Geochimica et Cosmochimica Acta最新文献

{"title":"Iron and calcium isotopic fractionation during calcic carbonatite–silicate liquid immiscibility","authors":"Yan Liu ,&nbsp;Haoyu Luo ,&nbsp;Hongjie Wu ,&nbsp;Zengqian Hou","doi":"10.1016/j.gca.2026.01.017","DOIUrl":"10.1016/j.gca.2026.01.017","url":null,"abstract":"<div><div>The role of liquid immiscibility between carbonatitic and silicate melts in forming carbonatite-associated rare earth element (REE) deposits is controversial. Iron and Calcium isotopes have significant potential for identifying liquid immiscibility, particularly in natural calcic carbonatite–silicate systems that host the most economically significant REE mineralization. This paper presents high-precision Fe and Ca isotopic data, along with major and trace element and C–O–Sr–Nd isotopic data, for unaltered calcic carbonatites and spatially associated syenites from the Oligocene Maoniuping REE deposit, China. Uniform Sr–Nd isotopic compositions, low loss-on-ignition values, an absence of crustal contamination features, and mineralogical evidence confirm that the observed isotopic variations are primary magmatic features that did not result from fractional crystallization, source heterogeneity, or post-magmatic processes. The carbonatites have systematically lighter Fe isotopic compositions (δ⁵⁶Fe =  −0.26‰ to +0.09‰; average =  −0.13‰) than the syenites (δ⁵⁶Fe = +0.10‰ to +0.36‰; average = +0.24‰), with an average inter-phase fractionation of Δ⁵⁶Fe_carb–sil =  −0.37‰ ±0.31‰. Similarly, the carbonatites have slightly lighter Ca isotopic compositions (<em>δ</em>^44/42Ca = +0.26‰ to +0.33‰; average = +0.28‰) than the syenites (<em>δ</em>^44/42Ca = +0.37‰ to +0.42‰; average = +0.39‰), with Δ^44/42Ca_carb–sil =  −0.11‰ ± 0.07‰. Based on Zr saturation thermometry (1082 ± 35 K), the measured Δ⁵⁶Fe_carb–sil and Δ^44/42Ca_carb–sil values are consistent with experimental predictions for equilibrium fractionation at magmatic temperatures, supporting their origin as coeval products of liquid immiscibility. This study confirms that equilibrium Fe–Ca isotopic fractionation occurred during calcic carbonatite–silicate liquid immiscibility in the Maoniuping REE deposit. In addition, the low <em>δ</em>^44/42Ca values of both rock types suggest recycled marine carbonates contributed to their mantle source, which is consistent with regional geodynamic models for the Mianning–Dechang REE belt.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"416 ","pages":"Pages 17-28"},"PeriodicalIF":5.0,"publicationDate":"2026-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cerium speciation and anomaly formation in mature regolith: implications for ion-adsorption type REE deposit prospecting","authors":"Mei Lu, Wei Tan, Jing Liu, Xiaoliang Liang, Stefanie M. Brueckner, Shoushu Wei, Yiping Yang, Hanliang Liu, Hongping He","doi":"10.1016/j.gca.2026.01.015","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.015","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"1 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metal–silicate partitioning of Pb and implications for the accretion of moderately volatile elements to Earth","authors":"Jesse T. Gu, Rebecca A. Fischer, Lucy Jacobsen, Michail I. Petaev","doi":"10.1016/j.gca.2026.01.013","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.013","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"61 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calcium isotopic fractionation in plagioclase from mafic-ultramafic rocks: implications for magmatic processes and planetary differentiation","authors":"Wei Wu, Yigang Xu, Zhaofeng Zhang","doi":"10.1016/j.gca.2026.01.014","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.014","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"59 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Redistribution and oxidation of lead in experimentally heated zircons","authors":"Paulina Zieja, Monika A. Kusiak, Pilar G. Montero, Fernando Bea, Richard Wirth, Bożena Gołębiowska, Aitor Cambeses","doi":"10.1016/j.gca.2026.01.016","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.016","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"86 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preservation of sedimentary rubidium isotopic signatures in subduction zones: Insights from the Schistes Lustrés HP-UHP metasediments, Western Alps","authors":"Mary Clarich, Baoliang Wang, Vincent Busigny, Yan Hu","doi":"10.1016/j.gca.2026.01.011","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.011","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"15 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupling X-ray absorption spectroscopy and chemical extractions to investigate phosphorus phase partitioning in Ningxiang iron deposits","authors":"Qiang Zhou, Yafang Song, Kai Gan, Yijun Xiong, Than Dam, Mengqiang Zhu, Changzhi Wu, Jihua Hao, Simon W. Poulton, Wei Li","doi":"10.1016/j.gca.2026.01.012","DOIUrl":"https://doi.org/10.1016/j.gca.2026.01.012","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"5 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145962646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photochemical behavior between oxalate and Sb(V)/As(V)-bearing jarosite: Reaction mechanism, mineral transformation, and elemental fate","authors":"Qi Huang ,&nbsp;Guining Lu ,&nbsp;Xiaohu Jin ,&nbsp;Xiaodong Du ,&nbsp;Xiaofei Li ,&nbsp;Qian Yao ,&nbsp;Lijuan Zeng ,&nbsp;Xueqin Tao ,&nbsp;Jianmin Zhou ,&nbsp;Zhi Dang","doi":"10.1016/j.gca.2026.01.010","DOIUrl":"10.1016/j.gca.2026.01.010","url":null,"abstract":"<div><div>Jarosite is a common metastable iron mineral in acid sulfate-rich environments, which is known to retain antimony (Sb) and arsenic (As). Sunlight has emerged as a critical driver for the dissolution of iron minerals, especially in the presence of dissolved organic matter (DOM). However, the mechanisms governing jarosite dissolution and associated Sb/As migration under the coexistence of sunlight and DOM remain poorly understood. Here, we employed a series of techniques, including in situ attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning transmission electron microscopy (STEM), and chemical extraction, to investigated the photochemical behavior of Sb(Ⅴ)/As(Ⅴ)-bearing jarosite with the representative DOM-oxalate (OA) under simulated sunlight. The results indicated that OA was predominantly adsorbed onto the jarosite surface via mononuclear bidentate (MB) binding geometry. Under light irradiation, OA underwent photolysis on the jarosite surface, thereby inducing reductive dissolution of the mineral. The dissolution rate of jarosite was faster under anoxic conditions than under oxic conditions, and both rates increased with increasing OA dosage. Notably, high OA dosage (2.5 mM) induced jarosite transformation to humboldtine under anoxic conditions and to lepidocrocite under oxic conditions. This difference in transformation gave rise to distinct mobility of Sb and As, as the results demonstrated that the formed lepidocrocite exhibited a superior capability to fix Sb and As compared to humboldtine. Additionally, the photoaged Sb preferentially partitioned into the poorly crystalline phase, whereas As tended to adsorb onto the mineral surface. These findings provide new insights into the photochemical interactions between iron minerals and DOM, and reveal the differences in the photochemical transformation of jarosite under anoxic and oxic environments. These are crucial for predicting the behavior of Sb and As in sunlit environments.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"415 ","pages":"Pages 12-24"},"PeriodicalIF":5.0,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reprocessing of lunar crust at ∼4.3 Ga inferred from in situ U-Pb isotopic and trace element investigation of Northwest Africa 11479","authors":"Jingyou Chen ,&nbsp;Shaolin Li ,&nbsp;Shiyong Liao ,&nbsp;Jian Chen ,&nbsp;Alexander Nemchin ,&nbsp;Katherine H. Joy ,&nbsp;Xiaochao Che ,&nbsp;Weibiao Hsu ,&nbsp;Menghua Zhu","doi":"10.1016/j.gca.2026.01.007","DOIUrl":"10.1016/j.gca.2026.01.007","url":null,"abstract":"<div><div>The increasing identification of magnesian anorthosites (MAN) in lunar meteorites, along with inferences from remote sensing techniques, has intensified research interest in understanding their role in lunar crust formation. However, the lack of robust geochronological constraints for MAN impeded our comprehension of the timeline of crustal evolution. The lunar feldspathic breccia meteorite, Northwest Africa (NWA) 11479, is composed primarily of Mg-rich, KREEP-poor (K, rare earth elements, and P) highland lithic fragments, predominantly consisting of magnesian anorthositic lithologies (including anorthosite noritic/troctolitic anorthosites, and the associated magnesian granulites). The close chemical match between the bulk rock and lunar remote sensing data supports a farside origin, providing evidence for the presence of MAN in the Feldspathic Highlands Terrane (FHT).</div><div>Zircon and apatite grains have been discovered within the small Mg-rich anorthositic clasts in NWA 11479. Notably, the occurrence of these highly evolved accessory minerals contrasts with the depletion of incompatible trace elements in the coexisting silicates, suggesting their formation via interactions between the anorthositic crust and a later-stage KREEPy metasomatic melt. <em>In-situ</em> U-Pb isotopic analysis of the zircon and apatite yields a well-defined discordia line, with an upper intercept date of 4328 ± 9 Ma (2σ), and a lower intercept date of 140 ± 64 Ma (2σ). The younger age likely reflects a more recent impact event, whereas the upper intercept is consistent with both the concordant U-Pb zircon date (4327 ± 12 Ma, 2σ) and the weighted average ²⁰⁷Pb/²⁰⁶Pb date of the zircon and apatite (4326 ± 8 Ma, 2σ). This ∼ 4.33 Ga age is interpreted as the timing of metasomatism responsible for the formation of the zircon and apatite, or an impact event. Importantly, this age obtained from the putative-origin meteorite coincides with the period (4.3–4.35 Ga) of the active secondary magmatism recorded in nearside-collected Apollo samples, the proposed formation age of the giant South Pole–Aitken (SPA) basin. These temporal correlations suggest that this epoch represents a major phase of global reworking of the primordial lunar crust, likely driven by the overturn of mantle cumulates, and further associated with basin‑scale impact events, or both.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"415 ","pages":"Pages 56-70"},"PeriodicalIF":5.0,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative dissolution of iron-bearing minerals by catecholate and hydroxamate siderophores under oxic and anoxic conditions","authors":"Dongyi Guo ,&nbsp;Yizhi Sheng ,&nbsp;Owen W. Duckworth ,&nbsp;Hsin-Mei Kao ,&nbsp;Zihua Zhu ,&nbsp;David M. Gooden ,&nbsp;Oliver Barrs ,&nbsp;Hailiang Dong","doi":"10.1016/j.gca.2026.01.009","DOIUrl":"10.1016/j.gca.2026.01.009","url":null,"abstract":"<div><div>Siderophores play a crucial role in acquisition and mobilization of iron (Fe) and other trace metals by promoting weathering of Fe-bearing minerals and rocks via either ligand-exchange or redox cycling mechanism. While the dissolution effects of the hydroxamate siderophore desferrioxamine B (DFOB) have been investigated under oxic conditions, the roles of other naturally present catecholate siderophores in dissolving Fe-bearing minerals have yet to be fully elucidated. Herein, we investigated the dissolution behavior of four minerals and rocks (nontronite, goethite, basalt, and olivine) by the catecholate protochelin and the hydroxamate DFOB under both oxic and anoxic conditions. Our results revealed a dual role of siderophores—not only as Fe(II)/Fe(III) chelators but also as potential “electron shuttles” that can promote oxidation of Fe(II) under oxic conditions and reduce Fe(III) under anoxic conditions. Under oxic conditions, both siderophores promoted oxidation of structural Fe(II) in basalt and olivine, with DFOB showing a greater Fe(II) oxidation capacity than protochelin, driving dissolution through ligand-exchange and oxidative mechanisms. Under anoxic conditions, both siderophores reduced structural Fe(III) in nontronite and goethite, with protochelin demonstrating a substantially greater reduction capacity than DFOB, promoting dissolution via ligand-exchange and reductive mechanisms. Although siderophore-driven redox-cycling was expected to enhance Fe release, we found that, this mechanism did not result in additional Fe release beyond the effect of ligand-exchange alone. This is likely due to differences in siderophore adsorption, Fe(II) and Fe(III) binding affinities, and siderophore structural integrity, once Fe redox reaction occurred. Other than Fe, dissolution of other transition metals depended on elemental content, mineral composition, and siderophore type, revealing distinct metal- and siderophore-specific patterns. This systematic investigation highlights the role of siderophores in Fe redox cycling and metal mobilization, advancing our understanding of their distinct behaviors in microbial metal acquisition under redox-dynamic conditions, with implications for bioleaching, agriculture, and climate change mitigation.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"415 ","pages":"Pages 71-90"},"PeriodicalIF":5.0,"publicationDate":"2026-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}