Chemical Geology最新文献

{"title":"The predominance of SiO5 species in MgSiO3 melt at transition zone pressures from a dynamics point of view","authors":"Georg Spiekermann ,&nbsp;Maximilian Schulze","doi":"10.1016/j.chemgeo.2025.123194","DOIUrl":"10.1016/j.chemgeo.2025.123194","url":null,"abstract":"<div><div>Ab initio molecular dynamics (AIMD) simulations of melt and glass of MgSiO₃ and of other compositions at high pressure consistently observe the predominance of fivefold-coordinated silicon ( <figure><img></figure> ) over <figure><img></figure> and <figure><img></figure> in the pressure range of the mantle transition zone. However, the common approach to compute the abundance of different coordination states is only based on a static ‘sequential-3D’ structural analysis. The absence of a time scale in the analysis has led to concern about the validity of its results. To validate AIMD results, here we investigate the coordination dynamics beyond the static limit, by carrying out a dynamical coordination species analysis in ‘4D’ on the basis of the short-term part of the intermittent coordination autocorrelation function described in an earlier study. We found that the predominance of SiO₅ species at pressures of the transition zone is persistent even in a dynamical analysis. However, towards lower pressures and most pronounced at ambient pressure, the majority of all SiO₅ detected by the common static sequential-3D analysis are so short-lived that they should be considered ‘spurious’ rather than chemical species.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123194"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785274","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 signatures of mud and core gases from the Milun Fault Scientific Drilling (MiDAS), Taiwan: Implications for fluid pathways and crustal degassing","authors":"Ching-Chou Fu ,&nbsp;Kuo-Hang Chen ,&nbsp;Kuo-Wei Wu ,&nbsp;Pei-Ling Wang ,&nbsp;Ai-Ti Chen ,&nbsp;Vivek Walia ,&nbsp;Kuo-Fong Ma","doi":"10.1016/j.chemgeo.2025.123223","DOIUrl":"10.1016/j.chemgeo.2025.123223","url":null,"abstract":"<div><div>We investigated the fluid processes within the Milun Fault Zone (MFZ), eastern Taiwan, by combining continuous monitoring of dissolved gases in drilling mud and gases extracted from cores with the compositional and isotopic analyzers during the Milun Fault Scientific Drilling (MiDAS) project. Although atmospheric inputs dominate the background signal, distinct multi-gas anomalies of CH₄, C₂H₆, CO₂, H₂, He, and Rn occur at the discrete depths (∼440 m, 470–488 m, and ∼ 520 m). These anomalies coincide with the fracture zones, organic carbon-rich horizons, and the fault gouge core, delineating structurally controlled fluid pathways. Core δ¹³C_CO₂ values (−10 ‰ to −15 ‰) indicate organic degradation and methanogenesis as major sources of shallow CO₂, while clustered CH₄-C₂H₆ anomalies with He and Rn reflect episodic inflow of deep fluids along the fault conduits. Integration of the mud gas and core gas datasets demonstrated that the mud gas monitoring captured transient inflows and fracture controlled variability, whereas the core gases preserved in situ compositions and the isotopic fingerprints. Meanwhile, the data reveal the structural heterogeneity of the MFZ, providing geochemical confirmation of location near 520 m and the key horizons for long term hydrogeochemical monitoring. These findings highlight the potential of multi-parameter gas geochemistry to probe crustal fluid migration and its implications for fault activity and earthquake precursors.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123223"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823503","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":"Bioapatite crystallinity and Rare Earth Element signatures in fossil and Recent sharks: A window into Past and Present seas","authors":"Luca Medici ,&nbsp;Annalisa Ferretti ,&nbsp;Alberto Collareta ,&nbsp;Giulia Bosio ,&nbsp;Giovanni Bianucci ,&nbsp;Giorgio Carnevale ,&nbsp;Simone Casati ,&nbsp;Simona Clò ,&nbsp;Luca Lanteri ,&nbsp;Federico Lugli ,&nbsp;Giuseppe Marramà ,&nbsp;Frederik H. Mollen ,&nbsp;Martina Savioli ,&nbsp;Daniele Malferrari","doi":"10.1016/j.chemgeo.2025.123200","DOIUrl":"10.1016/j.chemgeo.2025.123200","url":null,"abstract":"<div><div>The advent of biomineralization represented a key evolutionary innovation, enabling vertebrates to form skeletons and teeth made of bioapatite, a nanocrystalline apatite phase with variable chemical composition. This adaptability has driven vertebrate morphological diversity and ecological success. Bioapatite structure is shaped by metabolic processes, with ionic substitutions and vacancies influencing its crystallographic parameters. Major elements alter the <em>a</em> and <em>c</em> parameters of the bioapatite cell, while trace elements have minimal impact. Rare Earth Element (REE) signatures in fossil bioapatite, once considered direct proxies for paleo-seawater, may reflect complex diagenetic histories. This study examines bioapatite crystallinity and REE patterns in Recent and fossil catsharks (Scyliorhinidae <em>s.l.</em>) using μ-XRD and LA-ICP-MS. Recent teeth and scales of <em>Galeus melastomus</em> and <em>Scyliorhinus canicula</em> from the Italian coasts were tested and compared with fossil Eocene to Pliocene counterparts from strata across Europe. Our results underscore the value of crystallographic parameters in tracing both biological and <em>post-mortem</em> transformations in bioapatite. In particular, diagenetic processes led to organic matter loss and increased carbon incorporation, especially in tooth regions that were originally rich in organics. Fossil samples showed reduced <em>a</em> lattice parameters and unit cell volumes, increased <em>c</em> parameters, and enhanced crystallinity. Tooth crowns had higher crystallinity and volume than roots, reflecting lower organic contents. Crystallographic differences between scales and teeth suggest functional adaptations, with teeth exhibiting variable crystallite sizes for biomechanical efficiency. Diagenetic effects are seemingly independent of geological age, being rather influenced by depositional conditions and, possibly, by original physiological traits.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123200"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145731854","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":"Insights from XAS, FTIR, and PHREEQC into mono- and poly-vanadate (V(V)O43−) adsorption to Hematite","authors":"Jing Zhang ,&nbsp;Victoria S. Coker ,&nbsp;J. Frederick W. Mosselmans ,&nbsp;Thomas L. Goût ,&nbsp;Luís A.E. Batista de Carvalho ,&nbsp;Samuel Shaw","doi":"10.1016/j.chemgeo.2025.123228","DOIUrl":"10.1016/j.chemgeo.2025.123228","url":null,"abstract":"<div><div>Vanadium (V) is a widespread trace element in the environment. At high concentration, due to anthropogenic emission such as mining activities and fossil fuels, it can be toxic to marine systems and terrestrial plants. However, the geochemical behaviour of V remains poorly understood. Here, this study aimed to understand the molecular scale V speciation, adsorption behaviour and bonding mechanisms of V(V) onto hematite as a function of geochemical factors (pH, ionic strength, and V(V) concentration), applying a multi-technique approach comprising aqueous chemical analysis and XAS supported by ATR-FTIR and PHREEQC geochemical speciation calculations. From these data, tetrahedral monovanadate formed a corner-sharing bidentate surface complex at 1.20 mM V(V) and pH 9 and 0.12 mM V(V) at all pH, while octahedral decavanadate formed at a V(V) concentration of 1.20 mM and pH &lt; 7. The dominant coordination environment changed gradually from a mixture of octahedrally and tetrahedrally coordinated V at pH 3 to tetrahedral monovanadate at pH 9. These results demonstrate the marked effects of pH and initial V concentration on V(V) speciation at hematite surfaces, in turn affording predictions of the environmental behaviour of heavy metals released during a variety of anthropogenic activities (e.g. mining) across a range of geochemical conditions. It is envisioned these results will contribute to strategies for the treatment of lands contaminated with heavy metals predominantly through adsorption processes (e.g. mine sites).</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123228"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145845298","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":"Epidote emerges as a pivotal player in the hydration dynamics of the mantle transition zone","authors":"Jing Gao ,&nbsp;Xueyin Yuan ,&nbsp;Xinyang Li ,&nbsp;Chaowen Xu ,&nbsp;Yue Wang ,&nbsp;Wanghua Wu","doi":"10.1016/j.chemgeo.2025.123206","DOIUrl":"10.1016/j.chemgeo.2025.123206","url":null,"abstract":"<div><div>Geophysical data has revealed anomalous water enrichment in the mantle transition zone (MTZ, 410–660 km depths), which is widely attributed to crustal water released from stagnant subducted slabs. However, the majority of hydrous minerals dehydrate completely at depths &lt;∼300 km, leaving the mechanism of water transport to the deeper mantle unresolved. The discovery of ‘epidote-phases’ in superdeep diamonds from the MTZ offers a potential solution, yet critical uncertainties persist regarding its stability under subduction-zone thermal gradients and MTZ conditions. This study experimentally demonstrates that the hydroxyl groups in epidote strengthen along cold-to-hot subduction geotherms (5–25 °C/km) across ∼250 km. In the deeper reduced mantle (buffered by FeO-Fe), epidote undergoes complete dehydration at ∼250 km via decomposition into grossular, andradite and wustite. Yet, kinetic barriers and the limited extent of reduced domains within slabs probably inhibit this process. Under oxidized conditions (Fe₂O₃-Fe₃O₄ buffer), epidote destabilizes at thermally perturbed slab interfaces, and is more likely to decompose via prolonged mantle-derived heating in the MTZ. This breakdown partially traps water in the newly formed grossular garnet. These findings redefine epidote as a dynamic agent in the hydration of the MTZ, offering a novel mineralogical perspective on the water-rich characteristics of this enigmatic region.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123206"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145766047","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":"In-situ sulfur isotope and microscopic analyses reveal multiple pyrite genesis mechanisms in the early Ediacaran Doushantuo Formation, South China","authors":"Shiqi Cheng ,&nbsp;Lianjun Feng ,&nbsp;Guoqiang Tang ,&nbsp;Yan Liu ,&nbsp;Hao Qiu ,&nbsp;Qiuli Li ,&nbsp;Xuelei Chu ,&nbsp;Xingliang Zhang ,&nbsp;Jinhua Li","doi":"10.1016/j.chemgeo.2025.123226","DOIUrl":"10.1016/j.chemgeo.2025.123226","url":null,"abstract":"<div><div>Sedimentary pyrite constitutes an invaluable geological archive for reconstructing Earth's ancient environments, yet interpreting its origins within deep geological records is often complicated by subsequent diagenetic modification. Here, we examine four distinct pyrite morphologies (framboidal pyrites hosted in chert nodules and matrix, euhedral pyrites within calcite rims of nodules, and pyrite aggregates within surrounding matrix rocks) preserved in the Ediacaran Doushantuo Formation of South China, utilizing a combination of high-resolution electron microscopy and in-situ secondary ion mass spectrometry sulfur isotope analysis. Our microscopic observations identify well-preserved framboidal pyrites, variably altered by post-depositional processes, alongside large euhedral pyrite crystals encapsulated by calcite, and irregular pyrite aggregates. Integrated nanoscale microscopic and in situ isotopic analyses consistently demonstrate that framboidal pyrites exhibit negative δ³⁴S values, indicative of microbial sulfate reduction within the water column or at the sediment-water interface during early diagenesis. Conversely, euhedral pyrites and irregular aggregates from nodule rims and surrounding matrix yield significantly positive δ³⁴S values, consistent with thermochemical sulfate reduction during late-stage burial diagenesis. This finding contrasts with previous interpretations that attribute positive δ³⁴S values to a diminished marine sulfate reservoir within a restricted paleoceanographic setting. Our results emphasize that post-depositional thermochemical sulfate reduction processes can significantly elevate δ³⁴S values of pyrites. This study underscores the critical necessity of deconvolving diagenetic overprinting from primary signatures by integrating in-situ isotopic and microscopic analyses, thereby refining paleoenvironmental reconstructions from pyrite archives.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123226"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823790","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":"Nitrogen partitioning and isotope fractionation during crustal Anatexis: New constraints from across-grade traverses and centimeter-scale Leucosome-Restite Pairs","authors":"Juan Felipe Bustos-Moreno ,&nbsp;Gray E. Bebout ,&nbsp;Rolf L. Romer ,&nbsp;Lorenzo Magnani","doi":"10.1016/j.chemgeo.2025.123219","DOIUrl":"10.1016/j.chemgeo.2025.123219","url":null,"abstract":"<div><div>We investigated nitrogen (N) partitioning and isotope fractionation during crustal anatexis, in three metapelitic migmatite suites: the Anatectic Complex of Toledo and Tormes Dome Anatectic Region in Spain, and the Adamello Pluton Contact Aureole (APCA) in Italy. Restites have N concentrations higher than those in corresponding leucosomes and pegmatites, related to higher modal abundances of biotite in restitic domains. In general, restites and migmatites (whole-rocks consisting of both leucosome and restite) have higher δ¹⁵N values, by up to 5.3 ‰, than the leucosomes and pegmatites. During partial melting, the mobility and isotope fractionation of N are strongly influenced by the stability and breakdown of muscovite and biotite. Differences in the δ¹⁵N of restites and leucosomes are inconsistent with the expectation of minimal fractionation at high temperatures among NH₄⁺-bearing micas and feldspars in equilibrium in closed-systems. These differences may instead reflect, open-system behavior during melting and conceivably also during partial retrograde reactions (back-reaction) between partial melts and restites. Possible additional evidence for open-system behavior during melting exists for the APCA, where shifts to lower δ¹⁵N values resulting from a series of up-grade melting reactions contrast with the shifts to higher values expected for Rayleigh N loss involving N₂, NH₃, and NH₄⁺. In general, the partial melts did not inherit the isotope compositions of their source rocks, but seem to record variably lower δ¹⁵N values, challenging the assumption that granitic melts directly reflect the isotope composition of their metasedimentary sources. The results of our study of these metapelitic migmatites indicate great compatibility of N in residues of partial melting, largely in biotite, and thus implicate highly devolatilized and partially melted sedimentary rocks as important sites of long-term N storage at mid- to deep-levels of the continental crust.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123219"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145813960","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":"δ88/86Sr and 87Sr/86Sr variability in fish otoliths: Implications for seawater temperature, growth-rate, and provenance","authors":"Arka Chakraborty ,&nbsp;Sourav Ganguly ,&nbsp;Arild Folkvord ,&nbsp;Steven E. Campana ,&nbsp;Prosenjit Ghosh ,&nbsp;Ramananda Chakrabarti","doi":"10.1016/j.chemgeo.2025.123208","DOIUrl":"10.1016/j.chemgeo.2025.123208","url":null,"abstract":"<div><div>We report stable (δ^88/86Sr) and radiogenic (⁸⁷Sr/⁸⁶Sr) Sr isotopic compositions of natural and laboratory-cultured aragonitic fish otoliths. The natural samples are from five different species collected from the Atlantic Ocean that grew over temperature ranges of 2–25 °C while the cultured samples grew in water temperatures of 4–16 °C. The otoliths exhibit significant variability in δ^88/86Sr values (−0.095 ‰ to 0.102 ‰) and incorporate the lighter ⁸⁶Sr isotope relative to ambient seawater in both natural and experimental settings. The δ^88/86Sr values in natural otoliths negatively correlate with ambient seawater temperature. They show positive and negative correlations with previously reported Δ₄₇ and δ^44/40Ca values, respectively, measured on the same powdered samples. A multi-proxy approach to determine seawater temperature combining δ^88/86Sr, δ^44/40Ca, and Δ₄₇ values and Sr/Ca ratio is proposed, which has an uncertainty of ±0.75 °C and is better than uncertainties when these proxies are used in isolation. Strong correlations are also observed between Sr elemental partitioning (K_D^Sr/Ca) and Δ^88/86Sr (δ^88/86Sr_otolith - δ^88/86Sr_seawater) values in natural otoliths. Although the lighter isotopes of both Sr and Ca are preferentially incorporated in the otolith carbonates, a negative correlation is observed between δ^88/86Sr and δ^44/40Ca values. Contrasting correlations are also observed between K_D^Sr/Ca and Δ^88/86Sr values as well as K_D^Sr/Ca and Δ^44/40Ca (δ^44/40Ca_otolith - δ^44/40Ca_seawater) values, suggesting different carbonate crystallization pathways for Sr and Ca isotopes.</div><div>The δ^88/86Sr values of cultured otoliths overlap with natural otolith samples but their K_D^Sr/Ca values are lower than the natural samples. While no relationship is observed between δ^88/86Sr values, water temperatures, and K_D^Sr/Ca values, growth rate shows a positive correlation with water temperature in cultured otoliths. The Δ^88/86Sr* values (Δ^88/86Sr normalized to growth rate) of the cultured otoliths show positive and negative correlations with K_D^Sr/Ca* (K_D^Sr/Ca corrected for growth rate) values and temperature, respectively, consistent with observations from natural otoliths. The δ^88/86Sr values do not show any correlation with ⁸⁷Sr/⁸⁶Sr ratios. Variability in ⁸⁷Sr/⁸⁶Sr ratios in the natural otoliths reflect their provenance from coastal oceans, which receive varying amounts of continent-derived freshwater.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123208"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785757","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":"Abundance, composition, and environmental implications of iron minerals in highly permeable sandy beaches","authors":"Yan Zhang ,&nbsp;Cheng Xing ,&nbsp;Liuqian Yu ,&nbsp;Tian Fu ,&nbsp;Shuoyu Zhang ,&nbsp;Yi Liu","doi":"10.1016/j.chemgeo.2025.123225","DOIUrl":"10.1016/j.chemgeo.2025.123225","url":null,"abstract":"<div><div>Iron minerals in sandy beaches play a crucial role in regulating chemical transport from terrestrial to marine ecosystems via coastal groundwater flow. This study investigated the abundance, composition, and distribution of iron minerals in sandy beaches (25 m long and 6 m deep; Guanghai Bay, China), assessed their role in intercepting phosphorus (P), elucidating the underlying geochemical mechanisms. We sequentially extracted 5 iron pools from sediment cores: carbonate-associated iron (Fe_Carb), easily reducible oxides (Fe_Ox1), reducible oxides (Fe_Ox2), magnetite (Fe_Mag), and silicate iron (Fe_Si). The results reveal that highly reactive iron (Fe_HR = Fe_Carb + Fe_Ox1 + Fe_Ox2 + Fe_Mag) constitutes 65 % of total iron indicating a significant enrichment in sandy aquifers compared to typical marine and river sediments (&lt;45 %) due to continuous groundwater supply and redox oscillation. Within Fe_HR, Fe_Ox2 is the most abundant form (39 %), followed by Fe_Ox1 (15 %), Fe_Carb (6 %) and Fe_Mag (5 %). The sandy beach exhibits a low Fe_Ox1/Fe_Ox ratio of 28 % (where Fe_Ox = Fe_Ox1 + Fe_Ox2), attributed to its higher permeability and more oxidizing conditions compared to typical mangroves and salt marshes (where ratios can reach 60 %). Reducing conditions intensified seaward and downward in the sandy beach facilitating the sediment organic carbon mediated transformation of Fe(III) to Fe(II) phases. More importantly, Fe_Ox2 acts as the primary phase storing P in the saturated zone and serves as a key mineral barrier intercepting land-derived P. This study provides a comprehensive investigation of iron mineral pools, highlighting the enrichment of Fe_HR and identifying Fe_Ox2 as the dominant and functionally significant phase in highly permeable sandy beaches.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123225"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823498","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":"Low-δ18O magmas at Batur, Indonesia: Evidence for slab-window melting beneath arc volcanoes","authors":"Guo-Rong Tang ,&nbsp;Wei Dan ,&nbsp;Adi Maulana ,&nbsp;Jian Wang ,&nbsp;Xiu-Zheng Zhang ,&nbsp;Xin Ma ,&nbsp;Qiang Wang ,&nbsp;Xi-Jun Liu ,&nbsp;Gong-Jian Tang","doi":"10.1016/j.chemgeo.2025.123224","DOIUrl":"10.1016/j.chemgeo.2025.123224","url":null,"abstract":"<div><div>Low-δ¹⁸O magmas (δ¹⁸O &lt; +5.5 ‰) record the assimilation of rocks that underwent high-temperature hydrothermal alteration. This study presents an integrated analysis of oxygen isotopes and major elements of olivines, along with whole-rock geochemistry and Sr–Nd–Hf isotopes for basaltic andesites and andesites from the Quaternary Agung and Batur volcanoes in Bali, Indonesia. Agung and Batur lavas exhibit similar trace element and Sr–Nd–Hf isotopic signatures but differ in their olivine oxygen isotopic compositions. Olivine phenocrysts from Agung lavas show δ¹⁸O values ranging from +4.65 ‰ to +5.38 ‰, with an average of +5.08 ± 0.21 ‰ (2SD, <em>n</em> = 20). Olivines from Batur lavas exhibit lower δ¹⁸O values (+3.70 ‰ to +5.15 ‰), with an average of +4.50 ± 0.14 ‰ (2SD, <em>n</em> = 120), and most are distinctly below the mantle olivine values. The low δ¹⁸O values observed in both Agung and Batur olivines are unlikely to result from assimilation of pre-existing hydrothermally altered crustal or <em>syn</em>-magmatic rocks. Instead, they provide evidence for the assimilation of recycled altered oceanic crustal materials. We propose that these assimilated oceanic crustal materials could have been derived from the partial melting of low-δ¹⁸O lower oceanic crust, possibly induced by hot asthenospheric flow through a slab window. This study highlights that slab windows may facilitate not only the formation of rear-arc ultrapotassic lavas but also significantly influence magmatism at the volcanic front.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"702 ","pages":"Article 123224"},"PeriodicalIF":3.6,"publicationDate":"2026-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823499","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}