Chemical Geology最新文献

{"title":"Synthesis and characterization of glycolates and implications for the genesis of glycolate minerals","authors":"Mingyang Hu ,&nbsp;Jiawen Hu ,&nbsp;Bin Lian","doi":"10.1016/j.chemgeo.2026.123244","DOIUrl":"10.1016/j.chemgeo.2026.123244","url":null,"abstract":"<div><div>Glycolate minerals are a newly discovered family of organic minerals and have currently become the second largest family of organic minerals. Due to their short discovery history, no reports on the genesis mechanism of this type of organic mineral have been published. In this study, we synthesized the seven glycolate minerals that have been reported so far. Their physical and chemical properties were investigated, including synthesis conditions, thermal stability, and solubility. The δ¹³C and δ¹⁴C of the glycolate mineral lazaraskeite-<em>M</em>_<em>1</em>, the high-temperature phase of the first and most commonly occurring glycolate mineral lazaraskeite, was also tested. The results show that there are significant differences in the synthesis temperatures and thermal stabilities among the seven glycolates. Specifically, lazaraskeite-<em>M</em>_<em>2</em> can synthesized at −50 °C and transforms into lazaraskeite-<em>M</em>_<em>1</em> when the temperature exceeds 0 °C, while the synthesis temperature for glecklerite exceeds 30 °C, and jimkrieghite only forms when the temperature is above 55 °C. All synthesized glycolates exhibit high solubility, range from 5.4 mg/mL to 2350 mg/mL. Lazaraskeite-<em>M</em>_<em>1</em> has δ¹³C of −35.318 ‰ and δ¹⁴C of −986.1 ‰. Based on these findings, it is believed that glycolate group in lazaraskeite-<em>M</em>_<em>1</em> originated from C3 plants during the late Eocene, between BCE 37,775 and 37,252. The formation of glycolate minerals may involve the following stages: biosynthesis of glycolic acid – fluid dissolution of glycolic acid and cations – mineralization – phase transition and dehydration/dissolution and re-mineralization/bioweathering. This study provides important information for understanding the genesis mechanism and preservation conditions of glycolate minerals.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123244"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Salinity and geochemical proxy responses to volcanism in small rift lakes: Insights from the Lower Cretaceous Erlian Basin","authors":"Wei Si ,&nbsp;Dujie Hou ,&nbsp;Xiong Cheng ,&nbsp;Zhe Zhao ,&nbsp;Ronghua Zheng ,&nbsp;Xiuli Wei ,&nbsp;Piao Wu","doi":"10.1016/j.chemgeo.2026.123242","DOIUrl":"10.1016/j.chemgeo.2026.123242","url":null,"abstract":"<div><div>The Early Cretaceous Erlian Basin, characterized by small-scale lacustrine sedimentary systems and <em>syn</em>-depositional volcanism, provides an exceptional setting to evaluate how volcanic forcing modulates lacustrine salinity. Through integrated organic/inorganic geochemical analyses (biomarkers, reduced sulfur/total organic carbon ratios [S/C], major and trace elements, carbonate isotopes) of volcanic ash-rich strata, this study demonstrates that volcanic forcing regulates lacustrine salinity through mineral dissolution, climatic feedbacks, chemical weathering, and hydrological alteration. Moderate volcanism elevates salinity (from brackish to saline) through ionic influx and evaporative concentration. However, large-scale eruptions (&gt;40 m tuff) reduce salinity via sulfate aerosol-driven cooling, increased rainfall, and tectonic subsidence-induced lake expansion. Conventional salinity proxies (carbonate isotope, elements, and biomarkers) exhibit reduced reliability under volcanic influence and diagenetic alteration. Elemental indicators (B/Ga, Sr/Ba) exhibit diagnostic correlations: positive (pristine deposition), negative (volcanic ash input), and non-significant (diagenetic overprinting). Boron concentrations correlate directly with volcaniclastic flux rather than ambient water salinity. Notably, biomarker parameters exhibit non-linear evolutionary trends under intense volcaniclastic input, requiring multi-proxy validation for reliable paleo-salinity reconstruction. This study establishes a volcanic-lacustrine salinity dynamics model, highlighting the interplay between eruption magnitude, climatic responses, and basin hydrology. The findings enhance paleoclimate reconstruction in volcanic terrains and provide insights into organic matter accumulation in volcanically active lacustrine basins.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123242"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145893632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering chemical complexity in monogenetic eruptions: Xitle Volcano, Mexico","authors":"J. Ahmadi ,&nbsp;E. Widom ,&nbsp;M.-N. Guilbaud ,&nbsp;C. Siebe ,&nbsp;D.C. Kuentz ,&nbsp;R. Sanchez ,&nbsp;M. Medina-Jaen ,&nbsp;J.J. Zamorano-Orozco ,&nbsp;S.M. Straub","doi":"10.1016/j.chemgeo.2025.123204","DOIUrl":"10.1016/j.chemgeo.2025.123204","url":null,"abstract":"<div><div>Xitle Volcano, an ∼1700-year-old scoria cone located at the southern edge of Mexico City and within the central Trans-Mexican Volcanic Belt (TMVB), provides a unique opportunity to investigate the causes of geochemical diversity in monogenetic eruptions. We present the first integrated major-trace element and Sr–Nd–Pb–Os isotopic dataset which, coupled with new stratigraphic mapping and petrologic observations of Xitle's eruptive products, provides constraints on the roles of mantle heterogeneity, subduction-related metasomatism, and crustal assimilation in Xitle magma genesis. The lavas and tephras range in composition from basalt to basaltic andesite and basaltic andesite/basaltic trachyandesite. All samples have arc-like trace element patterns with enrichments in large ion lithophile elements and depletions in high field strength elements, with early-stage magmas exhibiting stronger arc-like signatures, while later magmas trend toward intraplate affinities. Isotopic compositions span ⁸⁷Sr/⁸⁶Sr = 0.70335–0.70398, ¹⁴³Nd/¹⁴⁴Nd = 0.512790–0.512953, ²⁰⁶Pb/²⁰⁴Pb = 18.667–18.770, ²⁰⁷Pb/²⁰⁴Pb 15.570–15.612, and ²⁰⁸Pb/²⁰⁴Pb = 38.355–38.554. ¹⁸⁷Os/¹⁸⁸Os ratios range from 0.1368 to 0.1968, with Os concentrations between 10.7 and 168.4 pg/g. These ¹⁸⁷Os/¹⁸⁸Os values are more radiogenic than the primitive upper mantle (∼0.1296) and fall within the range observed for other arc magmas in the TMVB. The samples collectively define three distinct compositional groups, but the compositional variations do not evolve monotonically with time; rather abrupt compositional and isotopic shifts occur over the course of the eruption. Neither closed system fractional crystallization nor assimilation-fractional crystallization of a single parental magma can reproduce the observed geochemical range. Instead, we propose an open-system scenario involving high-temperature fractional crystallization periodically interrupted by recharge events from compositionally and isotopically distinct magmas, supported by MELTS and Magma Chamber Simulator (MCS) modeling. Isotope systematics argue against significant crustal assimilation and point to a heterogeneous, subduction-metasomatized mantle wedge as the primary source of the magmas from Xitle. The mantle source beneath Xitle was variably fluxed by two distinct slab-derived components, both dominated by terrigenous sediment with variable inputs of altered oceanic crust (AOC)-derived fluid/melts, in relative proportions that evolved over time. Our results demonstrate that Xitle's chemical complexity reflects serial addition of subduction fluids, partial melting of a compositionally evolving mantle source, and repeated magma recharge, emphasizing that even small monogenetic systems can record prolonged and multi-stage magmatic histories of mantle derived melts.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123204"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145731851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The evolution of phototrophic Fe(II)-oxidizing bacteria shaping the distribution of iron-bound phosphorus in water columns","authors":"Shan Huang ,&nbsp;Yuanyuan Ren ,&nbsp;Chao Peng ,&nbsp;Chao Zhong ,&nbsp;Jiahao Chen ,&nbsp;Yurong Deng ,&nbsp;Geng Wu ,&nbsp;Yuanyuan Liu ,&nbsp;Hailiang Dong ,&nbsp;Juan Liu","doi":"10.1016/j.chemgeo.2025.123229","DOIUrl":"10.1016/j.chemgeo.2025.123229","url":null,"abstract":"<div><div>The evolution of Fe(II)-oxidizing microorganisms has been closely linked to the evolution of Earth's iron biogeochemical cycle and redox history. However, its impact on the coupled biogeochemical cycling of iron and phosphorus, particularly the distribution of iron-bound phosphate (P_Fe) in water columns, remains largely unexplored. This study elucidates the distinct Fe(II) oxidation mechanisms of the anoxygenic <em>Rhodobacter ferrooxidans</em> SW2 and the oxygenic <em>Synechococcus</em> sp. PCC 7002, along with the properties, transformation processes, and phosphate interactions of their biogenic iron (oxyhydr)oxides. SW2-mediated Fe(II) oxidation via iron oxidase drove sequential transformation from ferrihydrite to green rust and then to goethite. The resulting cell-mineral aggregates had a large hydrodynamic diameter (<em>D</em>_<em>h</em>, up to 26 μm), a high Fe/C ratio (∼2.5), and a rapid sedimentation rate (up to 57.7 m/day), efficiently transporting P_Fe to deep-sea sediments. In contrast, PCC 7002 indirectly oxidized Fe(II) via oxygen production, forming poorly crystalline iron (oxyhydr)oxides stabilized by extracellular polymeric substances. The resultant small aggregates (<em>D</em>_<em>h</em> = ∼6.9 μm), with a slower sedimentation rate (∼3.9 m/day), exhibited high phosphorus retention and were susceptible to dissimilatory iron reduction, facilitating P_Fe recycling in surface waters. These findings suggest that biogenic iron (oxyhydr)oxides from anoxygenic iron oxidizers act as carriers, transporting phosphorus to deep sediments, whereas those from oxygenic cyanobacteria function as phosphorus traps in surface waters. This study provides new insights into how the evolution of Fe(II)-oxidizing microorganisms reshapes P_Fe cycling and distribution in water columns, emphasizing the need to integrate microbiological and geochemical perspectives in understanding Earth's biogeochemical cycles.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123229"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical records of Holocene environmental change in a high latitude coastal basin","authors":"Evalien Baas ,&nbsp;Niels A.G.M. van Helmond ,&nbsp;Marit R. van Erk ,&nbsp;Olga M. Żygadłowska ,&nbsp;Robin Klomp ,&nbsp;Lina Piso ,&nbsp;Rick Hennekam ,&nbsp;Gert-Jan Reichart ,&nbsp;Mike S.M. Jetten ,&nbsp;Caroline P. Slomp","doi":"10.1016/j.chemgeo.2026.123247","DOIUrl":"10.1016/j.chemgeo.2026.123247","url":null,"abstract":"<div><div>Climatic warming, eutrophication, and sea level rise are impacting coastal systems worldwide. High latitude coastal regions are particularly vulnerable to such environmental changes. Here, we assess temporal and spatial trends in salinity, bottom water redox conditions, and organic matter supply in the Bothnian Sea throughout the Holocene. To do so, we use sediment geochemical records for five sites based on discrete sampling and whole core X-ray-fluorescence (XRF) scanning. Our results reveal a basin-wide response to environmental changes, i.e. an abrupt shift from an oligotrophic and well‑oxygenated freshwater lake to a eutrophic and euxinic brackish/marine system that was followed by a return to oxygenated waters and a period of gradual freshening. Bottom water deoxygenation, as recorded by sedimentary enrichments in trace metals such as molybdenum, uranium, copper, arsenic (As), and elevated organic carbon to phosphorus (P) ratios, varied in intensity across the Bothnian Sea basin, and generally was more intense than in the Baltic Proper. Recent sediments show increased anthropogenic impact in the Bothnian Sea, reflected by increased deposition of the pollutants lead and As, and the nutrient P. High P burial aligns with recent signs of eutrophication and associated cyanobacterial blooms. Given the susceptibility for mobilization of sediment P to the water column, there is a potential risk for a positive feedback-loop between increased P recycling and primary productivity upon further eutrophication if there is also a decline in bottom water oxygen. Our work provides insight into the response of a high latitude coastal basin to both abrupt and gradual environmental changes, which is relevant for future projections of anthropogenic impacts in such regions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123247"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An experimental approach to understanding REE patterns in fluorite and application to the Baiyanghe Be-U-Mo deposit","authors":"I.J. Jacques,&nbsp;M. Fayek","doi":"10.1016/j.chemgeo.2026.123249","DOIUrl":"10.1016/j.chemgeo.2026.123249","url":null,"abstract":"<div><div>The geochemistry of fluorite associated with critical mineral deposits can provide valuable information on the source(s) of the ore-forming fluids. This is typically done by correlating the REE pattern in fluorite with patterns from accessory minerals in or the bulk rock composition of proximal igneous rocks. This simplified technique is controversial because the REE partitioning between fluorite and fluid has only been experimentally determined by a prior study at 120 °C without consideration of pH, ligands, or fluid Na content. In this study, we synthesized fluorite from H₂O solutions with 100–500 mg/L of each REE, pH 3–11, 25–150 °C, and &lt; 1 to 4 M NaCl. Our results show that increasing the pH of REE-bearing solutions results in a decrease in the total REE content and a depletion of HREEs. The synthesized fluorite has a nearly identical REE distribution pattern to the fluid in every experiment. Fluorite precipitated from acidic, neutral, and basic solutions yield partition coefficient values ranging 3–69, 6–43, and 1–2100, respectively. Applying these results to fluorite from the Baiyanghe Be–U–Mo deposit, China, indicates fluorite REE patterns must be interpreted with caution. Fluorite from Baiyanghe yields multiple REE patterns, but only a few match the local igneous rocks. Dissimilar patterns could represent incongruent dissolution of accessory minerals in the source rocks, incongruent precipitation of REE minerals, and post-depositional effects.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123249"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mobility of heavy rare earth elements in magmatic-hydrothermal systems: Experimental determination of DyPO4 solubility in supercritical fluids","authors":"Debarati Banerjee ,&nbsp;Laura E. Waters ,&nbsp;Nicole C. Hurtig ,&nbsp;Alexander P. Gysi ,&nbsp;Daniel Harlov ,&nbsp;Chen Zhu ,&nbsp;Artaches Migdisov","doi":"10.1016/j.chemgeo.2026.123248","DOIUrl":"10.1016/j.chemgeo.2026.123248","url":null,"abstract":"<div><div>Dysprosium (Dy) is part of the heavy rare earth elements (REE) and a critical component in the production of high-performance super magnets used in wind turbines, electric vehicles, and other green technologies. The HREE phosphate, xenotime, is commonly associated with hydrothermal systems, where the mobility, fractionation, and deposition of REE are controlled by the stability of aqueous complexes and solubility of REE minerals which depend on temperature, pressure, and fluid composition (salinity, pH, and ligand availability). We conducted a series of synthetic DyPO₄ solubility experiments in NaCl-HCl-bearing aqueous solutions (pH of 2 at 25 °C) from 500 to 700 °C and 1.5 kbar using externally heated pressure vessels. DyPO₄ displays a strong prograde solubility with temperature across all studied fluid salinities (0–0.5 m NaCl). The DyPO₄ solubility isotherms at 500 °C, 600 °C, and 700 °C show a complex relationship with salinity where DyPO₄ solubility is highest (39.2–1552 ppm at 500–700 °C) in 0 m NaCl solutions, decreases strongly (21–331 ppm at 500–700 °C) in the 0.06 m NaCl solutions and remains relatively constant in the 0.25 m (42.8–248 ppm) and 0.5 m NaCl (40.2–124 ppm) solutions. Thermodynamic modeling suggests that pH increases as a function of temperature and salinity, and controls solubility due to the stability of chloride complexes (i.e., DyCl⁺² and DyCl₂⁺) at 500–600 °C, transitioning to hydroxyl complexes (i.e., Dy(OH)₃⁰) dominating at 700 °C and relatively alkaline pH. Comparison with NdPO₄ <!--> solubility data indicates that the light REE in monazite is significantly more soluble than the heavy REE in xenotime in saline fluids at high temperature (500–700 °C), implying efficient light/heavy REE fractionation in supercritical fluids. The lower solubility of DyPO₄ relative to NdPO₄ suggests that at high temperatures, acidic (pH 2–4), low-salinity (∼5 wt% NaCl) fluids will favor the precipitation of xenotime over monazite as it will cool from 700 °C to below 500 °C. These observations align with paragenetic mineral assemblages in NYF pegmatites (e.g., Baveno, Italy), where xenotime commonly immobilizes heavy REE during the high-temperature hydrothermal stages.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123248"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal evolution and stabilization of the Arabian-Nubian Shield: Constraints from whole-rock SrNd and zircon U-Pb-Hf-O isotopes of bimodal volcanics","authors":"Hamed Gamaleldien ,&nbsp;Mabrouk Sami ,&nbsp;Jianfeng Ma ,&nbsp;Mohamed Abu Anbar ,&nbsp;Tehseen Zafar ,&nbsp;J. Brendan Murphy ,&nbsp;Noreen.J. Evans","doi":"10.1016/j.chemgeo.2026.123246","DOIUrl":"10.1016/j.chemgeo.2026.123246","url":null,"abstract":"<div><div>The Neoproterozoic Arabian-Nubian Shield (ANS) is one of the largest juvenile crustal provinces on Earth, providing a natural laboratory for investigating the processes of continental crust formation and stabilization. Although arc accretion is widely regarded as a key mechanism of crustal growth in the ANS, the subsequent transformation of juvenile terranes into stable continental lithosphere remains poorly constrained. Here, we present integrated geochemical, Sr<img>Nd isotopic, and in-situ zircon U–Pb–Hf–O data from the Ranga volcanic suite to evaluate the tectono-magmatic evolution of the late Neoproterozoic ANS. The Ranga volcanic rocks are bimodal with a tholeiitic affinity and yield a crystallization age of ∼585 Ma. The mafic rocks are characterized by low SiO₂ (49.8–54.1 wt%), high MgO (5.9–9.4 wt%), a negligible Eu anomaly (1.05–1.22), low initial ⁸⁷Sr/⁸⁶Sr ratios (0.702829–0.703946), and positive εNd(t) (+6.39 to +7.84), indicate that the mafic rocks formed through fractional crystallization of melts derived from a juvenile depleted source. The felsic rocks display high SiO₂ (72.5–78.9 wt%), low MgO (0.3–1.4 wt%), a negative Eu anomaly (0.50–0.79), low initial ⁸⁷Sr/⁸⁶Sr ratios (0.702994–0.703364), positive εNd(t) (+5.94 to +7.13), zircon εHf(t) (+7.38 to +15.14) values, and zircon δ¹⁸O signatures (4.37–6.18 ‰), consistent with partial melting of hydrothermally altered, MORB-like lithosphere. These results highlight juvenile magmatism and reworking of pre-existing juvenile crust as key drivers in the stabilization and maturation of juvenile crust within the ANS. Collectively, these data define an autogenic, two-step pathway in which juvenile arc addition is followed by intracrustal melting to yield felsic additions converting juvenile provinces into stable continents, a process likely widespread across accretionary orogens.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"703 ","pages":"Article 123246"},"PeriodicalIF":3.6,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mercury concentration: A new window into ancient diets and trophic levels in vertebrate paleontology","authors":"Felipe M.S. Cardia ,&nbsp;José Vicente E. Bernardi ,&nbsp;Carlos Eduardo M. Oliveira ,&nbsp;Marco B. Andrade ,&nbsp;Max C. Langer ,&nbsp;Sandra A.S. Tavares ,&nbsp;Fabiano V. Iori ,&nbsp;William R. Nava ,&nbsp;Thiago S. Marinho ,&nbsp;Luiz Carlos B. Ribeiro ,&nbsp;Jurandir R. Souza ,&nbsp;Rodrigo M. Santucci","doi":"10.1016/j.chemgeo.2025.123218","DOIUrl":"10.1016/j.chemgeo.2025.123218","url":null,"abstract":"<div><div>Direct evidence about feeding habits and trophic levels of extinct species is scarce in the fossil record. Typically, such information is based on geochemistry, stomach contents, anatomy, and, whenever possible, comparison with living counterparts. Despite the challenges involved, such reconstructions are vital for understanding the structure of past ecosystems. Here, we propose a novel geochemical approach in paleontology that uses total mercury concentration (THg) in fossil vertebrate tissues (bones and tooth enamel) and its bioaccumulation and biomagnification properties as geochemical indicators for the inference of feeding habits and trophic levels. Thin section and X-ray diffractometry (XRD) revealed that THg values found in bioapatite from the diverse and well-preserved fossil vertebrates of the Upper Cretaceous Bauru Group (Brazil) are not altered by diagenetic processes. The results show that each vertebrate group analyzed (e.g., fishes, turtles, amphibians, crocodylomorphs, avian, and non-avian dinosaurs) are characterized by different THg concentrations (ranging from 1.66 to 15 ng.g⁻¹ Hg). Notably, similar values were found in fossils of the same taxonomic group regardless of their geological unit of origin. More importantly, taxa with different feeding habits were positioned at different trophic levels based on the bioaccumulation and biomagnification of Hg. Reliable Hg analyses in fossils require confirming that bones are free from diagenetic contamination that may artificially elevate their Hg concentrations.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123218"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145813959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Viscosity and structure of Na2O-enriched haplogranitic melts: a DSC shift-factor calibration for peralkaline rhyolites","authors":"Veronica Stopponi ,&nbsp;Gabriele Giuliani ,&nbsp;Laura Calabrò ,&nbsp;Dmitry Bondar ,&nbsp;Sumith Abeykoon ,&nbsp;Claudia Romano ,&nbsp;Donald B. Dingwell ,&nbsp;Danilo Di Genova","doi":"10.1016/j.chemgeo.2025.123196","DOIUrl":"10.1016/j.chemgeo.2025.123196","url":null,"abstract":"<div><div>The influence of excess Na₂O on the structure, thermal properties and viscosity of haplogranitic melts was systematically investigated by integrating micropenetration viscometry, Raman spectroscopy (including Boson peak analysis) and differential scanning calorimetry (DSC).</div><div>This approach reveals fundamental structure-property relationships in these felsic melt analogs. We demonstrate that Na₂O-induced network depolymerization, clearly evidenced by Raman spectroscopy, provides a direct rationale for the observed dramatic, non-linear decrease in melt viscosity and a concurrent systematic increase in melt fragility.</div><div>Strong correlations are established between melt fragility and both nanoscale vibrational dynamics (Boson peak frequency, <span><math><mrow><msub><mi>ω</mi><mi>BP</mi></msub></mrow></math></span>) and macroscopic thermodynamics (configurational heat capacity change at the glass transition temperature, <span><math><mrow><mo>∆</mo><msubsup><mi>C</mi><mi>p</mi><mi>conf</mi></msubsup><mrow><mfenced><msub><mi>T</mi><mi>g</mi></msub></mfenced></mrow></mrow></math></span>), validating <span><math><mrow><msub><mi>ω</mi><mi>BP</mi></msub></mrow></math></span> and <span><math><mrow><mo>∆</mo><msubsup><mi>C</mi><mi>p</mi><mi>conf</mi></msubsup><mrow><mfenced><msub><mi>T</mi><mi>g</mi></msub></mfenced></mrow><mspace></mspace></mrow></math></span> as proxies for estimating melt fragility in experimentally challenging systems, such as those prone to nanostructuration. Furthermore, we provide DSC-viscosity shift factors <em>K</em>_{<em>onset</em>}<em>, K</em>_{<em>peak</em>}<em>, K</em>_{<em>endset</em>} applicable to peralkaline compositions. By addressing the role of thermal lag and thermal inertia in DSC analyses, our study refines the experimental accuracy of viscosity–temperature relationships and reinforces the robustness of the shift-factor approach across compositionally diverse silicate systems.</div><div>This work thus provides an integrated framework and predictive insights into the rheology of Na₂O-rich haplogranitic melts, relevant to understanding evolved magmatic systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123196"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145731858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}