Chemical Geology最新文献

{"title":"Oceanic serpentinisation in the Samail ophiolites: evidence from trace elements and O and B isotopes","authors":"Coralie Vesin ,&nbsp;Daniela Rubatto ,&nbsp;Marguerite Godard","doi":"10.1016/j.chemgeo.2025.122943","DOIUrl":"10.1016/j.chemgeo.2025.122943","url":null,"abstract":"<div><div>Oceanic serpentinisation represents a major link between the hydrosphere and the lithosphere, whereby aqueous fluids hydrothermally alter mantle rocks. The study of former oceanic lithosphere, now tectonically emplaced on land, can serve as a useful analogue to modern processes. In this study, we present the geochemical composition of serpentinised peridotites from the southern Samail ophiolites, a fast-spreading ridge axis active in the Neo-Tethys, in the Sumail and Wadi Tayin massifs. The combination of the fluid-mobile element (FME) composition, as well as O, B and Sr isotopes, of serpentine is utilised to decipher the source of the serpentinising fluid, which would constrain the loci of serpentinisation (i.e., oceanic domain, during obduction, after emplacement). The in situ analysis of the serpentine revealed FME contents ranging from 0.2 to 27.7 μg g⁻¹ B, 0.1–10.7 μg g⁻¹ Sr, and 600–1800 μg g⁻¹ Cl; high variability in δ¹⁸O values (+1.3 to +8.1 ‰); and δ¹¹B ranging from +33 to +41 ‰ in one sample, and between +2 and +47 ‰ for two others. A comparison of the data with the geochemical characteristics of potential sources of the serpentinising fluid (e.g., seawater, hydrothermally-altered fluid, subducted-slab-derived fluid, meteoric water) has failed to provide any evidence indicative of serpentinisation with subducted slab-derived fluid or meteoric water. Conversely, the geochemical characteristics of serpentine indicate that serpentinisation most likely occurred on the ocean floor in proximity to the spreading ridge axis, subsequent to reaction with seawater and hydrothermally-altered fluid following interaction with the overlying oceanic crust. Furthermore, the range of measured δ¹¹B in certain samples can be modelled on the basis of a two-step serpentinisation history in a closed system, at relatively low temperatures, calculated from the δ¹⁸O values (from 115 to 250 °C). This study demonstrates the efficacy of combining multiple in situ geochemical tools to trace the history of serpentinisation, particularly in obducted ophiolite where hydrothermal alteration may could have occurred on multiple occasions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122943"},"PeriodicalIF":3.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144523146","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":"Multistage melt–rock interaction and redox evolution during chromitite formation in the Bulqiza ophiolite (Albania): Constraints from Mӧssbauer spectroscopy, FeMg isotopes and chromitite geochemistry","authors":"Fahui Xiong ,&nbsp;Basem Zoheir ,&nbsp;Joseph Meert ,&nbsp;Xiangzhen Xu ,&nbsp;Tian Qiu ,&nbsp;Xuxuan Ma ,&nbsp;Ibrahim Milushi ,&nbsp;Jingsui Yang","doi":"10.1016/j.chemgeo.2025.122948","DOIUrl":"10.1016/j.chemgeo.2025.122948","url":null,"abstract":"<div><div>Fe<img>Mg isotopes integrated with Fe³⁺/∑Fe data provide robust constraints on the redox state of the oceanic lithospheric mantle, as both are sensitive to oxygen fugacity and mineral–melt equilibria. Fe isotopes track valence changes, while Mg isotopes reflect melt–rock interaction during partial melting and metasomatism. Applied to ophiolites, these proxies offer detailed insights into mantle melting, melt transport, and redox evolution. The Bulqiza ophiolite massif in Albania, a major chromite-bearing ultramafic complex in the Balkans, presents an ideal natural laboratory to investigate mantle processes during the evolution of the Mesozoic Tethys Ocean. This study integrates mineral chemistry, LA-ICP-MS trace element data, Mössbauer spectroscopy, and Fe and Mg isotope analyses to reconstruct mantle compositional changes and the genesis of ultramafic assemblages.</div><div>Harzburgites and dunites from Bulqiza show high forsterite (Fo_91–97) and Ni contents indicative of subsolidus equilibration between olivine and magnesiochromite. Two partial melting stages are identified: an initial ∼25 % melting forming harzburgite, followed by ∼30 % melting producing dunite and chromitite. Variations in spinel Cr# [100Cr/(Cr + Al + Fe³⁺)] and oxygen fugacity suggest that dunite-chromitite formation resulted from focused melt–rock interaction. Chromitites are enriched in Cr₂O₃ (53–61 wt%) and display variable FeO (12–21 wt%), reflecting mantle source heterogeneity and dynamic melt extraction. Isotopic trends, including a negative correlation between δ²⁶Mg and Cr# and a positive δ⁵⁶Fe-δ²⁶Mg relationship, indicate progressive melt–rock interaction and oxidation. Mössbauer spectroscopy reveals Fe³⁺/∑Fe ratios of 0.075–0.253 in magnesiochromite, documenting variable redox conditions during formation. Together, these data support a multistage genesis involving high-degree melting, melt percolation, and redox evolution within an upwelling asthenospheric mantle, consistent with localized mantle flow beneath a slow-spreading ridge or transform margin rather than a subduction-related setting.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122948"},"PeriodicalIF":3.6,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144523200","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":"Testing the robustness of the carbonate uranium isotope proxy: Evidence from a partial dissolution study","authors":"Jennifer L. Morford ,&nbsp;Maya Elrick ,&nbsp;Stephen Romaniello ,&nbsp;Thomas J. Algeo ,&nbsp;Geoffrey J. Gilleaudeau ,&nbsp;Tyler Goepfert ,&nbsp;Elvis Wilson ,&nbsp;Kate Meyers ,&nbsp;Lena Berry ,&nbsp;Elizabeth Driscoll ,&nbsp;Samuel Patzkowsky ,&nbsp;Carol de Wet","doi":"10.1016/j.chemgeo.2025.122949","DOIUrl":"10.1016/j.chemgeo.2025.122949","url":null,"abstract":"<div><div>Uranium isotopes in carbonates have been used extensively to determine past extent of global oceanic anoxia. However, local spatial and temporal variations in reducing conditions and/or subsequent diagenesis can result in isotopic variations of U (²³⁸U/²³⁵U) that complicate the extrapolation of U isotopic variation in ancient carbonate sediments to global estimates of ocean anoxia. The fidelity of the U isotopic signal can also be impacted by the co-dissolution of U-containing non‑carbonate phases, such as aluminosilicates, manganese-oxide coatings, and iron-containing minerals, that might introduce an independent U isotopic signal that alters or biases the global ocean-derived δ²³⁸U value recorded by the carbonate component. Leaching protocols and/or precleaning steps have been introduced to avoid the dissolution of these non‑carbonate phases and extract the primary carbonate signal; however, these methods can lengthen the sample preparation time while also potentially introducing contamination. The work presented here suggests that a one-step partial dissolution procedure using excess 0.08 M nitric acid or 2 M acetic acid results in Ca, Mg, and Mn concentrations that are similar to concentrations determined from total dissolution methods. This approach precludes the complete dissolution of Sr, U, Fe, and Al (and occasionally Mg and Mn) in insoluble non‑carbonate phases. When targeting the dissolution of only ∼80 % of the sample, the release of Fe and Al from non‑carbonate phases is minimized. This partial dissolution approach still results in release of sufficient U to permit interpretation of past reducing conditions. Measured δ²³⁸U values are nearly invariant regardless of acid type or concentration, suggesting that the dissolution of the non‑carbonate phases does not adversely affect the U isotopic signal.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122949"},"PeriodicalIF":3.6,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144503860","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 isotopes in texturally characterized pyrite, pyrrhotite and chalcopyrite by LA-ICPMS/MS for application in sulfide bearing systems","authors":"Crystal LaFlamme ,&nbsp;Guillaume Barré ,&nbsp;Bertrand Rottier ,&nbsp;Pierre Cartigny ,&nbsp;Laure Martin ,&nbsp;Georges Beaudoin","doi":"10.1016/j.chemgeo.2025.122946","DOIUrl":"10.1016/j.chemgeo.2025.122946","url":null,"abstract":"<div><div>The demand for in situ sulfur isotopes analysis has increased in recent years. Yet, no rapid method for collecting high-resolution texturally-constrained data with minimal sample preparation time has been available. In this study, we develop an analytical technique using LA-ICP-MS/MS to rapidly acquire in situ δ³⁴S measurements in thin section-hosted sulfides by removing interferences on the ³²S and ³⁴S mass via mass shifting. This new method required the development of matrix-matched reference material for pyrite, pyrrhotite, and chalcopyrite. New reference materials have been petrographically and chemically characterized, prior to being analysed by both high-precision bulk SF₆ isotope ratio mass spectrometry (IRMS) and in situ secondary ion mass spectrometry (SIMS) S isotope methods. The new reference materials include Iberia pyrite (δ³⁴S = 8.9 ± 1.1 ‰; Δ³³S = −0.02 ± 0.06 ‰), Sullivan pyrite (δ³⁴S = 6.0 ± 0.6 ‰; Δ³³S = −0.05 ± 0.05 ‰), 1869 chalcopyrite (δ³⁴S = 9.4 ± 0.2 ‰; Δ³³S = −0.03 ± 0.04 ‰), Pierre pyrrhotite (δ³⁴S = 4.7 ± 0.2 ‰; Δ³³S = −0.01 ± 0.06 ‰), and Montpellier pyrrhotite (δ³⁴S = 3.3 ± 0.2 ‰; Δ³³S = 0.18 ± 0.07 ‰). Using the developed method, the reproducibility of the primary reference material during each analytical run approximates ±1.5–2.0 ‰. The method was tested on sulfides previously measured by SIMS, with δ³⁴S values yielded being within-error of these, confirming the robustness of the technique. We apply the method to case study pyrite-enargite chalcopyrite veins from Cerro de Pasco deposit, Peru, a porphyry related epithermal polymetallic deposit. The results yield heavier sulfur isotope signatures in trace element (TE)-enriched pyrite domains (δ³⁴S = 2.2 ± 1.1 ‰) and lighter values (δ³⁴S = −1.2 ± 1.7 ‰) in TE-depleted domains. The grain-scale S isotope variation is coupled to microstructure and TE internal zonation, and is interpreted to indicate successive pulses of condensed magmatic vapour. This study opens new analytical opportunities for rapid in situ sulfur isotope analysis in petrographically-characterized thin sections in various sulfide-bearing geological systems.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122946"},"PeriodicalIF":3.6,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144503861","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":"No oxygen isotope fractionation for subfossil cellulose during diagenesis","authors":"Junbo Ren ,&nbsp;Chenxi Xu ,&nbsp;Brian A. Schubert ,&nbsp;Heng Zhong ,&nbsp;Fangming Jin ,&nbsp;Chunchun Wang ,&nbsp;Zhengtang Guo","doi":"10.1016/j.chemgeo.2025.122945","DOIUrl":"10.1016/j.chemgeo.2025.122945","url":null,"abstract":"<div><div>Nonpermineralized, subfossil wood samples collected from within Cenozoic aged sediments are an important substrate for reconstructing paleoclimate under different levels of atmospheric carbon dioxide. Stable oxygen isotope composition (δ¹⁸O) of cellulose chemically extracted from these samples have been used to quantify seasonal to interdecadal climate; however, the effect of diagenesis on δ¹⁸O values in subfossil cellulose is not clear. In this paper, (1) we experimentally simulate the factors influencing isotopic fractionation during diagenesis, including hydrothermal conditions and fungal degradation, and demonstrate that the δ¹⁸O values of the reacted residues remained nearly unchanged after cellulose extraction; (2) analyze intra-annual δ¹⁸O variation for a subfossil wood sample exhibiting varying degrees of diagenesis, and showed that δ¹⁸O across different degradation levels follow a similar pattern (<em>p</em> &lt; 0.001). Based on these results from both laboratory experiments and analysis of subfossil samples, we conclude that the δ¹⁸O value of cellulose is not affected by diagenesis. Thus, the δ¹⁸O of cellulose can be used to reliably reconstruct palaeoclimate in deep time.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122945"},"PeriodicalIF":3.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480104","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":"Geogenic enrichment of dissolved phosphorus in a calcareous aquifer: Surface adsorption versus organic-matter mineralization","authors":"Wen Shao ,&nbsp;Yvonne Oelmann ,&nbsp;Yao Li ,&nbsp;Carsten Leven ,&nbsp;Harald Neidhardt","doi":"10.1016/j.chemgeo.2025.122944","DOIUrl":"10.1016/j.chemgeo.2025.122944","url":null,"abstract":"<div><div>Calcareous aquifers represent vital water resources and may critically influence the retention, release, and transport of phosphorus (P) within catchments. To address the limited understanding of P cycling in pristine calcareous aquifers, where both P retention and release processes remain poorly constrained, we conducted a hydrogeochemical field study in the Ammer floodplain catchment in Southwest Germany. Here, we combined groundwater hydrochemical analyses, sediment geochemistry data (e.g., P speciation by sequential extraction) and geochemical modeling to examine controls on total dissolved P (TDP) in a shallow calcareous aquifer. Inorganic orthophosphate (PO₄³⁻) dominated within the aqueous phase and correlated with reducing redox conditions (Eh), DOC, and NH₄⁺ concentrations (<em>p</em> &lt; 0.05, respectively), suggesting in situ microbial mineralization of sedimentary organic matter (OM) as a key mobilization mechanism. Sediment extractions revealed a strong positive correlation of surface-adsorbed PO₄³⁻ and organic P (P_org) with organic carbon (C) concentrations (<em>p</em> &lt; 0.05), indicating that OM constituted an important sink for both PO₄³⁻ and P_org. Distribution coefficients (Kd values) further suggested that P_org was preferentially adsorbed over PO₄³⁻. Supersaturation regarding calcite (saturation indices &gt; + 0.25) and a negative correlation between inorganic C and total P concentrations in the sediments (<em>p</em> &lt; 0.5) suggest a limited role for Ca-mineral precipitation in active P immobilization. In summary, our study advances mechanistic insights into P cycling in calcareous groundwater systems, thereby emphasizing the dual function of OM as both a sink and a source for P, a dynamic previously overlooked in floodplain aquifers.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122944"},"PeriodicalIF":3.6,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144503873","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":"Optimized quantitative analysis of rare earth elements associated with typical secondary minerals in regolith-hosted deposits","authors":"Puqiu Wu ,&nbsp;Xurui Li ,&nbsp;Xiaoliang Liang ,&nbsp;Xiaoju Lin ,&nbsp;Jianxi Zhu","doi":"10.1016/j.chemgeo.2025.122942","DOIUrl":"10.1016/j.chemgeo.2025.122942","url":null,"abstract":"<div><div>Regolith-hosted rare earth element (REE) deposits are a major source of REEs, particularly the economically valuable heavy REEs (HREEs). Quantitative analysis of the various REE species is crucial for evaluating both the economic potential and mining efficiency of these deposits. The sequential extraction procedure (SEP) is widely used to quantify the speciation of heavy metals, but its applicability to REE analysis remains largely unexplored. Herein, SEP was optimized to quantify the occurrences of REEs associated with typical secondary minerals, specifically clay minerals and Fe (oxyhydr)oxides. The changes in mineral structure and morphology during extraction were examined using metal leaching experiments, transmission electron microscopy, and Mössbauer spectrum. These extractants demonstrated promising performance: 0.5 mol L⁻¹ (NH₄)₂SO₄ at pH 7 for ion-exchangeable REEs, 0.2 mol L⁻¹ (NH₄)₂C₂O₄ at pH 3 and 50 °C for amorphous Fe (oxyhydr)oxide–associated REEs; and a mixed solution of 0.2 mol L⁻¹ (NH₄)₂C₂O₄ and 0.1 mol L⁻¹ ascorbic acid at 90 °C for crystalline Fe (oxyhydr)oxide–associated REEs. This optimized protocol was successfully applied to separate REE fractions adsorbed on Fe (oxyhydr)oxide–clay mineral composites, the dominant REE carriers in regolith-hosted deposits. The results show that ion-exchangeable REEs, primarily associated with clay minerals such as kaolinite, constitute the main fraction, while Fe (oxyhydr)oxides such as goethite and hematite are preferentially enriched in HREEs. The efficiency and selectivity of the optimized SEP were further evaluated in relation to the chemical properties of extractants, mineral reactivity, and their relevance to geochemical applications.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122942"},"PeriodicalIF":3.6,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335527","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":"Changes in the global P cycle in the Neoproterozoic recorded by the compositions of arc lavas","authors":"Paul Sotiriou,&nbsp;Marcel Regelous,&nbsp;Karsten M. Haase","doi":"10.1016/j.chemgeo.2025.122937","DOIUrl":"10.1016/j.chemgeo.2025.122937","url":null,"abstract":"<div><div>The mafic lavas erupted at active subduction zones have higher P/Nd ratios than the bulk continental crust. This difference has been explained by the delamination of apatite-rich lower crust, transferring P from the crust to the mantle at subduction zones. Here we compile geochemical data from arc basalts (5.5–6.5 wt% MgO) that have formed in the last 2 Ga and show that Proterozoic arcs erupted basalts with lower average P₆/Nd₆ ratios than those of Phanerozoic fossil and active arcs. The P₆/Nd₆ ratios of active arc basalts are negatively correlated with Th₆/La₆ and positively correlated with Sr₆/Th₆, Ba₆/Th₆ and ¹⁴³Nd/¹⁴⁴Nd, indicating that high P₆/Nd₆ ratios in arc lavas are not inherited from subducted sediments, which generally have low P/Nd ratios. Phosphatised basaltic oceanic crust has high P contents and P/Nd ratios due to interaction with seawater, and metalliferous sediments deposited at active spreading ridges have very high P contents (2000–16,000 ppm) and P/Nd ratios (100–1456) due to coprecipitation of P with Fe-oxyhydroxides formed when reducing hydrothermal vent fluids mix with oxygenated deep ocean water. We propose that the lower P/Nd ratios of Proterozoic mafic arc lavas are the result of lower concentrations of P in seawater at that time. An increase in the P content of seawater at the end of the Proterozoic, coincident with the Neoproterozoic Oxygenation Event, is reflected in lower concentrations of P in marine sediments before 800 Ma, and in 1.3 Ga metalliferous sediments. The high P/Nd ratios of many young arc lavas are therefore not representative of those formed during most of Earth's history. Since most of the continental crust was formed before the end of the Proterozoic, less delamination of apatite-bearing lower crust may be needed to the explain the low P/Nd ratio of the bulk continental crust.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122937"},"PeriodicalIF":3.6,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335528","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":"Corrigendum to “Zinc isotopic composition of oceanic crust: Insights from oceanic gabbro cumulates and MORBs” [Chemical Geology 670 (2024) 122443 1–13]","authors":"Xia Wang ,&nbsp;Zaicong Wang ,&nbsp;Jakub Ciazela ,&nbsp;Zongqi Zou ,&nbsp;Wei Li ,&nbsp;Yuanyang Yu ,&nbsp;Ming Li ,&nbsp;Yongsheng Liu","doi":"10.1016/j.chemgeo.2025.122934","DOIUrl":"10.1016/j.chemgeo.2025.122934","url":null,"abstract":"","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"691 ","pages":"Article 122934"},"PeriodicalIF":3.6,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335529","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 impact of burial diagenesis on soil-formed minerals in paleosols using stable isotopes of phyllosilicates and carbonate clumped isotopes","authors":"Julia A. McIntosh ,&nbsp;Neil J. Tabor ,&nbsp;Isabel P. Montañez","doi":"10.1016/j.chemgeo.2025.122941","DOIUrl":"10.1016/j.chemgeo.2025.122941","url":null,"abstract":"<div><div>To understand the effects of burial diagenesis on the stable isotope geochemistry of soil-formed clay and carbonate minerals in paleosols, samples were collected from seven cores, spanning middle- to upper-Pennsylvanian strata of the Illinois Basin, with varied maximum burial depths of 1–3 km. Mixed-layer illite-smectite and kaolinite mixtures give δ²H and δ¹⁸O values of −83 ‰ to −36 ‰ and 11.9 ‰ to 21.1 ‰ (VSMOW), respectively. After carbonates were screened petrographically for diagenetic textures using transmitted light and cathodoluminescence, measured clumped isotope Δ₄₇ values range from 0.504 to 0.563 ‰ (I-CDES). Resulting mineral formation temperatures for phyllosilicate mineral mixtures are 28 to 66 °C (mean = 47 °C), whereas T(Δ₄₇) estimates for calcites are 36 to 61 °C (mean = 45 °C). Calculated δ¹⁸O_water values from which phyllosilicate minerals and calcites precipitated under isotopic equilibrium ranges from −7.1 to −1.2 ‰ and − 1.4 to +4.9 ‰, respectively. Closed and open-system phyllosilicate-fluid exchange modeling indicates that phyllosilicate alteration occurred in the presence of a low temperature brine or meteoric water and is interpreted to occur in a layer-by-layer illitization transformation. Due to the lack of diagenetic textures and positively correlated T(Δ₄₇) and δ¹⁸O_water, calcites are interpreted to have undergone solid-state bond reordering. Despite low to moderate temperatures (&lt;125 °C) and varying depths of shallow burial (1–3 km), solid-state transformation of phyllosilicates and calcites indicates paleosols had prolonged exposure to burial conditions which has implications for the use of paleosol minerals for paleoenvironmental reconstructions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122941"},"PeriodicalIF":3.6,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144335531","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}