season) and Pb (wet season) in fish samples, with the same trend occurring in macrophytes. Concentrations of potentially toxic elements in fish samples in wet weight (Cr: 1.80 ± 1.31 mg kg−1, Hg: 0.21 ± 0.11 mg kg−1 and Pb: 0.79 ± 0.80 mg kg−1) were lower than those reported before the disaster. Furthermore, As and Pb concentrations exceeded the safety threshold for fish consumption in 3% and 41% of samples, respectively, representing a matter of concern for public health.

Identifying hydrothermal quartz vein generations in the Taiyangshan porphyry Cu-Mo deposit (West Qinling, China) using cathodoluminescence, trace element geochemistry, and fluid inclusions

Porphyry-style mineralization is characterized by superposition of multiple generations of quartz growth, punctuated by dissolution and juxtaposed within a single vein. Such superposition inevitably obscures temporal relationships between quartz formation, alteration events, and fluid inclusion assemblages (FIAs), and consequently complicates the interpretation of fluid origin and evolution. Very detailed information of these relationships recorded within hydrothermal quartz from the Taiyangshan porphyry Cu-Mo deposit (NW China) is obtained using integrated cathodoluminescence (CL) imaging, trace element analyses, and fluid inclusion petrography.The CL characteristics range from bright blue-CL quartz (Q1) associated with early high-temperature potassic alteration, to dark blue-CL quartz (Q2) broadly coinciding with metal precipitation, to post-ore dull red-CL fine-grained, anhedral, and recrystallized quartz (Q3) subgrains. Early bright blue-CL quartz (Q1) crystals, generally at the edges of stockwork veinlets close to wallrock, are characterized by oscillatory growth zoning, and exhibit alignment of primary, equant-shaped, brine-bearing FIAs along the banded growth zones. Later dark blue-CL quartz (Q2) crystals are generally euhedral in shape and grow with c-axes pointing inward to the vein center. They exhibit well-defined, but rarely preserved, growth zones truncating Q1 and crystal terminations projecting into pyrite and chalcopyrite in the vein center although they are not spatially associated with sulfides. These vein features clearly indicate that Q2 crystals grow into an open cavity or fracture during the ore precipitation. This is also evident by coexisting, secondary, irregular-shaped, liquid-rich inclusions and vapor-rich inclusions along fractures transecting Q1 oscillatory growth bands. The coexistence of hypersaline and vapor-rich inclusions moreover provides unequivocal evidence for phase separation during mineralization. Dull red-CL quartz (Q3) crystals appear to coincide with or follow sericitic alteration, and cut and encompass preexisting Q1 and Q2 crystals. They spatially associated with sulfides. The Q3 grains contain rare well-defined FIAs, but show scattered, secondary, irregular-shaped, low-salinity aqueous inclusions with small- to medium-sized vapor bubbles (10–30 vol%), as well as complex fluid inclusions that have migrated to the margins of anhedral Q3 subgrains due to quartz dissolution and recrystallization.Formation of early blue-CL Q1 and Q2 crystals at moderate temperatures are consistent with enrichment of Ti in the quartz lattice compared to neighboring younger Q3. The Q2 crystals are typified by elevated concentrations of Al and K concentrations when compared to Q1 and Q3. The substitution of Ti4+ for Si4+ in the tetrahedral sites of quartz leads to an increased CL intensity from Q1, to Q2, and then to Q3 corresponding to a decrease in quartz precipitation temperature. Ore deposition, recorded by integration of CL textures, FIAs petrography, and trace element variations in Q2, in the Taiyangshan porphyry Cu-Mo deposit must have occurred over a significant change in physicochemical conditions. This suggests that phase separation due to fluid cooling/pressure drops during the transition from lithostatic to hydrostatic regimes is critical to porphyry mineralization. We further propose a complex hydrothermal quartz vein formation history involving multiple fluid inclusions under varying pressure and temperature conditions.

Zircon and titanite behaviors during partial melting of metabasite in the post-collisional stage: Constraints from garnet pyroxenite in the Dabie orogen, China

Abstract An integrated study of petrology, mineral inclusions, U-Pb ages and trace elements in zircon and titanite was carried out for garnet pyroxenites from the Dabie orogen, China. The results provide not only geochemical constraints on zircon and titanite behaviors during partial melting but also petrological insights into anatectic reworking of ultrahigh-pressure metamorphic eclogites in the collisional orogen. The target garnet pyroxenites were transformed from ultrahigh-pressure eclogites produced by the continental deep subduction in the Triassic, and underwent granulite facies metamorphic superimposition in the early Cretaceous under P-T conditions of 746–837 °C and 0.8–1.2 GPa, followed by amphibolite facies retrogression at 737–791 °C and 0.7 GPa. Both zircon and titanite contain two types of metamorphic domains at ca. 131 Ma based on CL images, mineral inclusions, REE patterns and trace element variations. Peritectic zircon domains (D3) contain abundant multiphase crystal inclusions of quartz and K-feldspar and exhibit variably high Nb, Ta, Th, U, P, REE and Y contents. In contrast, anatectic zircon domains (D4) are relatively free of crystal inclusion and display variably low Nb, Ta, Th, U, P, REE and Y contents. Metamorphic and peritectic titanite domains are clearly distinct by a series of differences in petrological and geochemical compositions. There are reduced 176Hf/177Hf ratios for both peritectic and anatectic zircon domains, indicating involvement of Hf-rich minerals in the anatexis of the ancient crust. Therefore, the discrimination between the polygenetic zircon and titanite domains in the metabasites not only provides a powerful means to decipher the nature of crustal anataxis in the collisional orogen, but also places constraints on the formation mechanism of metamorphic, peritectic and anatectic minerals.

Strontium isotope analysis of apatite via SIMS

We report the development of a SIMS analytical method for in situ Sr isotope analysis of the mineral apatite at an analytical scale of 15 μm or less. Experiments were conducted on a series of reference apatites of widely differing Sr contents at three different mass resolution settings: low (3000), moderate (4200) and very high (16000), using a large-geometry CAMECA 1280 ion microprobe retrofitted with a HyperionTM oxygen plasma ion source. Peak-stripping algorithms tailored to the different mass-resolution settings were developed to correct for significant interferences on the target strontium isotope species in the mass spectra, namely Ca dimers, CaPO, Rb and SrH, and for instrumental mass fractionation. The most consistently accurate and precise 87Sr/86Sr ratios were achieved at the 3000 mass resolution setting with appropriate energy filtering and use of a cold trap. On average, corrected 87Sr/86Sr ratios by this method were elevated by ~0.8‰ above equivalent TIMS and solution ICPMS data, with consistent behaviour across the range of Sr concentrations. Individual spot precision of ± 0.001 to 0.004 (2SE) was achieved, depending on Sr content. The key advantages of SIMS analysis compared to existing LA-MC-ICP-MS methods are the high spatial resolution, low sample consumption, and the high mass resolution that allows for the elimination of problematic isobaric interferences. Our approach is particularly useful for the analysis of small or valuable targets, such as mineral inclusions or meteoric samples, and for apatite with high REE contents. However, the much larger volume of material consumed during LA-MC-ICP-MS analysis allows for substantially better precision than the SIMS method presented here. The highly variable trace element composition of natural apatites, involving both cationic and anionic substitutions, necessitates careful characterisation of prospective targets prior to any in situ analysis, in addition to matching to appropriate reference materials.

Periodic Mixing of Magmas Recorded by Oscillatory Zoning of the Clinopyroxene Macrocrysts from an Ultrapotassic Lamprophyre Dyke

Abstract Ultrapotassic rocks are volumetrically minor, but widely distributed in different geological settings. Extensive studies have concerned mantle melting processes that generated these rocks. However, crustal processes that they may have involved are poorly known. In this paper, we describe complex oscillatory zoning patterns of clinopyroxene (Cpx) macrocrysts from an ultrapotassic lamprophyre dyke in the Kyrgyz North Tianshan orogen. These macrocrysts commonly have a corroded or patchy-zoned core surrounded by a mantle with distinct oscillatory zoning, which is, in turn, surrounded by a euhedral rim. The oscillatory zoning of the mantle is composed of alternating coarse and fine layers with a clear resorption surface, or closely packed layers with a straight or wavy boundary in back-scattered electron images. High-amplitude oscillation of Mg#, Ti, Al, Cr and Sr across the layers of the mantle is attributed to magma mixing. Low-amplitude, high-frequency oscillation of Mg# across the closely packed layers was probably developed as a result of kinetic effects or crystal movement under thermal and chemical gradients. In addition, cryptic sector zoning of some macrocrysts clearly shows a Si- and Mg-rich hourglass sector and an Al- and Ti-rich prism sector. The sector zoning indicates crystallization of these macrocrysts under low degrees of undercooling, and the presence of concentric Cr-rich and Cr-poor layers within the same grain indicates that the growth process was disrupted by multiple magma recharging events. The cores of the macrocrysts have Mg# with three distinctive ranges: <84–90 (Core I), 74–84 (Core II) and 60–70 (Core III). The mantles have Mg# ranging from 64 to 90 without a distinct gap. The rims have a narrow range of Mg# from 76 to 80. The cores and mantles with high Mg# (≥85) have variable La/Yb from 1·8 to 5·0 and Dy/Yb from 2·3 to 4·6. The macrocrysts overall have variable 87Sr/86Sr from 0·7072 to 0·7084. Highly variable trace elements and 87Sr/86Sr within a single grain indicate that both primary and evolved magmas with different compositions were periodically recharged into the crustal magma reservoirs. Modelling results reveal that the melts in equilibrium with the Cpx macrocrysts may have been derived from the magma reservoirs at three different depths equivalent to crystallization pressures of ∼5·4, ∼3·3 and ∼1·6 kbar, respectively, making up a transcrustal magmatic system. The Cpx-laden melts in deep magma reservoirs may have been frequently transported to shallower reservoirs. Magma mixing in the shallower reservoirs led to heterogeneous magmas with different cooling rates and chemical compositions. Early crystallized Cpx crystals were overprinted with diverse zoning patterns during overgrowth and accumulation. Thus, the complex zoning patterns and compositions of the Cpx macrocrysts have important implications for a transcrustal magmatic system in the formation of ultrapotassic rocks.

A Continuum from Iron Oxide Copper-Gold to Iron Oxide-Apatite Deposits: Evidence from Fe and O Stable Isotopes and Trace Element Chemistry of Magnetite

AbstractIron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of Fe, Cu, and Au. Magnetite is the modally dominant and commodity mineral in IOA deposits, whereas magnetite and hematite are predominant in IOCG deposits, with copper sulfides being the primary commodity minerals. It is generally accepted that IOCG deposits formed by hydrothermal processes, but there is a lack of consensus for the source of the ore fluid(s). There are multiple competing hypotheses for the formation of IOA deposits, with models that range from purely magmatic to purely hydrothermal. In the Chilean iron belt, the spatial and temporal association of IOCG and IOA deposits has led to the hypothesis that IOA and IOCG deposits are genetically connected, where S-Cu-Au–poor magnetite-dominated IOA deposits represent the stratigraphically deeper levels of S-Cu-Au–rich magnetite- and hematite-dominated IOCG deposits. Here we report minor element and Fe and O stable isotope abundances for magnetite and H stable isotope abundances for actinolite from the Candelaria IOCG deposit and Quince IOA prospect in the Chilean iron belt. Backscattered electron imaging reveals textures of igneous and magmatic-hydrothermal affinities and the exsolution of Mn-rich ilmenite from magnetite in Quince and deep levels of Candelaria (>500 m below the bottom of the open pit). Trace element concentrations in magnetite systematically increase with depth in both deposits and decrease from core to rim within magnetite grains in shallow samples from Candelaria. These results are consistent with a cooling trend for magnetite growth from deep to shallow levels in both systems. Iron isotope compositions of magnetite range from δ56Fe values of 0.11 ± 0.07 to 0.16 ± 0.05‰ for Quince and between 0.16 ± 0.03 and 0.42 ± 0.04‰ for Candelaria. Oxygen isotope compositions of magnetite range from δ18O values of 2.65 ± 0.07 to 3.33 ± 0.07‰ for Quince and between 1.16 ± 0.07 and 7.80 ± 0.07‰ for Candelaria. For cogenetic actinolite, δD values range from –41.7 ± 2.10 to –39.0 ± 2.10‰ for Quince and from –93.9 ± 2.10 to –54.0 ± 2.10‰ for Candelaria, and δ18O values range between 5.89 ± 0.23 and 6.02 ± 0.23‰ for Quince and between 7.50 ± 0.23 and 7.69 ± 0.23‰ for Candelaria. The paired Fe and O isotope compositions of magnetite and the H isotope signature of actinolite fingerprint a magmatic source reservoir for ore fluids at Candelaria and Quince. Temperature estimates from O isotope thermometry and Fe# of actinolite (Fe# = [molar Fe]/([molar Fe] + [molar Mg])) are consistent with high-temperature mineralization (600°–860°C). The reintegrated composition of primary Ti-rich magnetite is consistent with igneous magnetite and supports magmatic conditions for the formation of magnetite in the Quince prospect and the deep portion of the Candelaria deposit. The trace element variations and zonation in magnetite from shallower levels of Candelaria are consistent with magnetite growth from a cooling magmatic-hydrothermal fluid. The combined chemical and textural data are consistent with a combined igneous and magmatic-hydrothermal origin for Quince and Candelaria, where the deeper portion of Candelaria corresponds to a transitional phase between the shallower IOCG deposit and a deeper IOA system analogous to the Quince IOA prospect, providing evidence for a continuum between both deposit types.

Variability of essential and toxic trace elements in the follicular fluid of women undergoing in vitro fertilization (IVF)

Both essential and non-essential elements have been associated with female reproductive function in epidemiologic investigations, including those among IVF populations. To date, most investigators have used blood or urine to assess biomarkers of exposure, with few employing ovarian follicular fluid (FF). FF may offer a more direct 'snapshot' of the oocyte microenvironment, however previous studies report follicle-to-follicle variability in FF constituents which may contribute to exposure misclassification. Our objectives were to: investigate sources of trace element variability in FF among women undergoing IVF (n=34, ≤4 FF collections each; estimate biomarker reliability; and determine the minimum number of follicles to estimate mean concentrations at a 10% confidence level (m10%). We measured As, Cd, Hg, Pb, Cu, Mn, Se, and Zn in FF samples using ICP-MS/MS and employed linear mixed models using restricted maximum likelihood to generate variability components. Sources of variability between women contributed the greatest proportion of total variance for FF As (97.2%), Hg (97.8%), Cd (52.1%), Cu (60.4%), Se (48.1%), and Zn (56.8%), compared to sources between ovaries, between follicles, and analytical variation. The proportion of variability attributable to sources between follicles differed significantly (p<0.05) by age, BMI, race, and cigarette smoking for Cu, Se, and Zn, by BMI and cigarette smoking for As, by primary infertility diagnosis for Hg, Cu, Se, and Zn, and by ovarian stimulation protocol for Mn and Se. To estimate m10% for Cu, Se, and Zn 4 to 5 individual follicles were sufficient, while >14 were necessary for As, Cd, Hg, Pb, and Mn. Our results suggest that while FF As and Hg are suitable biomarkers, these elements and Cd, Pb, and Mn have comparatively higher between-follicle variability than the other analytes. Our findings may help elucidate the impact of trace element exposures on IVF outcomes and inform the design of future studies.

Diamond-forming HDFs tracking episodic mantle metasomatism beneath Nyurbinskaya kimberlite pipe (Siberian craton)

We present a new dataset on the composition of high-density fluids (HDFs) in cloudy (n = 25), coated (n = 10) and cuboid (n = 10) diamonds from the Nyurbinskaya kimberlite pipe. These diamonds represent different populations each showing distinct growth histories. The cores of coated diamonds display multiple growth stages and contrasting sources of carbon. Fibrous coats and cuboid diamonds have similar carbon isotopes and nitrogen systematics, suggesting their formation in the last metasomatic events related to kimberlite magmatism, as is common for most such diamonds worldwide. The HDFs in most of these diamonds span a wide range from low-Mg carbonatitic to hydrous silicic compositions. The major- and trace-element variations suggest that the sources for such HDFs range in composition between the depleted mantle and more fertile mantle reservoirs. Hydrous-silicic HDFs could originate from a 13C-enriched source, which originates through subduction of crustal metasedimentary material. Percolation of such HDFs through carbonated eclogites and peridotites facilitates the formation of cuboid diamonds and fibrous coats in the mantle section beneath the corresponding area of the Siberian craton. Cloudy diamonds represent an apparently older population, reflecting continuous diamond formation predominantly from high-Mg carbonatitic HDFs that caused discrete episodes of diamond precipitation. Their high Mg# and enrichment in incompatible elements support a metasomatized peridotitic source for these HDFs.

Petrogenesis of a low-87Sr/86Sr, two-mica, garnet-bearing leucogranite (Donkerhoek batholith, Damara orogen, Namibia)

Syn-tectonic 530.6 ± 0.8 Ma pegmatites and aplites from the Donkerhoek batholith in the Damara orogen (Namibia) are moderately to strongly peraluminous, ferroan, alkalic to calc-alkalic leucogranites. Major and trace element variations and strongly fractionated REE patterns with positive Eu anomalies indicate that the leucogranites represent highly fractionated melts that accumulated or retained feldspar that may account, in part, for their alkalic composition. Elemental variations imply that biotite, garnet, and feldspar were the main fractionating minerals. The pegmatites have lower 87Sr/86Sr (0.7053–0.7097) than—but similar unradiogenic initial εNd (−4.1 to −10) to—the least evolved Donkerhoek granites. Two aplites have similar εNd values but unreasonably unradiogenic 87Sr/86Sr ratios as a result of late-stage disturbance and associated overcorrection due to their extremely high 87Rb/86Sr ratios. Subtle variation in Nd isotope compositions coupled with LREE fractionation indicate limited AFC or contamination processes. Lead isotope compositions are more radiogenic than those from published Donkerhoek samples, indicating derivation from or involvement of a component with a considerable crustal residence time. Based on the alkalic to calc-alkalic and ferroan composition and the similarity in Nd–Sr isotopes, meta-igneous basement rocks from the nearby Kalahari craton are likely sources. This study confirms previous studies on the Donkerhoek batholith that have shown that giant batholiths consist of distinct magma batches that are derived from various sources. The new age constraints in conjunction with published ages show that the large-scale Donkerhoek batholith, with a spatial extent of >5000 km2, grew incrementally over a period of at least 30 Myr.

Crust-mantle interaction during syn-collisional magmatism – Evidence from the Oamikaub diorite and Neikhoes metagabbro (Damara orogen, Namibia)

The early-syntectonic 563.7 ± 6.1 Ma old Oamikaub diorite (Damara orogen, Namibia) consists of metaluminous, magnesian, calc-alkalic to calcic diorites, granodiorites and granites. Associated gabbro-diorites and gabbros belong to the Neikhoes metagabbro. Linear major and trace element variations imply that the rock suite evolved through fractional crystallization processes involving amphibole, biotite, Fe-Ti oxides, zircon and apatite. Initial Sr (87Sr/86Sr: 0.7058–0.7123) and Nd (ε Nd: −2.1 to −18.8) isotopic compositions are highly variable and negatively correlated indicating that assimilation of crustal components occurred. Unradiogenic initial 206Pb/204Pb (16.23–17.23) and 207Pb/204Pb ratios (15.50–15.57) suggest derivation from or interaction with ancient crust with low U/Pb. Two gabbro-diorites have MgO, Ni and Cr abundances that are compatible with derivation of these rocks from upper mantle lithologies. Their initial ε Nd values (−2.1 and – 7.4) and 87Sr/86Sr ratios (0.7058 and 0.7076) imply derivation from an aged metasomatized lithospheric mantle. Other mafic samples have MgO abundances and compatible element concentrations that exceed the values commonly accepted for primary mafic melts implying some accumulation of clinopyroxene and amphibole. The granodiorites form a homogenous group in which the isotope data (initial ε Nd: −12.4 to −14.1; initial 87Sr/86Sr: 0.7083–0.7096) imply a lower crustal source. The granites are also magnesian and calc-alkaline but two of them are strongly peraluminous. Their isotope data (initial ε Nd: −13.2 to −18.8; initial 87Sr/86Sr: 0.7099 to 0.7123) imply derivation from more ancient sources, alternatively these samples gained their isotope systematics through extensive AFC processes from parental granodiorites. A common subduction zone environment as suggested from negative Nb-Ta anomalies in multi-element diagrams seems unlikely for all samples because of a lack of isotopically depleted signatures. The data from the Oamikaub diorite and other mafic complexes are better explained by a “flat” subduction model involving mainly continental mantle lithosphere and crust with limited, if any, melting of asthenospheric mantle.