Chemical Geology最新文献

{"title":"Corrigendum to “Chemical variability in volcanic gas plumes and fumaroles along the East African Rift System: New insights from the Western Branch” [Chemical Geology 596 (2022) 120811]","authors":"G. Boudoire , G. Giuffrida , M. Liuzzo , N. Bobrowski , S. Calabrese , J. Kuhn , J.-C. Kazadi Mwepu , F. Grassa , S. Caliro , A.L. Rizzo , F. Italiano , M. Yalire , K. Karume , A. Muhindo Syavulisembo , D. Tedesco","doi":"10.1016/j.chemgeo.2025.122643","DOIUrl":"10.1016/j.chemgeo.2025.122643","url":null,"abstract":"","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122643"},"PeriodicalIF":3.6,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102402","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":"Water-air-CO2-flux changes after damming rivers loaded with suspended basaltic particles","authors":"T. Linke ,&nbsp;E.S. Eiriksdottir ,&nbsp;G.N. Petersen ,&nbsp;S.R. Gislason","doi":"10.1016/j.chemgeo.2025.122662","DOIUrl":"10.1016/j.chemgeo.2025.122662","url":null,"abstract":"<div><div>Contributions of CO₂ emissions from reservoirs to the atmosphere are continuously increasing with rising energy demand. Therefore, it is important to quantify the emissions and define the rate determining mechanism of CO₂ fluxes in man-made reservoirs. Here we present results from two reservoirs in Iceland over a total time span of 16 years. The partial pressure of CO₂ within the Hálslón reservoir, fed by glacier meltwater loaded with suspended basaltic particles, was considerably less than the CO₂ pressure of the atmosphere during the years 2008–2013. The specific CO₂ uptake from the atmosphere into Hálslón was estimated at 121 ± 67.9 g_CO2 m⁻² yr during the 6 months ice-free period or 5000 t annually. The uptake rate was governed by the CO₂ gradient across the water-air-interphase and windspeed but less by temperature. However, temperature will affect water-rock interactions and sub-zero temperature can result in ice cover, terminating water-air interactions. Atmospheric CO₂ concentration dictates the maximum upper limit of the CO₂ influx rate at fixed wind speed.</div><div>The downstream mixing of Hálslón reservoir water with the CO₂ emitting Lagarfljót reservoir lowered the CO₂ emissions from Lagarfljót from 5335 t CO₂ yr⁻¹ to 1670 t CO₂ yr⁻¹ after the damming. This study shows that dissolution of basalt in glacier melt waters leads to direct CO₂ uptake from the atmosphere, which can potentially be utilised for future carbon removal from the atmosphere.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122662"},"PeriodicalIF":3.6,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103219","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":"Volcanism-induced generation of high-silica A-type granite: A snapshot from Yandangshan caldera, southeastern China","authors":"Jing-Yuan Chen ,&nbsp;Jin-Hui Yang ,&nbsp;Ji-Heng Zhang ,&nbsp;Yu-Sheng Zhu","doi":"10.1016/j.chemgeo.2025.122641","DOIUrl":"10.1016/j.chemgeo.2025.122641","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Silicic magmatism was extensively developed in the coastal regions of southeast China. The abundant volcanic fields and granitic plutons in this region provide exceptional opportunities to investigate upper crustal magmatic processes and their evolution. We investigate the petrogenetic connections among alkali feldspar granites (AFGs), porphyritic enclaves, porphyritic rocks (including porphyritic monzonites and porphyritic syenites), and rhyolites from the Yandangshan caldera and surrounding area using zircon U&lt;img&gt;Pb dating, trace elements, Hf isotopic ratios, and bulk-rock geochemistry. Zircon U&lt;img&gt;Pb dating reveals that the plutonic and volcanic rocks of the Yandangshan caldera crystallized concurrently (98–102 Ma), with consistent Hf isotopic compositions and trace element trends in low-U zircons further supporting that lithological variations within the caldera result from crystal-melt segregation. The porphyritic rocks and enclaves are rich in Sr and Ba, display high Zr/Hf ratios, and show positive to weakly negative Eu anomalies, suggesting they represent cumulate residues from crystal-melt segregation. The AFGs and rhyolites are enriched in Rb but exhibit depletions in Sr, Ba, and Eu, characterized by low Eu/Eu&lt;sup&gt;⁎&lt;/sup&gt; and high Rb/Sr ratios. Both units are interpreted as evolved silicic melts extracted from a crystal-rich magma reservoir. Compared to the erupted rhyolites, the AFGs display higher silica content and Rb/Sr ratios, along with lower Eu/Eu&lt;sup&gt;⁎&lt;/sup&gt; ratios. Moreover, high-U zircons are exclusively found in the AFGs and exhibit the most evolved trace element signatures within the entire suite, characterized by elevated Hf and U concentrations, as well as low Eu/Eu&lt;sup&gt;⁎&lt;/sup&gt; ratios. These characteristics indicate that the AFGs, which exhibit A-type features, are more evolved than the rhyolites, reflecting extended in-situ crystallization and differentiation following the eruption of the rhyolitic magmas. We propose that the magma responsible for the AFGs originated from the underlying feldspar-rich mush, following the rhyolite eruption. These melts then underwent in-situ crystallization and melt differentiation, leading to the formation of A-type granites that are more evolved than the rhyolites. By comparing the geochemical characteristics of contemporaneous silicic plutonic and volcanic rocks from southeastern China, we demonstrate that large volumes of high-silica granitic magma accumulated after silicic melt eruptions. Our study further reveals that the compositional diversity of A-type granites primarily results from crystal-melt segregation processes rather than distinct magma sources, emphasizing the importance of shallow crustal differentiation in granite formation. Recognizing these processes enhances our understanding of how similar geological mechanisms generate diverse granite compositions across various tectonic environments, ultimately deepening our insight into the evolution of silicic magmas w","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122641"},"PeriodicalIF":3.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143061996","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":"Seawater temperatures during the early to middle Ediacaran: Phosphate oxygen isotope records","authors":"Haifeng Fan ,&nbsp;Zhigang Chen ,&nbsp;Fang Zhang ,&nbsp;Chuanwei Zhu ,&nbsp;Shengjiang Du ,&nbsp;Yuxu Zhang ,&nbsp;Hanjie Wen ,&nbsp;Danish Khan ,&nbsp;Thomas J. Algeo","doi":"10.1016/j.chemgeo.2025.122642","DOIUrl":"10.1016/j.chemgeo.2025.122642","url":null,"abstract":"<div><div>Early multicellular eukaryotes are hypothesized to have first evolved in deep-water (i.e., subphotic) environments with a narrow temperature range and low oxygen levels (pO₂). However, seawater paleotemperature estimates for the Ediacaran Period remain poorly known. To address this issue, we measured the oxygen isotopic compositions of phosphate (δ¹⁸O_P) in fine-grained marine siliciclastic sedimentary rocks from two slope sections of the Doushantuo Formation (∼635–551 Ma) in the Nanhua Basin, South China. The bulk δ¹⁸O_P values (∼19–26 ‰) found in early-middle Ediacaran phosphatic marine shales represent the oldest known records of modern seawater-like δ¹⁸O_P values. These values are inferred to record original seawater signatures and suggest that subtropical surface temperatures had a modern-like range of 15–30 °C. Based on these estimates, we propose that the extreme greenhouse conditions of the earliest Ediacaran following the Marinoan Ice Age were of quite short duration (&lt;∼0.1 Myr). Subsequently, the oldest known metazoan fossil assemblage, the Lantian Biota (∼602 Ma), thrived in a deep-water environment characterized by low oxygen levels and a relatively cold, narrow temperature range (∼7–8 ± 2 °C). In contrast, the slightly younger Weng'an Biota (∼587 Ma) inhabited shallower waters with higher oxygen levels and a broader temperature range (16–30 °C). Finally, our evidence shows that the oxygen isotopic composition of phosphate in fine-grained siliciclastic marine sedimentary rocks can serve as a valuable proxy for reconstructing the temperature of ancient seawater. Such paleotemperature information, combined with oxygen concentration data, is crucial for understanding the origin and evolution of early animal life.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122642"},"PeriodicalIF":3.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103286","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":"Constraining sulfate sources and its implications on atmospheric pCO2 in Arid Regions: Evidence from the Tarim Basin","authors":"Guo-Dong Jia ,&nbsp;Jun Zhong ,&nbsp;Si-Liang Li ,&nbsp;Sen Xu ,&nbsp;Han Luo ,&nbsp;Cong-Qiang Liu","doi":"10.1016/j.chemgeo.2025.122644","DOIUrl":"10.1016/j.chemgeo.2025.122644","url":null,"abstract":"<div><div>The pyrite oxidation-driven weathering has important implications for carbon cycle over geological timescales. Despite extensive researche using SO₄²⁻ as information carriers across diverse climatic zones, studies in arid regions remain limited, underscoring the urgency for research in these areas. This study collected and analyzed water samples from rivers and lakes in the Tarim Basin, one of the driest regions worldwide and China's largest endorheic basin. The samples were analyzed for physical, chemical and isotopic parameters e.g., water temperature, pH, electrical conductivity, concentrations of major anions and cations, and isotopic compositions of SO₄²⁻ (δ³⁴S_SO4 and δ¹⁸O_SO4). The results reveal pronounced spatial variations in δ³⁴S_SO4 and δ¹⁸O_SO4 values, which ranged from −2.4 to +14.8 ‰ and + 0.6 to +16.8 ‰, respectively. Post-simulation with a Monte Carlo inversion model suggests that carbonates (i.e., calcite and dolomite) weathering, evaporites (i.e., gypsum and halite) dissolution and pyrite (i.e., FeS₂) oxidation predominantly control water chemical compositions, contributing ∼72.9 % to 97.7 % (median 91.8 %) to dissolved solutes. The findings indicate that pyrite oxidation and gypsum dissolution are the primary sources of SO₄²⁻, accounting for 32.7 % to 80.9 % (median 55.9 %) and 13.4 % to 66.5 % (median 39.7 %), respectively. The estimated SO₄²⁻ fluxes in the study area amount to 0.108 Tmol/year, representing ∼3.2 % of the global SO₄²⁻ flux, underscoring the significance of SO₄²⁻ in arid regions for global sulfur cycle. Furthermore, the saturation indices of calcite, aragonite and dolomite are all greater than 0, indicating carbonate precipitation occurring in current environment. The high evaporation under arid conditions and wide distribution of evaporites (e.g., gypsum) in the study area can promote carbonate precipitation, enhancing the carbon sink capacity of rock weathering. This research provides critical data for elucidating the role of pyrite oxidation-driven weathering and evaporite dissolution on carbonate budget in arid regions influenced by the Westerlies, offering novel empirical evidence on continental weathering.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122644"},"PeriodicalIF":3.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143061995","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":"Could rear-arc volcanism be driven by mantle instability?","authors":"Alex C. Davidson ,&nbsp;Chris W. Firth ,&nbsp;Simon P. Turner ,&nbsp;Shane J. Cronin","doi":"10.1016/j.chemgeo.2025.122647","DOIUrl":"10.1016/j.chemgeo.2025.122647","url":null,"abstract":"<div><div>The drivers of rear-arc volcanism remain poorly understood. Taranaki volcano, in the North Island of New Zealand, offers an ideal location to investigate the causes of such volcanism. Taranaki erupts hydrous, amphibole-bearing, high-K calc-alkaline magmas with trace element and Sr-Nd-O isotope compositions characteristic of arc-like fluid-flux melting regimes. Its location 150 km behind the arc front and &gt;250 km above the subducting slab, however, has led some geodynamic models to consider convective removal of lithosphere as an alternative driver of magmatic activity. Unlike typical arc magmas, late Pleistocene-Holocene eruptives from Taranaki preserve up to 40 % excesses of ²³⁰Th over ²³⁸U. These cannot be explained by crystal fractionation or assimilation processes and are unlikely to be imparted by sediment melting at the slab interface. We present a geochemical case to hypothesise that Taranaki magmas result from mantle instability associated with convective removal of lithosphere. In this model magmas represent variable mixtures of asthenospheric melts resulting from decompression melting with melts from downwelling lithosphere that have arc-like trace element signatures inherited from past (Miocene) metasomatism. Calculated upwelling rates for the asthenospheric component are similar to surface uplift and the timescales from melting to eruption must be less than 5 kyr, similar to eruptive periodicity. High-K rear-arc magmas with ²³⁰Th-excesses are common globally (e.g., Stromboli, Sangeang Api, Rishiri) suggesting mantle instability could be a more common scenario to explain rear-arc volcanism.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122647"},"PeriodicalIF":3.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103218","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":"Interaction between dissolution and precipitation during olivine carbonation: Implications for CO2 mineralization","authors":"U.C. Iyare ,&nbsp;L.O. Boampong ,&nbsp;W. Li ,&nbsp;C.W. Neil ,&nbsp;L.P. Frash ,&nbsp;J.W. Carey ,&nbsp;R. Feng ,&nbsp;Emmanuel Detournay ,&nbsp;H.S. Viswanathan","doi":"10.1016/j.chemgeo.2025.122645","DOIUrl":"10.1016/j.chemgeo.2025.122645","url":null,"abstract":"<div><div>Large-scale carbonation of olivine is considered a promising approach for in situ mineral carbonation, offering a permanent and stable method for CO₂ storage. A critical aspect of this process is understanding how dissolution and precipitation interact, as this could drive fracturing and enhance further reactions. In this study, we conducted carbonation experiments on olivine using CO₂-saturated aqueous solutions of NaHCO₃ and NaCl. Two experimental setups were used: one representing an open geochemical system and the other a closed system, corresponding to reaction-limited and flow-limited scenarios, respectively. Post-reaction textural analysis using scanning electron microscopy (SEM) revealed surface coatings of reaction products in the closed system, while etch pits and etch channels were prevalent in the open system. Although no direct evidence of reaction-driven fracturing was observed, etch pits and etch channels may serve as initiation points for subcritical crack formation and growth, potentially maintaining permeability and exposing new unreacted surfaces. Using linear elastic fracture mechanics (LEFM) model, we estimate that microcracks could propagate under a pressure of 0.1 GPa if reaction products accumulate within the etch pits. Our findings offer new insights into the mechanisms governing olivine carbonation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122645"},"PeriodicalIF":3.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103285","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":"Triple oxygen isotopic fractionation in CO2-CaCO3-H2O system during CO2-H2O exchange, carbonate precipitation, and acid digestion","authors":"Pallab Roy ,&nbsp;Amzad H. Laskar ,&nbsp;Sangbaran Ghoshmaulik ,&nbsp;S.K. Bhattacharya ,&nbsp;Ravi Rangarajan ,&nbsp;Mao-Chang Liang","doi":"10.1016/j.chemgeo.2025.122634","DOIUrl":"10.1016/j.chemgeo.2025.122634","url":null,"abstract":"<div><div>The triple oxygen isotope composition of carbonate deposits provides a proxy for understanding changes in the past hydrological cycle. The reconstruction relies on knowing the temperature dependence of ¹⁷O and ¹⁸O fractionation factors, ¹⁷α and ¹⁸α, and θ = ln¹⁷α/ln¹⁸α, associated with the carbonate precipitation which can take place at various temperatures in nature. To determine these parameters, we synthesized carbonates at temperatures ranging from 10 °C to ∼50 °C from various substrate waters. The oxygen isotope composition of the waters was obtained using the CO₂-H₂O exchange method at 25 °C and the composition of the carbonate was derived from that of CO₂ generated by reacting the carbonate with phosphoric acid at 25 °C. In both cases, the δ¹⁷O and δ¹⁸O values of the CO₂ were measured. To convert the δ¹⁷O and δ¹⁸O values of the water equilibrated CO₂ to the corresponding values of the water phase, a prior knowledge of the ¹⁷O and ¹⁸O fractionations during the CO₂-H₂O exchange is necessary. Liang et al. (2023) previously determined these fractionations by equilibrating CO₂ with VSMOW2 (δ¹⁷O and δ¹⁸O = 0 ‰) at 25 °C and measuring the resulting isotope values. Building on this work, we present rescaled and refined fractionation values: ¹⁷α = 1.02135 ± 0.00001, ¹⁸α = 1.04122 ± 0.00002, and θ = 0.5230 ± 0.0001. With this knowledge, we calculated the values of θ relating the CO₂ derived from acid–reacted carbonates (precipitated at different temperatures) and the parent water (θ_CO2(carb)-w). The θ_CO2(carb)-w (mean ± SE) at 10 °C, 25 °C, and 35 °C are 0.5232 ± 0.0001, 0.5233 ± 0.0003, and 0.5229 ± 0.0002, respectively. We also did these experiments at 50 °C. However, the θ_CO2(carb)-w (0.5129 ± 0.0004) at 50 °C was likely affected by kinetic isotope fractionation. We also determined the acid digestion fractionations at various temperatures ranging from 0 °C to 110 °C. We did not observe significant temperature dependence in Δ′¹⁷O values of the acid digested CO₂ across the above temperature range, the triple oxygen isotope slope (relating δ’¹⁷O and δ’¹⁸O) is 0.5220 ± 0.0002.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122634"},"PeriodicalIF":3.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103217","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":"Comparisons of pretreatment extraction methods for tree-ring radiocarbon analysis","authors":"Jingdi Qin ,&nbsp;Zhenchuan Niu ,&nbsp;Weijian Zhou ,&nbsp;Yunfei Huang ,&nbsp;Xue Feng ,&nbsp;Dan Liang ,&nbsp;Guowei Wang ,&nbsp;Xuefeng Lu ,&nbsp;Yu Huang ,&nbsp;Hong Wang","doi":"10.1016/j.chemgeo.2025.122648","DOIUrl":"10.1016/j.chemgeo.2025.122648","url":null,"abstract":"<div><div>An appropriate method for tree-ring pretreatment is essential to ensure the reliability of ¹⁴C data. This study compared three pretreatment methods for tree rings: acid-base-acid-bleaching (ABA-B), Jayme-Wise and an improved method proposed in this research. The improved method utilizes an ultrasonic bath instead of Soxhlet extraction in the Jayme-Wise method. We assessed the ¹⁴C results of the three methods using subfossil tree-ring samples from the Sixth International Radiocarbon Intercomparison and contemporary tree-ring samples from Shangdianzi. The ¹⁴C results showed that both the improved and the Jayme-Wise methods were effective for extracting α-cellulose from subfossil and modern tree-ring samples. The ABA-B method was sufficient only for subfossil wood, while unstable for the modern tree-ring samples when the heartwood-sapwood transition was presence. The Fourier-Transform Infrared spectroscopy results indicated that the purity of α-cellulose extracted by the improved method was similar to that of pure α-cellulose. In comparison to the Jayme-Wise method, the improved method reduced the extraction time and the amount of organic solvent, while increased batch processing capacity.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"678 ","pages":"Article 122648"},"PeriodicalIF":3.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143163785","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":"Microbial sulfate reduction regulated by relative sea level change in a Pleistocene – Holocene sedimentary record: Insights from Loch Duart, Scotland, UK","authors":"L.G. Podrecca ,&nbsp;A.L. Masterson ,&nbsp;M.T. Hurtgen ,&nbsp;J. Taylor ,&nbsp;J.M. Lloyd ,&nbsp;D. Selby ,&nbsp;B.B. Sageman","doi":"10.1016/j.chemgeo.2025.122633","DOIUrl":"10.1016/j.chemgeo.2025.122633","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A Pleistocene–Holocene-aged sediment core recovered near Loch Duart, located in the coastal Assynt region of NW Scotland, UK, provides new insight into the relationship between the sulfur isotope composition of iron sulfides (pyrite) and organic sulfur under rapidly changing environmental conditions. Since the Late Glacial period, shifts in local marine connectivity at Loch Duart have been driven by the competition between two fundamental Earth surface processes: eustatic sea level rise due to post-glacial meltwater contributions since the Last Glacial Maximum and relative sea level (RSL) fall associated with glacial isostatic rebound. These processes, imprinted on the sedimentary record, have been evaluated via lithology, microfossil assemblages, elemental analysis, and isotopic measurements. Over the last 17 kyr, Loch Duart has transitioned from (1) marine conditions, when eustatic rise due to deglaciation exceeded glacial isostatic rebound, to (2) non-marine conditions, where land uplift caused by isostatic rebound exceeded eustatic rise, to (3) marine conditions, as the eustatic contribution outpaced isostatic rebound, followed by (4) brackish-water conditions, as the eustatic contribution reduced while glacial isostatic uplift continued, with marine inundation limited to part of the tidal cycle at the present day.&lt;/div&gt;&lt;div&gt;Here, we evaluate marked perturbations in the local sulfur (S) cycle related to the aforementioned environmental changes. The marine interval coincides with relatively stable and low δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;sulfide&lt;/sub&gt; values (average ∼ −27.2 ‰), the non-marine interval records an abrupt positive δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;sulfide&lt;/sub&gt; excursion of over 30 ‰ (average ∼ 9 ‰), and the brackish interval preserves intermediate values (average ∼ −16.2 ‰). The δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;org&lt;/sub&gt; values shift sympathetically with δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;sulfide&lt;/sub&gt;, although the magnitude of δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;org&lt;/sub&gt; change is nominal by comparison, particularly during the transition from freshwater to marine facies. As expected, marine and brackish sections preserve higher δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;org&lt;/sub&gt; values than coeval δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;sulfide&lt;/sub&gt;. Interestingly, this relationship is reversed in the freshwater facies, where sulfides are &lt;sup&gt;34&lt;/sup&gt;S-enriched relative to organic S by as much as 20 ‰, suggesting that RSL modulates the isotopic composition of non-pyrite phases in the bulk S pool. We hypothesize that this inverse relationship (δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;org&lt;/sub&gt; &lt; δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;sulfide&lt;/sub&gt;) may arise from a spatial decoupling of pyrite and organic S formation within the water column and/or sediments in a system with low sulfate concentrations. Evaluating shifts in the local S-cycle associated with RSL changes allows for a novel comparison between S and osmium isotope records, demonstrating that these proxies may have joint applications for paleoenvironmental investigations in shallow coastal systems. We","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"677 ","pages":"Article 122633"},"PeriodicalIF":3.6,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143061998","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}