Trace Element Compositions Research Articles

Geology and antimony mineralization of the Yangla polymetallic orefield in northwestern Yunnan, SW China: Trace element geochemistry of sulfides and calcite

The Yangla is the largest and highest-grade antimony deposit (10 kt Sb @ 14.87 %) in the Jinshajiang suture zone, northwestern Yunnan (SW China). Pyrite and stibnite are the main sulfides, and calcite is the main gangue mineral in the antimony ores. Antimony mineralization can be divided into three stages: pre-ore stage pyrite and quartz, syn-ore stage (incl. early, main and late sub-stage) stibnite-pyrite-calcite-quartz, and supergene stage valentinite and limonite. The trace element compositions of the three pyrite and two stibnite generations have been analyzed by (LA-)ICP-MS here. The bulk ore-related calcite trace element compositions were also measured by ICP-MS. Trace element correlations and principal component analysis (PCA) show that the majority of trace elements occur as solid solution and micro-/nano-inclusions in pyrite and stibnite. In pyrite, the Sb substitutes into the crystal lattice with Tl, Cu and Ag via (Tl++Cu++Ag+) + Sb3+ ↔ 2Fe2+. Gold occurs as invisible gold (Au+) and enters pyrite via the coupled substitution of As3+Au3+□ ↔ 3Fe2+ and/or As3+Au3+□ ↔ 3Cu2+. In stibnite, the Cu, Pb and As enter the crystal lattice via the coupled substitution of 2Sb3+ ↔ Cu+ + Pb2+ + As3+. Trace element features of calcite are highly similar to the Devonian Linong Formation (2nd member) marble, suggesting that the ore-forming fluid is closely associated with the marble. Syn-ore calcite is characterized by its higher Fe, Mn and MREE concentrations than the pre-/post-ore calcite, and can be regarded as a geochemical fingerprint for metallogenic prediction. The δCe (0.67–0.83, avg. 0.75) and δEu (1.40–2.51, avg. 1.89) values suggest that the antimony precipitation occurred under reducing to weakly oxidizing conditions. The atomic Yb/Ca, Yb/La, Tb/Ca, and Tb/La ratios of the syn-ore calcite imply that the antimony mineralization can be attributed to hydrothermal genesis. This deduction is also supported by that data of pyrite Ⅰ, Ⅱ, and Ⅲ mainly plotted inside the hydrothermal fields in the Co/Ni, As/Ag, Sb/Bi and Co-Ni-As discrimination plots. The Yangla stibnite ore samples mimic stibnite from typical hydrothermal mineralization systems (e.g., Woxi Au-Sb-W deposit, South China) in the Cu vs. Pb plot, which further supports a hydrothermal origin of the antimony. Therefore, we propose that the hydrothermal Sb mineralization is closely related to the Devonian carbonate rocks at Yangla.

Matrix Corrected SIMS In Situ Oxygen Isotope Analyses of Marine Shell Aragonite for High Resolution Seawater Temperature Reconstructions

AbstractMarine shells incorporate oxygen isotope signatures during growth, creating valuable records of seawater temperature and marine oxygen isotopic compositions. Secondary ion mass spectrometry (SIMS) measures these compositions in situ at finer length‐scales than traditional stable isotope analyses. However, determining oxygen isotope ratios in aragonite, the most common shell mineral, is hampered by a lack of ideal reference materials, limiting the accuracy of SIMS‐based seawater temperature reconstructions. Here, we tested the capability of SIMS to produce seawater temperature reconstructions despite the matrix calibration challenges associated with aragonite. We cultured Anadara trapezia bivalves at four controlled seawater temperatures (13–28°C) and used strontium labeling to mark the start of the temperature‐controlled shell increment, allowing for more spatially precise SIMS analysis. An improved matrix calibration was developed to ensure more accurate bio‐aragonite analyses that addressed matrix differences between the pure abiotic reference materials and the bio‐aragonite samples with intricate mineral‐organic architectures and distinct minor and trace element compositions. We regressed SIMS‐IRMS biases of abiotic and biogenic aragonites that account for their systematic differences in major, minor, and trace elements, allowing for more accurate SIMS analyses of the temperature‐controlled shell increment. The thorough matrix calibration allowed us to provide a SIMS‐based seawater‐corrected oxygen isotope thermometer of T(°C) = 23.05 ± 0.36 − 4.48 · (δ18Oaragonite [‰ VPDB] − δ18Oseawater [‰ VSMOW] ± 0.25) and 103lnαaragonite‐seawater = (17.78 ± 0.88) · 103/T (K) − (29.44 ± 2.40) that agrees with existing aragonitic IRMS‐based thermometer relationships and improves the applicability of SIMS‐based paleo‐environmental reconstructions of marine bio‐aragonites.

The mid-Cretaceous Hohonu Batholith (South Island, New Zealand): Identifying magmatic sources and processes during onset of crustal extension

The Hohonu Batholith is an aggregation of mostly mid-Cretaceous granitoid plutons on the West Coast of the South Island of New Zealand emplaced during a transitional period between subduction-related compression and continental lithospheric extension. This study reports an integrated dataset, comprising in-situ UPb, O and Hf isotope compositions and REE, Ti and other trace and major elements (ZrHf, ThU) for zircons extracted from four representative plutons within the batholith. Our results provide detailed insight into the protracted thermal, chronological and geochemical histories. LA-ICPMS UPb zircon ages indicate a primary episode of magma genesis and emplacement from 107 to 113 Ma, confirming published SIMS dating. However, a younger previously unrecognized age population of ~91–96 Ma is identified, primarily (although not exclusively) in zircon rims. This younger age event coincides with the timing of protracted lithospheric extension and crustal thinning of the Zealandia continent. The cryptic younger zircon ages suggest that Hohonu granitoids experienced a partial thermal overprint (accompanied by Pb loss) mostly recorded in rims. Differences in bulk rock geochemistry between plutons are inferred to reflect variable conditions of partial melting controlled by source mineralogy and H2O content. Isotope and trace element compositions, along with Ti-thermometry, measured on the same micro-volume of CL-imaged zircons, are used to test if source characteristics were imparted from melt to minerals in zircon-saturated silicic systems. Similarities are revealed in the zircon record of the selected plutonic rocks, confirming their broadly consanguineous relationship and the fundamental role of open-system behaviour, involving hybridization or assimilation between mantle-derived (or juvenile mafic) and a crustal-derived components, as previously inferred from whole rock NdSr isotope systematics. However, intra-sample decoupling of zircon OHf isotope systematics may also be linked to residual source component unmixing. This possibility, in addition to mafic recharge, may have obscured melt source compositional characteristics, and hence zircon REE appear as unsuitable fingerprints of source(s) and conditions of partial melting in this granitoid system. Simple compositional and thermal magma evolution trends appear punctuated by episodes of mafic recharge, presumably during lithospheric thinning.

Mesozoic lithospheric mantle evolution in South China: Evidence from Ar-Ar dating, geochemistry and Sr-Nd-Pb isotopes of lamprophyres

Understanding the Mesozoic lithospheric mantle beneath South China is challenging, primarily because mantle-derived magmatic rocks are rare, whereas granitic magmatism is far more abundant. In this study, we present new 40Ar/39Ar geochronology, major and trace elemental composition, and Sr-Nd-Pb isotopic data for lamprophyres from northern and central Guangxi Province, South China. Our results reveal two intrusion phases: an earlier phase at 207.7 ± 1.2 Ma, and a later phase between 95.6 ± 0.6 Ma and 102.3 ± 0.7 Ma. The earlier phase, represented by the Danyang lamprophyres, is marked by low Cr (330–355 ppm) and Ni (241–258 ppm) contents and strongly fractionated REE patterns with (La/Yb)n ratios of 57.5 to 62.8. The later phase, represented by the Leidong, Nongchang, and Longchang lamprophyres, shows higher Cr (490–781 ppm) and Ni (237–377 ppm) contents, with less fractionated REE patterns and (La/Yb)n ratios of 20.2 to 27.8. Despite their temporal differences, the lamprophyres share similar isotopic characteristics, including high initial 87Sr/86Sr (0.707940–0.721310), negative εNd(t) (−9.19 to −5.31), and radiogenic Pb isotopic compositions (206Pb/204Pb: 18.200–18.331, 207Pb/204Pb: 15.62–15.72, 208Pb/204Pb: 38.53–38.84). These features suggest derivation from low-degree partial melting of a phlogopite-bearing, refractory peridotite lithospheric mantle, modified by olivine and clinopyroxene fractionation. This refractory mantle was metasomatically enriched by Proterozoic subduction processes beneath the Yangtze Craton. By synthesizing published Sr-Nd-Pb isotopic data, we propose that the lithospheric mantle beneath South China shifted from enriched to depleted mantle between ~220 Ma and ~ 100 Ma, possibly due to extension associated with the subduction and rollback of the Paleo-Pacific Plate.

In-situ trace element and sulfur isotope compositions of Multi-Stage sulfides in the Buzhu orogenic gold (Antimony) Deposit, southern Tibet: Implications for the metallogenic process

The Buzhu gold (antimony) deposit, located within the gold-antimony polymetallic belt of southern Tibet in the Tethys Himalayan belt, is a recently discovered medium-sized gold polymetallic deposit. The orebody consists primarily of gold-bearing quartz sulfide veins. Currently, the metallogenic mechanism of the deposit remains largely unexplored. Utilizing results from the mineralogical observation of principal ore minerals, LA-ICP-MS trace element analysis, and in-situ sulfur isotope analysis of pyrite, investigations reconstruct the evolution process of pyrite-arsenopyrite and constrain the metallogenic process of the Buzhu gold (antimony) deposit. It has been discovered that the gold-bearing sulfides in the Buzhu gold (antimony) deposit are primarily pyrite and arsenopyrite. Pyrite can be categorized into six generations: framboidal pyrite Py0, dissolution cavity pyrite Py1a (some exhibiting oscillatory zoning), disseminated pyrite Py1b, euhedral pyrite Py2a, irregular pyrite Py2b, and Py3. Arsenopyrite, on the other hand, can be classified into three generations: early arsenopyrite Apy0, disseminated arsenopyrite Apy1, and euhedral Apy2. The analysis of δ34S in pyrite throughout the ore-forming process indicates sulfur derives from multiple sources, with Py0 indicative of a biological sulfur source. The evolutionary process of pyrite, supported by trace element analysis, suggests that the remaining pyrite derives from sedimentary fluid transformation, with sulfur primarily sourced from metamorphic sediments. Elemental spectrum analysis and BSE observations indicate that the Buzhu gold (antimony) deposit primarily undergoes two distinct stages of mineralization: the initial stage is the gold-antimony mineralization phase, during which antimony precipitates in the fissures of Py1a as stibnite, while gold is primarily found in Py1-Apy1 as invisible gold, with the highest gold content in Apy1 (28.20–60.13 ppm, average 40.51 ppm). The subsequent stage of mineralization is characterized by gold mineralization, with gold primarily residing in the internal fissures of Apy2 as micron silver gold ore. The evolution characteristics of gold-bearing sulphide and the solubility curve of Au indicate that gold mainly derives from gold-bearing unsaturated fluid, rather than from early framboidal pyrite Py0 (0.52–1.06 ppm, average 0.79 ppm). Only a minor fraction of gold (originating from early sediments) in Py0 was liberated and integrated into subsequent pyrites. The content of antimony in Py0 significantly reduces after dissolution, suggesting that antimony predominantly originates from Py0 (206–440 ppm, average 335 ppm). Throughout the genesis of the Buzhu gold (antimony) deposit, the gold constituent underwent a sequence of pre-enrichment, re-enrichment, liberation, and precipitation. The processes of coupled dissolution-reprecipitation (CDR) and boiling fostered the reactivation and reenrichment of gold. The recrystallization into cubic pyrite led to the expulsion of gold from the pyrite lattice, and fluid oxidation resulting from multistage fluid boiling, coupled with a decrease in sulfur fugacity, led to gold precipitation.

Trace element and isotope composition of calcite, apatite, and zircon associated with magmatic sulfide globules

AbstractThe formation of volatile-rich phases in magmatic sulfide systems has been interpreted at least in six different ways. The most popular model attributes their origin to secondary processes, mostly due to the presence of serpentine, chlorite, phlogopite, amphibole, and calcite. While chlorite and serpentine are likely to form as alteration products, the other volatile-rich minerals have the potential to originate in a range of ways, including by primary magmatic processes. Based on mineralogical and petrological studies, it was recently suggested that volatile- and incompatible element-rich halos around sulfide globules may form due to the interaction between three immiscible liquids: silicate, carbonate, and sulfide. This hypothesis was confirmed by experimental data revealing the systematic envelopment of sulfide globules by carbonate melt, indicating their mutual affinity. In this study, we present data on isotopic signatures and trace element distributions of three minerals commonly found in spatial association with sulfides—calcite, apatite, and zircon—to address the question of the source and nature of volatiles and other incompatible elements involved in the formation of the halos. Here we compare our new hypothesis with all the previously proposed explanations to show if they can be consistent with obtained results. Our findings indicate that both mantle and crustal sources play a role in the formation of volatile- and incompatible element-rich halos, strongly correlating with sulfur isotope data previously reported for the sulfide globules in the same intrusions. This correlation confirms the shared origin of sulfides, carbonate and fluids during ore-forming processes, ruling out the secondary origin of volatile-rich phases. The isotope and trace element signatures support the newly proposed hypothesis that volatile- and incompatible element-rich halos could have been formed due to the interaction of immiscible sulfide, carbonate, and silicate melts. The volatile-rich carbonate melt could be sourced from the mantle or it could be added from the crust. Regardless of the origin, carbonate melt and sulfide liquid both immiscible with mafic magma tend to stick to each other resulting in the formation of volatile- and incompatible element-rich halos commonly documented in magmatic sulfide deposits.

LATE MESOZOIC RARE-METAL GRANITES, PEGMATITES, AND GREISENS OF MONGOLIA: AGE, MINERALOGY, GEOCHEMISTRY, ORE POTENTIAL, AND PETROGENESIS

Comparative analysis of the earlier obtained and new geological data, age, mineral, petrological, and geochemical compositions of plutons of calc-alkalic granitoids and rare-metal Li–F granites shows their evolution in a wide time interval during the formation of Mesozoic areas of granitoid magmatism. Mineralogical and geochemical analysis of the evolution of plutons of palingenetic calc-alkalic granitoids (Baga Hentiyn (MZ1) and Ikh Narotiin = Hiid (MZ2)) and intrusions of rare-metal Li–F granites of Central and Eastern Mongolia revealed their petrological and geochemical differences. The closure of the Mongol–Okhotsk Basin with the formation of large plutons of calc-alkaliс granitoids, obviously related to collisional processes, did not cause significant enrichment of the late granite phases with lithophile and ore elements. Within the peripheral zones of еру MZ1 and MZ2 magmatic areas, mineralization is often associated with Mongolian multiphase plutons and small intrusions of rare-metal Li–F granites. The rare-metal granites are characterized by a decrease in indicative K/Rb, Nb/Ta, and Zr/Hf values and a regular increase in F, Li, Rb, Cs, Sn, W, Be, Ta, and Nb contents during the evolution of Li–F magmas. Igneous and, particularly, metasomatic rocks in most intrusions of ore-bearing rare-metal Li–F granites are characterized by significant variations in Sn and W contents. At the magmatic stage, the pegmatoid varieties of amazonite–albite granites and pegmatites of the zonal Baga Gazriin (MZ1) and Barun Tsogto (MZ2) plutons are significantly enriched in both Sn and W. Maximum Sn and W enrichment has been established in greisenized granites and zoned greisen bodies (zwitters), which is due to the percolation of ore-bearing solutions into the upper horizons and the mineralization of ore elements in the late phases of intrusions and in metasomatites. The wide variations in the age (321–126 Ma) and trace element and isotope compositions of Mongolian rare-metal Li–F granites within various zones of large magmatic areas suggest the influence of mantle plume sources on the composition of rare-metal granitic magmas and on their ore potential in intermediate chambers in the continental crust.

Accretion and Core Formation of Earth-like Planets: Insights from Metal–Silicate Partitioning of Siderophile and Volatile Elements

The origin of volatile elements, the timing of their accretion and their distribution during Earth’s differentiation are fundamental aspects of Earth’s early evolution. Here, we present the result of a newly developed accretion and core formation model, which features the results of high P–T metal–silicate partitioning experiments. The model includes well-studied reference elements (Fe, Ni, Ca, Al, Mg, Si) as well as trace elements (V, Ga, Ag, Au, S) covering a wide range from refractory to volatile behavior. The accretion model simulates the different steps of planet formation, such as the effects of continuous, heterogenous core formation at high P–T, the effect of the Moon-forming giant impact and the addition of matter after the core formation was completed, the so-called “late veneer”. To explore the “core formation signature” of the volatile depletion patterns and the quantitative influence of a late veneer, we modeled planets that would have formed from known materials, such as CI, CM, CV, CO, EH and EL meteorites, and from a hypothetical volatile depleted material, CI*. Some of the resulting planets are Earth-like in key properties, such as overall core size, major element composition, oxygen fugacity and trace element composition. The model predicts the chemical signatures of the main planetary reservoirs, the metallic core and bulk silicate planet (BSP) of the modeled planets, which we compare with the chemical signature of Earth derived previously from core formation models and mass balance-based approaches. We show that planets accreted from volatile depleted carbonaceous chondrites (CM, CV, CO and CI*) are closest in terms of major element (Si, Mg, Fe, Ca, Al, Ni) and also siderophile volatile element (Ge, Ga, Au) concentrations to the components from which Earth accreted. Chalcophile volatile elements (S, Ag), instead, require an additional process to lower their concentrations in the BSP to Earth-like concentrations, perhaps the late segregation of a sulfide melt.

Role of metasomatism in formation of the Yichun rare-metal deposit, China

What role post-magmatic processes have played in the development and mineralization of rare-metal peraluminous granites and how important that role can be, are questions that researchers have been wrestling with for decades. The Yichun Li-Ta-Nb deposit is an example that has been the subject of such a debate. The granitic appearance of rocks, the inert nature of tantalum, and the scarcity of mineralization in country rocks have been taken to suggest that fluid overprints were limited to within the granites and were unimportant in rock- and ore-forming processes. In this study, the identification of two types of abundant Li- and Cs-rich pseudomorphs in both the topaz-lepidolite granite and overlying pegmatite, the only two mineralized units at Yichun, suggests that extensive metasomatism was involved in rock and ore formation. The textural and chemical similarities of lepidolite in comparable mineral assemblages from a variety of occurrences, including lepidolite in pseudomorphs, veins, and miarolitic cavities from both the topaz-lepidolite granite and pegmatite, suggest that all lepidolite at Yichun is metasomatic and largely inherited its chemical signatures from a magmatic-hydrothermal transitional fluid, rich in Li, Cs, and Ta, derived possibly from the Li-muscovite granite that lies beneath the topaz-lepidolite granite. We propose that this transitional liquid, composition of which lies between a silicate melt and aqueous fluid, was not in equilibrium with the original igneous mineralogy, thus bringing about significant metasomatism along its infiltration and evolution upwards. Variations in the trace-element composition of lepidolite likely reflect the influence on mineral compositions by precursor minerals. The ambiguous boundary between the topaz-lepidolite and Li-muscovite granites, combined with the intensely metasomatized nature of the former, is most consistent with the topaz-lepidolite granite being the extensively altered upper portion of the Li-muscovite granite, which is itself somewhat metasomatized. Although magmatic fractionation played a key role in the initial concentration of Nb, Li, and Ta in both granite and pegmatite formation, the Li-Ta-Nb-Cs mineralization and its host rocks were largely formed through magmatic-hydrothermal rejuvenation and re-enrichment.

Unravelling different mechanisms of metasomatism and geodynamic evolution of pyroxenite-veined subcontinental lithospheric mantle beneath the Central European Variscides

Abstract Pyroxenite-veined garnet peridotites from the Gföhl Unit of the Moldanubian Zone in the Bohemian Massif provide direct constraints on diverse mechanisms of mantle metasomatism and refertilization driven by a single pulse of melt beneath the Central European Variscides. Here, we provide a detailed study on an intriguing example of this rock association where the garnet peridotites show a fertile character (high Al2O3, CaO, TiO2), corresponding to the subcontinental lithospheric mantle (SCLM). By contrast, their conspicuous LREE depletion and Sr–Nd isotopic signatures (87Sr/86Sr338 ≤ 0.7028; εNd338 ~7.3) are typical of depleted mantle residue after melt extraction. Such signatures reflect transformation of an original refractory protolith (likely harzburgite) to fertile lherzolite through percolation of primitive tholeiitic melts, parental to garnet pyroxenite in veins. The SCLM refertilization is further documented by the whole-rock positive correlation between incompatible elements (Zr, Yb, Sc, V), and trace element composition of clinopyroxene (high Ti/Eu and Ti/Nb) and garnet (elevated ∑REE, Zr, Ti). Trace element and Sr–Nd isotopic systematics of pyroxenites (87Sr/86Sr338 ~0.7025–0.7029; εNd338 ≤ 7.9) correspond to a source of melt similar to the depleted MORB mantle (DMM). Three mechanisms of metasomatism related to the interaction of this melt with the host peridotites were distinguished: (i) stealth metasomatism, reflected by extensive clinopyroxene and garnet crystallization in lherzolite adjacent to pyroxenite veins, (ii) cryptic metasomatism, recorded by lower Mg# values of orthopyroxene and olivine in lherzolite, and (iii) modal metasomatism, resulting in crystallization of amphibole and phlogopite in lherzolite close to the veins. The percolating basaltic melt was hydrous, moderately enriched in fluid-mobile elements (Cs, Rb, Ba, Pb, U, Li). Immiscible liquids, dense Ti-Mg-Fe-rich oxide melt and C-O-H fluid, trapped and crystallized as mono/multiphase solid inclusions in garnet, likely separated from a basaltic melt upon cooling. The lherzolite-pyroxenite interface reveals strong micro-scale element fractionation due to differentiation of a basaltic melt within the percolation channel. Volatile-bearing liquids that segregated from the melts migrating through wall-rock peridotites most likely caused chromatographic enrichment in highly incompatible elements (e.g. LREE) in distal peridotites relative to the LREE-depleted lherzolites adjacent to the veins. The DMM-like affinity of pyroxenites and pressure-temperature estimates for lherzolite (3.9–5.4 GPa/1010–1200 °C) and pyroxenites (2.8–4.2 GPa/860–1020 °C) point towards exhumation-driven SCLM refertilization. This was linked to decompression-induced partial melting of upwelling asthenosphere producing basaltic melts penetrating through and metasomatizing the SCLM beneath the Variscan orogenic belt in Central Europe.

SOURCES OF MAGMAS OF PERMIAN GABBROS OF THE KHANGAI MOUNTAINS (Western Mongolia)

We present Sm–Nd and Rb–Sr isotope composition data on mafic–ultramafic massifs in the Khangai Mountains of Western Mongolia: Oortsog-Uul, Nomgon, and Yamaat-Uul. The U–Pb age of zircon and its Lu–Hf isotope and trace-element compositions were determined by LA–ICP–MS. New and previous geochronological data obtained by SIMS and LA–ICP–MS support the Permian age of the studied gabbros. The trace-element composition of zircon, characterized by strong HREE enrichment ((Lu/Gd)n > 7) and cerium positive (Ce/Ce* > 6.6) and europium negative (Eu/Eu* = 0.16–0.49) anomalies, indicates its magmatic genesis and the possibility of using isotope characteristics to assess the origin of mafic magmas. The formation of zircon from a residual mafic melt is inferred from the enrichment of zircon in U and Th with increasing Th/U, reflecting the accumulation of these highly incompatible elements in the residual melt, and from the crystallization temperature of zircon (810–880 °С). The geochemical characteristics of the rocks, their isotopic composition, the absence of xenogenic ancient zircons, and the lack of correlation between εNd(T) and major indices of crustal contamination indicate that crustal contamination did not influence the composition of the gabbros. Isotopic data on rocks and zircon indicate the involvement of two mantle sources in the formation of the mafic–ultramafic massifs of the Khangai Mountains: (a) depleted, predominant for the Nomgon and Yamaat-Uul massifs (εHf = 16.1–2.0; εNd = 4.5–0.0; and ISr = 0.70385–0.70537), and (b) enriched, predominant for the second phase of the Oortsog-Uul massif (εHf = 1.4–0.2; εNd = –3.6… –5.7; and ISr = 0.70704–0.70933).

Constraints of in-situ elemental compositions and U–Pb ages of cassiterite on the origin of the Cretaceous Gejiu and Dulong tin deposits, SW China: Implications for the linkage of tin belts in SE Asia

The western Yunnan tin belts in SW China and the southern Myanmar tin belt in SE Asia are traditionally thought to be part of the SE Asian tin metallogenic province. However, the tectonic setting of the Youjiang tin belt in SW China and its genetic relationship to the other tin belts are poorly documented. In this belt, the giant Gejiu and Dulong tin deposits are typical of skarn-type deposits and both contain contact and distal skarn orebodies. Tin ores of distal orebodies in these two deposits are composed of cassiterite, sulfide and calcite. In both deposits, most cassiterite grains from these ores are rich in Fe and W and depleted in Nb and Ta. They have 238U/206Pb ages between 81.4 and 84.1 Ma, similar to hosting granitic plutons. Two generations of cassiterite with distinctly different microtextures and trace elemental compositions can be recognized. The first generation (Cst-I) is compositionally and texturally homogeneous, but the second generation (Cst-II) displays distinctly oscillatory zoning. Cst-II contains Nb, W, and U lower, and Fe, Ta, Zr and chalcophile elements (Ga, Ge, In, and Sb) higher than Cst-I. These textural and compositional variations reflect the potential involvement of meteoric water in the magmatic-hydrothermal system. In this system, ore-forming fluids were evolved to more alkaline and oxidized to facilitate the precipitation of cassiterite. Our study indicates that these two deposits in the Youjiang tin belt have mineralization styles similar to those in the adjacent western Yunnan and southern Myanmar tin belts and all these tin belts belong to the SE Asian metallogenic provinces. A westward-younging trend of tin mineralization in these three belts can be explained by the rollback of the subducted Neo-Tethyan oceanic slab. This setting is different from the one related to the subduction of the Paleo-Pacific plate.

Bones or Stones: How Can We Apply Geophysical Techniques in Bone Research?

Some studies have used physical techniques for the assessment of bone structure and composition. However, very few studies applied multiple techniques, such as those described below, at the same time. The aim of our study was to determine the chemical and mineralogical/organic composition of bovine tibial bone samples using geophysical/geochemical reference techniques. X-ray diffraction (XRD), thermogravimetry (TG), Fourier-transform infrared spectrometry with attenuated total reflectance accessory (FTIR-ATR), inductively coupled mass spectrometry (ICP-MS) and inductively coupled optical emission spectrometry (ICP-OES) were applied to measure the organic and inorganic composition of 14 bovine bone samples. In addition, peripheral quantitative CT (QCT) was used to assess BMD in these bones. We were able to define the total composition of the studied bone samples. ICP-OES and ICP-MS techniques were used to determine the major and trace element composition. The X-ray analysis could detect inorganic crystalline compounds of bones, such as bioapatite, and its degree of ordering, indicating whether the bones belong to a younger or older individual. The total volatile content of the samples was calculated using TG and resulted in about 35 weight% (wt%). This, together with the 65 wt% total resulting from the chemical analysis (i.e., inorganic components), yielded a total approaching 100 wt%. As a large portion of the volatile content (H2O, CO2, etc.) was liberated from the organic components and, subordinately, from bioapatite, it could be concluded that the volatile-to-solid ratio of the examined bone samples was ~35:65. The FTIR-ATR analysis revealed that the organic portion consists of collagens containing amide groups, as their typical bands (OH, CH, CO, NC) were clearly identified in the infrared spectra. Numerous parameters of bone composition correlated with BMD as determined by QCT. In conclusion, we performed a complex evaluation of bovine bones to test multiple geophysical/geochemical techniques in bone research in association with QCT bone densitometry. From a medical point of view, the composition of the studied bones could be reliably examined by these methods.

Composition and age constraints on a Hadean enriched mantle source revealed by the Paleoarchean São Tomé layered intrusion, NE Brazil

Evidence for Hadean depleted mantle reservoir(s) is well-established by mantle-derived rocks from multiple Archean complexes showing excesses in 142Nd compared to the modern mantle. Yet, the existence of an early enriched mantle source, which should have concomitantly formed during these Hadean silicate differentiation event(s), has only been recently confirmed by well-resolved 142Nd deficits measured in Paleoarchean mafic amphibolites from the São José do Campestre massif of the Borborema Province, NE Brazil. To investigate the nature and extent of this early-formed enriched reservoir, a series of samples from the Seridó belt, NE Brazil, have been investigated for their geochemical and coupled 147,146Sm-143,142Nd isotopic compositions, focusing on the Paleoarchean São Tomé layered intrusion. The São Tomé intrusion is composed of layers of metamorphosed mafic and ultramafic rocks with whole-rock trace element compositions and high olivine crystal Ni contents consistent with an incompatible trace element enriched pyroxenitic mantle source. Most analyzed samples from the Seridó belt yielded negative µ142Nd, as low as ∼ -20 (representing the lowest 142Nd/144Nd ratio ever measured in terrestrial rocks), with an average µ142Nd for the São Tomé intrusion of -9.6 ± 1.4. The São Tomé samples interpreted as the least isotopically disturbed yielded an 147Sm-143Nd isochron age of 3551 ± 368 Ma, consistent with previous zircon U-Pb ages, with an initial ε143Nd = -1.7 ± 1.2. Coupling the long-lived 147Sm-143Nd and the short-lived 146Sm-142Nd systems for the São Tomé rocks suggests a Hadean enriched mantle source formed at ∼4.44 Ga with a 147Sm/144Nd of ∼0.18, which may be complementary to the early depleted mantle recorded by Eoarchean rocks from the North Atlantic Craton, possibly formed during magma ocean crystallization. These results also imply that the record of this Hadean enriched mantle source is not restricted to the São José do Campestre massif but extends to a larger portion of the Borborema Province.

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.

Trace elements in thermal waters of the northern Tien Shan: distribution and fate

The article presents new data on the abundance and ways of soluted trace elements (Si, Fe, F, Al, Sr, Br, B, Mn, Ba, Ti, Li, Rb, Mo, As, U, Th, W, Sc, Y, REE, Hf) in thermomineral, surface and groundwaters of the northern Tien-Shan (Issyk-Kul intermountain depression). It is established that trace element composition of thermomineral waters is able to be a marker of hydrogeological settings of water formation and flow: waters of sedimentary rocks of the intermountain artesian basin are enriched with Sr, Ba, Mn, B, Mo and U, while waters of rock massifs contain increased concentrations of F, Rb, W and Sc. Thermodynamic calculations performed for certain trace elements using Visual-MINTEQ 3.1 and GWB 14 programmes allowed us to identify the water migration patterns of the surveyed water points. Calculation of water migration coefficient showed the dependence of microcomponent accumulation rate on the type of water-bearing strata and hydrogeological conditions of water formation.

Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes

Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ18O, δ44/40Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ18O values of olivine (δ18Ool = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ18O values (δ18Ocpx = +5.31 ± 0.10‰; δ18Ogrt = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ44/40Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ44/40Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ18O and high δ44/40Ca values. In general, Δ18Ocpx-ol and Δ18Ogrt-ol (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ18Ogrt and Δ18Ogrt-ol and garnet major and trace element composition (Na2O, H2O, La/YbN). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ18O, δD, and high δ44/40Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.

INDIVIDUAL FORAMINIFERAL ANALYSES: A REVIEW OF CURRENT AND EMERGING GEOCHEMICAL TECHNIQUES

Abstract The trace element (TE) and isotopic composition of calcareous foraminifera has been invaluable in advancing our understanding of environmental change throughout the geological record. Whereas “bulk” geochemical techniques, typically requiring the dissolution of tens to hundreds of foraminiferal tests for a single analysis, have been used for decades to reconstruct past ocean-climate conditions, recent technological advances have increased our ability to investigate foraminiferal geochemistry from an individual test to a micron-scale domain level. Here we review current and emerging techniques and approaches to studying the trace element and stable isotope geochemistry of individual foraminifera (i.e., individual foraminiferal analyses or “IFA”), covering spatial scales including whole-test analysis, intratest spot analysis, and cross-sectional chemical mapping techniques. Our discussion of each technique provides an overview of how the specific analytical tool works, the history of its usage in foraminiferal studies, its applications, considerations, and limitations, and potential directions for future study. Lastly, we describe potential applications of combining multiple IFA techniques to resolve key questions related to paleoceanography, (paleo)ecology, and biomineralization, and provide recommendations for the storage, dissemination, and transparency of the vast amounts of data produced through these methods. This review serves as a resource for budding and experienced foraminiferal geochemists to explore the wide array of cutting-edge approaches being used to study the geochemical composition of modern and fossil foraminifera.

Sulfide trace element enrichments in the metamorphic basement-hosted Xinhua Pb-Zn-Cu vein-type deposit, eastern Guizhou province (SW China)

Cambrian carbonate formations are widespread in the western Hunan-eastern Guizhou (WHEG) region (southwestern China), which hosts many Mississippi Valley-Type (MVT) lead–zinc (Pb-Zn) deposits. Regional Pb-Zn mineralization is well developed in the low-grade metamorphic rocks of the basal Proterozoic Banxi Group. The mineralization is associated with quartz veins and generally distributed along NE-trending fault zones. Moreover, these deposits have an extensive distribution and high grade, and are associated with Cu-Ag endowment. However, geological and geochemical research on these Pb-Zn vein-type deposits is relatively limited, and their relationship with the regional MVT mineralization remains unclear. The representative Xinhua deposit in Danzhai district is selected as the study subject. We conducted in situ trace element analyses on the sphalerite and chalcopyrite from the various metallogenic stages, and compared them with published sphalerite trace element data from the MVT Pb-Zn deposits in the western Hunan-eastern Guizhou metallogenic belt. Seven orebodies in Xinhua Pb-Zn deposit have been discovered so far, with a metal resource of over 120,000 metric tonnes of Zn + Pb. Field geology and microscopic petrography have revealed two mineralization stages: An early-stage black sphalerite (Sp-I) followed by reddish-brown sphalerite (Sp-II) mineralization, which corresponds to the main chalcopyrite mineralization stage, and a later-stage light-yellow sphalerite (Sp-III), Cu ore-barren mineralization.LA-ICPMS data indicate that the sphalerite from Xinhua has similar trace element compositions to those from the MVT Pb-Zn deposits in the region. They are relatively enriched in Ga, Cd, and Ge, while depleted in Fe, Co, and Mn. Critical metal Ge and Ga are particularly enriched in sphalerite, especially in Sp-I (Ge max 937 ppm, Ga max 824 ppm). The substitution mechanism of Ge and Ga in sphalerite are likely 2Cu+ + Ge4+ ↔ 3Zn2+ and Cu+ + Ga3+ ↔ 2Zn2+. Indium and Sn are mainly present in Sp-I and Sp-III. Chalcopyrite contains Zn and Sn both exceeding 100 ppm. Contents of Se, Ag, In, and Sn in chalcopyrite are significantly higher than those in sphalerite. Calculation of the sphalerite trace element geothermometer (GGIMFis) suggests that the average sphalerite ore-forming temperatures are 164 °C (Sp-I), 156 °C (Sp-II), and 205 °C (Sp-III), implying medium- to low-temperature mineralization. This indicates a possible influx of high-temperature, in-bearing fluid during the late-stage mineralization.In summary, the faults-controlled vein-type Pb-Zn deposits (e.g., Xinhua) may have been products of the same Kwangsian orogeny as other strata bound MVT deposits, and the Xinhua deposit features two mineralization stages with multiple ore metal sources. During the ore-forming fluid ascent, some ore-forming materials may have precipitated in the fluid conduits. And exposed after the erosion of the shallower stratiform orebodies and strata. Consequently, the Xinhua Pb-Zn deposit represents the preserved ore-fluid conduit phase (in the basement strata) of the MVT mineralization.

Assessing the Precision and Accuracy of Foraminifera Elemental Analysis at Low Ratios

AbstractThe minor and trace element compositions of biogenic carbonates such as foraminifera are important tools in paleoceanography research. However, most studies have focused primarily on samples with element to calcium (El/Ca) ratios higher than the El/Ca range often found in benthic foraminifera. Here, we systematically assess the precision and accuracy of foraminifera elemental analysis across a wide range of El/Ca especially at relatively low ratios, using a method on a Thermo Scientific iCAP Qc quadrupole Inductively Coupled Plasma Mass Spectrometer (ICP‐MS). We focus on two benthic foraminifera species, Hoeglundina elegans and Cibicidoides pachyderma, and prepared a suite of solution standards based on their typical El/Ca ranges to correct for signal drift and matrix effects during ICP‐MS analysis and to determine analytical precision. We observe comparable precisions with published studies at high El/Ca, and higher relative standard deviations for each element at lower El/Ca, as expected from counting statistics. The overall long‐term analytical precision (2σ) of the H. elegans‐like consistency standard solutions was 6.5%, 4.6%, 5.0%, for Li/Ca, Mg/Ca, Mg/Li, and 6.4%, 10.0%, 4.2% for B/Ca, Cd/Ca, Sr/Ca. The precision for H. elegans‐like Mg/Li is equivalent to a temperature uncertainty of 0.5–1.1°C. Measurement precisions were also assessed based on three international standards (one solution and two powder standards) and replicate measurements of H. elegans and C. pachyderma samples. We provide file templates and program scripts that can be used to design calibration and consistency standards, prepare run sequences, and convert the raw ICP‐MS data into molar ratios.