Chemical Geology最新文献

{"title":"Iron isotopic fractionation during seafloor hydrothermal alteration of oceanic upper crust, as recorded in Geotimes lavas of Semail ophiolite, Oman","authors":"Rong-Zhong Bo ,&nbsp;Yildirim Dilek ,&nbsp;Wei-Qiang Li ,&nbsp;Sobhi Nasir ,&nbsp;Peng-Jie Cai ,&nbsp;Hui-Chao Rui ,&nbsp;De-Hong Du ,&nbsp;Shi-Chao An ,&nbsp;Yu-Xiao Lu ,&nbsp;Hao-Chen Duan ,&nbsp;Dong-Yang Lian ,&nbsp;Jing-Sui Yang ,&nbsp;Ahmed E. Masoud","doi":"10.1016/j.chemgeo.2025.122717","DOIUrl":"10.1016/j.chemgeo.2025.122717","url":null,"abstract":"<div><div>The Semail ophiolite in Oman features a crustal stratigraphy akin to a fast-spreading modern oceanic lithosphere. Its Geotimes pillow lavas, the stratigraphically oldest extrusive sequence at the bottom, share geochemical traits with contemporary mid-ocean ridge basalts, offering a unique opportunity to examine iron (Fe) isotopic fractionation during hydrothermal alteration under varied redox conditions. Significant alteration transformed primary minerals, evidenced by the dissolution of clinopyroxene, plagioclase, and ilmenite, alongside the precipitation of chlorite, albite, and magnetite-hematite. The ⁸⁷Sr/⁸⁸Sr ratios of 18 basalt subsamples from altered pillow lava range from 0.705110 to 0.705680, indicating extensive seawater interaction. The δ⁵⁶Fe values show systematic variations at a centimeter scale (0.037–0.291 ‰), primarily resulting from hydrothermal processes rather than source inheritance. Notably, the pillow lava's core displays higher δ⁵⁶Fe values, suggesting the initial dissolution of Fe-bearing minerals under reduced conditions. In contrast, the edges show lower δ⁵⁶Fe values akin to mean mid-ocean ridge basalt, indicating that strong oxidation conditions minimally affected these isotopic values. In conclusion, this study reveals the complex variations of the Fe concentrations and Fe isotopic compositions of altered basalt that suffered hydrothermal alteration during the various redox conditions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122717"},"PeriodicalIF":3.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618283","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":"Comprehensive modification of cratonic lithospheric mantle beneath the central North China Craton: Insights from Li isotope systematics of olivine xenocrysts in Cenozoic basalts","authors":"Yao Xu ,&nbsp;Hong-Fu Zhang ,&nbsp;Yan-Jie Tang ,&nbsp;A-Bing Lin ,&nbsp;Juan Zhang ,&nbsp;Ming-Jie Zhang","doi":"10.1016/j.chemgeo.2025.122721","DOIUrl":"10.1016/j.chemgeo.2025.122721","url":null,"abstract":"<div><div>The flat subduction and subsequent rollback of the Paleo-Pacific plate played a critical role in the destruction of the eastern North China Craton (NCC), manifested by a drastic transformation of the subcontinental lithospheric mantle (SCLM) in physico-chemical properties. However, the nature of the SCLM beneath the central NCC remains poorly defined. This study presents in situ major element compositions and Li systematics (concentrations and δ⁷Li) of olivine xenocrysts from Cenozoic Xiyang–Pingding basalts to investigate the impacts of circum-craton plate subduction on the SCLM. Olivine grains from the basalts are classified into four types based on core forsterite (Fo) contents and mineralogical traits. Types 1–3 xenocrysts show sub-rounded shapes, kink bands, and geochemical affinities with xenolithic olivines, distinct from Type 4 phenocrysts. Xenocrystic zoned textures resulted from re-equilibration with host magma, while large xenocrystic cores retain the SCLM composition. Type 1 cores (Fo = 92.1–93.5) exhibit Li contents (1.0–1.7 ppm) comparable to mantle olivines and δ⁷Li values within or slightly above the normal mantle range (2–6 ‰), representing relicts of ancient refractory SCLM enriched by Paleo-Pacific slab-derived silicate melts. Type 2 (Fo = 90.0–92.0) and high-Fo (88.6–89.9) Type 3 xenocrysts display Li enrichment (1.3–3.5 ppm) and δ⁷Li depletion (down to −20 ‰). Positive relationships between δ⁷Li and both Fo and 1/Li indicate their formation through interaction between Archean refractory SCLM and asthenospheric carbonated silicate melts. Low-Fo (84.7–88.2) Type 3 cores record the highest Li (1.7–4.9 ppm) and δ⁷Li (9 ‰ to 14 ‰), marking the recent refertilization by asthenospheric silicate melts. Combined with previous studies, these Li-δ⁷Li variations reflect the most comprehensive record of SCLM modification beneath the NCC, offering crucial insights into the dynamics of cratonic evolution.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122721"},"PeriodicalIF":3.6,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143563280","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":"Diffusive Mg isotope fractionation in silicate melts during mineral dissolution","authors":"Youxue Zhang (张有学),&nbsp;Bobo Bai (白博博)","doi":"10.1016/j.chemgeo.2025.122720","DOIUrl":"10.1016/j.chemgeo.2025.122720","url":null,"abstract":"<div><div>Diffusion can generate much larger isotope fractionation than equilibrium isotope fractionation. Previous experimental studies on diffusive isotope fractionation have used diffusion couple experiments. Here, we report a study investigating diffusive Mg isotope fractionation in melts during mineral dissolution experiments in andesite, basalt, and Fe-free “basalt”. The goal of the study is to (a) use mineral dissolution experiments to determine the empirical β factor for diffusive isotope fractionation in melts, and (b) evaluate the variability of β for diffusive Mg isotope fractionation because literature data showed a range of 0.045 to 0.10. We first derive the analytical solution for diffusive isotope fractionation in melts during mineral dissolution and examine the dependence of the interface isotope ratio on other parameters and the behavior of the isotope diffusion profile. We then report SIMS measurement of Mg isotope diffusion profiles during anorthite dissolution in basalt and olivine dissolution in andesite. Mg isotope diffusion profiles during anorthite dissolution are as expected and can be modeled well leading to β_Mg of 0.052 ± 0.011 in a mid-ocean ridge basalt and 0.077 ± 0.012 in an FeO-free “basalt”, but the δ²⁶Mg profile during an olivine dissolution experiment in andesite is not as expected. We suspected that the latter was due to significant matrix effect on analyzed δ²⁶Mg values because of the large compositional variation along the diffusion profile. To examine this effect, glass standards with compositions similar to those in points along the diffusion profile were synthesized using MgO powders from the same bottle (meaning the same Mg isotope ratio). The matrix effect is indeed significant. After correcting for it, the diffusion profile of Mg isotope ratios is as expected and can be modeled well with β_Mg of 0.074 ± 0.002.</div><div>Combining the new result with previous results, the β_Mg value for diffusive isotope fractionation in andesite to basalt is 0.052 to 0.077 based on anorthite and olivine dissolution experiments, which lies within literature values. The range of β_Mg values can be reconciled using diffusion mechanisms inferred from multicomponent diffusion studies. The method developed in this study can be applied to investigate diffusive isotope fractionation in other mineral dissolution studies. Furthermore, diffusive isotope fractionation in melt during rapid phenocryst growth in natural basalt may also be measurable under favorable conditions, potentially opening a new perspective in understanding crystal growth and fractionation.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122720"},"PeriodicalIF":3.6,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143593592","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":"Paired mass-dependent and mass-independent Hg isotope excursions through non-euxinic intervals: Signals of post-depositional Hg isotope fractionation?","authors":"Guanyu Zhao ,&nbsp;Qian Deng ,&nbsp;Bin Cheng ,&nbsp;Yunpeng Wang ,&nbsp;Zewen Liao","doi":"10.1016/j.chemgeo.2025.122718","DOIUrl":"10.1016/j.chemgeo.2025.122718","url":null,"abstract":"<div><div>Mercury (Hg) in sedimentary deposits has become a widely used proxy for reconstructing paleo-volcanic activity. However, a comprehensive understanding of Hg accumulation pattern and the isotope variation during early diagenesis is still lacking. A thorough diagenetic evaluation of sedimentary rocks is crucial prior to the interpretation of geochemical data, as diagenetic changes can lead to considerable differences between the original seawater signatures and the sedimentological records. We observed a Hg isotopic pattern characterized by a negative trend in δ²⁰²Hg with a concurrent gradual positive shift in Δ¹⁹⁹Hg throughout non-euxinic intervals in multiple marine sedimentary successions. We propose that the synchronous Hg mass dependent fractionation (MDF) and mass independent fractionation (MIF) were driven by diagenetic events. The release of organic-bound Hg and its subsequent diffusion downward to sites where it complexed with pyrite in early diagenetic stages may induce δ²⁰²Hg shift towards more negative values in the Hg precipitate, and in turn, contribute to the concurrent positive shift of Δ¹⁹⁹Hg observed in these sections.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122718"},"PeriodicalIF":3.6,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552598","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":"Platinum-group elements (PGEs) and rhenium in Permian-Triassic boundary sediments from southern China and Japan linked to concurrent eruptions of the Siberian Traps","authors":"Monika A. Misztela ,&nbsp;Michael R. Rampino ,&nbsp;Ian H. Campbell","doi":"10.1016/j.chemgeo.2025.122715","DOIUrl":"10.1016/j.chemgeo.2025.122715","url":null,"abstract":"<div><div>The end-Permian mass extinction (EPME) (251.9 Ma) was the most severe recorded extinction event. A pulse of sill-complex formation and volcanism during the Siberian Traps continental flood basalt (CFB) was apparently synchronous with the EPME, and has been proposed as a major cause of the environmental perturbations that led to the mass-extinction event. Abundances of PGEs and rhenium in sediments have been used in the past as signatures of CFB volcanism. We performed analyses of PGEs and rhenium concentrations and diagnostic PGE ratios across the Permian-Triassic boundary and EPME in three localities in southern China (Meishan, Zhongzhai, Xinmin), and one locality from SW Japan (Ubara). We compared these results with similar PGE and rhenium analyses of: 1) the upper continental crust (UCC), 2) basaltic samples from the Siberian, Deccan and Paraná CFBs, 3) the Cretaceous/Paleogene (K-Pg) boundary layer, and 4) average black shales. We also compared our results with previous PGE analyses of EPME/P-T boundary sections in China and elsewhere.</div><div>In the four EPME sections studied here, PGEs (especially Pt, Pd, and Ru) and rhenium are commonly enriched relative to the upper continental crust (UCC) baseline. These enrichments occur in sediments usually having low PGE background (e.g., carbonates and cherts), and are interpreted as indicative of a source in CFB volcanism. Values of Ir/Pt &lt; 0.03 in all sections also indicate a volcanic source, and there is no evidence of extraterrestrial PGEs. Volatile rhenium with Re/Ir &gt; 10 is highly anomalous in all of the EPME sections, with Re anomalies up to 1300 times the UCC of apparent CFB origin in the Ubara, Japan deep-sea locality.</div><div>Concurrent mercury and nickel anomalies, and related isotopic shifts, further support a CFB volcanic source for the volatile rhenium at the EPME. These results suggest that the Siberian CFB eruptions, especially an early pulse of emplacement of sill complexes, coincident with the EPME, were a source of the PGEs and rhenium in the EPME/P-T boundary sediments, and potentially an important factor in the environmental crisis that led to the major mass extinction.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122715"},"PeriodicalIF":3.6,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143610417","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":"Twice the global average carbon burial efficiency in the Helgoland Mud Area of the North Sea: Insights into carbon sequestration in small-size depocenters on sand-dominated shelves","authors":"Bingbing Wei ,&nbsp;Daniel Müller ,&nbsp;Stephanie Kusch ,&nbsp;Lu Niu ,&nbsp;Jens Hefter ,&nbsp;Lasse Sander ,&nbsp;Ulrike Hanz ,&nbsp;Gesine Mollenhauer ,&nbsp;Guodong Jia ,&nbsp;Sabine Kasten ,&nbsp;Moritz Holtappels","doi":"10.1016/j.chemgeo.2025.122712","DOIUrl":"10.1016/j.chemgeo.2025.122712","url":null,"abstract":"<div><div>Continental shelves are integral to the global carbon cycle, yet uncertainties persist about the nature and extent of carbon burial, particularly in sand-dominated areas. In the sand-dominated North Sea, the Helgoland Mud Area (HMA) emerges as a small-size mud depocenter, surrounded by sandy sediments that do not accumulate organic carbon (OC) and are separated from adjacent rivers. Such small-size depocenters, common on high-energy shelves, have underexplored OC degradation and burial efficiencies due to their limited individual size. Since sandy sediments with interspersed small-size depocenter cover ∼50 % of global shelves, these depocenters may collectively offer greater OC burial capacity than previously recognized.</div><div>This study investigated the composition, degradation, and sequestration of OC from terrestrial (OC_terr) and marine (OC_mar) sources in surface sediments of the HMA and adjacent sandy areas using bulk (mean grain size, OC content, loading and ¹³C isotope composition) and molecular (fatty acids and alkanes) analyses. Our results, derived from a two end-member mixing model based on δ¹³C values of bulk OC, revealed that OC_terr dominates (∼74 %) the sedimentary OC in both areas, with OC_mar contributing ∼26 %. The HMA exhibited OC_terr and OC_mar contents ∼5 times higher than in the sandy areas. Both OC_terr and OC_mar loadings negatively correlated with mean grain size, indicating reduced OC degradation in muddy sediments. Molecular analysis further revealed that OC_terr in the HMA is less refractory compared to adjacent sandy regions. These differences are attributed to differences in porewater transport, oxygen penetration depths and exposure times, all of which influence OC preservation, despite the important role of mineral protection. OC_terr and OC_mar accumulation fluxes in the HMA were calculated at (6.75 ± 0.61) × 10⁻³ and (2.54 ± 0.68) × 10⁻³ Tg C/yr, respectively, representing 34.3 % of OC_terr export from adjacent rivers and 2.8 % of net OC_mar production in the HMA. These values are twice the global average for shelf areas, highlighting the exceptional efficiency of the HMA as a carbon sink and hinting at the significance of small-size depocenters within sandy areas in the global carbon cycle.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"681 ","pages":"Article 122712"},"PeriodicalIF":3.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552597","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":"The rheological evolution of a phonotephritic melt upon variable degrees of carbonate assimilation and deformation regimes","authors":"Gabriele Giuliani ,&nbsp;Danilo Di Genova ,&nbsp;Fabrizio Di Fiore ,&nbsp;Silvio Mollo ,&nbsp;Serena Dominijanni ,&nbsp;Chiara Maria Petrone ,&nbsp;Claudia Romano ,&nbsp;Alessandro Vona","doi":"10.1016/j.chemgeo.2025.122711","DOIUrl":"10.1016/j.chemgeo.2025.122711","url":null,"abstract":"<div><div>The dynamic interplay between magmas and carbonate wall rocks within volcanic plumbing systems heavily influences the chemical and physical properties of erupted magmas. In this study we present results from isothermal static experiments (ISEs) and isothermal deformation experiments (IDEs) aimed at investigating the rheological evolution of a phonotephritic melt from Somma-Vesuvius (Italy) under variable shear rates and CaO and CaO + MgO doping levels. Flash differential scanning calorimetry is also used to determine the viscosity of interstitial melt, allowing for the first direct assessment of how crystallization affects melt rheology without relying on empirical viscosity models. Two distinct rheological scenarios emerge from IDEs: 1) a viscous deformation, characterized by uniform flow, and 2) a non-homogeneous deformation, featuring shear localization and viscous/brittle rupture of the magma. As both shear rate and doping level increase, a non-Newtonian melt behavior is observed due to stress localization and rupture, facilitated by the development of the crystal network. The narrower viscosity range measured from IDEs, compared to models of pure viscous behavior, suggests that shear localization and fracturing reduce the resistance to flow in doped, crystal-rich samples. The complex rheology of doped melts reflects the disaggregation of skarn shells at the margins of magma chambers, thereby facilitating skarn recycling and enhancing magma contamination.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122711"},"PeriodicalIF":3.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550161","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":"Contrasting variations in solid acidity of smectite and kaolinite in acid-base environments and implications for organic matter sequestration","authors":"Jiazong Du ,&nbsp;Jingong Cai ,&nbsp;Xiang Zeng ,&nbsp;Tianzhu Lei ,&nbsp;Qian Chao ,&nbsp;Kuihua Zhang ,&nbsp;Xuejun Wang","doi":"10.1016/j.chemgeo.2025.122714","DOIUrl":"10.1016/j.chemgeo.2025.122714","url":null,"abstract":"<div><div>The nanoscale interactions between clay mineral active sites and organic matter (OM) determine OM sequestration and transformation. Smectite and kaolinite, prominent OM adsorbing minerals, are sensitive to acid-base fluctuations, but dynamics of their active sites remain unexplored, limiting our knowledge of the mineral matrix-related fate of OM. Solid acidity (Brønsted and Lewis acid sites) is a tangible indicator to quantify the active sites. This study examined the dynamics of solid acidity in smectite and kaolinite subjected to acid-base environmental variability, exploring implications for OM sequestration. Results revealed that both acid and alkaline environments increased the number of total acid sites (Q_T) for both smectite and kaolinite, with higher Brønsted acid site fraction (<em>f</em>_B) as pH decreased, but smectite and kaolinite exhibited contrasting behaviors. Smectite underwent more prominent structural rearrangements under acid environments, with interlayer cations substitution and preferential dissolution of octahedron. This process exposed Al³⁺ and/or facilitated re-adsorption of Al³⁺/Fe³⁺, contributing to Lewis acid sites, while exposed silanols and enhanced interlayer water polarization contributed more to Brønsted acid sites, yielding substantial Q_T and <em>f</em>_B increases. Acid environments exposed silanols in kaolinite, but it responded more strongly to alkaline environments, where disrupted Si-O-Al bonds at edges exposed incompletely coordinated Al³⁺, contributing to Q_T increase and <em>f</em>_B decrease. Increased Q_T enhanced the adsorbed lysine content; therefore, the mineral- and environment-specific dynamics of solid acidity have the potential to shape OM sequestration capacity of clay minerals, and their catalytic efficiency and mechanisms in driving the diagenetic fate of OM.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122714"},"PeriodicalIF":3.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550908","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":"Extracellular metabolites relieve the inhibitory effect of ferrous ions on microbial reduction of schwertmannite","authors":"Changdong Ke ,&nbsp;Qian Yao ,&nbsp;Yanping Deng ,&nbsp;Siyu Zhang ,&nbsp;Zhiliang Li ,&nbsp;Renren Wu ,&nbsp;Chuling Guo ,&nbsp;Zhi Dang","doi":"10.1016/j.chemgeo.2025.122709","DOIUrl":"10.1016/j.chemgeo.2025.122709","url":null,"abstract":"<div><div>In the environment, microbe-mineral-metabolites are tightly linked. Currently, the microbe-mineral interactions have been studied, but the effect of microbial metabolites on the microbe-mineral interactions is unclear. This study investigated the effect of metabolites of <em>Shewanella oneidensis</em> (an iron-reducing bacterium, FeRB) (or <em>Desulfosporosinus meridiei</em> [a sulfate-reducing bacterium, SRB]) on SRB (or FeRB) mediated transformation of schwertmannite (Sch), a mineral in acidic soils rich in sulfate (SO₄²⁻). The results showed that microbial metabolites relieved the inhibition of FeRB and SRB by complexing ferrous ions (Fe²⁺), thus promoting the microbial reduction of Sch. Besides, metabolites altered the pathways of microbial reduction and mineral transformation. In the absence of metabolites, FeRB mediated Fe(III) reduction mainly by increasing the cell abundance, while in the presence of metabolites, FeRB upregulated gene expression (<em>mtrC</em> and <em>omcA</em>) to enhance the Fe(III) reduction, and the Sch transformation pathway was Sch → goethite → siderite. For SRB, metabolites upregulated the <em>dsr</em> gene expression to accelerate SRB reducing SO₄²⁻, and the Sch transformation pathway was Sch → goethite and mackinawite → siderite, mackinawite and pyrite. Metabolomics and high-performance liquid chromatography analysis revealed a large amount of phenylalanine (∼1.5 mM) and citric acid (∼0.2 mM) were present in the metabolites of FeRB and SRB, respectively, which complexed Fe²⁺ and promoted the microbial reduction of Sch. This study highlighted the important role of metabolites in maintaining soil biological activity and provided new insights into the microbe-mineral-metabolite interactions.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122709"},"PeriodicalIF":3.6,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143510655","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":"Precise 40Ar/39Ar dating of multiple potassic minerals constrain the age and rapid cooling history of the Walgidee Hills lamproite pipe, Kimberley Region, Western Australia, at 17.49 Ma","authors":"Simon A. Wilde ,&nbsp;Fred Jourdan ,&nbsp;Lynda Frewer ,&nbsp;Monika A. Kusiak","doi":"10.1016/j.chemgeo.2025.122698","DOIUrl":"10.1016/j.chemgeo.2025.122698","url":null,"abstract":"<div><div>To determine the emplacement age of the initial eruptive phase of the Walgidee Hills lamproite pipe in the Kimberley region of Western Australia, the veracity of utilizing multi-mineral dating of the non-standard potassium-bearing minerals potassic richterite, wadeite, jeppeite, and priderite and was tested by ⁴⁰Ar/³⁹Ar dating, along with the more traditionally-utilized potassium-rich mineral phlogopite. All minerals give excellent single-crystal plateau ages ranging from 17.82 ± 0.53 to 17.0 ± 1.6 Ma (2σ), and with age uncertainties ranging from ±0.14 Ma to ±1.6 Ma. The variation in precision is dependent on both the volume and K₂O content of the crystal analyzed. The mean age of the combined data set is 17.487 ± 0.083 Ma [± 0.086; inclusive of all sources of uncertainties] (<em>n</em> = 10; MSWD = 0.50; <em>P</em> = 0.87) and represents the initial crystallization age of the Walgidee Hills diatreme, the largest known and youngest diamondiferous lamproite in the world. The lack of age difference, despite the probable variation in mineral closure temperatures, confirms rapid cooling. Although most of the minerals analyzed are rare to absent in common magmatic rocks, some are widely distributed in alkaline complexes and in lamproite, kamapugite and kimberlite intrusions. Our results show these K-rich minerals are excellent for ⁴⁰Ar/³⁹Ar dating and can be used singly or in combination to obtain precise magmatic crystallization ages, and possible cooling rates, of ultrapotassic rocks. For a suite of potassic rocks generated in a plume setting, they can track the rate of plate motion.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"680 ","pages":"Article 122698"},"PeriodicalIF":3.6,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519350","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}