Lithos最新文献

{"title":"Petrogenesis of the Daquandian granitoids in the Dabie orogenic belt, eastern China: Tectonic shift from compression to extension caused by the Paleo-Pacific Plate in the early Cretaceous","authors":"Zeqiu Qi ,&nbsp;Jun He ,&nbsp;Naizhen Zhang ,&nbsp;Jingxin Zhao ,&nbsp;Wolfgang Siebel ,&nbsp;Fukun Chen","doi":"10.1016/j.lithos.2025.108109","DOIUrl":"10.1016/j.lithos.2025.108109","url":null,"abstract":"<div><div>This paper discusses the petrogenesis of the Daquandian granitoid pluton exposed in northern Dabie Mts. and the tectonic implications for the Dabie orogen. Rocks of this pluton yield Early Cretaceous ²⁰⁶Pb/²³⁸U ages between 133 and 129 Ma. They are high-K calc-alkaline and of I-type affinity, with A/CNK values ranging from 0.95 to 1.12, and variable (La/Yb)_N, Eu/Eu^⁎ and Sr/Y values. Rock samples with Sr/Y values &lt;20 show remarkable variations in Sr/Y and Eu/Eu^⁎ ratios due to the fractional crystallization of feldspar, while those with Sr/Y ratios &gt;20 also show variations in Sr/Y ratios, but have relatively consistent Eu/Eu^⁎ ratios, which is linked to the change in the crustal architecture and thickness and the appearance of plagioclase as a residual mineral phase. Whole-rock initial ⁸⁷Sr/⁸⁶Sr ratios range from 0.7075 to 0.7085, initial ε_Nd values from −21.9 to −16.1, and initial Pb isotope ratios vary from ²⁰⁶Pb/²⁰⁴Pb = 16.24–16.84, ²⁰⁷Pb/²⁰⁴Pb = 15.27–15.41, and ²⁰⁸Pb/²⁰⁴Pb = 37.22–37.89. These isotopic characteristics are similar to those of other Cretaceous granitoids in the Dabie Mts. Inherited zircon grains of different ages (Archean, Neoproterozoic, and Triassic) were identified in the Daquandian pluton, indicating a multi-source origin. By integrating existing geological, chronological, and geochemical data, we propose that the magma(s) of the Daquandian pluton were sourced from different crustal lithologies, mainly from the Northern Dabie Complex with a contribution from the Yangtze and/or North China lower crust. Crustal anatexis responsible for the generation of the granitoid magmas is proposed to have taken place in a post-collision extensional setting.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108109"},"PeriodicalIF":2.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143890582","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":"Triassic lamprophyre dyke in the Palaeozoic basement of NE Sardinia, Italy: Petrogenesis and geodynamic significance","authors":"Gabriele Cruciani ,&nbsp;Dario Fancello ,&nbsp;Mattia Ferrari ,&nbsp;Alessandro Bragagni ,&nbsp;Simone Tommasini ,&nbsp;Marcello Franceschelli","doi":"10.1016/j.lithos.2025.108106","DOIUrl":"10.1016/j.lithos.2025.108106","url":null,"abstract":"<div><div>A Triassic, Si-undersaturated, alkaline lamprophyre from NE Sardinia is studied to decipher its magma source, genesis, and P-T conditions of crystallization and emplacement. It is also compared with similar and coeval rocks occurring throughout Europe to depict a geodynamic scenario associated with the opening of the Pangea. The lamprophyre, crosscutting the Palaeozoic basement, shows a porphyritic texture with centimeter-sized amphibole macrocrystals and biotite, ulvöspinel and apatite phenocrystals. The lamprophyre also contains feldspar clusters, carbonate-rich inclusions, and xenolith nodules. The incompatible trace element patterns show weak positive anomalies for Ba, Nb, K and P and negative ones for Th and Ta, whereas the chondrite-normalized Rare Earth Elements (REE) pattern reflects a constant fractionation from light REEs to heavy REEs without Eu anomaly. The core of the amphibole reflects the deepest crystallization conditions, whereas rims and groundmass amphiboles indicate slightly higher temperature and lower pressure. The bulk Sr and Nd radiogenic isotope composition falls between the <em>E</em>-DMM and BSE mantle components at 220 Ma, ruling out a significant contribution of the local lithospheric mantle, which was metasomatized during the Hercynian orogeny. The comparison with other European lamprophyres along with a palaeogeographic reconstruction suggests that the Sardinia lamprophyre lies along the eastern branch of the fault system responsible for to the opening of the Alpine Tethys. The trace element and radiogenic isotope signature of the Sardinian and the other European lamprophyres is consistent with a progressive transition from the post-collisional orogenic magmatism to anorogenic rift-related alkaline magmatism occurring during Early Mesozoic break-up of Pangea and opening of the Tethys Ocean.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108106"},"PeriodicalIF":2.9,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143882066","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":"Crustal growth from collision to post-collision: implications from Cretaceous back-arc magmatism flare-up in southern Qiangtang of central Tibet","authors":"Sheng-Qiang Zhang ,&nbsp;Neng Gong ,&nbsp;Hui Qi ,&nbsp;Yun-Chuan Zeng ,&nbsp;Guo-Li Yuan ,&nbsp;Pei-Pei Dong ,&nbsp;Ying-Jie Li ,&nbsp;Gen-Hou Wang ,&nbsp;Zhi-Bo Liu ,&nbsp;Xiao Liang","doi":"10.1016/j.lithos.2025.108102","DOIUrl":"10.1016/j.lithos.2025.108102","url":null,"abstract":"<div><div>Collision zones are primary sites for crustal growth and maturation, where magmatic activities play a crucial role in elucidating the formation and evolution of the crust. Previous studies suggest crustal growth mainly occurs in the continental-arc region during subduction to collisional period, while back-arc area primarily experience stretching and thinning. However, Cretaceous geological records from Bangong-Nujiang suture zone indicates that the original “back-arc region” experienced extensive magmatic activities and crustal thickening during the collision to post-collision period, and the specific mechanism of crustal growth differs from that in the continental-arc region. In this study, intermediate-felsic and high Ba, Sr magmatic rocks from the Cretaceous Bangong-Nujiang suture zone were utilized to constrain the magma sources and mantle metasomatic processes in the back-arc region. Furthermore, the newly identified samples, together with pre-existing mafic rocks and sedimentary evidence, were uesd to constrain the tectonic environment. In contrast to the previously established crustal growth patterns in continental arc regions, the process of crustal growth in the back-arc region can be divided into two stages: (1) Collision Period—during which the overall tectonic setting of the collisional zone was characterized by compression, the slab break-off created a localized extensional environment within the back-arc region. The upwelling asthenosphere through the slab window induced partial melting of the subducting slab, facilitating the continuous underplating and intrusion of mantle-derived magmas into the continental crust; (2) Post-Collisional Period—where the ongoing compression, combined with the underplating of mantle-derived magmas, lead to the continued thickening of the continental crust and lithospheric mantle. Ultimately, local structural weaknesses in the back-arc region resulted in the development of linear fractures oriented perpendicular to the direction of compression. The ascent of mantle-derived magmas through these structural ruptures triggered the partial melting of the enriched lithospheric mantle, which had undergone prior subduction-related metasomatism, thus supplying necessary materials for the growth of the continental crust.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108102"},"PeriodicalIF":2.9,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873159","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 Miranda-Sayago batholith (NW Iberia): Implications on mantle-crust hybrid zone generation during Variscan collision","authors":"Antonio Castro ,&nbsp;Daniel Gómez-Frutos ,&nbsp;Gabriel Gutiérrez-Alonso ,&nbsp;Helena Sant'Ovaia ,&nbsp;Joana Ferreira ,&nbsp;Manuel Francisco Pereira ,&nbsp;Jesús de la Rosa","doi":"10.1016/j.lithos.2025.108107","DOIUrl":"10.1016/j.lithos.2025.108107","url":null,"abstract":"<div><div>The Miranda-Sayago Batholith (MSB) is a large NW-SE trending intrusive body primarily composed of granodiorites and monzogranites, with minor intrusions of K-rich mafic-intermediate rocks (vaugnerites-sanukitoids), extending from Miranda do Douro in Portugal to northern Zamora in Spain (Sayago region). A geochemical and geochronological analysis reveals complex relations between granodiorites and vaugnerites. Key findings that shed light on the origin of the magmas forming the MSB include: (1) Vaugnerites and granodiorites represent two distinct but genetically-linked and coeval magma series. (2) Vaugnerites were emplaced over a period of approximately 13 million years, from ca. 320 to 307 Ma. (3) Contamination with the surrounding metamorphic and granitic host rocks is recognized in the granodiorites. Also, the autolithic mafic microgranular enclaves, which are isolated from contamination with host migmatites, as well as some vaugnerites, display A/CNK &gt;1, suggesting an Al-rich material involved in the hybridization of the putative mantle source of the intermediate magmas. We propose that granodiorites in the MSB originated by melting of a heterogeneous source rooted in a hybrid mantle that was fluxed by crustal, peraluminous, components during Variscan collision through continental subduction and/or mantle-crust imbrication. Initial Sr and Nd isotopic ratios point to the Cambro-Ordovician “Ollo de Sapo” Formation as the crustal end-member of the hybrid magmas. Parental vaugnerites with values about ε_Nd = −4 and initial ⁸⁷Sr/⁸⁶Sr within a narrow range from 0.705 to 0.709 (at the reference age of 307 Ma), likely originated from melting of mantle material contaminated by 10–20 % crustal components. Granodioritic and vaugneritic magmas ascended through shared channels, promoting further hybridization between magmatic pulses. We conclude that collision played a key role in conditioning fertile mantle sources for post-collisional batholith generation in this sector of the Iberian massif.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108107"},"PeriodicalIF":2.9,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143890581","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":"Rapid tectonic transition, crust-mantle interaction, and gold metallogenesis in the Jiaodong Peninsula, eastern China: Revealed by Early Cretaceous granitoids and microgranular mafic enclaves","authors":"Bin Wang ,&nbsp;Zheng-Jiang Ding ,&nbsp;Jian-Bo Zhou ,&nbsp;Kun-Feng Qiu ,&nbsp;Feng-Yue Sun","doi":"10.1016/j.lithos.2025.108101","DOIUrl":"10.1016/j.lithos.2025.108101","url":null,"abstract":"<div><div>The Early Cretaceous granitoids and mafic enclaves (MEs) are extensively distributed throughout the Jiaodong Peninsula, providing valuable insights into the region's tectono–magmatic evolution and gold mineralization processes. This contribution presents zircon geochronology, whole–rock major and trace element compositions, and Sr–Nd–Pb isotopic data for the Early Cretaceous Guojialing and Weideshan suites, as well as related magmatic enclaves in the Jiaodong Peninsula. These rocks were emplaced at approximately 128 Ma and 118 Ma, corresponding to two distinct magmatic events. Whole–rock and isotope geochemical characteristics indicate that the Early Cretaceous granitoids were formed through the interaction and mixing of lower crustal and lithospheric mantle magmas. Adakitic Shangzhuang MEs of the Guojialing suite originated from the mingling and homogenization of lower crustal felsic magma with mantle–derived basaltic magma. The mafic components of arc–like Aishan MEs of the Weideshan suite were derived from partial melting of metasomatized lithospheric mantle. The Early Cretaceous magmatism in the Jiaodong Peninsula reflects the geodynamic evolution, marking the transition from the subduction and collision of the Paleo-Pacific Oceanic Plate (PPOP) beneath the Eurasian Plate to the roll-back of the subducted PPOP slab. This transition is characterized by a shift from crustal thickening to lithospheric thinning and from a compressional setting to an extensional setting. The early Early Cretaceous magmatism marks the culmination of the crustal thickening event in the Jiaodong Peninsula. The short interval (approximately 10 Ma) between the Guojialing and Weideshan magmatic events supports the hypothesis of intensified lithospheric delamination. During this period, the intense tectonic, magmatic, and fluid activities served as the material source, migration pathways, and spatial hosts for the intense metallogenic processes in the Jiaodong Peninsula.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108101"},"PeriodicalIF":2.9,"publicationDate":"2025-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143881952","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":"Formation of the giant Jinduicheng porphyry Mo deposit in East Qinling, Central China: Evidence from geochemical and isotopic compositions of magmatic accessory minerals","authors":"Kai Xing ,&nbsp;Qihai Shu ,&nbsp;David Lentz ,&nbsp;Rong Xu ,&nbsp;Fangfang Zhang ,&nbsp;Jinyu Liu ,&nbsp;Fan Yu ,&nbsp;Xudong Niu ,&nbsp;Qingfei Wang ,&nbsp;Jun Deng","doi":"10.1016/j.lithos.2025.108100","DOIUrl":"10.1016/j.lithos.2025.108100","url":null,"abstract":"<div><div>The East Qinling Mo belt is one of the most important Mo provinces in the world where there are abundant collision-related porphyry deposits. As a representative Mesozoic porphyry Mo deposit in this region, Jinduicheng provides an excellent opportunity to investigate the physical-chemical processes of the ore-forming magmas leading to the significant Mo endowment. In this study, magmatic apatite and zircon from the causative granite porphyry have been selected for in situ chemical and Sr-Nd-Hf isotopic analyses to investigate the key factors controlling the magmatic Mo fertility. The Jinduicheng granite porphyry yields zircon U-Pb age of 143.9 ± 1.7 Ma, which coincides with the previously published molybdenite Re-Os ages. Magmatic apatite grains display relatively high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7076–0.7106) and negative ε_Nd(t) values (−18.0 to −13.3), revealing that the causative magma was derived dominantly from ancient lower crust. The interpretation is also supported by the negative zircon ε_Hf(t) values (−26.2 to −4.6) with T_DM2 ages ranging between 2844 and 1488 Ma. The high zircon Ce and Eu anomalies (Ce_N/Ce_N* = 3–323 and Eu_N/Eu_N* = 0.32–0.65), magma oxygen fugacities (ƒ_O2 = −16.53 to −12.63 and ΔFMQ = +1.0 to +3.6), together with the relatively high apatite Eu contents (43.7 ppm in average), all suggest a high magma oxidation state. The magmatic S concentrations have been further estimated, while the results (22–57 ppm) are relatively low. These results highlight the importance of high oxygen fugacities, rather than the enrichments of magmatic S and/or Mo, in the formation of the giant Jinduicheng Mo deposit.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108100"},"PeriodicalIF":2.9,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143867833","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":"When did the Chicheng eclogite form? Revisiting the Paleoproterozoic-late Paleozoic controversy via zircon inclusion and U-Pb dating","authors":"Xiao-Bo Wang ,&nbsp;Jia-Lin Wu ,&nbsp;Ming-Guo Zhai ,&nbsp;Le Zhang ,&nbsp;Bo Hu","doi":"10.1016/j.lithos.2025.108094","DOIUrl":"10.1016/j.lithos.2025.108094","url":null,"abstract":"<div><div>Since its discovery in 2002, the tectonic significance of the Chicheng eclogite along the northern margin of the North China Craton (NCC) has been debated, with conflicting interpretations regarding its peak metamorphic age (Paleoproterozoic vs. Late Paleozoic). This controversy arises from unclear correlations between isotopic ages and metamorphic mineral assemblages. Here, we resolve this issue by integrating mineral inclusion analysis with zircon textural characteristics to constrain metamorphic generations of zircons. Systematic investigations of two eclogite samples (CC26 and CC28) reveal three distinct indicator mineral assemblages preserved in zircon domains: (1) eclogite-facies indicators (omphacite, kyanite and rutile); (2) non-eclogite-facies indicators (plagioclase, diopside, orthopyroxene, amphibole and ilmenite); and (3) persistent phases (garnet and quartz). LA-ICPMS U-Pb geochronology delineates three metamorphic stages: (1) peak eclogite-facies metamorphism at 334–339 Ma recorded in eclogite-facies indicators bearing zircon domains or metamorphic cores; (2) prograde metamorphism at 357–361 Ma preserved in a few zircon cores or the domains with non-eclogite-facies indicators; and (3) retrograde stage at 320–316 Ma recorded in zircon rims, respectively. Notably, scattered ages of 283–304 Ma likely reflect post-collisional magmatic thermal events. The Hongqiyingzi Complex (hosting the Chicheng eclogite) exhibits contrasting lithological and tectono-thermal records compared to the NCC's Dantazi Complex. These findings support a Late Paleozoic origin for the Chicheng eclogite, related to orogenic processes of the Central Asian Orogenic Belt (CAOB), rather than Paleoproterozoic NCC amalgamation events.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108094"},"PeriodicalIF":2.9,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854969","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":"Tracking crystal-melt segregation and accumulation in mushy reservoirs: Implication for silicic magma formation in tarim large igneous province","authors":"ChangQuan Li,&nbsp;Zhaochong Zhang,&nbsp;Changhong Wang,&nbsp;Zhiguo Cheng,&nbsp;Dan Gao","doi":"10.1016/j.lithos.2025.108099","DOIUrl":"10.1016/j.lithos.2025.108099","url":null,"abstract":"<div><div>The genesis of silicic (SiO₂ &gt; 70 wt%) magmas in Large Igneous Provinces (LIPs) has traditionally been related to partial melting of pre-existing crust and/or crystal fractionation of mantle-derived basaltic magma. Recent petrological studies highlight crystal-melt segregation as a significant mechanism for generating silicic magmas and establishing genetic links between volcanic and plutonic rocks. The identification of complementary cumulate residues at the base of crystal mush and the necessary mafic magmas for mush reactivation has proven challenging, leading to the elusive recognition of crystal accumulations in plutonic rocks with intermediate to silicic compositions. The Xiaohaizi complex in the Tarim LIP in NW China consists of plutonic rocks ranging from mafic to silicic (45–75 wt% SiO₂). This complex provides a natural laboratory for investigating the in-situ crystal-melt segregation process in the shallow crust. Rayleigh fractionation modeling of Ba, Sr, Eu, and Rb reveals that quartz syenites and granites embody highly evolved, extracted melts, while amphibole syenites and fayalite syenites correspond to the complementary cumulate residues. The quartz syenite porphyry likely represent well-preserved snapshot of the parental magma's initial chemical characteristics. Mineral textures and crystal size distribution (CSD) patterns effectively differentiate between cumulate residues and extracted melts. Variations in Eu/Eu*, Rb, and Ba in alkaline feldspars support feldspar accumulation in mush. During magmatic evolution, temperature and pressure of the Xiaohaizi intermediate to silicic magmatic rock gradually decrease from 950 °C to 700 °C and 300 MPa to 100 MPa, respectively. High melt water content (H₂O_melt = ∼4 wt%) in these magmas enhances the efficiency of crystal-melt segregation. The injection of deep, high-temperature (1000 °C ∼ 1100 °C, 300–500 MPa) wehrlite magmas can prolong the crystal-melt segregation process. The similarity in magmatic oxygen fugacity and melt water contents among the mafic, intermediate, and silicic rocks suggests a physicochemical inheritance throughout the magma evolution process. This complex can preserve records of crystal-melt separation process to produce silicic magmas in the shallow crust, providing new evidence for mush model during the Permian within the Tarim LIP.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108099"},"PeriodicalIF":2.9,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon and monazite perspectives on the origin and evolution of Gaowu leucogranites in Yadong area, southern Tibet","authors":"Zhiqiu Xiong ,&nbsp;Zhidan Zhao ,&nbsp;Zhenzhen Wang ,&nbsp;Dong Liu ,&nbsp;Yan Tang ,&nbsp;Qing Wang ,&nbsp;Liang-Liang Zhang ,&nbsp;Jin-Cheng Xie ,&nbsp;Di-Cheng Zhu","doi":"10.1016/j.lithos.2025.108097","DOIUrl":"10.1016/j.lithos.2025.108097","url":null,"abstract":"<div><div>The Himalayan Orogen, formed during the ongoing India-Asia continental collision, experienced a tectonic regime transition during the Middle Miocene, which resulted in a complex extension. This tectonic evolutional history is recorded in leucogranites intruding into the Himalayan crust. However, the source characteristics of leucogranites are difficult to determine because of the strong interaction between the magma and country rock. In this study, we performed U-Pb dating and trace element analysis of zircon and monazite, Hf isotope analysis of zircon, and mineral composition, elemental, and Sr-Nd isotopic geochemistry analyses of leucogranites from the Gaowu pluton in the Yadong area, southern Tibet. Three types of leucogranites (two-mica, tourmaline, and garnet) were collected from the pluton. These leucogranites show S-type and peraluminous granite affinities with SiO₂ content ranging from 71.58 to 76.91 wt% and A/CNK ratios of 1.06–1.2. Episodic leucogranitic magmatism occurred at ∼27 Ma, 23–21 Ma, 20–17 Ma, and ∼ 13 Ma, with variable ε_Hf(t) values ranging from −27.1 to −6.7. The oldest leucogranites showed relatively low Nb_N/Pb_N and Sm_N/La_N ratios, distinct from those with ages of 23–21 and 20–17 Ma. Additionally, leucogranites with ages of ∼27 Ma and 20–17 Ma (Eu/Eu* = 0.01–0.04) showed more significant negative Eu anomalies than those with ages of 23–21 Ma (Eu/Eu* = 0.03–0.09), which was attributed to compositional variations in the host magmas. Inherited zircons from the Gaowu leucogranites display scattered ages with a peak at approximately 492 Ma, and were characterized by lower Th and Pb concentrations, similar to the High Himalayan Crystalline Series (HHCS), indicating their derivation from the HHCS. Zircon trace element data identified Paleozoic gneissic granites and pegmatites as the potential source rocks of leucogranites in the Yadong area. According to zircon saturation thermometry, the peak melt temperature of two-mica leucogranites was approximately 715 °C, which was 55 °C and 115 °C higher than those of tourmaline leucogranites (660 °C) and garnet leucogranites (600 °C), respectively. After combining our results with previous findings, we propose that the Gaowu leucogranites were derived from muscovite fluid-absent melting at 27–17 Ma and muscovite fluid-present melting at ∼13 Ma. This transition in melting behavior could be linked to the activity of the South Tibetan Detachment System (STDS) and the Yadong–Gulu rift, which led to decompression and water infiltration, respectively. Concurrently, the eastern Himalayas tectonic regime transitioned from N-S extension and HHCS exhumation to E–W extension at ∼13 Ma. Thus, Middle Miocene Himalayan leucogranite rocks provide valuable insights into this tectonic regime transitions and deep geodynamic processes.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108097"},"PeriodicalIF":2.9,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143864876","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 and spatial scales of garnet growth associated with serpentinization: A case study from Belvidere Mountain, Vermont, USA","authors":"John M. Brigham ,&nbsp;Suzanne L. Baldwin ,&nbsp;Kyra L. Schroeder ,&nbsp;Stephanie Walker ,&nbsp;Ethan F. Baxter","doi":"10.1016/j.lithos.2025.108098","DOIUrl":"10.1016/j.lithos.2025.108098","url":null,"abstract":"<div><div>Serpentinites and rodingites can inform scientists about the evolution of the Earth's upper mantle, including metamorphic processes that occur in subduction zones. Serpentinization and rodingitization are metasomatic processes that are hypothesized to be geochemically and temporally related. Garnets that form in rodingites have the potential to constrain the temporal evolution of their host lithologies. However, garnet is stable in rodingites over a wide pressure and temperature range, and rodingites can contain multiple generations of garnet. In a serpentinite-hosted rodingite zone from Belvidere Mountain, Vermont, USA, three generations of texturally and chemically distinct garnets occur within ∼1 cm of each other in a single sample. We present results from electron microprobe, whole-rock geochemistry, phase equilibria modelling, and garnet Sm-Nd ID TIMS analyses for each garnet generation from this locality. Massive garnets occur as large anhedral masses (&gt;1 cm) along with interstitial diopside, titanite, and chlorite, and yielded a Sm-Nd isochron age of 477.3 ± 6.1 Ma (<em>n</em> = 6; MSWD = 3.1). Massive garnets are interpreted to have formed by rodingitization of mafic blocks in a subduction setting during the Taconic Orogeny and provide a minimum temporal estimate for serpentinization of the Belvidere Mountain ultramafic rocks. Fine-grained (∼100–200 μm) anhedral garnets define the dominant foliation in the rodingite, and are surrounded by fine-grained diopside, epidote, and chlorite. The fine-grained garnets yielded an imprecise isochron age of 426.1 ± 26.7 Ma (<em>n</em> = 4, MSWD = 0.81) which may be compromised by non-garnet inclusions and diffusive loss of Nd, precluding an accurate interpretation. Garnetite veins (∼1 cm) crosscut the foliation and yielded an isochron age of 410.0 ± 4.0 Ma (n = 4, MSWD = 1.9). Garnetite veins are interpreted to date post-Taconic, synextensional, low-temperature metasomatism. Results indicate that multiple generations of garnet can form in rodingites over centimeter spatial scales and ∼70 Myr timescales.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108098"},"PeriodicalIF":2.9,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143864875","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}