Lithos最新文献

{"title":"Property and composition of fluids from the subducting oceanic slab: Constraints from multiple veins from SW Tianshan, China","authors":"Zheng-Hua Pan ,&nbsp;Ren-Xu Chen ,&nbsp;Tie-Nan Chen ,&nbsp;Zhuang-Zhuang Yin ,&nbsp;Bing Gong ,&nbsp;Xiang-Ping Zha ,&nbsp;Chuang Wang","doi":"10.1016/j.lithos.2025.108231","DOIUrl":"10.1016/j.lithos.2025.108231","url":null,"abstract":"<div><div>Fluid properties and compositions play critical roles in element mobility and crust-mantle interactions in subduction zones. Veins within high/ultrahigh-pressure metabasites record fluid flow in subduction zones. A comprehensive study combining whole-rock and mineral major and trace element contents, halogen contents and zirconology was conducted on various veins—omphacite, garnet-quartz, quartz and epidote-quartz veins—from SW Tianshan. The results are used to quantitatively reconstruct the properties and compositions of slab-derived fluids during oceanic subduction and exhumation. Omp veins formed during prograde metamorphism (1.8–2.2 GPa; 466–544 °C), whereas Grt-Qz veins formed during early exhumation (1.2–1.4 GPa; 544–621 °C; 303 ± 4 Ma). Qz veins and some Ep-Qz veins formed at ∼287 Ma during eclogite- to amphibolite-facies retrogression (∼1.0 GPa; 493–557 °C), whereas the remaining Ep-Qz veins precipitated during late exhumation (0.6–0.8 GPa; 485–521 °C; 229 ± 7 Ma). Mineral element and isotope data indicate that Omp, Grt-Qz, and Ep-Qz veins formed from aqueous fluids derived from dehydration of metamafic rocks, whereas Qz veins involved serpentinite-derived fluids. Vein-forming aqueous fluids contained 0.04–0.88 wt% F and up to 4.56 wt% Cl. High-pressure fluids forming Omp and Grt-Qz veins exhibit elevated abundances of Ca, Al, Mg, Fe, LILE, HFSE, REE and halogens compared to low-pressure fluids forming Qz and Ep-Qz veins, confirming the role of halogens in enhancing element solubility in aqueous fluids. Whole-rock F/Cl ratios of the veins positively correlate with metal ion, LREE, MREE and HFSE contents. Apatite F/Cl ratios also correlate strongly with rutile Nb/Ta ratios across all vein types. These observations suggest that halogen compositions critically control element solubility in aqueous fluids, particularly for HFSE. As halogen signatures vary in slab-derived fluids during progressive oceanic subduction, they generate distinct element mobility patterns.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108231"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933816","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":"Boundary conditions for the petrogenesis of plagioclase ultraphyric basalts (PUB) from the northeast (NE) pacific ridge system: Constraints from plagioclase-hosted melt inclusions","authors":"Madison X. Betts ,&nbsp;Gokce K. Ustunisik ,&nbsp;Roger L. Nielsen ,&nbsp;Olivia G. Daynes","doi":"10.1016/j.lithos.2025.108232","DOIUrl":"10.1016/j.lithos.2025.108232","url":null,"abstract":"<div><div>The crystal cargo in plagioclase ultraphyric basalts (PUB) together with their melt inclusions (MI) record changes in the major, trace, and isotopic compositions of magmas as they evolve. That geochemical signature provides evidence for the identity and relative significance of the igneous processes such as fractionation, mixing, assimilation, and degassing that modify their host magmas during transport from the melting regime to the surface. This investigation focuses on a case study quantifying the relative roles of these processes active globally at mid-ocean ridges (MOR) based on data collected from plagioclase megacrysts and their homogenized MI from a set of PUB lavas sampled at Blanco Fracture Zone (BFZ), Gorda Ridge, and Endeavor segment of Juan de Fuca (JdF) Ridge in the Northeast (NE) Pacific Ridge system. We combine results for major element phase equilibria calculations based on the MELTS algorithm and apply the major element chemistry, including phase proportions and compositions, to estimate the impact of fractional crystallization and partial melting in the generation and differentiation of these PUB lavas. Our results, in the form of a set of simulations that are based on a range of conditions, enclose the MI, megacryst, and associated lava data and suggest that much of the compositional variation exhibited can be bracketed by 8–20 % incremental batch melting of a heterogeneous mantle protolith, followed by a combined 65–75 % polybaric and isobaric fractional crystallization during ascent. Therefore, only 25–35 % of magma generated in the melting regime survive as liquids to be erupted as lavas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108232"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144989536","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":"Melting and metasomatic history of the lithospheric mantle in the Erzgebirge UHP terrane: Constraints from trace elements, Sr–Nd–Hf–Os isotopes and Lu-Hf dating","authors":"J. Kotková ,&nbsp;R. Čopjaková ,&nbsp;M. Kubeš ,&nbsp;L. Ackerman ,&nbsp;J. Sláma ,&nbsp;E. Schmädicke ,&nbsp;M. Holá","doi":"10.1016/j.lithos.2025.108234","DOIUrl":"10.1016/j.lithos.2025.108234","url":null,"abstract":"<div><div>Garnet peridotites provide a unique insight into the early processes in collisional belts as well as crust-mantle interactions through their elemental and Sr–Nd–Hf–Os isotopic signatures. Here, we focus on (ultra)mafic rocks (peridotite, pyroxenite, eclogite and garnetite) from the Erzgebirge Crystalline Complex, Bohemian Massif, associated with diamond and coesite-bearing crustal rocks. We combine data from petrography, mineralogy, multiphase solid inclusions, major and trace element composition of rocks and minerals as well as Sr–Nd–Hf–Os compositions. We demonstrate that each peridotite type reveals a distinct process of the complex mantle evolution in terms of melting and depletion, superposed metasomatism/refertilization and its timing. Garnet peridotites show SCLM affinity as demonstrated by the presence of amphibole and its composition, high Cr# values of spinel, as well as bulk rock LILE enrichment, HFSE depletion, and flat to LREE-enriched REE patterns. The peridotite from Oberlochmühle records depletion after about 20–30 % of partial melting, while its present fertile character reflects superposed extensive modal metasomatism/refertilization by hydrous alkaline basaltic melts in supra-subduction zone setting. In comparison, the nearby Zöblitz peridotite has undergone about 10–20 % of melt extraction. In addition, the peridotite next to pyroxenite was subject to metasomatism by carbonated silicate (basaltic) melts expressed by the precipitation of garnet, clinopyroxene and phlogopite. Moreover, both lithologies show enrichment in incompatible elements (LREE, LILE – Li, Cs, Ba), U, Th, Pb, and negative HFSE (Nb, Ta, Ti) and Eu anomalies, and contain multiphase solid inclusions composed of silicates (amphibole, barian mica and olivine), carbonates (magnesite, dolomite) and LREE, U and Th-rich phases (apatite, monazite, thorianite). The radiogenic Sr-Os, but negative ε_Nd (down to −1.6) values detected in both pyroxenite and garnetite from Zöblitz indicate the presence of recycled crustal component in the source of metasomatizing basaltic melt. The Voigtsdorf eclogite composition corresponds to subalkaline basaltic rocks with radiogenic ε_Nd and ε_Hf values of clinopyroxene plotting close to mantle array. The Lu-Hf age of ⁓390 Ma obtained for Oberlochmühle peridotite reflects Devonian burial and mantle refertilization, while the ⁓370 Ma age for Zöblitz pyroxenite dates carbonated metasomatism close to UHP conditions. The latter provides evidence for the pre-Carboniferous deep crustal subduction and crust-mantle interaction.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108234"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145046769","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":"Prolonged crustal storage for mantle xenolith-bearing basanite lava","authors":"Xin Zhang ,&nbsp;Tong Hou ,&nbsp;Martin Oeser ,&nbsp;Stefan Weyer","doi":"10.1016/j.lithos.2025.108228","DOIUrl":"10.1016/j.lithos.2025.108228","url":null,"abstract":"<div><div>It is widely accepted that magmas must ascend rapidly to transport dense mantle xenoliths to the surface, with minimal residence or evolution during ascent. Here, we investigate the prolonged storage of xenolith-bearing magma within the crust beneath the Cenozoic alkali basalts at Hannuoba, North China. Petrographic observations identify three distinct olivine types. Olivine xenocrysts are relatively large (&gt;500 μm), with pronounced core-to-rim zoning [Fo₉₀₋₉₁ to Fo₆₄₋₆₅; Fo = molar 100 × Mg/ (Mg + Fe)] and distinctively low CaO contents in the cores (&lt;0.1 wt%), which clearly distinguish them from other olivine types. Trace element and Fe-Mg isotope analyses of these xenocrysts reveal strong compositional zoning, with highly variable δ⁵⁶Fe (−2.70 ‰ to 0.40 ‰) and δ²⁶Mg (−0.69 ‰ to 0.68 ‰), strongly indicating Fe-Mg exchange diffusion with the melt. Phenocrysts are smaller (∼100 μm) than xenocrysts, exhibit compositions similar to the rims of the latter, and lack compositional zoning. Olivine microlites in the fine-grained sample matrix, with an abundance of ∼10 %, show a slightly different NiO–Fo systematic, indicative of fractional crystallization.</div><div>Zoning in Fe-Mg concentrations and Fe-Mg isotopes from the core to the rim of the xenocrysts was used for diffusion modeling to obtain their residence timescales in the magma prior to eruption. Fo zoning, modeled using DIPRA for six olivine grains, yields timescales of 520–3914 days, while dynamic diffusion modeling of Fe-Mg (Fo) provides longer timescales of 4026–18,139 days (i.e., up to 50 years). Fe-Mg isotopic diffusion modeling yields timescales of 542–3333 days. These values represent minimum estimates for the magma residence time, as xenocrystal olivine may have been mechanically detached from entrained xenoliths during magma ascent. These findings contrast with previous interpretations that xenolith- or xenocryst-bearing magmas ascended to the surface within hours to days and instead suggest that the xenolith-bearing alkali basaltic lavas were stored for an extended period in the crustal plumbing system. Such prolonged storage may have facilitated interaction between xenocrysts and the host magma, potentially modifying the magma's bulk composition. Caution is advised when using these magmas to trace their mantle source, as their bulk composition may have been altered by crustal assimilation or interaction with xenoliths/xenocrysts during extended crustal storage.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108228"},"PeriodicalIF":2.5,"publicationDate":"2025-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933631","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":"U-Pb-age from undeformed granite pebbles in Carboniferous Culm conglomerates: new geochronological constrains on the Variscan events in the Pyrenees","authors":"Josep M. Casas ,&nbsp;Eloi González-Esvertit ,&nbsp;Aratz Beranoaguirre ,&nbsp;Diego Domínguez-Carretero ,&nbsp;Àngels Canals ,&nbsp;Enrique Gomez-Rivas ,&nbsp;Aina Margalef ,&nbsp;Francesc Figueras ,&nbsp;Axel Gerdes","doi":"10.1016/j.lithos.2025.108227","DOIUrl":"10.1016/j.lithos.2025.108227","url":null,"abstract":"<div><div>U-Pb ages of zircon and apatite in undeformed granite pebbles of synorogenic Carboniferous Culm conglomerates confirm the existence of an early Carboniferous (Visean to Bashkirian) magmatic event in the core of the Pyrenees. In this so-called Axial Zone, early Carboniferous magmatism developed in at least two main pulses, at ca. 340 Ma and ca. 320 Ma. Obtained ages constrain a mid-Bashkirian maximum age (ca. 320 Ma) for the base of Bellver Culm conglomerates. Together with the well-expressed late Variscan Moscovian-Asselian (ca. 310 to 295 Ma) granites that crosscut Culm rocks, this Visean to Bashkirian magmatism depicts three pulses of Variscan magmatism, grouped in two cycles of magmatic and tectono-thermal events recorded in the basement rocks of the Pyrenean Axial Zone. This complex Variscan evolution argues against previously proposed models claiming for a synkinematic emplacement of the Moscovian-Asselian granites linked to the main Variscan deformational events. Data obtained confirm the occurrence of Variscan events from the Visean to the Moscovian-Asselian in the Pyrenees. In this way, the Variscan basement rocks of the Pyrenees exhibit an evolution that aligns with that described for the rest of the European Variscan realm.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108227"},"PeriodicalIF":2.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145005006","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":"Trace element partitioning among high-temperature pegmatite fluid and wallrock biotite and amphibole, Seridó Pegmatite Province, northeastern Brazil: Implications on thermochronometry of fluid exsolution and advection","authors":"Ricardo Sallet ,&nbsp;Carlos Ribeiro ,&nbsp;Marlina A. Elburg ,&nbsp;Jonathan D. Price ,&nbsp;Marcos Sales ,&nbsp;Robert Moritz","doi":"10.1016/j.lithos.2025.108225","DOIUrl":"10.1016/j.lithos.2025.108225","url":null,"abstract":"<div><div>Pegmatites are recognized for generating wallrock dispersion halos because of fluid exsolution and advection from the crystallizing melt. Nonetheless, the mechanisms governing trace element partitioning between wallrock minerals and migrating fluids remain insufficiently understood. This study reports trace element partition coefficients among biotite, amphibole, and fluid, determined through metric concentration vs. distance profiling at the Areias pegmatite sill wallrock gneiss, Seridó Pegmatite Province, northeastern Brazil. The investigated gneiss maintained its metamorphic mineral assemblage and fabric, with only minor occurrences of local tourmalinization observed. LA-ICP-MS analyses of biotite proximal to the pegmatite reveal enrichment in Li, F, Mg, Cu, Zn, and Ba, and depletion in Ti, V, Cs, and W. In contrast, amphibole exhibits enrichment in Li, F, Mn, Cu, Rb, Ba, and Pb, and depletion in Mg, Ca, Sc, and Ti. Partition coefficient data indicate that biotite preferentially incorporates Cs (214), Rb (67), Ba (27), Li (22), Ta (2.6), Ti (2.1), W (1.9), F (1.7), Ni (1.5), Zn (1.4), Co<img>Nb (1.3), Ga (1.2), Cr (1.1), and V (1.0). Conversely, Be-Sr-Th (0.1), Sc (0.2), B<img>Pb (0.3), Cu (0.4), U (0.5), and Mn (0.7) exhibit greater affinity for amphibole. Biotite/fluid partition coefficients derived from previously modeled Areias pegmatite fluid compositions are Zn (4.63), Cs (1.23), Rb (0.98), F (0.95), Li (0.47), and Nb (0.19); amphibole/fluid values are Zn (3.28), F (0.55), Nb (0.16), Li<img>Rb (0.02), Cs (0.01), and U (0.003). The obtained fluid/melt partition coefficients are Li (19.9), F (7.95), Zn (4.6), Rb (0.97), Cs (0.61), and Nb (0.35). Compared to compiled trace element data from fluid inclusions and geothermal waters, the Areias pegmatite fluid high Rb/Cs and Zn/Nb ratios, along with biotite and amphibole Ti geothermometry temperatures near 673 °C, indicate an unfractionated magmatic origin. Additionally, low Cs/Li and Rb/Li ratios imply substantial fractionation of Li from the melt into the exsolved fluid. Thermochronometric analysis indicates that fluid advection persists for 20 to 100 years, representing a timescale 2 to 4 orders of magnitude longer than thermal models predict for pegmatite crystallization, thereby suggesting that fluid migration commences early and continues beyond pegmatite solidification.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108225"},"PeriodicalIF":2.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933817","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":"A microstructural investigation of the Portrush Sill, County Antrim, Northern Ireland: constraints on sill thickness and evidence for crustal assimilation","authors":"M.B. Holness ,&nbsp;E. Geifman ,&nbsp;M.J. Stock ,&nbsp;M.R. Cooper ,&nbsp;J. Beckwith ,&nbsp;C. Huber ,&nbsp;D. Chew ,&nbsp;J.C.Ø. Andersen","doi":"10.1016/j.lithos.2025.108226","DOIUrl":"10.1016/j.lithos.2025.108226","url":null,"abstract":"<div><div>The Portrush Sill of Northern Ireland, intruded into Lower Jurassic mudstones, has geometries of clinopyroxene-plagioclase-plagioclase three-grain junctions consistent with a maximum overall thickness of 170-180 m, although only the central ∼100 m of the stratigraphy is exposed on the mainland. The exposures of mudstones previously thought to represent either the roof of the sill, or a thin screen between two closely-related sills, are argued to be numerous isolated rafts within a single intrusion, in agreement with the profiles of maximum contact metamorphic temperature established by previous workers, and evidence of only localised chill zones. Emplacement of the Portrush Sill therefore occurred along multiple bedding planes in the Jurassic mudstones, resulting in the incorporation of numerous stoped blocks of pyrite-rich mudstone into the intrusion. The sill can be divided into three divisions, with the Lower and Upper Divisions characterised by uniform dolerite (with some olivine-rich layers in the lowest exposures of Lower Division). The Middle Division is defined by the presence of cm-scale mafic blobs set in a felsic matrix. The Middle Division is offset downwards relative to the morphological evolution of clinopyroxene, which changes from ophitic interstitial grains in the upper and lower exposed parts of the sill, to (commonly clustered) elongate primocrysts in the central ∼20 m of the entire body, consistent with similar rates of inwards-propagation of the solidification fronts at the roof and floor of the sill and concomitant fractionation of a magma originally saturated only in olivine and plagioclase. We argue that the bimodal character of Middle Division records cm-scale unmixing of two immiscible silicate liquids, as a consequence of significant assimilation of the pyrite-rich country rock. That it is offset from the centre of the entire body is perhaps a consequence of a greater concentration of (now completely assimilated) blocks of country rock in the lower parts of the remaining magma when Middle Division was solidifying.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108226"},"PeriodicalIF":2.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933818","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":"Hydration of Archean komatiites on the seafloor: Evidence from trace elements and oxygen isotopes","authors":"Renée Tamblyn ,&nbsp;Jörg Hermann ,&nbsp;Daniela Rubatto ,&nbsp;Anne-Sophie Bouvier","doi":"10.1016/j.lithos.2025.108235","DOIUrl":"10.1016/j.lithos.2025.108235","url":null,"abstract":"<div><div>In the modern Earth, mantle rocks hydrated by seafloor serpentinisation play an important role in the geological (deep) water cycle. In the Archean, however, the geological water cycle may have been different. Ultramafic rocks were present as komatiites, high-MgO plume derived lavas which erupted onto oceanic plateaux or the margins of continents. Previous work has shown that these komatiites dominantly erupted in submarine environments and contain significant amounts of water bound in antigorite, chlorite and tremolite (∼6 wt%). We present in situ trace element and oxygen isotopic data of hydrated komatiites from the Kaapvaal, Superior, Singhbhum, Yilgarn and Pilbara Cratons, which further constrain thermal conditions and element uptake during seafloor hydration. Silicate phases are enriched in fluid mobile elements such as B, W, As, Sb and Pb, compared to likely komatiitic melt compositions. These fluid mobile elements were derived from seawater, or possibly seawater-sediment equilibrated fluids. The δ¹⁸O composition of olivine is mantle-like (∼5.5 ‰), and the δ¹⁸O compositions of antigorite are homogenous within sample, with most falling in a range between +1.5–4.1 ‰. Oxygen isotope modelling of serpentine in equilibrium with Archean seawater with a δ¹⁸O composition of −1 ‰ suggests that these samples were hydrated at temperatures of ∼150–210 °C, after komatiite crystallisation. The pervasive hydration of komatiite lavas was likely due to their high surface area, as they erupted as extensive but thin flows. Temperature-driven fluid circulation in the komatiites may have been promoted by the cooling of underlying and overlying lava flows, magmatic injections or proximity to the mantle plume. Despite their relatively low abundance in the geological record, komatiite lava flows in the Archean may have impacted the geochemistry of the oceans and atmosphere. Additionally, deep burial of these hydrated komatiites would release water at high temperatures, promoting the fluid-fluxed melting of basalts and in turn contributing to the formation of the early tonalite-trondhjemite-granodiorite (TTG) continental crust.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"516 ","pages":"Article 108235"},"PeriodicalIF":2.5,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997536","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":"Pre-eruptive processes and timescales of shallow silicic magma reservoir beneath the Iheya Graben in the middle Okinawa Trough","authors":"Xinyu Luo ,&nbsp;Zhigang Zeng ,&nbsp;Yuxiang Zhang ,&nbsp;Zuxing Chen","doi":"10.1016/j.lithos.2025.108222","DOIUrl":"10.1016/j.lithos.2025.108222","url":null,"abstract":"<div><div>Intensive magmatic activity in the middle Okinawa Trough (MOT) is well recognized, yet the pre-eruptive processes and residence times of silicic magmas remain poorly constrained. Here, we present a detailed investigation of the textures, in situ elements, and isotopic compositions of minerals in the magmatic enclaves (MEs), glomerocrysts, and their host rhyolite from the Iheya Graben to elucidate pre-eruptive processes and associated timescales. In the host rhyolite, the complex textures and wide compositional range of the phenocrysts suggest that pre-eruptive processes may involve multiple magmas. The normally zoned phenocrysts within the MEs provide direct evidence for the injection of andesitic magma into the shallow silicic reservoir. Nearly parallel trace element and rare earth element distribution patterns of plagioclase and orthopyroxene, along with the similar Sr isotopic compositions of plagioclase, suggest that these magmas may be co-genetic. In the glomerocrysts, the plagioclase composition changes gradually from core to rim (An, La, Ce, Eu, Mg, Fe, and Sr/Ba), indicating that the shallow silicic system developed via fractional crystallization of intermediate–mafic magmas. The occurrence of glomerocrysts in the erupted material also provides irrefutable evidence for the existence of crystal mush zones beneath the Iheya Graben. Fe<img>Mg interdiffusion profiles in zoned orthopyroxene from the host rhyolite capture a wide range of timescales, from ∼3 months to ∼700 years. These timescales correlate positively with Mg^#: profiles containing high-Mg^# bands yield longer durations (up to 700 years), whereas those composed of low-Mg^# bands are shorter (&lt;200 years), indicating that perturbation of the shallow silicic system by andesitic magma was initiated ∼700 years before eruption, while episodic interactions between silicic pockets occurred relatively late. Overall, mineralogical evidence illustrates a complex, dynamic, crystal-dominated shallow silicic system beneath the Iheya Graben, which is recharged by andesitic magma.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108222"},"PeriodicalIF":2.5,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144892114","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 and evolution of synchronous Miocene leucogranite dykes and porphyritic granitoid pluton in the Tangste region of Pangong metamorphic complex, Ladakh Trans-Himalaya, India: Constraints from geochemistry and zircon U-Pb-Hf isotopes","authors":"Sita Bora ,&nbsp;Santosh Kumar ,&nbsp;Kapil S. Panwar ,&nbsp;Keewook Yi ,&nbsp;Youn-Joong Jeong ,&nbsp;Umesh K. Sharma","doi":"10.1016/j.lithos.2025.108223","DOIUrl":"10.1016/j.lithos.2025.108223","url":null,"abstract":"<div><div>The Pangong Metamorphic Complex (PMC) lies within the Karakoram Fault (KF) zone that separates the Ladakh batholith from the easternmost Karakoram terrain in the Ladakh Trans-Himalaya. The PMC is intruded by an extensive network of leucogranite dykes and veins. K-feldspar megacryst-bearing porphyritic granitoid pluton is exposed widely in Tangste region located to the south of the PMC. Geochemistry, zircon U<img>Pb SHRIMP geochronology and Hf isotopes of leucogranite, porphyritic granitoid, and geochemistry of associated orthogneiss (migmatized) and amphibolite (refractory residuum) have been conducted to unravel the source-to-sink melt history during the KF development. All the studied rocks are metaluminous (molar Al₂O₃/CaO + Na₂O + K₂O = 0.46–1.02), except for one peraluminous orthogneiss (A/CNK = 1.16), and dominantly magnesian and calc-alkalic to alkali-calcic. Leucogranite and porphyritic granitoid exhibit adakite-like affinity, while orthogneiss has a magmatic arc signature. The geochemical features support that melting of calc-alkaline orthogneiss and infracrustal magmatic source rocks produced leucogranite and porphyritic granitoid melts in a syntectonic environment. U<img>Pb geochronology of leucogranite inherited zircon cores yielded a range of ²⁰⁶Pb/²³⁸U ages from 73.6 ± 0.8 Ma to 46.7 ± 0.5 Ma with a weighted mean age of 72.1 ± 1.9 Ma. The positive ɛHf values (+3.81 to +11.30) of dated inherited zircon cores suggest that the sources for leucogranite melts were juvenile crust-derived magmatic rocks (ca. 73–46 Ma) formed in a subduction zone, similar to the granitoids of the Ladakh-Kohistan and Karakoram batholiths. Leucogranite zircon rims grown over the inherited cores provide a crystallization age of 18.27 ± 0.29 Ma, synchronous to the zircon mean crystallization age of 18.50 ± 0.16 Ma in the porphyritic granitoid. The range of ɛHf (−11.81 to +0.11) of leucogranite zircon rims overlaps remarkably with ɛHf (−10.38 to −0.02) of porphyritic granitoid zircon, which show striking evidence of recycling of a common crustal source (calc-alkaline magmatic rocks) in the formation of leucogranite dyke and porphyritic granitoid pluton. The Miocene leucogranite dyke melts thus likely acted as “feeders” to the porphyritic granitoid plutonism during the development of the KF zone in the PMC of Ladakh Trans-Himalaya.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108223"},"PeriodicalIF":2.5,"publicationDate":"2025-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144896189","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}