Chemical Geology最新文献

{"title":"Multiple magmatic processes and seawater circulation into the uppermost mantle of the Oman ophiolite: Evidence from Sr isotope and geochemical data for CM1A core samples from the Oman Drilling Project","authors":"Masako Yoshikawa ,&nbsp;Tomoyuki Shibata ,&nbsp;Ryoko Senda ,&nbsp;Yumiko Harigane ,&nbsp;Muhamad Asyraf Aminuddin ,&nbsp;Tomoaki Morishita","doi":"10.1016/j.chemgeo.2025.123072","DOIUrl":"10.1016/j.chemgeo.2025.123072","url":null,"abstract":"<div><div>Continuous sampling between the lower crust and uppermost mantle was achieved at the CM1A drill site of the Wadi Tayin massif, the southern Oman ophiolite, during the Oman Drilling Project. We analysed the ⁸⁷Sr/⁸⁶Sr and trace element compositions of relatively fresh gabbroic rocks and extensively serpentinised peridotites (dunite and harzburgite) from the drill core. Most trace element data combined with spinel Cr# (atomic Cr/[Cr + Al] ratios) indicate at least two magmatic processes. The initial ⁸⁷Sr/⁸⁶Sr ratios of the gabbroic rocks (⁸⁷Sr/⁸⁶Sr_96Ma = 0.70303–0.70320) and peridotites (⁸⁷Sr/⁸⁶Sr_96Ma = 0.70377–0.70418) are clearly higher than previously reported primary igneous rocks of the Oman ophiolite (⁸⁷Sr/⁸⁶Sr_100Ma = 0.70265, <span><span>Kawahata et al., 2001</span></span>), but significantly lower than seawater at 96 Ma/present and ophicarbonates formed during/after obduction in the Oman ophiolite. Estimated ⁸⁷Sr/⁸⁶Sr ratios of the involved fluids to the CM1A peridotites are consistent with those of endmember hydrothermal vent fluids from East Pacific Rise and Mid Atlantic Ridge. These ⁸⁷Sr/⁸⁶Sr signatures, together with mesh texture of serpentine, indicate seawater penetration into the uppermost mantle at temperatures of &lt;500 °C in an off-axis setting. These observations suggest that the uppermost mantle was hydrated by hydrothermal fluids circulating probably through microcracks formed during serpentinisation, and that the ⁸⁷Sr/⁸⁶Sr ratios of fluids reaching the uppermost mantle were homogenised during their transport through the crust as a hydrothermal system at off-axis.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123072"},"PeriodicalIF":3.6,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145261796","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":"Temporal evolution of enriched mantle sources in the southeastern Canadian Cordillera revealed by zircon geochronology and Hf isotopes in carbonatites","authors":"Lindsey Abdale ,&nbsp;Leo J. Millonig ,&nbsp;JoAnne Nelson ,&nbsp;Lee A. Groat ,&nbsp;Axel Gerdes","doi":"10.1016/j.chemgeo.2025.123044","DOIUrl":"10.1016/j.chemgeo.2025.123044","url":null,"abstract":"<div><div>Zircon from carbonatites and syenites of the Blue River area and Monashee Complex (southeast British Columbia, Canada) were analyzed for cathodoluminescence textures, trace elements, and Lu-Hf isotopic compositions. U-Pb geochronology reveals two distinct pulses of carbonatite magmatism: Early Cambrian (ca. 505 Ma) at Gum Creek, associated with continental margin extension, and Upper Devonian (ca. 358 Ma) at Howard Creek, linked to back-arc extension. Neoproterozoic to Cambrian samples from Perry River, Ren, and Gum Creek exhibit slightly enriched mantle Hf signatures, consistent with metasomatized mantle influenced by plume activity and early rifting along western Laurentia. In contrast, Devonian–Carboniferous carbonatites and syenites show a wider range of <span><math><mi>ɛ</mi></math></span>Hf values, reflecting depleted to very enriched mantle components. Mount Grace and Three Valley Gap carbonatites display enriched <span><math><mi>ɛ</mi></math></span>Hf (+3.5 to +7.6), suggesting derivation from a metasomatized mantle with minimal crustal input, while the Trident Mountain syenite and Howard Creek carbonatite yield negative <span><math><mi>ɛ</mi></math></span>Hf values (-3.7 to -1.1), indicative of enriched mantle and possible crustal sources. These results highlight a tectonic transition from homogeneous enriched mantle sources prior to subduction to increasingly heterogeneous mantle reservoirs during subduction-related extension, documenting evolving mantle dynamics beneath western Laurentia.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123044"},"PeriodicalIF":3.6,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145261798","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":"Modification of oceanic lithospheric mantle by percolated melts sourced from recycled ancient crust: Evidence from CaOs isotopes of refractory harzburgites","authors":"Hui-Chao Rui ,&nbsp;Olivier Namur ,&nbsp;Dong-Yang Lian ,&nbsp;Peng-Jie Cai ,&nbsp;Jie Li ,&nbsp;Yurisley Valdes-Mariño ,&nbsp;Jing-Sui Yang ,&nbsp;Hong-Ping He","doi":"10.1016/j.chemgeo.2025.123077","DOIUrl":"10.1016/j.chemgeo.2025.123077","url":null,"abstract":"<div><div>Oceanic lithospheric mantle, initially formed beneath the oceanic plate's spreading center, is frequently altered through interaction with mantle-derived mafic melts migrating upward to the crustal regions. Highly refractory harzburgites often retain trace interstitial clinopyroxene and base-metal sulfides (BMS) that precipitate during the interaction with percolating melts. In this study, we present the whole-rock and mineral Ca as well as <em>Re</em><img>Os isotope compositions of harzburgites from the Moa-Baracoa ophiolite in Cuba, to uncover the melt-peridotite interaction processes and evaluate their impact on the composition of the lithospheric mantle. Thermodynamic modeling indicates that the studied harzburgites have undergone a high degree (20–30 %) of partial melting compared to the depleted mid-ocean ridge basalts mantle, followed by interaction with a very small amount (&lt;2 %) of fore-arc basaltic melts within the lithospheric mantle. The whole-rock δ⁴⁴/⁴⁰Ca values, ranging from 1.06 ‰ to 1.31 ‰, are lower than those calculated for highly refractory harzburgites that have experienced 20–30 % partial melting. This suggests an offset caused by interstitial clinopyroxene with light δ⁴⁴/⁴⁰Ca. Moreover, the elevated ¹⁸⁷Os/¹⁸⁸Os ratios (0.1271–0.1401), combined with low Re concentrations (0.03–0.64) and ¹⁸⁷Re/¹⁸⁸Os ratios (0.08–1.40), imply the addition of radiogenic Os derived either from the subducted slab or ancient crustal components recycled in the mantle. The negative trend of increasing ¹⁸⁷Os/¹⁸⁸Os ratios with decreasing δ⁴⁴/⁴⁰Ca values further validates the co-precipitation of sulfides and clinopyroxene in the Moa-Baracoa harzburgite. Notably, similar mineral assemblages and whole-rock radiogenic Os compositions are observed in certain abyssal peridotites and ophiolitic peridotites. Binary mixing calculations demonstrate that such <em>Re</em><img>Os characteristics can only occur when rare BMS precipitate from percolating mafic melts with small fractions originating from recycled ancient crust.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123077"},"PeriodicalIF":3.6,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145261843","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":"Siderite transformation pathways in early diagenesis: Effects of phosphate, silicate, humic acid and sulfide","authors":"Zhe Zhou ,&nbsp;Heng Xiao ,&nbsp;Baorong Huang ,&nbsp;Jiangtao Li ,&nbsp;Shouye Yang","doi":"10.1016/j.chemgeo.2025.123075","DOIUrl":"10.1016/j.chemgeo.2025.123075","url":null,"abstract":"<div><div>Siderite (FeCO₃) is a widely distributed authigenic mineral found in marine and terrestrial sediments, playing a crucial role in benthic biogeochemical cycling and preserving key paleoenvironmental information. Despite its importance, the transformation pathways of siderite under complex sedimentary environments remain poorly understood. Here batch experiments were conducted to investigate the transformation of siderite (containing 10 mM Fe(II)) in the presence of phosphate (P/Fe ratios of 0.2, 0.5, and 1), sulfide (S/Fe ratios of 0.5, and 1), silicate (Si/Fe ratios of 0.5, and 1), and humic acid (C/Fe ratios of 0.5, and 1) over hours to 6 days under strictly anoxic conditions. Our results show that phosphate induced a rapid dissolution-reprecipitation process of siderite at pH 7.8, forming nanocrystalline vivianite first and gradually integrating into the lath-like structure, effectively sequestering phosphate. However, after transition into sulfidic conditions, vivianite rapidly converts into mackinawite, releasing nearly all immobilized phosphate, underscoring its transient role as a phosphate reservoir. Silicate and humic acid, though inert in directly transforming siderite under anoxic conditions, significantly influence sulfide-induced siderite transformation. Sulfide can rapidly transform siderite into FeS (e.g., mackinawite) while preserving the pseudomorph of siderite and generating a highly porous ultrastructure on the surface. The presence of silicate promotes mackinawite crystallization, while humic acid suppresses secondary iron mineral formation, resulting in smoother, less porous FeS structures. These findings highlight the dynamic interplay between siderite and environmental factors, offering new insights into phosphorus cycling mediated by siderite. Importantly, this study provides a refined understanding of the mineralogical and morphological evolution of siderite, enhancing the accuracy of applying this redox proxy for sedimentary history reconstructions, and informing biogeochemical models of the coupled Fe-P-S cycling in early diagenesis.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123075"},"PeriodicalIF":3.6,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217520","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":"Origin of rodingites in the Xigaze ophiolite, SW Tibet: Constraints from Ca and Sr isotopes","authors":"Yu-Wei She ,&nbsp;Jian Sun ,&nbsp;Zhi-Yong Zhu ,&nbsp;Qiu-Hong Xie ,&nbsp;Chen-Xu Pan","doi":"10.1016/j.chemgeo.2025.123071","DOIUrl":"10.1016/j.chemgeo.2025.123071","url":null,"abstract":"<div><div>Rodingites, extremely calcium-rich but sodium- and silicon-poor rocks forming through fluid-rock reactions, are crucial for understanding the oceanic cycling of materials. However, the source of calcium in rodingites remains debated. Here, we investigate whole rock Ca and Sr isotopic compositions of samples collected across a continuous section of a rodingite dyke from the Xigaze ophiolite, SW Tibet. The rodingite dyke exhibits progressive metasomatism from core to margin, defining central, transitional, and marginal zones. The dyke displays a wide range of δ^44/40Ca values from 0.28 ‰ to 1.63 ‰ but limited variation in Sr isotope (⁸⁷Sr/⁸⁶Sr_(<em>i</em>) = 0.70308–0.70438). The slightly metasomatized central rodingites exhibit lower δ^44/40Ca values (0.53 ‰ to 0.68 ‰) than MORB, whereas the moderately metasomatized transitional rodingites display significantly lighter Ca isotope compositions (δ^44/40Ca = 0.28 ‰ to 0.61 ‰). The intensively metasomatized marginal rodingites show the highest δ^44/40Ca values (0.64 ‰ to 1.63 ‰). The transverse profile of δ^44/40Ca values across the rodingite dyke reveals clear oscillatory zoning, suggesting multiple fluid sources for Ca during rodingitization. In the early-stage, the mafic dyke was metasomatized by a carbonate-bearing fluid characterized by low δ^44/40Ca values, which originated from the mixing of deserpentinization-related fluids with marine carbonates during subduction. Subsequently, the dyke experienced more intense metasomatism by a high-δ^44/40Ca serpentinizing fluid, leading to additional Ca input and an elevation of δ^44/40Ca values. The gradual increase in ⁸⁷Sr/⁸⁶Sr_(<em>i</em>) ratios from the central zone to the marginal zone indicates that the primary fluids were derived from seawater-triggered serpentinization. This study proposes that during the initial stages of subduction fluids released by serpentinite dehydration dissolved sedimentary carbonates on the subducted oceanic slab. As subduction progressed, extensive dehydration of the surrounding serpentinites produced high-δ^44/40Ca serpentinizing fluids, which further elevated both δ^44/40Ca and ⁸⁷Sr/⁸⁶Sr_(<em>i</em>) values of the dyke. The highly variable δ^44/40Ca values of rodingites from diverse tectonic settings support the model involving multiple fluid contributions with distinct Ca isotopic compositions during rodingitization.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123071"},"PeriodicalIF":3.6,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217586","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":"Chemical features of sediment-derived supercritical fluid-melt at subduction zone conditions","authors":"Alexander G. Sokol,&nbsp;Olga A. Kozmenko,&nbsp;Alexey N. Kruk","doi":"10.1016/j.chemgeo.2025.123073","DOIUrl":"10.1016/j.chemgeo.2025.123073","url":null,"abstract":"<div><div>Phase relations and partitioning of major and some trace elements are studied in samples of metasediment (natural schist) poor in H₂O (2.2 wt%) and CO₂ (0.9 wt%) in diamond trap experiments at pressures of 3.0 GPa, 5.5, and 7.8 GPa and temperatures from 750 to 1090 °C. At the applied <em>P-T</em> parameters simulating the conditions of warm and hot subduction, the run products comprise a mobile phase and a residue composed of garnet, phengite, clinopyroxene, coesite, kyanite, as well as accessory monazite, rutile, and zircon. The mobile phase is a hydrous melt of a granitic composition till 3.0 GPa and 750–900 °C but transforms into a supercritical fluid-melt (SCFM) with SiO₂ &gt; Al₂O₃ ≈ K₂O &gt; Na₂O ≈ CaO ≈ MgO ≈ FeO at 5.5 GPa and 850–1030 °C. The transformation is accompanied by increase in the contents of H₂O + CO₂ from 17–24 wt% to &gt;40 wt%, at the weight ratio H₂O/(H₂O + CO₂) ∼0.75. SCFM remains almost invariable in its fraction and amounts of H₂O + CO₂ and solutes within the 5.5–7.8 GPa and 850–1090 °C intervals. At higher pressures and temperatures, the coefficients of Al and Na partitioning between the mobile phase and the residue (<em>D</em> = C_SCFM/C_Residue) become lower and that of K increases, whereby the K₂O/Na₂O ratio in SCFM becomes an order of magnitude greater than in hydrous melt. The revealed trend can be used as a criterion for discriminating between hydrous melt and SCFM proceeding from the bulk composition of multiphase inclusions in mantle minerals. The K₂O/H₂O ratio in metasediment-derived SCFM increases with pressure but does not vary much with temperature. This provides experimental evidence for the potash-depth relationship inferred earlier for primitive arc lavas. The partition coefficients of Sr, K, Rb and P become progressively higher with pressure and temperature to make these elements least compatible at 7.8 GPa and 940–1090 °C in the presence of SCFM. The partition coefficient of Li is &gt;1 at moderate temperatures only. Thus, SCFM can originate in pre-devolatilized metasediment poor in H₂O and CO₂ subducting to depths of 150 to 240 km. The low contents of volatiles in the metasediment ensure stability of the residue monazite and phengite which are main carriers of LREE and LILE recycled by slabs into the mantle wedge. K-rich silicic SCFM penetrating into the mantle can be an important agent in the generation of arc and back-arc magmas, as well as in metasomatism of lithospheric mantle.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123073"},"PeriodicalIF":3.6,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217584","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":"Elemental signatures of metamorphic, diagenetic, and pedogenic magnesites from Central Queensland, Australia","authors":"Carl Swindle ,&nbsp;Paulo Vasconcelos ,&nbsp;Zoe Dimarco ,&nbsp;Nathan Dalleska ,&nbsp;Ai Nguyen ,&nbsp;Emily Cardarelli ,&nbsp;Surjyendu Bhattacharjee ,&nbsp;Kenneth Farley ,&nbsp;Theodore Present","doi":"10.1016/j.chemgeo.2025.123068","DOIUrl":"10.1016/j.chemgeo.2025.123068","url":null,"abstract":"<div><div>Magnesium carbonates record information on water-rock interactions during and after mineral precipitation. The Marlborough Terrane in central Queensland, Australia, contains magnesite-bearing serpentinite highlands surrounded by low-lying sedimentary basins that host authigenic magnesite (MgCO₃). Open pit mines in both settings provide exposures of serpentinites (Gumigil) and Cenozoic sediments and overlying black soils (Yaamba) that host the magnesite and other authigenic phases. The Gumigil mine contains deeply weathered serpentinite hosting metamorphic magnesite veins that formed <em>syn</em>-tectonically; both serpentinite and magnesite are now partially dissolving, silicifying, and ferruginizing. Aqueous Mg²⁺ is being exported into the basins surrounding the serpentinite ridges. The Yaamba magnesite mine in the surrounding plains exposes diagenetic magnesite formation within unlithified alluvial sediments, where ascending magnesium-rich groundwaters replace arkosic sands and silts by magnesite cements, nodules, and pinnacles. Late-stage pedogenic processes at Gumigil and Yaamba drive retrograde transformation of magnesite into geochemically distinct exterior regions of second-generation cryptocrystalline magnesite recording interactions with Fe/Mn-oxides/hydroxides via cerium anomalies, yttrium anomalies and manganese concentrations in zoned magnesites from Yaamba. The complex history of mineral precipitation, dissolution, diagenetic replacement, and supergene alteration is recorded in the major, minor and trace element compositions of magnesites at each site. Serpentinite ridges and magnesite-bearing valley floors in Central Queensland provide a useful analog to the processes that might occur in the ultramafic highlands and carbonated lowlands at Jezero crater, Mars.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123068"},"PeriodicalIF":3.6,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217585","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":"Modeling seawater-basalt interaction at 10–100 °C: Controlling parameters and effects on the composition of the oceanic crust and seawater","authors":"Simon Prause ,&nbsp;Barbara I. Kleine-Marshall ,&nbsp;Tobias B. Weisenberger ,&nbsp;Andri Stefánsson","doi":"10.1016/j.chemgeo.2025.123074","DOIUrl":"10.1016/j.chemgeo.2025.123074","url":null,"abstract":"<div><div>Chemical reactions and element mobilization during seawater-basalt interaction play a central role in regulating global element fluxes between seawater and the oceanic crust. This study uses kinetic reaction path modeling to investigate basalt alteration by seawater at 10–100 °C, assessing the influence of reaction time, temperature, pH, rock crystallinity and CO₂ concentration on alteration mineral formation and seawater composition during crustal aging and cooling. Early alteration involves dissolution of basaltic glass and primary minerals, releasing Si, Al, Fe, Ca, Mg, Na and K, followed by the formation of oxides, hydroxides, pyrite, Fe(III)- and Fe(II)-bearing clays, carbonates, celadonite and zeolites. At elevated CO₂ concentrations, for example due to deep magmatic degassing, water pH remains buffered at slightly acidic to circumneutral values. In contrast, at lower CO₂ concentrations, corresponding to standard seawater, H⁺ consumption during basalt dissolution increases pH and drives the system towards more reducing conditions, thereby favoring the formation of zeolites, Ca-silicates and Mg-rich clays. Reaction progress, redox conditions, pH and CO₂ concentration are the primary controls on alteration mineralogy and seawater chemistry. Basalt crystallinity mainly influenced reaction rates and timescales while having minor effects on the mineralogical and chemical outcome of alteration. Temperature likewise mostly affected kinetics but also had an additional effect on K fluxes during seawater-basalt interaction, with K being removed from seawater below ∼50 °C, but added to seawater at higher temperatures. The model predicts significant long-term sinks of both K and Mg due to the formation of clay minerals and celadonite over the course of crustal aging and cooling. Calcium behaved variably, being mostly removed from seawater by early carbonate formation but becoming increasingly released over the cause of crustal aging due to basalt leaching. These results emphasize the need to constrain key parameters controlling seawater-basalt interaction when evaluating its role in low-temperature hydrothermal alteration and seafloor weathering.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123074"},"PeriodicalIF":3.6,"publicationDate":"2025-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155692","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":"Systematic evaluation of the effects of post-entrapment modifications to fluid inclusion properties and implications to data interpretation in the H2O-NaCl system","authors":"Wei Mao ,&nbsp;Thomas Ulrich","doi":"10.1016/j.chemgeo.2025.123069","DOIUrl":"10.1016/j.chemgeo.2025.123069","url":null,"abstract":"<div><div>Fluid inclusion studies typically report temperature, pressure and fluid composition data of hydrothermal systems. The inclusions follow specific evolution paths after their entrapment. Post-entrapment modifications will alter the paths to form fluid inclusions with a different homogenization behavior if phase boundaries are crossed. Low-salinity fluid inclusions may cross the locus of critical points due to post-entrapment processes, forming assemblages with variable bubble sizes and different homogenization behavior, while their homogenization temperature may only slightly change. Homogenization temperature, pressure, and homogenization behavior of high-salinity inclusions are generally changed to a larger extent by volume contraction/expansion than this is the case for low-salinity inclusions. Water loss commonly accompanies volume changes of the host mineral by the hydrolytic weakening process. Therefore, the lowest salinity inclusion should have lost the least water in a fluid inclusion assemblage (FIA).</div><div>The linear relationship between salinity and homogenization temperature in FIAs from many porphyry deposits can be produced by the combination of volume contraction and water loss, and the variable slopes rely on the relative contribution of each process. The hydrolytic weakening of quartz is prone to occur at relatively high temperature conditions, therefore, there is a characteristically increasing trend in the variation of homogenization temperature with temperature for individual FIAs. Decreased homogenization temperature in the early-trapped high-temperature fluid inclusions will lead to under-estimation of the trapping temperature and hinder the understanding of timing and mechanism of metal precipitation in magmatic-hydrothermal deposits.</div><div>Post-entrapment modifications of fluid inclusions may significantly change the homogenization behavior and the temperature-pressure-composition data, obstructing the reconstruction of ore-forming conditions, metamorphic processes, basin fluid evolution, etc. We comprehensively reviewed the effects of post-entrapment modifications to fluid inclusion properties by numerical calculations and reevaluated published fluid inclusion data from many hydrothermal deposits.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123069"},"PeriodicalIF":3.6,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145261849","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":"New He-O-Sr-Nd isotopes and chronology of Quaternary lavas from the Kula volcanic field (western Türkiye): Implications for temporal changes in the magma source","authors":"Duru Cesur ,&nbsp;Halim Mutlu ,&nbsp;Ercan Aldanmaz ,&nbsp;Finlay M. Stuart ,&nbsp;Ana Carracedo ,&nbsp;Robert M. Ellam ,&nbsp;Nilgün Güleç","doi":"10.1016/j.chemgeo.2025.123070","DOIUrl":"10.1016/j.chemgeo.2025.123070","url":null,"abstract":"<div><div>The Quaternary Kula volcanic field in western Turkey comprises predominantly sodium-rich alkaline basaltic products from several eruption periods. We report new bulk-rock major-trace element, Sr<img>Nd isotopes, helium and oxygen isotope determinations of olivine phenocrysts and Ar/Ar and cosmogenic He ages to investigate the mantle source characteristics and the temporal change in melt source isotope compositions. The volcanic activity in the Kula field continued episodically from 1.28 Ma to around 8 ka and can be divided into three main eruption phases characterized by distinct eruption type and lava morphology. The lava compositions from these phases evolve from basanite to phonolitic tephrite. ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd range from 0.703012 to 0.703407 and 0.512968 to 0.513032, respectively, becoming less enriched in time. The earliest basalts display a small degree of crustal contamination that reduces with time that may be the result of rapid ascent of magmas in the volcanic conduit, likely resulting from gradually increasing rate of extensional deformation and enhanced lithospheric fracturing. ³He/⁴He ratios vary from 3.50 to 8.04 Ra, while δ¹⁸O values vary from 4.7 to 5.2 ‰. The less differentiated samples are characterized by higher ³He/⁴He with &gt;7 Ra, indicating melt derivation from a low-³He/⁴He OIB-type sub-lithospheric mantle source. The relatively large range in ³He/⁴He and δ¹⁸O values with insignificant change in ⁸⁷Sr/⁸⁶Sr for the entire suite further indicates mixing of melts from a multi-component mantle source.</div></div>","PeriodicalId":9847,"journal":{"name":"Chemical Geology","volume":"695 ","pages":"Article 123070"},"PeriodicalIF":3.6,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145155129","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}