Lithos最新文献

{"title":"Slab-derived fluid contributes to subducted material recycling and crust growth: Insights from the arc volcanics in East Junggar (NW China)","authors":"Rui An ,&nbsp;Guochun Zhao ,&nbsp;Yigui Han ,&nbsp;Jianhua Li ,&nbsp;Zengchan Dong","doi":"10.1016/j.lithos.2025.108114","DOIUrl":"10.1016/j.lithos.2025.108114","url":null,"abstract":"<div><div>Arc volcanic rocks provide important insights into material recycling and crustal growth in subduction zones; however, the recycling mechanism (i.e., slab-derived fluid versus mélange diapirs) is poorly constrained. Here, we focus on Devonian basalts and andesites identified recently in the Shaerbulake area, in the northern part of the East Junggar (EJ) terrane. Zircon U-Pb ages indicate that the samples were formed at ∼390 Ma, and the zircon ε_Hf(t) values range from +13 to +14.2. The investigated samples yield variable SiO₂ (48.4–62.9 wt%) and MgO (1.6–6.9 wt%) contents and similar subduction-related trace-element patterns, with enrichment in Ba, Pb, and Sr and depletion in Nb, Ta, and Ti. Whole-rock Sr-Nd isotopic compositions and geochemical discrimination diagrams (Ba/Th versus La/Sm and Th/Nb), along with quantitative modelling, suggest low-degree (2 %–5 %) partial melting of a sub-arc mantle source that had been metasomatized by ∼10 % slab-derived fluid, which consisted of 95 % altered oceanic crust-derived fluid and 5 % subducted sediment melt. Our whole-rock SiO₂, MgO, trace-element, and Sr-Nd isotopic data and zircon Hf isotopic compositions, together with previously published data from across the EJ terrane, argue for a considerable contribution from slab-derived fluid to the recycling of subducted slab material and crustal growth during the Devonian in the EJ terrane. This implies that slab-derived fluid might not only be metasomatic agents responsible for material recycling in subduction zones, but might also contribute to arc magmatism and crustal growth.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"510 ","pages":"Article 108114"},"PeriodicalIF":2.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144108253","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 global deep carbon cycle started in the Paleoproterozoic Era","authors":"Zhicheng Liu ,&nbsp;Lifei Zhang ,&nbsp;Ailin Jin ,&nbsp;Chunyuan Lan ,&nbsp;Han Hu ,&nbsp;Cheng Xu","doi":"10.1016/j.lithos.2025.108113","DOIUrl":"10.1016/j.lithos.2025.108113","url":null,"abstract":"<div><div>The deep carbon cycle plays a crucial role in Earth's evolution by regulating atmospheric composition and ensuring planetary habitability over geological timescales. However, the timing of when the global deep carbon cycle started remains debated. In this study, we synthesize data from basalt, carbonatite, kimberlite, and diamond samples to propose that significant global carbon deposits subducted into the deep mantle during the Paleoproterozoic era, where they were retained for an extended period. This major event of deep carbon subduction in the Paleoproterozoic may mark the beginning of the first global deep carbon cycle by which the surface materials can be subducted into upper mantle. Our findings suggest that the Earth's mantle, the primary reservoir for carbon, underwent its first substantial carbon infusion during Paleoproterozoic era. Acting as a vast carbon buffer, the mantle played a critical role in balancing carbon distribution between the atmosphere, oceans and crust, thus supporting Earth's transition towards a more habitable state.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"510 ","pages":"Article 108113"},"PeriodicalIF":2.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144083707","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 ferrogabbro-anorthosite suite of rocks from the Neoproterozoic Koraput alkaline complex, India: Implication for the Rodinia breakup","authors":"Manojit Koley ,&nbsp;Biswajit Ghosh ,&nbsp;Jiří Sláma ,&nbsp;Jitka Míková ,&nbsp;Soumi Chattopadhaya ,&nbsp;N.V. Chalapathi Rao ,&nbsp;Tomoaki Morishita ,&nbsp;Archisman Dhar ,&nbsp;Sankhadeep Roy ,&nbsp;Rajib Kar ,&nbsp;Sachin Kumar Tripathi ,&nbsp;Samarendra Bhattacharya","doi":"10.1016/j.lithos.2025.108111","DOIUrl":"10.1016/j.lithos.2025.108111","url":null,"abstract":"<div><div>The origin and evolution of the Koraput Alkaline Complex (KAC), situated in the western part of the Eastern Ghats Granulite Belt (EGGB), India, have long been debated. The complex consists of a variety of rock types including ferrogabbro, foid gabbro (or essexite), hornblendite, nepheline syenite, syenite, and some anorthositic variants. Comprehensive petrology, geochemistry and geochronology of the rock types carried out in this study provides a critical assessment of their petrogenetic linkage with past supercontinent cycle. Using quantitative geochemical modelling, we explain geochemical variability of the lithounits from a high aluminous parental melt, equivalent to fine-grained ferrogabbro representative of the complex. The geochemical modelling using alpha-MELTS indicates that anorthosite, essexite, and hornblendite are the product of fractional crystallisation whereas, ferrogabbro formed by equilibrium crystallisation from the residual melt. On the other hand, nepheline syenite and syenite are the product of assimilation-fractional crystallisation (AFC) from a hybridized melt assimilating the continental crust within which the parental magma was emplaced. Whole rock geochemistry of parental magma, along with Hf isotopic ratios of the zircons of nepheline syenite and anorthosite, suggest subcontinental lithospheric mantle (SCLM) source for the KAC primary melt in an intraplate tectonic setting. The primary melt had a high Mg# (71), and was formed at a mantle potential temperature and pressure of 1570 °C and 3.45 GPa respectively. U-Pb dating of zircon from nepheline syenite and anorthosite suggests that the KAC was emplaced between 741.8 ± 2.9 and 732.2 ± 2.8 Ma, which bears implication for the Rodinia supercontinent breakup.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108111"},"PeriodicalIF":2.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143935766","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":"Not all Neoproterozoic continental crust exposed in the Sulu belt was deeply subducted","authors":"Zhuocheng Wang ,&nbsp;Lu Wang ,&nbsp;Michael Brown ,&nbsp;Tim E. Johnson ,&nbsp;Christopher L. Kirkland ,&nbsp;Chris Clark ,&nbsp;Eleanore Blereau","doi":"10.1016/j.lithos.2025.108116","DOIUrl":"10.1016/j.lithos.2025.108116","url":null,"abstract":"<div><div>A newly identified tectonic sliver of low-grade Neoproterozoic continental crust comprising hybrid granitoids is exposed between Triassic ultrahigh-pressure (UHP) metamorphic rocks of the Sulu belt and the Cretaceous Laoshan granite. Outcrop evidence of magma mingling combined with the granitic mineral assemblages and primary igneous microstructures suggest &gt;100 km difference in likely depth of subduction compared to the proximal UHP metamorphic rocks. The granitoids are cut by a brittle-to-ductile shear zone and extensional fractures that focussed fluid flow and allowed low-temperature fluid–rock alteration. Integrated accessory mineral geochronology from zircon, allanite and apatite records crystallization ages of c. 835–700 Ma and alteration ages of c.120–90 Ma. There is no evidence of the Triassic UHP metamorphic event recorded in the Neoproterozoic granitoids. The hybrid granitoids were likely generated during Neoproterozoic rifting of Rodinia, forming part of the northern margin of the Yangtze craton, but they did not experience deep subduction like other Neoproterozoic continental crust within the Sulu belt. The adjacent Cretaceous Laoshan granite was emplaced when all units were at shallow crustal depths, after &gt;100 km of exhumation of the UHP eclogites. The Cretaceous ages retrieved from the hybrid granitoids date the brittle deformation and fluid alteration of these rocks in the Laoshan granite aureole. Cretaceous subduction retreat (slab roll back) of the paleo-Pacific plate caused extension and lithosphere thinning of the upper plate (eastern China), forming extensional shear zones and core complexes, associated with numerous granitoid intrusions, including the Laoshan granite. The extensional geological setting also facilitated preservation of this thin sliver of hybrid granitoids at the margin of the Laoshan granite adjacent to the UHP metamorphic terrane, and likely contributed to the final exhumation of the UHP metamorphic rocks of the Sulu belt. Our study shows that post-collisional extensional could be a common mechanism promoting final exhumation and exposure of deeply subducted terrains in orogens worldwide.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"510 ","pages":"Article 108116"},"PeriodicalIF":2.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144069070","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":"Fluid evolution of the Yemaquan Fe-polymetallic deposit in the East Kunlun metallogenic belt, western China: Insights from garnet geochronology and geochemistry","authors":"Tong Liu,&nbsp;Shao-Yong Jiang,&nbsp;Wei Wang,&nbsp;Hui-Min Su","doi":"10.1016/j.lithos.2025.108119","DOIUrl":"10.1016/j.lithos.2025.108119","url":null,"abstract":"<div><div>Garnet, as a reliable indicator for illustrating fluid evolution, is commonly found in skarn deposits and can serve as an effective mineral for determining the age of geological processes. This study provides major and trace element analyses, high-precision in situ U-Pb geochronological data, and X-ray mapping of garnets from the Yemaquan Fe–polymetallic skarn deposit. Results indicate that the Yemaquan Fe-polymetallic deposit formed at ∼235 Ma and is closely related to K-feldspar granite. Based on the intercalated relationships of garnets, they can be classified into 4 generations. Furthermore, according to the major element characteristics of these four generations, they can be further divided into two groups: andradite (Grt-I) and grossular (Grt-II-IV). Trace element analyses of the four generations of garnets reveal two stages of fluid evolution (F1 and F2). F1 represents the early magmatic fluid, characterized by its acidic in nature, enrichment in LREE, depletion in HREE, and relatively high Fe concentrations, leading to the formation of Grt-I. F2 represents the late magmatic fluid, which is neutral in nature, depleted in LREE, enriched in HREE, and has significantly higher HFSE concentrations—three orders of magnitude greater than those in F1—resulting in the formation of Grt-II, Grt-III, and Grt-IV. By integrating garnet U-Pb dating results with published ⁴⁰Ar-³⁹Ar ages of hydrothermal phlogopite, we deduce that mineralization at the Yemaquan deposit began as early as ∼235 Ma. The span from 235 to 222 Ma indicates potential multiple mineralization stages. Notably, the overlap between the garnet U-Pb age and the emplacement age of the K-feldspar granite (previously considered barren) suggests a possible genetic link. Despite Although direct field evidence is limited, this correlation supports a genetic association between them. These findings propose the hypothesis that the Yemaquan mineralization may be related to potassium feldspar granite and involve multiple stages. They also provide guidance for future exploration at Yemaquan and the broader North Qimantagh belt.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108119"},"PeriodicalIF":2.9,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927936","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":"Age and origin of NYF pegmatites from the Mesoproterozoic Orange River pegmatite belt (Namaqualand, South Africa): insights from monazite and titanite U-Pb geochronology and Nd isotope systematics","authors":"Minenhle S. Maphumulo ,&nbsp;Christophe Ballouard ,&nbsp;Marlina A. Elburg","doi":"10.1016/j.lithos.2025.108110","DOIUrl":"10.1016/j.lithos.2025.108110","url":null,"abstract":"<div><div>The 450 km long Orange River pegmatite belt consists of &gt;30,000 pegmatite dykes that intruded the Namaqua Sector of the Mesoproterozoic Namaqua-Natal Metamorphic Province in Southern Africa at ca. 1 Ga. The extremities of the belt mostly host pegmatites with Li-Cs-Ta (LCT) signatures. In contrast, the Kakamas Domain, located in the central part of the Namaqua Sector, is dominated by the occurrence of Nb-Y-F-enriched (NYF) pegmatites with economic potential for REE and Th. The origin of NYF pegmatites, including processes of REE-Th enrichment, remain poorly understood. Here, we provide in-situ U-Pb ages along with Sm-Nd isotopic compositions of titanite and monazite from those pegmatites in order to constrain their source and tectonomagmatic context of emplacement.</div><div>The Kakamas NYF pegmatites consist of (i) simple, relatively homogeneous dykes with low concentrations of REE-Y-Th-U-rich minerals, contrasting with (ii) complex, variably zoned dykes, characterised by a higher proportion of monazite, thorite, and xenotime. Similar to other pegmatites from the Namaqua Sector, simple and complex NYF pegmatites from the Kakamas Domain yield U-Pb ages from 1043 ± 5 to 1025 ± 6 Ma (titanite) and from 991 ± 15 to 962 ± 3 Ma (monazite), respectively, suggesting an increase in the ‘rare metal-fertility’ of pegmatite-forming magmatism over time. Pegmatite crystallisation postdates I- and A-type granitic magmatism in the Kakamas Domain from 1120 to 1080 Ma, and complex pegmatite emplacement was coeval with a major transcurrent deformation event in the Namaqua Sector dated by previous studies at ca. 1005–960 Ma. Vertical structures associated with strike-slip tectonics likely facilitated the upward migration of rare metal-rich melts. Simple pegmatites have average ɛNd(<em>t</em>)_titanite values between - 5.8 and - 2.9 and complex pegmatites have average ɛNd(<em>t</em>)_monazite values of - 4.1 to - 3.1, corresponding to similar two-stage depleted mantle model ages (T_2DM) of 2.1 to 1.9 Ga and 1.9 to 1.8 Ga, respectively. Those model ages are younger than those of Namaqua LCT pegmatites, but overlap with those of orthogneissic, granitic and granulite-facies metapelitic country rocks from the Kakamas Domain suggesting a potential local crustal source for NYF pegmatites. Granulite-facies restitic metapelites as well as A-type and I-type granitoids that constitute a voluminous component of the Kakamas crust show appreciable concentrations of elements characteristically enriched in NYF pegmatites. This geochemical background may explain the prevalence of NYF pegmatites in the Kakamas Domain.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"510 ","pages":"Article 108110"},"PeriodicalIF":2.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144137872","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 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":"Latest Early Cretaceous tectonic transition from contraction to large-scale extension in Southeast China: Insights from the magmatism along the Changle-Nan'ao Fault Zone","authors":"Hanqiao Zheng,&nbsp;Junfeng Gong,&nbsp;Hongxiang Wu,&nbsp;Hongdan Deng,&nbsp;Yantao Hao,&nbsp;Kongyang Zhu,&nbsp;Zhiquan Yu,&nbsp;Jiakang Huang,&nbsp;Hanlin Chen,&nbsp;Shufeng Yang","doi":"10.1016/j.lithos.2025.108108","DOIUrl":"10.1016/j.lithos.2025.108108","url":null,"abstract":"<div><div>Long-lived subduction and variable plate geometry of the Paleo-Pacific (Izanagi) plate resulted in multiple episodes of both extensional and contractional deformation. The tectono-magmatic activities along the convergent margins provide critical insights into the tectonic evolution of the South China Block (SCB) during the Cretaceous. However, the timing and dynamic mechanisms of the transition from contraction to large-scale intraplate extension in the late Early Cretaceous remain contentious. Here, we present zircon U-Pb ages, geochemical data, and Hf isotopic data from the NNE-trending dioritic dikes and granodiorites in the Changle-Nan'ao Fault Zone, Southeast China, which shed new light on the pivotal tectonic transition in the late Early Cretaceous. The samples exhibit comparable zircon U-Pb ages (105–103 Ma) and certain geochemical characteristics such as right-sloping REE patterns, enrichment in LILEs, and pronounced depletion in HFSEs. We suggest that magma mixing and fractional crystallization played key roles in the formation of the Huxi and Liuao plutons. The intrusion of the dioritic dikes along the fault zone highlights a phase of extensional activity. The magmatic geochemistry and thermochronological records, coupled with crustal thickness data, suggest that the SCB underwent two tectonic transitions at ∼120–115 Ma and ∼105 Ma, respectively. It is noteworthy that the extension observed in the coastal region due to slab break-off was manifested as coeval contraction in the inland region at ∼105 Ma, which was subsequently inherited by widespread extension across SE China. We propose that the tectonic transitions were driven by changes in subduction angle of Paleo-Pacific (Izanagi) slab.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108108"},"PeriodicalIF":2.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143916893","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":"Mineralogy and petrology of the late cretaceous rinkite-bearing Başören nepheline-sodalite syenite, Central Türkiye","authors":"E. Yalçın Ersoy ,&nbsp;Aniket Chakrabarty ,&nbsp;Dirk Müller ,&nbsp;İbrahim Uysal ,&nbsp;Osman Candan ,&nbsp;Serhat Köksal ,&nbsp;Ayca Yıldırım","doi":"10.1016/j.lithos.2025.108103","DOIUrl":"10.1016/j.lithos.2025.108103","url":null,"abstract":"<div><div>Late Cretaceous nepheline-sodalite syenites from the Başören area in central-eastern Türkiye include complex Na-K-Ca-Fe-bearing silicates such as rinkite-(Ce) and represents the first occurrence of agpaitic rocks among the extensive Late Cretaceous magmatic units in the region. The Başören nepheline syenites include three distinct rock types: (1) rinkite-bearing early-, (2) rinkite-free late-magmatic rocks, and (3) pyrochlore-bearing, cumulate-like rocks akin to lujavrite found in other layered alkaline igneous complexes such as the Ilímaussaq, South Greenland and the Lovozero, Kola Peninsula, Russia. The Başören rocks exhibit a sodic affinity and demonstrate silica-undersaturated compositions at a minimum pressure of 1 kbar, consistent with their highly fractionated characteristics. The alkalinity indexes [AI = molar [(Na + K) / Al)] and Fe# values [= molar Fe / (Fe + Mg)] of the early- and late-magmatic rocks vary in the ranges of 0.88–1.09, and 0.89–1.00, respectively. The clinopyroxene in these rocks are essentially aegirine augite in composition. However, the cumulate-like lujavritic rocks display higher AI values of 1.16–1.70 and Fe# values of 0.99–1.00 and contain aegirine. Both the early- and late-magmatic samples exhibit several common characteristics, including pronounced depletion in Ba, Sr, Ti, and P, a limited presence or complete absence of high field strength elements relative to the large ion lithophile elements, and considerable variability in the abundances of rare earth elements (REE). The early-magmatic rocks show steep patterns from light REE to medium REE (La to Eu), and convex-upward patterns from medium to heavy REE (Gd to Lu). The late-magmatic samples exhibit similar patterns to the early-magmatic ones but have lower REE abundances. However, the lujavritic rocks display significantly lower REE abundances with convex-downward patterns. Overall, the nepheline-sodalite syenites in the Başören area represent undersaturated melts that were formed by extreme fractionation of silica-undersaturated K-alkaline basaltic magmas generated in a back-arc setting.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"508 ","pages":"Article 108103"},"PeriodicalIF":2.9,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143935767","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}