Chemical Geology最新文献

{"title":"Testing selenite gypsum crystals from caves for reconstructing the stable isotope composition of paleo-aquifers","authors":"Fernando Gázquez ,&nbsp;Xuefeng Wang ,&nbsp;Wuhui Duan ,&nbsp;Paolo Forti ,&nbsp;Stein-Erik Lauritzen ,&nbsp;José María Calaforra","doi":"10.1016/j.chemgeo.2025.123134","DOIUrl":"10.1016/j.chemgeo.2025.123134","url":null,"abstract":"<div><div>Selenite is a variety of gypsum (CaSO₄·2H₂O) that typically forms large, transparent prismatic crystals. In recent decades, meter-sized selenite crystals have been found in several caves worldwide. These gypsum speleothems formed underwater, in highly stable, epithermal or low-temperature aquifers. Here we investigate the U-Th ages of decimeter-sized selenite crystals from Cueva de los Cristales (Naica mine, northern Mexico) and the Giant Geode of Pulpí (Almería, southeastern Spain). Furthermore, the hydrogen and oxygen isotope compositions of gypsum hydration water measured along the crystal growth axes were used to reconstruct the isotopic evolution of the Naica and Pulpí paleo-aquifers. Extremely low uranium concentrations (&lt;2 ppb in Pulpí and &lt; 0.1 ppb in Naica) make obtaining reliable age models challenging. However, repeated independent measurements of each sample and using large sample sizes can yield reliable and accurate ages. A Naica crystal that grew over the last 31 ± 6 kyr recorded a stepwise change in the isotope composition of paleo-aquifer water, likely reflecting a shift in recharge isotopic composition (rainfall) due to Glacial–Holocene climate change in northern Mexico. A crystal from the Giant Geode of Pulpí that began growing at 191 ± 26 kyr recorded relatively constant δ²H groundwater values, likely reflecting stable climatic conditions during its formation. We critically discuss the caveats of using selenite gypsum crystals from caves as paleohydrological archives and conclude that, despite the challenges, they have strong potential for reconstructing the isotopic composition of paleo-aquifers and past rainfall.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123134"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145462065","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":"Volatile loss during heating of lunar mare simulants and related compositions","authors":"Jennifer Sutherland ,&nbsp;Kai-Uwe Hess ,&nbsp;Thilo Bissbort ,&nbsp;Simon Stapperfend ,&nbsp;Axel Müller ,&nbsp;Thomas C. Hansen ,&nbsp;Alexander Rack ,&nbsp;Donald B. Dingwell","doi":"10.1016/j.chemgeo.2025.123115","DOIUrl":"10.1016/j.chemgeo.2025.123115","url":null,"abstract":"<div><div>Due to the scarcity of returned lunar regolith samples, simulants are currently widely used for testing and validation of technologies destined for resource extraction and manipulation on the Moon's surface. Deductions about thermal processing parameters (such as temperature ranges associated with sintering and melting) and material properties rely on a close fidelity of the terrestrially-sourced simulant materials. To evaluate the degassing behaviour of lunar regolith simulants during heating and thereby inform the validity of comparisons to the behaviour expected of actual lunar regolith, we compare profiles via simultaneous differential scanning calorimetry (DSC)<em>,</em> thermogravimetric analysis (TGA), and evolved gas analysis (EGA) across a range of designated mare simulants, freshly recovered volcanic samples, and synthesised lunar-like glasses. Simulants generally exhibit higher mass loss (related to volatile release at sub-solidus temperatures) than fresh volcanic material, though overlap is observed with one simulant (JSC-1A). Of the fresh sources, Etna ash most closely limits the anticipated water loss difference to original lunar soils to within one order of magnitude. Results from complementary neutron powder diffraction (NPD) indicate that a lowering of the melting onset due to volatile fluxing persists ca. 200–300 °C beyond the major degassing range in samples of several grams. The possibility to reduce the simulant fidelity gap through critical source selection and their inherent limitations are discussed, and refined pre-treatment recommendations are made.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123115"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145396659","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":"Magnesium isotopic evidence for intensified continental chemical weathering during the Smithian-Spathian transition","authors":"Xingyu Ma ,&nbsp;Kangjun Huang ,&nbsp;Yan Chen ,&nbsp;Yadong Sun ,&nbsp;Ying Zhou ,&nbsp;Graham A. Shields ,&nbsp;Fang Huang ,&nbsp;Genming Luo","doi":"10.1016/j.chemgeo.2025.123133","DOIUrl":"10.1016/j.chemgeo.2025.123133","url":null,"abstract":"<div><div>The Smithian-Spathian (S-S) transition (∼249.7 to 248.7 Ma) of the Early Triassic was marked by profound paleoenvironmental upheavals, including a pronounced temperature decline following the hyperthermal event in the late Smithian, a major positive excursion in carbonate carbon isotope composition (δ¹³C_carb), and a significant biotic crisis. Yet, the mechanisms and causal linkages underlying these coeval phenomena remain elusive. In this study, we present high-temporal-resolution magnesium isotope data from siliciclastic residues within carbonate rocks (δ²⁶Mg_residue), a well-established proxy for continental chemical weathering intensity, across the S-S boundary in the Waili and Jiarong sections in South China. Our results document a distinct positive δ²⁶Mg_residue shift in the lowermost Spathian in both sections, signifying intensified continental chemical weathering. This isotopic shift broadly coincides with the positive δ¹³C_carb excursion and the recovery of terrestrial ecosystems but postdates the late Smithian thermal maximum. We interpret this temporal sequence to suggest that the recovery of terrestrial ecosystems, particularly the expansion of vascular land plants, acted as a primary driver of enhanced continental chemical weathering. The resulting increase in continental chemical weathering likely amplified nutrient flux to the ocean, potentially promoting local marine anoxia and climate cooling observed in the earliest Spathian. These findings underscore the critical role of terrestrial-marine coupling in modulating Early Triassic biogeochemical feedbacks and global climate evolution.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123133"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145485564","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":"Mineralogical evidence of acid mine drainage on spoil tips of the Nord Pas-de-Calais coal mining basin (Northern France): A high-resolution characterization of the black shale weathering","authors":"Yensinga Bafounga ,&nbsp;Franck Bourdelle ,&nbsp;Pauline Claisse ,&nbsp;Sandra Ventalon ,&nbsp;Annette Hofmann ,&nbsp;Emily Lloret","doi":"10.1016/j.chemgeo.2025.123132","DOIUrl":"10.1016/j.chemgeo.2025.123132","url":null,"abstract":"<div><div>The northern France is renowned for its 200 spoil tips, vestiges of coal mining during the 19th and 20th centuries. These tailings composed of Carboniferous black shales are subject to supergene conditions, leading to weathering and potential release of contaminants into the environment. However, it was long accepted that element release process did not occur in this area, and no acid mine drainage (AMD) was observable at the regional scale. Here, we conducted a detailed characterization of the primary and secondary mineral phases comprising the weathered black shales from three selected vegetated spoil tips. Through a combination of macro, micro, and nanoscale analyses (XRD, SEM, FIB, TEM, STXM-XANES), we reveal that AMD occurs on at least the first 30 cm of the entire vegetated surfaces of the spoil tips. This AMD forms an “alteration front” at the surface of the fragmented shale blocks, consisting of two distinct submicrometric layers: an inner Fe-rich layer composed of iron oxyhydroxides and a few nanometric neoformed smectite or illite/smectite, and an outer S-rich layer, featuring euhedral and anhedral jarosite, with a few rosette-like iron oxyhydroxides. Petrographic and textural signatures suggest that these two layers form independently and successively, by direct precipitation from fluids enriched with K, Fe²⁺, Fe³⁺, and S. The 2-layer structure of this alteration front indicates a sharp change in the physico-chemical conditions, in particular a decrease in pH to below 3, during the weathering process. Results also suggest element transfers to the environment; S, Fe and K are released by the shale and fixed at least temporarily at the shale surface, as well as metals and metalloids like As, Sr, Mo and Ge. By highlighting the acidification process, the formation of secondary minerals typical of AMD, and the release of elements from shale, this study sheds light on a long-term process that, although not clearly observable twenty years ago, is now visible at the spoil tips scale and whose consequences could become evident at the landscape scale in the coming decades.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123132"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145462064","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":"Rare earth elements (REE) as indicators of geochemical processes in permafrost systems of the Arctic Foothills, Northern Alaska","authors":"W. Brad Baxter ,&nbsp;Joseph P. Smith ,&nbsp;Thomas A. Douglas ,&nbsp;Robyn A. Barbato ,&nbsp;Shawn Gallaher ,&nbsp;Amanda J. Barker","doi":"10.1016/j.chemgeo.2025.123131","DOIUrl":"10.1016/j.chemgeo.2025.123131","url":null,"abstract":"<div><div>In permafrost environments, distinct soil thermal regimes create unique influences on pedogenic processes and hydrological systems. Rare earth elements (REE) provide utility as indicators of soil geochemical cycling that can improve our understanding of permafrost soil-hydrological systems and their change over time, yet a greater understanding of the factors governing permafrost REE distribution is needed. We assess cryogenic controls on soil REE cycling in permafrost and active layer from three pedogenic environments in the Arctic Foothills of Alaska, and REE of adjacent surface waters. Soil parent material influenced the relative REE species abundance across sites while total extractable REE varied with soil material properties. REE reservoir transfer functions revealed differences in fractionation between permafrost and active layer in middle REE of a peat-rich site, and heavy REE for two sites with higher mineral content, potentially reflecting preferred degradation of heavy REE inorganic complexes in the active layer. Each soil profile revealed accumulation of REE above the near-surface permafrost table which could serve as an important sourcing zone for suprapermafrost flow. REE (&lt;0.45 μm) of two tundra streams featured fractionation toward heavier REE that varied throughout the thaw season, likely with changing flux of species-preferred ligands driven by top-down seasonal soil thaw. Heavy REE enrichment in permafrost translated to elevated heavy REE in the surface waters of an active thermokarst, suggesting that catchment permafrost degradation may be identifiable by increased loading of heavy REE to streams at our sites. Our results demonstrate the importance of soil thermal status on influencing chemical weathering and translocation in permafrost environments and illustrate the potential utility of REE in tracking catchment permafrost stability.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123131"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145462097","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":"Influence of phosphate on hexavalent chromium immobilization by ferrihydrite under light irradiation","authors":"Chaorong Chen ,&nbsp;Sailan Wang ,&nbsp;Yixuan Yang ,&nbsp;Gaofeng Wang ,&nbsp;Jing Liu ,&nbsp;Qingze Chen ,&nbsp;Fei Ge ,&nbsp;Runliang Zhu","doi":"10.1016/j.chemgeo.2025.123144","DOIUrl":"10.1016/j.chemgeo.2025.123144","url":null,"abstract":"<div><div>Ferrihydrite is an important geosorbent and catalyst that is ubiquitous in natural environments, and plays a critical role in regulating the speciation and migration of hexavalent chromium (Cr(VI)). Phosphate has a strong affinity for ferrihydrite surfaces, but it remains unclear how phosphate influences the immobilization of Cr(VI) by ferrihydrite in sunlight-influenced surface environments. Herein, the surface interactions of ferrihydrite and Cr(VI) in the presence of phosphate were studied under mercury lamp irradiation. Results showed that mercury lamp irradiation significantly attenuated the inhibitory effect of phosphate on Cr(VI) removal by ferrihydrite compared to that under dark conditions. X-ray photoelectron spectroscopic (XPS) analysis revealed that Cr(III) was the predominant chromium species immobilized on ferrihydrite surfaces. Specifically, the reduction of Cr(VI) produced CrPO₄ precipitates, whereas the released Fe(III) can also co-adsorb with phosphate (i.e., FePO₄) onto ferrihydrite surfaces. The reduction of Cr(VI) mediated by the generated Fe(II) species and photoelectrons effectively reduces the electrostatic repulsion between Cr(VI) and phosphate, thereby enhancing the immobilization of these two ions on ferrihydrite. Energy dispersive X-ray spectrometer (EDS) results provide direct quantitative evidence that mercury lamp irradiation substantially enhances the immobilization of Cr(VI) and phosphate by ferrihydrite. The above-described results account for the effect of phosphate on the light-induced coupling process of ferrihydrite reductive dissolution and Cr(VI) reductive immobilization, advancing our understanding of the geochemical cycle of Cr(VI) pollution in sunlight-influenced surface environments.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123144"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145485562","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":"Evaluating solute dynamics and methane transformation in high-elevation Rocky Mountain fens using a transporter-transformer framework","authors":"Valerie Martin ,&nbsp;Matthew Winnick ,&nbsp;Brian Saccardi ,&nbsp;Markus Bill ,&nbsp;Mark E. Conrad ,&nbsp;Rosemary W.H. Carroll ,&nbsp;Kate Maher","doi":"10.1016/j.chemgeo.2025.123129","DOIUrl":"10.1016/j.chemgeo.2025.123129","url":null,"abstract":"<div><div>Peat wetlands at high latitudes have been a key focus for geochemical and hydrologic research due to their roles in carbon storage and greenhouse gas emissions. At the local scale, fens facilitate nutrient cycling and methane production via microbial processes. At the watershed scale, their distribution and hydrologic connectivity with surface waters can substantially influence water quality. However, the role of mid-latitude montane fens in moderating watershed functions remains understudied, despite their susceptibility to pronounced redox shifts driven by high-elevation seasonal dynamics.</div><div>We conducted a comprehensive analysis of (1) base cations, (2) biologically active, redox-sensitive nutrients and metals, and (3) carbon compounds in Rocky Mountain fens and surface waters along an elevational gradient in the East River watershed (Upper Gunnison Basin, Colorado, USA). Our aim was to evaluate whether fens act as passive <em>transporters</em> or active <em>transformers</em> of these solute groups. Fen base cation chemistry was largely indistinguishable from surface water and groundwater, suggesting transport-dominated behavior controlled by bedrock lithology. In contrast, anoxic conditions in fens produced distinct redox-sensitive nutrient signatures. A quasi-linear relationship between Cl-normalized NO₃²⁻ and PO₄³⁻ in high-elevation fens and surface waters suggests a possible mixing signal originating from nutrient-enriched fen waters and more dilute surface or groundwater sources. Stable isotope data for dissolved methane, unlike conservative cations, indicate active carbon transformation via methanogenesis, with limited microbial methane oxidation.</div><div>Collectively, our study offers an integrated assessment of the aqueous geochemistry of montane fens and their potential to modulate surface water chemistry across mid-latitude alpine watersheds.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"698 ","pages":"Article 123129"},"PeriodicalIF":3.6,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145447692","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 fidelity of reef carbonates: Contrasting δ34S/δ18O (CAS) and δ138Ba signature preservation under mineralogical and depositional control","authors":"Shanggui Gong ,&nbsp;Yongshi Huang ,&nbsp;Songlin Liu ,&nbsp;Xinyu Jiang ,&nbsp;Jörn Peckmann ,&nbsp;Huiwen Huang ,&nbsp;Dong Feng","doi":"10.1016/j.chemgeo.2025.123114","DOIUrl":"10.1016/j.chemgeo.2025.123114","url":null,"abstract":"<div><div>Shallow-water carbonates record seawater sulfate and barium isotope signatures, offering valuable insight into ocean biogeochemistry. However, the robustness of these proxies can vary with carbonate origin, mineralogy, and the extent of diagenesis. Here, we assess δ³⁴S and δ¹⁸O compositions of carbonate-associated sulfate (CAS; hereafter δ³⁴S_CAS and δ¹⁸O_CAS) and barium isotope compositions of carbonates (δ¹³⁸Ba_carb) of three lithologies, aragonite-rich mud, high-Mg calcite-rich clusters with coralline algae remains, and coral-microbialite facies from a reef environment in the South China Sea. Aragonitic mud shows lower CAS/Ca and higher Ba/Ca molar ratios than calcitic components, reflecting mineralogical control on trace element incorporation. While δ³⁴S_CAS values of carbonate clusters and coral-microbialite facies closely resemble seawater values, δ¹⁸O_CAS values are about 1 ‰ higher, consistent with moderate oxygen isotope fractionation. In contrast, aragonite-rich mud displays lower δ³⁴S_CAS values (∼0.9 ‰ lower) and δ¹⁸O_CAS values (∼2.0 ‰ lower) than seawater, likely due to incorporation of sulfate deriving from sulfide oxidation. Notably, δ¹³⁸Ba_carb values remain constant across all carbonate facies – regardless of mineralogy, biological origin, or diagenesis – highlighting the robustness of the barium isotope proxy. This study recognizes different degrees of primary fractionation during formation and preservational biases among the analyzed proxies: δ¹³⁸Ba_carb values exhibit constant isotope offset with seawater composition irrespective of the archive or the degree of alteration, while δ³⁴S_CAS values and even more so δ¹⁸O_CAS values are compromised by different degrees of primary fractionation upon incorporation of sulfate into the carbonate mineral lattice and secondary alteration. Calibrated offsets from seawater composition for reef carbonates are ca. ± 1 ‰ (2σ) for δ³⁴S, 1.0 ± 2.2 ‰ (2σ) for δ¹⁸O, and − 0.23 ± 0.08 ‰ (2σ) for δ¹³⁸Ba. Our findings help to assess the reliability of isotope-based reconstructions for mixed carbonate lithologies and underscore the robustness of δ³⁴S_CAS and δ¹³⁸Ba_carb values as proxies for past seawater chemistry.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"697 ","pages":"Article 123114"},"PeriodicalIF":3.6,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145383404","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":"Zircon Zirconium isotope fractionation during the arc magmatic differentiation and crustal reworking: Implications for the differentiation of the continental crust","authors":"Yunxuan Zhang ,&nbsp;Liang Guo ,&nbsp;Wen Zhang ,&nbsp;Hongfei Zhang ,&nbsp;Tao Luo ,&nbsp;Xueqiu Wang ,&nbsp;Fabin Pan","doi":"10.1016/j.chemgeo.2025.123113","DOIUrl":"10.1016/j.chemgeo.2025.123113","url":null,"abstract":"<div><div>The upper continental crust is isotopically enriched in heavy stable zirconium (Zr) isotopes compared to the mantle, indicating significant Zr isotope fractionation during crustal differentiation, though the mechanisms remain elusive. Here, we present zircon in-situ Zr isotope data for two magmatic suites of distinct origins (the 91–88 Ma Lilong Complex and the 83–74 Ma Wolong granites) from the Gangdese arc lower crust in southern Tibet. The Lilong Complex, comprising garnet gabbro, quartz diorite, and tonalite, represents a continuous differentiation sequence of arc magma, whereas the Wolong granites were derived from partial melting of the migmatitic garnet gabbro in the Lilong Complex. Zircon from both suites exhibit consistent core-to-rim increases in <em>δ</em>^94/90Zr values, coupled with the negative correlation between <em>δ</em>^94/90Zr and Zr/Hf ratios, indicating that zircon preferentially incorporates light Zr isotopes during crystallization. In the Lilong Complex, zircon <em>δ</em>^94/90Zr increases with rising whole-rock SiO₂, suggesting gradual enrichment of heavy Zr isotopes during arc magma differentiation. Rayleigh modeling indicates that zircon crystallization primarily controls the Zr isotopic evolution of melts. The Wolong granites have higher zircon <em>δ</em>^94/90Zr than their garnet gabbro source, reflecting Zr isotope fractionation between melt and residue during partial melting. These observations indicate that enrichment in the heavy Zr isotopes in felsic magmas results from both fractional crystallization of isotopically light zircon and retention of light Zr isotopes in restites during partial melting. Our findings highlight the roles of magmatic differentiation and crustal reworking in arc settings in shaping the Zr isotopic composition of the continental crust.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"697 ","pages":"Article 123113"},"PeriodicalIF":3.6,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145374374","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":"Unveiling rodingite metasomatism using B and Sr isotopes: Insights from the Voltri Massif, Western Ligurian Alps, Italy","authors":"E. Cannaò","doi":"10.1016/j.chemgeo.2025.123125","DOIUrl":"10.1016/j.chemgeo.2025.123125","url":null,"abstract":"<div><div>The recycling of volatiles and incompatible elements at subduction zones is a key driver of Earth's geochemical evolution, with metasomatic reactions governing elemental fluxes. Rodingites, found at mafic–ultramafic interfaces, may transform into metarodingites during subduction, often accompanied by chlorite-rich blackwall zones. While these rocks are potential geochemical reservoirs, their role in boron (B) cycling remains unclear. This study presents new <em>in-situ</em> δ¹¹B data from chlorite, along with trace element and Sr isotope analyses of clinopyroxene and clinozoisite, from metarodingite–blackwall assemblages in the Voltri Massif (Western Ligurian Alps, Italy). The metarodingites exhibit assemblages of clinopyroxene + garnet + chlorite ± epidote, consistent with rodingitization under oceanic conditions. Preserved mantle-like ⁸⁷Sr/⁸⁶Sr and REE signatures in igneous clinopyroxene cores suggest limited overprinting by seawater-derived fluids. Trace element redistribution in metamorphic minerals (<em>e.g.,</em> HFSE loss, Eu anomalies) points to prograde subduction overprint, and Sr isotopes suggest seawater-derived recycling during burial. Chlorite δ¹¹B values vary spatially in metarodingites, reflecting differences in water/rock ratios and interaction with B-rich fluids during oceanic metasomatism. In contrast, blackwall chlorite shows more uniform δ¹¹B, possibly due to Mg-metasomatism at high water/rock ratios and equilibration at the mafic–ultramafic boundary. Whether these signatures are oceanic or subduction-related remains unresolved, pending geochronological constraints. These data suggest chlorite may serve as a previously unrecognized B reservoir, releasing ¹¹B-enriched fluids during high-pressure breakdown, thereby influencing deep volatile cycling.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"697 ","pages":"Article 123125"},"PeriodicalIF":3.6,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145424077","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}