Lithos最新文献

{"title":"The operation of plate tectonics in Earth's middle age: Constraints from ∼1.4 Ga calc-alkaline arc magmatism in the southern CAOB","authors":"Qiao Zhang ,&nbsp;Jinlong Yao ,&nbsp;Guochun Zhao ,&nbsp;Yigui Han ,&nbsp;Hang Yang ,&nbsp;Wei Han ,&nbsp;Yuxuan Zhang","doi":"10.1016/j.lithos.2025.108170","DOIUrl":"10.1016/j.lithos.2025.108170","url":null,"abstract":"<div><div>The Mesoproterozoic (1.6–1.0 Ga) era recorded the supercontinent transition from Nuna to Rodinia supercontinent. However, the global tectonic style within this age interval remains highly debated (plate tectonics vs lid tectonics), largely due to the occurrence of widespread continental rifting sequences, alkaline and anhydrous magmatism, along with high T/P metamorphism. We here systematically investigated the whole-rock geochemical, geochronological, and Nd-Hf isotopic characters of metamorphosed Mesoproterozoic granodiorite and monzogranite within the Alxa Block in the central segment of the southern CAOB. The field geology and obtained data indicate that they are typical of I-type granitoids emplaced at 1.43–1.40 Ga, with their parental magmas generated by partial melting of preexisted juvenile mafic crusts. These granitoids belong to the calc-alkaline and magnesian series, and are enriched in LREE and LILE. Moreover, their parental magma contains high magmatic H₂O contents (&gt;7 %). The data patterns, combined with regional geology, indicate these granitoids are continental arc magmatic rocks. Our data, together with those published data in the microcontinental blocks of southern CAOB, argue that the protracted (1.51–1.40 Ga) calc-alkaline granitic magmatism in these blocks was generated in a continental marginal arc. This prolonged continental arc system coincides well with the Great Proterozoic Accretionary Orogen (GPAO) in the Mesoproterozoic and must have been formed outboard the GPAO. Furthermore, a review of global geological and geochemical data patterns favor widespread subduction on the periphery of Nuna and the operation of plate tectonics in the Mesoproterozoic.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108170"},"PeriodicalIF":2.9,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522066","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":"Mg-Fe isotopic constraint on the role of the lithosphere mantle in arc magmatism","authors":"Yang Yu ,&nbsp;Xiao-Long Huang ,&nbsp;Fan Yang ,&nbsp;Yu Wang ,&nbsp;Yi-Gang Xu ,&nbsp;Iwan Setiawan ,&nbsp;Sun-Lin Chung ,&nbsp;Le Zhang ,&nbsp;Guan-Hong Zhu","doi":"10.1016/j.lithos.2025.108166","DOIUrl":"10.1016/j.lithos.2025.108166","url":null,"abstract":"<div><div>Arc magmatism is commonly envisaged as generation through a two-endmember petrogenetic process involving the subducted components and asthenospheric mantle wedge. The contribution of sub-arc lithospheric mantle, as a key chemical reservoir in subduction zone, to arc magmas remains poorly constrained. Here we present, for the first time, a systematic dataset of Mg<img>Fe isotopes on continental arc basalts (CABs) from the Sunda Arc for deciphering the role of sub-arc lithospheric mantle in arc magmatism. The Sunda CABs show significant variations in δ²⁶Mg (−0.28 ‰ to −0.05 ‰) and δ⁵⁶Fe values (−0.19 ‰ to 0.14 ‰), with mean values of −0.17 ‰ and 0.02 ‰, respectively, resembling those of global arc magmas. These samples mainly display low TiO₂/Yb (0.3–0.5) and Fe/Mn (30–60) ratios, indicating their derivation from peridotite melting within the depleted asthenospheric mantle wedge. The weak correlations of Mg and Fe isotopes with ε_Nd suggest that subduction-related metasomatism has not significantly influenced the Mg and Fe isotopic compositions of the asthenospheric mantle wedge. The majority of Sunda CABs exhibit a negative correlation between δ²⁶Mg and Fe/Mn, as well as a positive correlation between δ⁵⁶Fe and Fe/Mn, both also observed in global arc magmas. These significant variations in Mg<img>Fe isotopes and Fe/Mn ratios within arc magmas likely result from their intensive interactions with the sub-arc lithospheric mantle through incorporations of the low Fe/Mn (30–50) pyroxenite and high Fe/Mn (50–70) peridotite in different proportions. The interactions may have also elevated the oxygen fugacity as evidenced by the co-variations of Mg<img>Fe isotopes and V/Sc ratios for the Sunda CABs and global arc basalts. We therefore conclude the crucial role played by the sub-arc lithospheric mantle in global arc magmatism, which has long been overlooked in popular petrogenetic models for subduction zone magmatism.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108166"},"PeriodicalIF":2.9,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518473","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":"Magmatic genesis, magmatic plumbing system, and geodynamic mechanism of Changbaishan volcanoes: New evidence from mineralogical, geochemical, and geothermobarometric data","authors":"Zhihao Sun ,&nbsp;Bin Zhang ,&nbsp;Jing Wu ,&nbsp;Zeyang Zhu ,&nbsp;Chunqing Sun ,&nbsp;Zhengfu Guo ,&nbsp;Jiaqi Liu","doi":"10.1016/j.lithos.2025.108167","DOIUrl":"10.1016/j.lithos.2025.108167","url":null,"abstract":"<div><div>The Changbaishan volcanic field (mainly comprising Tianchi, Wangtian'e, Namphothe, and Tumen River volcanoes), located in the intraplate domain of the eastern Eurasian plate, has exhibited vigorous Cenozoic volcanism. However, the magmatic system and deep geodynamic mechanisms related to the volcanic activity underlying this active region remain controversial; namely, whether the magma originates from the mantle or subducted Pacific slab; whether the magma reservoir is multi- or single-layered with a large scale; and the source of the driving force of volcanic activity. In this study, we present an integrated analysis of newly acquired geochemical and geochronological data spanning all eruptive phases since the Pliocene, combined with existing datasets, and reconstruct the volcanic evolution of Changbaishan volcanic field. Geochemical results reveal homogeneous trace element patterns and Sr-Nd-Pb isotopic compositions across the Tianchi, Wangtian'e, and Tumen volcanic centers, indicating that the magma originated from an enriched mantle source formed by the mechanical mixing and fluid-melt metasomatism between the asthenosphere mantle and subducted Pacific slab components. Fractional crystallization is identified as the dominant magma differentiation mechanism. Mineral thermobarometers reveal a multi-tiered magma storage system, with shallow (ca. 3–5 km), intermediate (ca. 8–18 km), and deep-seated (ca. 25–36 km) reservoirs beneath Tianchi volcanoes. Moreover, the magma reservoirs of Wangtian'e volcano are located at depths of 8–15 and 25–36 km, contrasting with deeper magma sources (ca. 26–50 km) beneath the Tumen River volcano. These findings demonstrate that the stagnant Pacific slab in the mantle transition zone exerts fundamental control over regional volcanism through both material contributions and dynamic forces and resolves the genetic connections between surface volcanism and deep mantle processes. Furthermore, we also reconcile previous controversies regarding the origin of magma from the mantle and subducted Pacific slab with a multi-layered magma reservoir.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108167"},"PeriodicalIF":2.9,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518018","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":"Shear zone memory revealed by in-situ Rb-Sr and 40Ar/39Ar dating of Pyrenean and Alpine tectonic phases in the external Alps","authors":"L. Boschetti ,&nbsp;C. Boullerne ,&nbsp;Y. Rolland ,&nbsp;S. Schwartz ,&nbsp;G. Milesi ,&nbsp;D. Bienveignant ,&nbsp;E. Macret ,&nbsp;D. Charpentier ,&nbsp;P. Münch ,&nbsp;J. Mercadier ,&nbsp;A. Iemmolo ,&nbsp;P. Lanari ,&nbsp;M. Rossi ,&nbsp;F. Mouthereau","doi":"10.1016/j.lithos.2025.108168","DOIUrl":"10.1016/j.lithos.2025.108168","url":null,"abstract":"<div><div>The combination of Rb-Sr and ⁴⁰Ar/³⁹Ar dating methods with high-resolution mineralogical investigation allows deciphering the multiphase history of shear zones and serves as a tool for tectonic reconstructions. However, the interpretation of dates obtained by these two methods in relation to cooling, fluid circulation or to deformation-induced (re)crystallization remains controversial. Here, we apply the in situ ⁸⁷Rb/⁸⁷Sr and ⁴⁰Ar/³⁹Ar dating methods to shear zone minerals used together with step heating ⁴⁰Ar/³⁹Ar dating in several case studies with contrasting structural and metamorphic histories along the External Crystalline Massifs (ECMs) of the SW Alps. Our results emphasize polyphase deformation and highlight a variable behaviour of Rb-Sr and K-Ar systems in shear zones. This study provides new constraints about the timing, conditions and mechanisms of deformation in the southern ECMs of the Western Alps. The inherited crustal-scale Variscan shear zones have been reactivated several times in a thick-skin mode since the Late Cretaceous. An early N-S compressional phase impacted the SW Alps mainly at around ∼80–70 and ∼40 Ma in the Argentera and Pelvoux shear zones, but this signal is not documented further north. This signal is better preserved in the southern Pelvoux massif, with a Rb-Sr age of 79.7 ± 3.7 Ma. There is also a significant compressional deformation on the W-Alpine scale at 34–32 Ma, associated with underthrusting beneath the Penninic Frontal Thrust (PFT). Two compressional deformation pulses occur at 26 and 22–20 Ma in the southern Argentera Massif, corresponding to the onset of transpressive deformation induced by the anti-clockwise rotation of the Adriatic Plate. Finally, the last phase of deformation around 18–15 Ma concerns only the NW Alps, in the Beaufortain massif, which was buried under the Mont-Blanc massif, during the propagation of deformation leading to the development of the frontal fold and thrust belt of the SW Alps. Our results also show that the southern Pelvoux massif already reached a temperature around 300 °C at a depth of 10–15 km depth during the Late Cretaceous. This range of temperature and pressure conditions is broadly similar to that reached in the ECMs during the Cenozoic deformation stages.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108168"},"PeriodicalIF":2.9,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144548452","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":"Tectono-thermal evolution of Luqu ultramafic rocks in the Xigaze ophiolites, Tibetan Plateau: Implications for oceanic lithosphere accretion at slow-to-ultraslow spreading ridges","authors":"Yi Cao ,&nbsp;Jian Ma ,&nbsp;Junfeng Zhang ,&nbsp;Chuanzhou Liu ,&nbsp;Qing Xiong ,&nbsp;Zhaoyi Dai ,&nbsp;Jinxue Du","doi":"10.1016/j.lithos.2025.108169","DOIUrl":"10.1016/j.lithos.2025.108169","url":null,"abstract":"<div><div>The Luqu ultramafic rocks from the Xigaze ophiolites in the Yarlung–Tsangbo Suture Zone, southern Tibet, are interpreted as remnants of the Neo-Tethyan oceanic mantle formed at slow-to-ultraslow spreading ridges. As such, they offer valuable insights into sub-ridge mantle dynamics and evolution in this tectonic setting. This study presents a comprehensive investigation of the major- and trace-element compositions of minerals, as well as deformation microstructures, in representative harzburgites and associated pyroxenite veins. The harzburgite hosts are characterized by extreme depletion in incompatible elements and enrichment in compatible ones, consistent with high degrees (∼13–18 %) of anhydrous partial melting in a shallow (spinel-facies) sub-ridge mantle. The pyroxenite veins, with mineral compositions similar to those of the host harzburgites, likely crystallized from silica-rich melts derived from the asthenosphere, which subsequently interacted and equilibrated with the host rocks at the lithosphere–asthenosphere boundary (LAB) beneath a mid-ocean ridge. Microstructural features—including porphyroclastic texture, intracrystalline plasticity indicators (e.g., undulose extinction, subgrain boundaries, kink bands, and bent exsolution lamellae), curved olivine grain boundaries, and well-defined crystallographic-preferred orientations in olivine (A/D-type), orthopyroxene (type-AC), and clinopyroxene—indicate high-temperature (∼1000–1200 °C), low-pressure (∼3 kbar) deformation dominated by dislocation creep. This plastic deformation postdated the melt–rock interaction and was accompanied by relatively slow cooling from &gt;1200 °C to ∼1000 °C at an estimated rate of ∼8.5 × 10⁻⁴ °C/year, driven by sub-horizontal basal shearing and conductive heat transfer at the LAB. A later, lower-temperature (&lt;800 °C) brittle deformation stage is evidenced by widespread hydrous minerals (e.g., tremolite, anthophyllite, chlorite, talc, and serpentine) occurring along fractures and grain boundaries. This stage likely resulted from seawater infiltration along oceanic detachment faults, promoting hydration reactions and triggering rapid cooling from ∼1000 °C to &lt;700 °C at a rate of ∼1.4 × 10⁻¹ °C/year. Based on these observations, we propose a tectono-thermal model for the evolution of the Luqu ultramafic rocks within a Neo-Tethyan slow-to-ultraslow spreading ridge environment.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108169"},"PeriodicalIF":2.9,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518016","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":"The interplay of crystal fractionation, magma recharge, assimilation and mixing in Archean volcanic systems revealed in the geochemical diversity of the Deloro assemblage, Abitibi Greenstone Belt","authors":"Kieran A. Iles,&nbsp;Pierre-Simon Ross,&nbsp;Octavio Vite-Sánchez","doi":"10.1016/j.lithos.2025.108161","DOIUrl":"10.1016/j.lithos.2025.108161","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Volcanic rocks from greenstone belts represent major records of Archean geologic history. One such belt, the Abitibi Greenstone Belt, which forms the eastern part of the Abitibi-Wawa Subprovince (one of several terranes in the Superior Province, Canada) is notable for its relatively high proportion of supracrustal rocks and rich mineral endowment. Greenstone belt volcanic rocks do, however, present a challenge for geochemical modelling due to the variable extent to which their primary signatures can be overprinted by hydrothermal alteration and metamorphism. Nevertheless, the use of immobile elements for data exploration, and focussing on the least-altered samples for petrogenetic modelling, can overcome these challenges. Furthermore, modern modelling tools, like the Magma Chamber Simulator, offer unprecedented opportunities to constrain the origin and evolution of volcanic rocks, such as the Deloro Assemblage in the Abitibi Greenstone Belt, and thereby gain insights into Archean petrogenesis. The 2734–2724 Ma Deloro Assemblage is widespread, well sampled, geochemically diverse, and of economic interest due to a rich endowment of volcanogenic massive sulphide deposits. A large geochemical compilation and petrogenetic modelling using the Magma Chamber Simulator demonstrates that the major element diversity can be explained through a combination of processes, using a tholeiitic basaltic parental magma at approximately 3 kbar and a wallrock of average SE Superior Province TTG as a contaminant. This modelling highlights the roles not just of fractional crystallisation and assimilation, but also the previously unrecognised role of magma recharge in contributing to the geochemical diversity of the Abitibi volcanic systems. Additionally, the modelling provides constraints on what ranges of oxygen fugacities and parental magma water contents are suitable. The trace element evolutions of these models clarify the different petrogenetic pathways that give rise to the Deloro Assemblage rocks. We show that the volcanic rocks can be organized into nine geochemical groups, mostly based on a Th/Yb versus Yb/Ti diagram. Furthermore, trace element modelling illustrates the utility of this diagram for differentiating (a) between open- versus closed-system behaviour, and (b) between different types of open-system processes. The most primitive group, Tholeiitic basalts, has trace element patterns that suggest melting of primitive mantle at a range of depths. The Tholeiitic basalts, Transitional intermediate group, Tholeiitic dacites and Tholeiitic rhyolites record progressive evolution via fractional crystallisation and magma recharge. In contrast, coupling assimilation to fractional crystallisation accounts for the progression from Tholeiitic basalts to High-Th basalts and further onwards to the Calc-alkaline andesites, Calc-alkaline dacites and Calc-alkaline rhyolites. The high Th/Yb, low Yb/Ti character of the HREE-depleted intermediate group cannot be e","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108161"},"PeriodicalIF":2.9,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518015","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":"Mesozoic highly oxidized and hydrous adakitic magmatism controlling porphyry Cu mineralization in NE China: Evidence from the Baoquan deposit","authors":"Yan Cao ,&nbsp;Qihai Shu ,&nbsp;Kai Xing ,&nbsp;Jinyu Liu ,&nbsp;Xudong Niu ,&nbsp;Lijun Liu ,&nbsp;Zhonghai Zhao ,&nbsp;Yubao Yang ,&nbsp;Zhaolong Liu","doi":"10.1016/j.lithos.2025.108164","DOIUrl":"10.1016/j.lithos.2025.108164","url":null,"abstract":"<div><div>In northeastern China, Mesozoic porphyry Mo-dominated deposits are abundant but porphyry Cu deposits are rare. Investigating the mechanisms controlling the formation of the limited number of the porphyry Cu deposits is critical in understanding the regional Cu metallogeny. Here, we present geochronological and geochemical data for the Cu-mineralized and barren intrusions in the newly discovered Baoquan porphyry deposit in the northern Great Xing'an Range. Zircon U-Pb dating indicates that the mineralized quartz diorite porphyry and barren syenogranite were emplaced at ∼115 Ma and ∼312 Ma, respectively. The quartz diorite porphyry (SiO₂ = 62.7–63.9 wt%) has high alkaline contents (Na₂O + K₂O = 6.82–8.28 wt%), is enriched in LILEs (K, Rb, Ba, and Sr) and depleted in HFSEs (Th, Nb, Ta, Zr and Ti), and exhibits low initial ⁸⁷Sr/⁸⁶Sr ratios (0.7049–0.7067) and positive ε_Nd(t) values (+1.9 to +2.0), as well as positive zircon ε_Hf(t) values (+4.9 to +13.6), indicating that the parental magma was predominantly derived from the mantle, likely metasomatized by fluids derived from the subducted Paleo-Pacific slab. In contrast, the barren syenogranite (SiO₂ = 76.4–78.0 wt%) is depleted in Sr (40.6–82.4 ppm) and Ba (348–498 ppm), with high Zr + Y + Ce + Nb values (206–277 ppm), showing A-type granite affinities. The Baoquan ore-related porphyry is oxidized (ΔFMQ = +1.2 in average) as calculated using magmatic oxybarometer using trace elements in zircon, in contrast with that of the barren syenogranite with lower magmatic ΔFMQ values (+0.6 in average). The porphyry also has low Zr contents (average 151 ppm) and Sr/Zr ratios (average 7.96), consistent well with other Cu-fertile magmas. Additionally, it also displays adakitic signatures with relatively high Sr/Y ratios (78–130), low Dy/Yb ratios (1.86–2.03) and negligible Eu anomalies (Eu/Eu* = 0.79–0.96). These findings suggest that zircon and hornblende fractionation, rather than plagioclase separation, has dominated magma crystallization, further indicating a high magmatic water content. Together with previously published data for the other Cu-mineralized intrusions in NE China, it is proposed that the magmas with high oxygen fugacities and H₂O contents that have experienced high-pressure fractionation are favorable for Cu mineralization. Notably, the intrusions with such characteristics are mainly distributed in the northern Great Xing'an Range characterized by thickened Mesozoic crust, where should be prioritized for future Cu exploration.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108164"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534804","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":"Petrogenesis of aquamarine-bearing granitic pegmatite: The case of Haramosh pegmatite field (northern Pakistan)","authors":"Shah Ismail ,&nbsp;Lian-Xun Wang ,&nbsp;Chang-Qian Ma ,&nbsp;Le-Guang Li ,&nbsp;Khan Hawas ,&nbsp;Yu-Xiang Zhu ,&nbsp;Alam Masroor","doi":"10.1016/j.lithos.2025.108162","DOIUrl":"10.1016/j.lithos.2025.108162","url":null,"abstract":"<div><div>The Haramosh pegmatite field in northern Pakistan is renowned for numerous granitic pegmatites, containing economically significant quantities of aquamarine, tourmaline, and topaz. This study investigates the petrogenesis of aquamarine-bearing pegmatite and its genetic relationship with the country rock (Iskere gneiss) and an adjacent intrusion (Jutial leucogranite). The studied pegmatite is composed predominantly of feldspar, quartz, muscovite and tourmaline, resembles the S-type Jutial leucogranite and shows internal zonation with gem-quality aquamarine and topaz forming in the miarolitic cavities. Zircon U<img>Pb dating yields ages of 4.3 ± 0.9 Ma for the pegmatite and 10.3 ± 0.2 Ma for the leucogranite, distinct apparently from the Iskere gneiss (1881 ± 27 Ma). Lu<img>Hf isotopic data suggest a common crustal source for the studied pegmatite and leucogranite, with εHf(t) values ranging from −35.9 to −19.7 (mean = −26.5) and − 29.5 to −24.4 (mean = −26.0), respectively. These results significantly deviated from those observed in the Iskere gneiss (−16.0 to +6.5, mean = −6.0), thereby precluding the possibility of a partial melting model of the country rock. The pegmatite, classified as LCT-type, shows high SiO₂ (71.53–77.17 wt%), Al₂O₃ (13.50–15.82 wt%), Li (14.62–224 ppm), Ta (0.01–4.51 ppm) concentrations and ASI values (1.34–2.37), with higher differentiation-index values (DI = 92–97) and lower K/Rb ratios than the leucogranite. Compositional variations of tourmaline, plagioclase and muscovite also indicate a higher degree of magma evolution in the pegmatite compared to the leucogranite. The plagioclase in the pegmatite displays a decrease in CaO content from the border to core zones, while whole rock Be concentrations exhibit an increase along this gradient, indicating a progressive enrichment of Be during magma evolution within the pegmatite dyke. Based on all results, we propose that the Haramosh aquamarine-bearing pegmatite was likely generated by magmatic fractional crystallization from a leucogranitic parent magma. The formation of aquamarine gems can be attributed to a progressive enrichment of Be during magma evolution process within the pegmatite dykes. The observed widespread occurrence of miarolitic cavities associated with aquamarine gems, coupled with the observed decrease of fluorine content in tourmaline from the pegmatite border to core zones, indicates the involvement of a magmatic volatile phase (MVP) exsolution process during the final stage of magma cooling. This process reduces the solubility of Be in the melt, thereby promoting the crystallization of aquamarine.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108162"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518017","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":"Xonotlite and pectolite in rodingites from the Samail ophiolite: Markers of reducing conditions and element transfer during peridotite-gabbro interaction","authors":"Alireza Eslami ,&nbsp;Benjamin Malvoisin ,&nbsp;Mayuko Fukuyama ,&nbsp;Marguerite Godard ,&nbsp;Yuji Ichiyama ,&nbsp;László Előd Aradi ,&nbsp;Katsuyoshi Michibayashi ,&nbsp;Zaicong Wang ,&nbsp;Ming Li ,&nbsp;Alessandro Cavallo ,&nbsp;The Oman Drilling Project Science Team","doi":"10.1016/j.lithos.2025.108160","DOIUrl":"10.1016/j.lithos.2025.108160","url":null,"abstract":"<div><div>The Oman Drilling Project cored Holes BA1B, BA3A and BA4A into serpentinized peridotites in Wadi Lawayni of the Samail ophiolite, Oman. These mantle peridotites are crosscut by numerous gabbro, olivine gabbro and clinopyroxenite dikes that are altered to calc-silicate assemblages (hydrogarnet, diopside, xonotlite, vesuvianite and pectolite), chlorite, and phlogopite. These mineralogical assemblages are typical of rodingites. Xonotlite [Ca₆Si₆O₁₇(OH)₂] and pectolite [NaCa₂Si₃O₈(OH)] forming as fibrous or acicular/radial crystals in milk-white vein-like are common in these holes. In contrast, only a few occurrences of these minerals have been reported worldwide. Bulk rock analyses indicate two types of altered dikes: chlorite-bearing dikes displaying enrichments in Mg, Fe, Mn, Ti, Cr, Ni and volatiles as well as loss of Na compared to lower crustal gabbros; and rodingitized dikes with enrichments in Ca and Na during alteration. Mass gains in chlorite-bearing dikes are consistent with intense mass transfer from peridotite to gabbroic dikes. These results are consistent with thermodynamic modelling showing a strong control of the peridotite-gabbro ratio on the mineralogy of the altered gabbro: wollastonite, pectolite, and vesuvianite present here are predicted to form in peridotite-dominated systems, whereas prehnite, epidote and pumpellyite not reported in the studied boreholes are predicted to form in gabbro-dominated systems. Fluid inclusions containing H₂ and CH₄ are observed in both primary orthopyroxene and pectolite. They indicate the presence of a carbon-rich reduced fluid during rodingitization. The xonotlite stability field calculated with thermodynamic modelling is indeed limited by carbonate formation as oxygen fugacity increases. The rodingites from Oman display numerous markers of strong fluid/rock interactions, including enrichment in mobile elements such as Na, K and Li, typically associated with seawater interaction and hydrothermal fluid transport. The presence of xonotlite, pectolite and phlogopite is consistent with the addition of external elements during rodingitization since the extent of the calculated stability fields of these minerals increases when adding Ca, Na and K to the system. High δ^44/40Ca values in chlorite-bearing dikes (1.65 ± 0.09 ‰ to 1.91 ± 0.09 ‰), rodingitized dikes (0.28 ± 0.09 ‰ to 1.25 ± 0.02 ‰) and serpentinized harzburgites (1.04 ± 0.05 ‰ to 1.64 ± 0.06 ‰) reveals mineral-fluid fractionation of Ca isotopes and/or interaction of seawater with gabbro-peridotite samples.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108160"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144513681","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":"Multistage petrogenesis and suprasubduction metasomatism of orthopyroxenites in the Ab-Bid ultramafic complex (Iran): Insights from open-system mantle melting","authors":"Mahdieh Mohammadi ,&nbsp;Hamid Ahmadipour ,&nbsp;Abbas Moradian ,&nbsp;Daniele Brunelli ,&nbsp;Reza Derakhshani","doi":"10.1016/j.lithos.2025.108163","DOIUrl":"10.1016/j.lithos.2025.108163","url":null,"abstract":"<div><div>The Ab-Bid ultramafic complex, located within the Esfandagheh–Hadji Abad ophiolite mélange in southern Iran, hosts numerous orthopyroxenite intrusions emplaced as dykes and irregular bodies within mantle peridotites. These orthopyroxenites exhibit sharp contacts with the host rocks and display cumulate textures characterized by early-crystallizing orthopyroxene and spinel, followed by intercumulus olivine and clinopyroxene. While the Ab-Bid ultramafics show textural and compositional similarities to abyssal mantle residues, they also record subtle geochemical signatures consistent with limited slab-derived metasomatism. This study presents the first detailed petrographic and geochemical dataset from orthopyroxenites in the Ab-Bid massif, including field observations, mineral chemistry, whole-rock and in-situ trace element analyses. Petrogenetic modeling of clinopyroxene trace element distributions in lherzolite, harzburgite, and orthopyroxenite supports a multistage evolutionary scenario involving open-system melting of a depleted oceanic mantle source variably modified by suprasubduction fluids. The resulting high-Mg tholeiitic melts triggered localized remelting, melt-peridotite interaction, and sequential lithological transformation across the complex. Our results indicate a genetic link among the lithological units and demonstrate that localized metasomatic processes—without the need for boninitic melt involvement—can produce high-Mg tholeiitic magmas in suprasubduction settings. These findings provide new constraints on mantle heterogeneity, melt evolution, and the complex dynamics of subduction-modified ultramafic systems within the Tethyan ophiolite belt.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108163"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502225","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}