Chemical Geology最新文献

{"title":"Quantifying the contribution of biogenic iron sulfides to magnesite formation in the Basque Lakes, British Columbia, Canada","authors":"Colton J. Vessey ,&nbsp;Maija J. Raudsepp ,&nbsp;Maria L. Arizaleta ,&nbsp;Sasha Wilson ,&nbsp;Anna L. Harrison ,&nbsp;Kelly J. Rozanitis ,&nbsp;Helen E.A. Brand ,&nbsp;Kurt O. Konhauser ,&nbsp;Kwon Rausis ,&nbsp;Ian M. Power","doi":"10.1016/j.chemgeo.2025.122952","DOIUrl":"10.1016/j.chemgeo.2025.122952","url":null,"abstract":"<div><div>Understanding terrestrial carbon cycling is important to develop carbon dioxide removal (CDR) technologies. Neutralization of carbonic acid (H₂CO₃) to make carbonate minerals provides a secure, long-term sink for CO₂ in natural and anthropogenic systems. In the sediment, dissimilarly sulfate reduction has the potential to generate alkalinity and induce biogenic precipitation of carbonate minerals, however, the proportion of Fe-sulfides to carbonate minerals is rarely quantified. Saline and hypersaline lakes containing carbonate minerals are excellent environments to examine closed system geochemical cycles of carbon, sulfur and iron. Here, we quantified the contribution of biogenic Fe-sulfide minerals and buried organic carbon to magnesite (MgCO₃) formation in the sediment of Basque Lake #2, a Mg-Na-SO₄ hypersaline lake near Ashcroft, British Columbia, Canada. While the overlying surface water contains over 2 M SO₄²⁻, the total solid iron sulfide content of the sediment was &lt;0.4 wt%. The Basque Lake #2 sediment core had much more abundant carbonate minerals than sulfide minerals, suggesting the biogenic processes that form Fe-sulfides have a minimal role in magnesite formation (&lt;1.0 wt%). Laboratory experiments were also conducted to study the relative influence of microbial sulfate and iron reduction on alkalinity generation and biogenic mineral formation with different organic carbon amendments. Filter-sterilized sulfate-rich waters (∼800 mM SO₄²⁻) from Basque Lake #1 were inoculated with anoxic Basque Lake sediment and microbial communities with or without the addition of ferrihydrite [Fe₁₀^IIIO₁₄(OH)₂]. Biogenic magnetite (Fe^III₂Fe^IIO₄) and mackinawite (Fe^IIS) formed when ferrihydrite was added to microbial experiments and siderite (Fe^IICO₃) precipitated in the lactate-amended experiment. The bulk analysis techniques used in these laboratory experiments suggest there is minimal to no additional magnesite precipitation. This study highlights that in closed systems, such as Basque Lake #2, the role of dissimilatory sulfate reduction in net carbonate precipitation will be limited by ferric iron input into lakes, which therefore inhibits biogenic Fe-sulfide formation, even with extremely high aqueous sulfate concentrations. Ultimately, it is unlikely that sulfate and iron reduction play important roles in Mg‑carbonate formation within Fe-limited environments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122952"},"PeriodicalIF":3.6,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580554","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":"Isotopic evidence for dew uptake by land snails from Bayesian modeling of body water δD and δ18O","authors":"Jiawei Da","doi":"10.1016/j.chemgeo.2025.122953","DOIUrl":"10.1016/j.chemgeo.2025.122953","url":null,"abstract":"<div><div>Land snail shells serve as valuable paleoclimate archives, with their isotopic compositions recording past changes in regional ecology and hydrology. To quantitatively reconstruct paleoclimate parameters such as the oxygen isotopic composition of precipitation (δ¹⁸O_p), a flux balance model targeting snail body fluid was developed by <span><span>Balakrishnan and Yapp (2004)</span></span>. However, previous applications of the flux balance model based on modern observations have consistently reported offsets between modeled and observed δ¹⁸O_p values. In this study, I re-evaluated the model input parameters using a published high-resolution dataset and Bayesian inversion to refine estimates of the isotopic compositions of the snail's drinking water (δ¹⁸O_in, δD_in). The modeled δ¹⁸O_in and δD_in plot above the local meteoric water line, indicating substantial contributions of atmospheric vapor to the snail body water via dew uptake. Assuming that the ambient water vapor forms through evaporation of meteoric water, the updated flux balance model suggested that dew accounts for up to ∼50 % of snail's water intake in the study site. This finding highlights a critical oversight in previous paleoclimate reconstructions that ignored dew uptake, potentially leading to underestimation of δ¹⁸O_p.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122953"},"PeriodicalIF":3.6,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580553","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":"Impact of iron biogeochemical cycling in deep-sea environments on rare earth element enrichment","authors":"Pengcong Wang ,&nbsp;Yinan Deng ,&nbsp;Ganglan Zhang ,&nbsp;Deng Liu ,&nbsp;Jiayi Ma ,&nbsp;Chutong Liu ,&nbsp;Xiaoxuan Zheng ,&nbsp;Yangtao Zhu ,&nbsp;Jun Cao ,&nbsp;Fang Chen","doi":"10.1016/j.chemgeo.2025.122951","DOIUrl":"10.1016/j.chemgeo.2025.122951","url":null,"abstract":"<div><div>The enrichment mechanisms of deep-sea rare earth elements and yttrium (REY) are critical for both strategic resource exploration and paleoceanographic reconstruction. Iron biogeochemical cycling plays a central role in the dynamics of REY, mediating their pre-enrichment in seawater and their remobilization at sediment-porewater interfaces. However, the spatial heterogeneity of iron (oxyhydr)oxides distributions and their associated microbial processes in REY enrichment remain poorly understood. Here, we employ a multidisciplinary approach, integrating geochemical, magnetic, microscopic, and metagenomic analyses, to compare iron cycling regimes in two contrasting Pacific REY-rich provinces: the ferruginous southeastern Pacific and the oligotrophic northwestern Pacific basins. Our results reveal that quantitative scavenging by iron (oxyhydr)oxides dominates REY pre-enrichment in the southeastern Pacific, whereas selective adsorption prevails in the iron-depleted northwestern Pacific. Additionally, microbial iron reduction coupled with secondary mineralization enhances the remobilization of REY to porewater and their ultimate accumulation in both regions. This study advances our understanding of the biogeochemical coupling between marine iron and REY, providing new insights into their co-evolution in deep-sea environments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122951"},"PeriodicalIF":3.6,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144564046","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":"Volatilities and diffusivities of Tl, Ag, Cu, Pb, Cd, Zn, Ga, and As from a Cl-bearing shoshonitic basalt and their application to volcanic degassing","authors":"Enrico Califano, Silvio Mollo, Paolo A. Sossi, Lorenzo Tavazzani, Piergiorgio Moschini, Alessio Pontesilli, Piergiorgio Scarlato","doi":"10.1016/j.chemgeo.2025.122947","DOIUrl":"https://doi.org/10.1016/j.chemgeo.2025.122947","url":null,"abstract":"The emission of trace metals during volcanic eruptions is modulated by their diffusion rates through the silicate melt and their affinity for the gas phase. However, due to the multicomponent nature of natural magmas, the prevailing controls on emission rates remain poorly understood. To constrain how the presence of Cl affects the diffusivities and volatilities of trace metals (Cl, Tl, Ag, Cu, Cd, Zn, Pb, Ga and As) in a nominally anhydrous shoshonitic basalt, a series of degassing experiments was conducted at 1 atm and 1200, 1300 and 1400 °C, with initial Cl contents of ~0.6 and ~ 1.2 wt% Cl for durations of 1 and 4 h. The resulting concentration gradients perpendicular to the gas-melt interface attest to the diffusive transport of trace metals within the silicate framework in response to their evaporative loss. Diffusivities scale inversely with the ionic field strength, with monovalent cations diffusing at rates (~10<ce:sup loc=\"post\">−10</ce:sup> m<ce:sup loc=\"post\">2</ce:sup> s<ce:sup loc=\"post\">−1</ce:sup>) two orders of magnitude faster than trivalent cations (~10<ce:sup loc=\"post\">−12</ce:sup> m<ce:sup loc=\"post\">2</ce:sup> s<ce:sup loc=\"post\">−1</ce:sup>). The presence of Cl causes a near-uniform increase in diffusivity of roughly 0.5 logarithmic units across all trace metals. Evaporation rates, defined as the rates at which volatile elements are lost from the melt surface to the coexisting vapor phase, are found to be fastest for Tl, Ag and Cd (~10<ce:sup loc=\"post\">−9</ce:sup>–10<ce:sup loc=\"post\">−8</ce:sup> m s<ce:sup loc=\"post\">−1</ce:sup>), whereas Ga and As (~10<ce:sup loc=\"post\">−10</ce:sup>–10<ce:sup loc=\"post\">−9</ce:sup> m s<ce:sup loc=\"post\">−1</ce:sup>) are the least volatile trace metals. Thermodynamic calculations indicate that all evaporating metal-bearing species are present as chlorides in the gas phase, except for As. A positive correlation is observed between evaporation mass transfer coefficients from this study and the gas-melt partition coefficients determined for volcanic gases, with Ga becoming relative more volatile, while As, Cd and Tl becoming less volatile in the experiments than observed in natural volcanic settings. Furthermore, modeling of bubble growth in magmas reveal that diffusive fractionation of slow- and fast-diffusing trace metals may substantially change the concentration ratio of the two species at the bubble-melt interface, with profound implications for the interpretation of volcanic gas compositions.","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"11 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144613283","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":"Secular compositional changes in granitoids and felsic volcanics: the tectonic setting control","authors":"Kent C. Condie ,&nbsp;Stephen J. Puetz ,&nbsp;Christopher J. Spencer ,&nbsp;Nick M.W. Roberts","doi":"10.1016/j.chemgeo.2025.122950","DOIUrl":"10.1016/j.chemgeo.2025.122950","url":null,"abstract":"<div><div>Abstract</div><div>This study presents results for secular compositional change of 12 geochemical variables in granitoids and felsic volcanics in the last 3 Gyr grouped into two tectonic settings, orogenic and within-plate. Time series are constructed from median values of geochemical data compiled in 250-Myr bins. Within-plate granitoid and felsic volcanic time series (high SiO₂, (Na₂O + K₂O)/CaO, Fe Index, Y + Nb, Ga/Al; low Sr/Y, Eu/Eu*, La/Nb) are displaced from the orogenic series, consistent with shallow depths of magma generation and an overall lower degree of partial melting or/and more fractional crystallization for within-plate magmas through time. Orogenic granitoid and felsic volcanic geochemical time series for La/Yb, Th/Yb, La/Nb, Y + Nb, and Yb are similar and show a transition at the end of the from dominantly restitic garnet-amphibole-rutile to plagioclase control, the latter reflecting shallower depths of magma generation. Relatively high Eu/Eu* in Archean granitoids and felsic volcanics (and high Sr/Y in Archean granitoids) may imply that plagioclase accumulation is more effective before 2.5 Ga than afterwards, consistent with large volumes of TTG (tonalite-trondhjemite-granodiorite) in the Archean. Low Sr/Y and Eu/Eu* of granitoids and felsic volcanics in the last 1750 Myr likely require significant plagioclase removal by fractional crystallization or/and plagioclase presence in the melting restite. Fractionation of Th from La beginning at 1500 Ma may reflect a change to an apatite-dominated restite, perhaps in response to greater amounts of subducted P-rich sediments entering the sources of felsic magma. Increases in Yb, Y + Nb, and Fe Index and decreases in La/Nb, Eu/Eu*, Sr/Y, La/Yb and Th/Yb in orogenic settings during assembly of Columbia (1800–1500 Ma) reflect shallowing of magma sources, perhaps in hot back-arc basins. Our findings show the importance of tectonic setting on the compositional evolution of felsic magmas, highlighting the need to consider the differences between orogenic and within-plate processes when reconstructing the compositional history of the continental crust into deep time.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"692 ","pages":"Article 122950"},"PeriodicalIF":3.6,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144535967","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":"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}