Chemical Geology最新文献

{"title":"Modeling Li isotope fractionation during the coal-combustion process and evaluating its capacity as an environmental tracer","authors":"Jing Chen ,&nbsp;Yilin Xiao ,&nbsp;Jack Geary Murphy ,&nbsp;Dong-Bo Tan ,&nbsp;Yang-Yang Wang ,&nbsp;Biao Fu ,&nbsp;Guijian Liu ,&nbsp;Ru-Wei Wang ,&nbsp;Xiaoxia Wang ,&nbsp;Feng-Tai Tong","doi":"10.1016/j.chemgeo.2025.122631","DOIUrl":"10.1016/j.chemgeo.2025.122631","url":null,"abstract":"<div><div>Coal-fired power plants (CFPPs) utilizing lithium-rich coal are significant sources of anthropogenic Li emissions, highlighting the importance of effective tracing of potentially toxic Li for environmental monitoring and regulation. Lithium isotopes are a promising tracer, yet the dynamics of isotopic behavior during coal combustion are not well understood. This study investigates the elemental and isotopic behavior of Li in feed coals and combustion products from two pulverized coal-fired boilers (PC-H and PC-X) and one circulating fluidized bed boiler (CFB-H). The results showed that Li was primarily captured in fly ash (66.4 % to 84.8 %), with a fraction (1.3 % to 25.2 %) emitted into the atmosphere (stack emission). The isotopic composition of Li in feed coal ranged from −0.6 ‰ to +0.3 ‰, contrasting with δ⁷Li values in bottom ash and fly ash, which range from −2.7 ‰ to +0.1 ‰ and − 1.9 ‰ to +0.5 ‰, respectively. Notably, bottom ash samples consistently exhibit lower δ⁷Li values than their corresponding feed coal, suggesting the volatilization of heavier Li isotopes during combustion. Mass balance calculations reveal that stack emissions are enriched in heavier isotopes, with δ⁷Li values reaching up to +17.8 ‰. A Rayleigh fractionation model, with a fractionation factor of α = 1.0044, indicates that light lithium isotopes preferentially condense onto fly ash, while heavier isotopes are predominantly found in stack emissions. This model provides a quantitative framework for understanding isotopic segregation during cooling, significantly advancing methodologies for tracing and quantifying Li emissions for environmental impact assessments and source attribution of anthropogenic Li from CFPPs.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122631"},"PeriodicalIF":3.6,"publicationDate":"2025-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143061999","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":"Distribution of bacterial 3-OH-FAs in Chinese saline lakes and its implication for paleoclimate reconstruction","authors":"Yi Yang ,&nbsp;Canfa Wang ,&nbsp;Yan Yan ,&nbsp;Ao Sun ,&nbsp;Huan Yang ,&nbsp;Shucheng Xie","doi":"10.1016/j.chemgeo.2025.122630","DOIUrl":"10.1016/j.chemgeo.2025.122630","url":null,"abstract":"<div><div>Microbial communities in saline lakes are sensitive to environmental changes and showed promise for paleoclimate reconstruction. However, how the Gram-negative bacterial communities and their related membrane lipids, 3-hydroxy fatty acid (3-OH-FA), adapt to salinity change is still unclear. Here, we report the potential impacts of salinity and pH on 3-OH-FA distributions, based on saline lake samples, including lacustrine sediments and surrounding soils, collected from the Balikun Lake of the Xinjiang Province and 12 shallow lakes of the Inner Mongolia Province, China. Our results revealed that 3-OH-FAs in saline lakes are mainly derived from in situ production. The 3-OH-FA distributions are sensitive to salinity and pH variations. Specifically, in brackish lakes (&lt; 30 ‰), salinity and pH dominated the distribution of 3-OH-FAs. However, in hypersaline lakes, salinity predominated the 3-OH-FA distributions. Moreover, multiple linear regression has been used to explore the potential salinity proxies based on 3-OH-FAs. The result revealed the promising potential of using 3-OH-FAs for paleoenvironment reconstruction, which provides alternative tools for investigating the paleoclimate changes in saline environments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122630"},"PeriodicalIF":3.6,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143062001","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":"Formation of non-equilibrium accessory mineral paragenesis in S- / I-type granitic rocks (example from the Western Carpathians)","authors":"Sergii Kurylo,&nbsp;Igor Broska","doi":"10.1016/j.chemgeo.2025.122625","DOIUrl":"10.1016/j.chemgeo.2025.122625","url":null,"abstract":"<div><div>Granite typology in terms of identification I- and S-types is based on granite composition and accessory mineral characteristics. Mixing of mafic and felsic melts during the formation of granite massifs can lead to non-equilibrium accessory paragenesis formed from mixture of typical I- type accessory pragenesis (Ti-magnetite, allanite, titanite, low Mn apatite) and S-type composed typically from monazite and high Mn apatite. The extensive mixing processes in the tectonically northern tilted Kriváň Fatra granite massif, where the tonalite zone is situated below granodiorite, provide evidences for the formation of non-equilibrium accessory paragenesises by two recognisable stages. The first stage, a deep crustal mixing of the mafic melts into the formed felsic magmatic chamber is indicated in presence of 1) relic plagioclase P1 (An₃₃_–₃₇ and An₄₀_–₅₆); 2) quartz with rutile needles; 3) quartz ocelli surrounded by trioctahedral micas; 4) inclusions of pyroxene and V, Cr relic mineral phases in an accessory pyrite. Quartz antecryst with rutile rods, antiperthitic plagioclase, and Ti-magnetite disintegration at 780 °C indicates a high temperature mixing in the low crustal MASH zone. High portion of the apatite was probably late in the early stage transformed to monazite by fluids from early magmatic allanite-(Ce) giving an evolved sulphur content to this monazite. The second stage occurred in crustal conditions when the melt-mixing continued by convectional homogenization of initial mixed magma forming oscillatory-zoned plagioclases P2 (An₃₂_–₂₀), Ba and Na is high in K-feldspar giving a hybrid character of the Kriváň Fatra granodiorites. The late mixing stage effectively is indicated by abundant apatite with composite chemistry partly I-type (low Mn, Fe but high S, Cl) and partly S-type (high Mn, and LREEs). Apatite formation temperatures in the tonalite zone is 792 °C, and in the granodiorite zone is between 780 and 819 °C pointing to the evolution pathway from the inhomogeneous mixed granotonalite to relatively homogenous granotonalite in the granodiorite zone. The positional upper granodiorite zone with the transitional granite typology in the Kriváň Fatra granite massif resulted from high degree of magma mixing of former mafic gabbro (?) and felsic melt forming the non-equilibrium accessory paragenesis, as S-/I-type apatite mixture composition. In general view, not well homogenized granitic parts recognised in the upper north granodiorite zone of the Kriváň Fatra granite massif can be typologically defined according to <span><span>Castro (2001)</span></span> as a transitional mixed granotonalite.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122625"},"PeriodicalIF":3.6,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143062002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of HA-Fe(III) coprecipitation on •OH production in Fe(III)/O2 systems perturbed by sulfide","authors":"Elias Niyuhire ,&nbsp;Wenjing Xie ,&nbsp;Songhu Yuan","doi":"10.1016/j.chemgeo.2025.122612","DOIUrl":"10.1016/j.chemgeo.2025.122612","url":null,"abstract":"<div><div>Dark •OH production from sulfide perturbation of Fe(III)/O₂ and NOM/O₂ systems has been recently documented. In spite of the ubiquity of natural organic matter (NOM)-Fe(III) coprecipitates in the environment, the effect of NOM-Fe coprecipitation on •OH production in such systems remains unexplored. This study showed that •OH production from sulfide reaction with oxic HA-Fe(III) coprecipitates was influenced by sulfide concentration and C/Fe molar ratios. With increasing sulfide concentration from 0 to 5 mM, the cumulative •OH concentration within 120 min increased to 71.8 μM for 11.2 mM Fe in HA-Fe(III) coprecipitates (C/Fe molar ratio = 1.4). At this C/Fe ratio, the cumulative •OH concentrations at this C/Fe ratio in the presence of ≤2.5 mM S(-II) were lower than those produced from lepidocrocite control mineral, while it was higher at 5 mM S(-II). •OH production was attributed to enhanced HA-Fe(II)/FeS production coupled to HA desorption and reduction. These reduced species could activate O₂ to generate •OH. In the presence of 2.5 mM S(-II), the cumulative •OH concentration decreased with C/Fe molar ratios of the HA-Fe(III) coprecipitates. Depending on the carbon content of the NOM-Fe coprecipitates, •OH production might be affected by the interaction of NOM and sulfide. The addition of 2.5 mM S(-II) into 100 g/L of field sediments also produced significant levels of •OH, and it was more efficient with clayed sediments than sandy sediments. The results of this study suggest that the influence of HA-Fe(III) coprecipitation should be cautiously considered for •OH production in sulfide-perturbed Fe(III)/O₂ systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122612"},"PeriodicalIF":3.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437590","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":"P-T-ƒO2-X constraints on the partitioning behavior of trace elements between clinopyroxene and alkali melts: An experimental study","authors":"Andrés Fabián Salazar-Naranjo,&nbsp;Silvio Roberto Farias Vlach","doi":"10.1016/j.chemgeo.2025.122629","DOIUrl":"10.1016/j.chemgeo.2025.122629","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Titanian Ca-clinopyroxene (Ti-Cpx) is one of the most characteristic phases and main carriers of trace elements in alkali ultrabasic to intermediate magmas, making it a key mineral for geochemical studies on the origin and evolution of this type of system. Starting from natural basanite and tephrite compositions, we conducted a series of experiments under one atmosphere pressure (1-atm) with oxygen fugacity (&lt;em&gt;fO&lt;/em&gt;&lt;sub&gt;&lt;em&gt;2&lt;/em&gt;&lt;/sub&gt;) controlled from QFM-2 to QFM+2 and moderate pressure (0.5–2.0 GPa) with &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt; around the CCO buffer. The results allowed a better examination of the &lt;em&gt;P&lt;/em&gt;, &lt;em&gt;T&lt;/em&gt;, ƒO&lt;sub&gt;2&lt;/sub&gt;, and compositional controls on &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;element&lt;/mi&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Cpx&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;melt&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, and indicated that: (1) the Lattice Strain Model (LSM) successfully fits the divalent and trivalent cations into the M2 site and trivalent cations into the M1 site; (2) divalent cations are strongly influence by clinopyroxene composition, with their compatibility decreasing at the M1 site and increasing at the M2 site as the DiHd component rises; (3) redox-sensitive elements, such as Cr, V, and Eu exhibit systematic variation with ƒO&lt;sub&gt;2&lt;/sub&gt; and &lt;em&gt;T&lt;/em&gt;; (4) high-field strength elements (HFSEs) replace Mg via the Tschermak reaction, resulting in a variation in &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;HFSE&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;Cpx&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;melt&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; along the clinopyroxene compositional trend from Mg-rich augite to ferroan diopside; (5) the crystal and melt compositions determine the compatibility of the rare earth elements (REEs), where the latter particularly substitute Na instead of Ca; (6) the thermodynamic model based on the activity of the Na&lt;sub&gt;0.5&lt;/sub&gt;(REE)&lt;sub&gt;0.5&lt;/sub&gt;MgSi&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt; component reproduces closely the observed partitioning of the REEs under 1-atm. Esseneite (CaFe&lt;sup&gt;3+&lt;/sup&gt;AlSiO&lt;sub&gt;6&lt;/sub&gt;) component increases with the oxygen fugacity and facilitates the incorporation of REEs, meaning that Ti-Cpx crystallized under oxidizing conditions will be REE-rich (except Eu). &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mfenced&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;Ta&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;Nb&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/mfenced&gt;&lt;mrow&gt;&lt;mi&gt;Cpx&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;melt&lt;/mi&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mfenced&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;Zr&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;Hf&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/mfenced&gt;&lt;mrow&gt;&lt;mi&gt;Cpx&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;melt&lt;/mi&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; remains almost constant, while &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mfenced&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;mi&gt;Th&lt;/mi&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/mfenced&gt;&lt;mrow&gt;&lt;mi&gt;Cpx&lt;/mi&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;melt&lt;/mi&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; correlates positively with the EnFs component, generating fractionation degrees variable of U/Th and constant of Ta/Nb and Zr/Hf during the evolution of cr","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122629"},"PeriodicalIF":3.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143062003","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":"Re-evaluation of the spherules proposed origin recovered from the Pacific Ocean site of the CNEOS 2014-01-08 (IM1) bolide","authors":"N.G. Rudraswami ,&nbsp;V.P. Singh ,&nbsp;M. Pandey","doi":"10.1016/j.chemgeo.2025.122628","DOIUrl":"10.1016/j.chemgeo.2025.122628","url":null,"abstract":"<div><div>In a recent publication by Loeb et al. (2024), the collection of spherules from the Pacific Ocean was classified as extraterrestrial, specifically micrometeorites. We critically evaluate their findings and conclusions, pointing out inaccuracies in their data interpretation. A comprehensive re-examination of these spherules is essential to classify them as micrometeorites accurately. We argue that the spherules they studied are primarily volcanic or terrestrial in origin, and we emphasize that a revision of their classification is crucial given the flawed observations. This work highlights the challenges faced by researchers and specialists who are not focused on micrometeorites when attempting to locate specific meteor particles from the ocean's depths, a task often regarded as nearly impossible due to the complexities involved in identifying and retrieving these objects. It is advisable to adopt standardized protocols to reduce the possibilities of unreliable interpretations in micrometeorite research. Additionally, “cosmic spherules” should not be used indiscriminately to describe recovered particles, underscoring the importance of adhering to specific chemical and textural characteristics.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122628"},"PeriodicalIF":3.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021232","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 investigation of the relationship between morphology and chemistry of the D-type spherules from the recovery expedition of the CNEOS 2014-01-08 bolide: Implications for origins","authors":"Eugenia Hyung ,&nbsp;Juliana Cherston ,&nbsp;Stein B. Jacobsen ,&nbsp;Abraham Avi Loeb","doi":"10.1016/j.chemgeo.2025.122627","DOIUrl":"10.1016/j.chemgeo.2025.122627","url":null,"abstract":"<div><div>Cosmic spherules have largely been classified into S-, I-, and G-types according to their compositions, and are identified to have chondritic or achondritic materials as precursors. A recent recovery expedition attempted to sample fragments of the CNEOS 2014-01-08 bolide retrieved roughly 850 magnetic particles, some of which have unknown origins. Among those identified was a new group of highly differentiated materials consisting of close to 160 specimens categorized as “D-type” particles.</div><div>We studied the D-type particles with the goal of comparing their various morphological features to their chemical compositional groupings. Four morphological classifications are considered: “scoriaceous,” “stubby,” “blocky,” and “vesicular.” The specimens from the “scoriaceous” and “stubby” groups exhibit a spinel/magnetite rim in at least one instance, characteristic of atmospheric entry, and textures indicative of quenching such as dendritic microcrystalline structures, suggesting that a subset of specimens from these groups are candidates for materials of extraterrestrial origin. The particles exhibiting “blocky” and “vesicular” textures are likely to be terrestrial in origin, with no obvious quench features or signs of ablation. The D-type particles identified and characterized in this study have a spectrum of terrestrial and probable extraterrestrial origins.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122627"},"PeriodicalIF":3.6,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143062004","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":"Metal enrichment in the Cambrian black shale: Evidence from pyrite overgrowth and NanoSIMS sulfur isotopes","authors":"Shixiang Li ,&nbsp;Zhilin Wang ,&nbsp;Youwei Chen ,&nbsp;Daniel D. Gregory ,&nbsp;Erke Peng ,&nbsp;Deru Xu ,&nbsp;Yufei Wang ,&nbsp;Shaohao Zou ,&nbsp;Huan Li","doi":"10.1016/j.chemgeo.2025.122623","DOIUrl":"10.1016/j.chemgeo.2025.122623","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Lower Cambrian black shale has attracted much attention due to its role in elucidating the chemical evolution and sulfur cycles of the global ocean, as well as its economic significance as a source of phosphate, barite, and high-grade Ni&lt;img&gt;Mo polymetallic sulfide ores. However, the occurrence of abnormally high metal accumulation within thin ore layers across extensive areas remains contentious. Pyrite, that occurs as framboids or fine- to coarse-grained euhedral-subhedral crystals, is a ubiquitous sulfide found in both host black shale and metalliferous ore horizons. This study delineates a three-stage growth of pyrite within the Chuanyanping and Sancha Ni&lt;img&gt;Mo sulfide layers in western Hunan Province, South China, based on the micro-textures, chemical compositions, and sulfur isotopes. The earliest pyrite (PyI) appears as framboids (3–7 μm) or as small euhedral-subhedral grains (&lt;20 μm). It exhibits a depletion in trace elements and negative δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;V-CDT&lt;/sub&gt; values spanning from −34.2 to −17.4 ‰, indicating the formation in a euxinic water column via microbial sulfate reduction (MSR) during syngenesis. The later pyrite (PyII), which is associated with gersdorffite, appears as thin overgrowth rings encircling PyI or euhedral to subhedral crystals displaying complex oscillatory and lacy zoning patterns. It is characterized by elevated Cu (up to 5.84 wt%), Ni (up to 3.56 wt%), and As (up to 1.70 wt%) concentrations and highly variable sulfur isotopic compositions. The overgrowth rings exhibit δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;V-CDT&lt;/sub&gt; values spanning from −9.6 to 12.4 ‰, while the euhedral to subhedral crystals have inhomogeneous sulfur isotopic signatures, with the cores enriched in heavy sulfur (31.7 to 33.7 ‰ δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;V-CDT&lt;/sub&gt;) and the rims marked by comparatively light sulfur (−7.1 to 7.2 ‰ δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;V-CDT&lt;/sub&gt;). This isotopic variation reflects the joint effect of thermochemical sulfate reduction (TSR) and hydrothermal-derived sulfur. Specifically, the initial influx of high-temperature hydrothermal fluids produced minimal isotopic fractionation between sulfide and seawater sulfate via TSR, facilitating the formation of heavy‑sulfur PyII. Subsequently, hydrothermal sulfur became the dominant source for the deposition of light‑sulfur PyII, with a minor contribution from dissolution of PyI. Given the close association of organic matter with ores, hydrocarbons may significantly facilitate metal transport via organometallic complexing, with Ni primarily derived from hydrothermal fluids and Mo from seawater as indicated by previous Ni and Mo isotopic analyses. The barren pyrite (PyIII), which presents as overgrowth matrix cementing early PyI and PyII, has positive δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;V-CDT&lt;/sub&gt; values (15.5 to 34.6 ‰), suggesting formation via MSR in closed, sulfate-limited environment, most likely following deep burial. Collectively, the chemical and sulfur isotopic evidence, coupled with petrogr","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"676 ","pages":"Article 122623"},"PeriodicalIF":3.6,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021234","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":"BrGDGTs sources in eastern China marginal seas and their constraints on seawater temperature reconstruction","authors":"Fengmin Pan ,&nbsp;Huamao Yuan ,&nbsp;Jinming Song ,&nbsp;Xuegang Li ,&nbsp;Liqin Duan ,&nbsp;Yueqi Wang","doi":"10.1016/j.chemgeo.2025.122624","DOIUrl":"10.1016/j.chemgeo.2025.122624","url":null,"abstract":"<div><div>Branched glycerol dialkyl glycerol tetraethers (brGDGTs) serve as promising proxies for paleotemperature in both terrestrial and marine settings. However, their application in reconstructing seawater temperature in marginal seas is complicated by uncertainties arising from mixed land and marine sources, isomer effect, and variability in depth and seasonality. To explore these factors, we examined brGDGTs in surface sediments from the eastern China marginal seas (ECMS) and reanalyzed previously published brGDGT data from the ECMS and Chinese soils. Using a three-end-member mixing model based on source indicators of ∑IIIa/IIa and #Rings_tetra, we found that the autochthonous fraction of sedimentary brGDGTs accounted for 59.6 ± 14.4 %, 47.8 ± 21.7 %, and 33.2 ± 17.7 % in the Bohai Sea (BS), Yellow Sea (YS) and East China Sea (ECS), respectively. For temperature reconstruction, the relationship with annual mean surface seawater temperature (SST) was better captured by the methylation index of 6-methyl brGDGTs (MBT’_6Me) than by that of 5-methyl brGDGTs (MBT’_5Me). This is due to the higher abundance of 6-methyl brGDGT producers compared to those producing 5-methyl isomers, resulting in the predominance of 6-methyl brGDGTs and thus a better response of MBT’_6Me to SST changes. Additionally, brGDGTs in the ECMS were shown to reflect the annual mean rather than seasonal SST, as SST remains well above freezing throughout the year and supports continuous brGDGT production. In contrast to deep oceans, production in deep waters or sediments appears to have a negligible effect on sedimentary brGDGTs in the ECMS, as brGDGT-based indexes responded better to SST than to bottom seawater temperature (BWT). Furthermore, the methylation index of 6-methyl brGDGTs containing two rings (defined as MBT’_6Me-c) emerged as a robust potential indicator for annual mean SST in the ECMS, showing improved correlation with SST and reduced residual mean error (RMSE) compared to MBT’_6Me. The components (Ic, IIc’, and IIIc’) used to establish MBT’_6Me-c are mainly derived from in-situ production rather than terrestrial input. Therefore, the index was less influenced by terrestrial inputs and is a reliable tool for SST reconstruction in the China marginal seas.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"676 ","pages":"Article 122624"},"PeriodicalIF":3.6,"publicationDate":"2025-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021235","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":"Sulfate concentration and redox state control the pyrite formation and sulfur cycle in a T-OAE lake, Sichuan Basin, China","authors":"Xiang Qin ,&nbsp;Jian Cao ,&nbsp;Bing Luo ,&nbsp;Jinchao Liu ,&nbsp;Guang Hu","doi":"10.1016/j.chemgeo.2025.122622","DOIUrl":"10.1016/j.chemgeo.2025.122622","url":null,"abstract":"<div><div>The sedimentary pyrite formation and sulfur cycle have been extensively investigated, especially in marine systems. The Early Jurassic Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma) was marked by significant shifts in Earth’s climate and paleoceanographic conditions, and its global carbon cycle perturbations have been extensively studied. However, constraints on terrestrial sulfur cycling within the Earth system during this period are underexplored. To fill the knowledge gap, this study presents new constraints on the Da'anzhai Member of the Sichuan Basin in South China, a terrestrial record of the T-OAE, to explore the sedimentary pyrite formation and sulfur cycle in ancient lake environments. Results show that pyrite sulfur contents (S_pyr) of most samples are &lt;0.1 wt.%, and the stable sulfur isotopic compositions of pyrite (δ³⁴S_pyr) change from a low negative value of −11.5‰ to a positive value of 20.3‰ before the T-OAE. This variation was interpreted to be influenced by the oxygenated water and a relatively high sedimentation rate; the former confined microbial sulfate reduction (MSR) to the porewater space, while the latter reduced the efficiency of diffusive resupply of porewater sulfate. The T-OAE was associated with a marked increase in S_pyr values (mean = 0.52 wt%), and δ³⁴S_pyr values fluctuated by ∼10‰ (5.4‰–15.6‰), consistent with higher sulfate reduction rates driven by increased organic carbon contents and sulfate concentration ([SO₄²⁻]) during this stage. After the T-OAE, the S_pyr contents were &lt; 0.1 wt% and δ³⁴S_pyr values were ∼10‰. The δ³⁴S_pyr values correlated well with the salinity proxy Sr/Ba ratios, suggesting that sulfate levels on system openness were likely the dominant way controlling δ³⁴S_pyr. Compared with the marine systems, relatively lower sulfate concentrations are the main limiting factor on pyrite formation in freshwater lacustrine systems, and the sedimentation rate and sulfate contents may be the main factors responsible for the higher δ³⁴S_pyr values in lacustrine systems. During the T-OAE, elevated atmospheric <em>p</em>CO₂ and global climate warming triggered a series of chemical changes in lake systems (particularly in [O₂] levels), which in turn significantly disrupted lacustrine sulfur cycling. This represents a notable terrestrial response to the T-OAE. This study highlights the dynamic control of sedimentary environmental factors on lacustrine sulfur cycling and the broader impact of the T-OAE on lacustrine environments by focusing on the first documented case of a large lake system.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"676 ","pages":"Article 122622"},"PeriodicalIF":3.6,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142988038","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}