Lithos最新文献

{"title":"The old central igneous complexes of Sal, Boa Vista and Maio islands: Implications for 17 Ma of isotopic evolution of the Cape Verde archipelago","authors":"Carlos Villaseca ,&nbsp;David Orejana ,&nbsp;María J. Huertas ,&nbsp;Eumenio Ancochea ,&nbsp;Cristina de Ignacio ,&nbsp;Joao Mata ,&nbsp;Rita Caldeira ,&nbsp;María García-Rodríguez ,&nbsp;Juan A. Moreno ,&nbsp;Cecilia Pérez-Soba","doi":"10.1016/j.lithos.2025.107975","DOIUrl":"10.1016/j.lithos.2025.107975","url":null,"abstract":"<div><div>The central igneous complexes of the easternmost islands (Sal, Boa Vista and Maio) preserve some of the most ancient outcropping rocks of the Cape Verde (CV) archipelago. These Early to Middle Miocene (about 25 to 12 Ma) complexes show marked isotopic differences between mafic rocks from the northern (Sal and Boa Vista) and the southern Maio Island, the latter showing lower ¹⁴³Nd/¹⁴⁴Nd, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and higher ⁸⁷Sr/⁸⁶Sr ratios. The main mantle plume composition beneath Cape Verde is here considered to be dominated by the FOZO component. Our data supports previous models suggesting the incorporation to plume components of minor DMM mantle sources in the northern CV island alignment, whereas mixing with the EM1 pole is prevalent on the southern CV islands. These isotopic differences are evident since the early stages of Cape Verde magmatism. The Late Miocene to Holocene time period (7 to 1.7 Ma) is characterized by the irruption of silica-undersaturated and carbonatite magmas with a relatively homogeneous isotopic composition and highly radiogenic Pb signatures (²⁰⁶Pb/²⁰⁴Pb up to 20.6 in carbonatitic rocks and 20.2 in silicate rocks) throughout most of the Cape Verde archipelago. During this transitional stage, the input of this new HIMU mantle component overprinted the previous mixing of the main FOZO plume component with shallow mantle members (DMM, EM1) of minor contribution.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107975"},"PeriodicalIF":2.9,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378750","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":"Coupled U-Pb, Lu-Hf and trace element geochemistry of apatite reveals complex magmatic-hydrothermal Nb-REE remobilization of the Neoproterozoic Saint-Honoré carbonatite deposit (Quebec, Canada)","authors":"Hélène Legros ,&nbsp;Nils Van Weelderen ,&nbsp;Sarah Dare ,&nbsp;Stijn Glorie ,&nbsp;Michael Higgins ,&nbsp;Dany Savard ,&nbsp;L. Paul Bédard","doi":"10.1016/j.lithos.2025.107980","DOIUrl":"10.1016/j.lithos.2025.107980","url":null,"abstract":"<div><div>Niobium and REE are critical resources that are predominantly associated with carbonatite and alkaline complexes. The Saint-Honoré ore deposit, located in Québec, is a major producer of Nb (7 % of world production) with reserves of 630 thousand tons Nb and major REE resources (1058 thousand tons inferred). This deposit is composed of an outer syenite, inner syenite enclaves, multiple Nb-rich carbonatite intrusions and, a central REE-rich carbonatite. The carbonatites exhibit several generations of apatite (Ca₅(PO₄)₃(F,OH,Cl)) including a magmatic ‘white’ apatite associated with pyrochlore ((Na,Ca)₂Nb₂O₆(OH,F)) and a late hydrothermal ‘red’ apatite. Trace element geochemistry of apatite reveals a very distinct chemistry for both apatite types. The magmatic carbonatite stage is associated with the main Nb mineralization and is dated at 577 ± 14 Ma (U-Pb) and 580 ± 13 Ma (Lu-Hf), with a typical magmatic carbonatite signature whereas the hydrothermal stage has a mixed signature between carbonatite and external fluids which remobilized Nb-(REE) mineralization at 564 ± 16 Ma (Lu-Hf). While the magmatic and hydrothermal stage ages overlap and are also coeval to our lamprophyre apatite age of 569 ± 29 Ma (U-Pb), the late hydrothermal stage is distinctively marked by higher U, Cl, Ba, Fe, Nb and K concentrations in apatite. The late hydrothermal event is linked to a carbonatite fluid mixed with crustal fluids which may have contributed to the emplacement of the REE mineralization in the late stage of the carbonatite complex. This study also highlights the first detailed data on apatite geochemistry from lamprophyre.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107980"},"PeriodicalIF":2.9,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348780","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":"Mechanisms of shear zone development in Krossøy, the Bergen Arcs, Norway","authors":"Lorena H. Filiberto ,&nbsp;Håkon Austrheim ,&nbsp;Andrew Putnis ,&nbsp;José Alberto Padrón-Navarta ,&nbsp;Steven Reddy ,&nbsp;Christine V. Putnis","doi":"10.1016/j.lithos.2025.107977","DOIUrl":"10.1016/j.lithos.2025.107977","url":null,"abstract":"<div><div>The island of Krossøy in the Bergen Arcs, southwestern Norway, provides an ideal geological setting to study the mechanisms of grain size reduction in plagioclase during shear zone development. The transition from a granulite facies anorthosite to mylonitic textures under amphibolite facies conditions is investigated through field observations, petrographic analysis, electron microprobe analysis, and electron backscattered diffraction (EBSD) techniques. Initial ductile deformation, evidenced by complex twinning and intragrain misorientation, leads to strain hardening and subsequent brittle fracturing. This results in grain size reduction primarily through fragmentation, forming a bimodal grain size distribution. Syntectonic recrystallization produces compositionally similar neoblasts. Subsequent interactions with fluids induce compositional recrystallization, leading to further grain size reduction and the formation of zoned plagioclase grains. These processes highlight the critical role of fluid-mediated recrystallization in shear zone development and strain localization. The spatial variation in deformation and hydration stages across Krossøy is attributed to both mechanical anisotropy and chemical reequilibration driven by fluid pathways. These findings enhance our understanding of the interplay between mechanical anisotropy, brittle failure and fluid infiltration in the lower crust, providing insights into the conditions that facilitate the formation and evolution of shear zones in the Bergen Arcs.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107977"},"PeriodicalIF":2.9,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Partial melting of hydrated harzburgite at shallow pressures: An option to produce melts with boninitic characteristics","authors":"Jürgen Koepke ,&nbsp;Sandrin T. Feig ,&nbsp;Jasper Berndt ,&nbsp;Renat R. Almeev","doi":"10.1016/j.lithos.2025.107979","DOIUrl":"10.1016/j.lithos.2025.107979","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Water-saturated partial melting experiments were carried out using a refractory harzburgite from the Oman Ophiolite as starting material. The experiments were performed at pressures of 100, 200 and 500 MPa using both reducing (corresponding to the FMQ buffer) and oxidizing (FMQ + 3) conditions. Specially designed internally heated pressure vessels were used to control oxygen fugacity and allow rapid quenching. Temperatures varied between 980 and 1220 °C, and run durations were up to 82 h. The solidus and clinopyroxene-out curve show significant variation with pressure. As expected, the melts produced were generally SiO&lt;sub&gt;2&lt;/sub&gt;-rich, with SiO&lt;sub&gt;2&lt;/sub&gt; concentrations ranging between 55 and 65 wt%. These melts exhibit boninitic characteristics. Due to the refractory character of the starting material, the experimental melts are highly depleted in incompatible trace elements, showing chondrite-normalized REE patterns with a characteristic concave-upward shape. Calcium and sodium in the system are mainly derived from the clinopyroxene in the starting harzburgite, resulting in extremely high Ca/Na ratios in the experimental melts. Fractionation of such melts could potentially yield highly depleted gabbronorites as cumulate rocks, with anorthite (An) contents of plagioclase generally in excess of 90 mol%. At temperatures above the clinopyroxene breakdown, the residual mineral paragenesis exhibits characteristics similar to extremely refractory harzburgites, with Cr# in Cr-spinel (Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; /(Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; + Cr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;), molar) reaching up to 86, reminiscent of ophiolites formed under supra-subduction zone conditions.&lt;/div&gt;&lt;div&gt;While most of the melts produced have compositions of high-Mg andesite, only a few have compositions of true boninites. It is clear, therefore, that the partial melting of hydrous harzburgite at shallow pressure is not a general model for the formation of typical boninites in subduction zone initiation environments. However, our experimental results show that the formation of distinct rock types within the paleocrust of the Oman Ophiolite such as high-Ca boninites, high-Si boninites, high-Mg andesites, depleted gabbronorite cumulate rocks, and extremely refractory harzburgites containing Cr-spinel with Cr# &gt; 80, could, in principle, be attributed to a single process of fluid-induced partial melting of harzburgite below the crust/mantle boundary of the Oman paleocrust. The temperatures for the heating process (&gt; 1040 °C) for such a model, could be provided by ascending MORB magmas. The presence of water-rich fluids at the crust/mantle boundary or within the uppermost mantle which are necessary for such a model, could be derived from seawater via deep hydrothermal fault zones. In support of this contention, we present new amphibole data from cores drilled in the lower gabbros of the Oman Ophiolite by the International Continental Scientific Drilling Program (ICD","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107979"},"PeriodicalIF":2.9,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377378","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":"Alkaline magmatism in the post-orogenic Triassic Predazzo complex, Dolomites, NE Italy: Ages and significance","authors":"Dario Visonà ,&nbsp;Paolo Nimis ,&nbsp;Giancarlo Cavazzini ,&nbsp;Anna M. Fioretti ,&nbsp;Marinella A. Laurenzi ,&nbsp;Matteo Massironi ,&nbsp;Igor M. Villa","doi":"10.1016/j.lithos.2024.107912","DOIUrl":"10.1016/j.lithos.2024.107912","url":null,"abstract":"<div><div>The Predazzo pluton (Predazzo–Monzoni intrusive complex, Dolomites) is a multipulse calc-alkaline–shoshonitic body, which was emplaced at 238.075 ± 0.087 Ma to 235.9 ± 1.8 Ma. On the eastern flank of the pluton, smaller-volume alkaline rocks are also found, but their relationships with the main magmatic products are not well understood. New field, petrographic, geochemical and geochronological data indicate that these alkaline rocks infilled a small volcano-tectonic trough and consist of trachytic lavas and volcanoclastic tephra (V2 unit), studded by small monzonite and syenite bodies (MS unit) in mingling-mixing relationships, yielding ages of 238.1 ± 1.8 to 230.1 ± 0.6 Ma. Phonotephrite to phonolite dykes (MF unit) crosscut the entire volcanic sequence at 215.0 ± 0.3 Ma and 203 ± 1 Ma. The alkaline cycle thus developed soon after and, possibly, during the main calc-alkaline–shoshonitic stage. Lamprophyric dykes (camptonites) were also emplaced from 234.5 ± 0.3 to 219.2 ± 0.7 Ma. Whole-rock compositions suggest that the magmas enriched in asthenospheric component that produced the lamprophyres could generate the MS–V2 and MF magmas by Assimilation-Fractional-Crystallization, involving assimilation of various carbonatic and silicic crustal components. The very rapid passage from the “post-orogenic” calc-alkaline–shoshonitic to the “anorogenic” alkaline affinity in the Middle-Late Triassic thus appears to reflect a continuous transition within the same geodynamic context, characterized by the gradual development of extensional structures, representing the prodrome of the Jurassic rifting, and progressively deeper magma sources, rather than a sudden change in the regional geodynamic regime.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107912"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The mobilization of trace elements in apatite during metamorphic recrystallization: A record from the Huangmailing metamorphosed phosphorite, Hubei Province, Central China","authors":"Cheng-Lai Deng,&nbsp;Shao-Yong Jiang","doi":"10.1016/j.lithos.2024.107897","DOIUrl":"10.1016/j.lithos.2024.107897","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The chemical composition of apatite provides reliable constraints on petrogenetic processes. However, the behavior of apatite and the redistribution of elements during the metamorphism of phosphorite, a unique sedimentary rock type, remain unclear. This study presents textural, in situ U&lt;img&gt;Pb geochronology, trace and rare earth elements, and Sr isotope data for apatite from the Huangmailing metamorphosed phosphorite in Hubei Province, Central China. Four distinct metamorphic phosphorite samples were collected, namely, dolomitic phosphorite, black massive phosphorite, quartz-muscovite-bearing phosphorite, and quartz-muscovite-bearing phosphorite, with different mineral assemblages. We distinguished four types of apatite based on the mineral assemblage. Type 1 apatite occurred as a layer and interbedded with kutnohorite. In contrast, type 2 apatite is associated with the crumpled K-feldspar band, and type 3 apatite is commonly associated with quartz, muscovite, and calcite. Type 4 apatite is distinct from the other three types of apatite, which is characterized by larger grain size and associated with muscovite and monazite. Precise U&lt;img&gt;Pb isotope data for type 1 and 2 apatite were obtained to constrain the metamorphic age of the sedimentary phosphorite, which ranged from 218 ± 6.4 Ma to 214.9 ± 9.6 Ma. Compared with the apatites from the unmetamorphosed phosphorite in south China, the studied apatites are commonly enriched with rare earth elements and yttrium (REY) (except type 3 apatite) but depleted in Ba. These four types of apatite have different trace and rare earth element compositions, especially their REY patterns. The lower (La/Sm)&lt;sub&gt;N&lt;/sub&gt; of type 1 apatite than that of type 2 to 3 apatite may suggest the mobilization of light rare earth element (LREE) in type 1 apatite into the metamorphic fluid. A slightly positive Eu anomaly was observed for the type 2 apatite, suggesting the contribution of dissolved K-feldspar during the metamorphic recrystallization of type 2 apatite. The REY patterns of type 3 apatite differ slightly from those of primary apatite, whereas type 4 apatite presents distinct REY patterns in comparison with the other three types of apatite, with an obvious negative Eu anomaly and the highest LREE content. These findings suggest that the enrichment of Sr and the slightly positive Eu anomalies in type 2 apatite can be linked to the breakdown of K-feldspar during metamorphic reactions. This connection is supported by the comparatively elevated Sr isotopic composition of type 2 apatite. As muscovite and monazite decomposed, the released Th, Pb, Na, and LREEs were incorporated into type 4 apatite. The newly reported data from this study prove that the composition of apatite changes during metamorphism, depending on the local mineral assemblage. The trace elements released from associated minerals may be incorporated into apatite during metamorphic recrystallization, leading to diversity in the chemical sign","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107897"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161553","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":"Machine learning-based identification of marine and terrestrial Volcanic Rocks in the Tibetan Plateau","authors":"Xinwei Liu ,&nbsp;Qiuming Cheng","doi":"10.1016/j.lithos.2024.107930","DOIUrl":"10.1016/j.lithos.2024.107930","url":null,"abstract":"<div><div>Distinguishing between marine and terrestrial basalts is crucial for understanding geological processes, including plate tectonics, ocean–continent transition history, and paleoenvironmental changes. However, traditional geochemical methods for tectonic setting discrimination are often limited by issues such as data overlap and the difficulty in obtaining representative samples, making it challenging to accurately differentiate tectonic environments. Machine learning provides an effective approach to address these challenges in the context of large datasets and complex geological problems. In this study, advanced machine learning techniques are applied to global basalt geochemical data to develop a model specifically tailored for regional applications. This model, designed to differentiate between oceanic and continental tectonic environments, is then applied to the Tibetan Plateau basalt data, offering insights into the tectonic background of this specific region. The results show that both oceanic and continental basalt records existed in the region up to 90 million years ago, but the oceanic basalt record subsequently disappeared. This finding suggests that, for a prolonged period before the closure of the Neo-Tethys Ocean, oceanic volcanism was no longer occurring in the Tibetan Plateau. This discovery provides new evidence for the timing of the marine–terrestrial environmental transition in the Tibetan Plateau and is significant for understanding the tectonic evolution and geodynamic processes of the Tethys tectonic domain.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107930"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New magmatic record of Indian continental subduction at ca. 50 Ma: Evidence from ultrapotassic–potassic lamprophyre dikes in the Gangdese Batholith, Southern Tibet","authors":"Yulin Deng ,&nbsp;Xinghai Lang ,&nbsp;Reiner Klemd ,&nbsp;Xuhui Wang ,&nbsp;Juxing Tang ,&nbsp;Qing He ,&nbsp;You Zhou ,&nbsp;Yinhui Zuo ,&nbsp;Xiaoqian Tang ,&nbsp;Sangmu Zunzhu","doi":"10.1016/j.lithos.2024.107933","DOIUrl":"10.1016/j.lithos.2024.107933","url":null,"abstract":"<div><div>Geophysical and geochemical evidence confirmed the northward-directed Indian continental lithosphere subduction beneath the Gangdese orogen, however, the geodynamic processes responsible for the transition from the Neo-Tethyan subduction to the Indian continental subduction, particularly magma generation mechanisms regarding the 53–42 Ma magmatic flare-up events, remain poorly constrained. Here we have conducted a comprehensive investigation combining geochemical and geochronological studies of newly discovered Early Eocene (ca. 50–47 Ma) ultrapotassic–potassic lamprophyre dikes in the Lhasa terrane, Tibet. The ultrapotassic lamprophyres revealed highly evolved Sr–Nd–Pb isotopes and high concentrations of incompatible elements, and are thought to have originated from the Indian lithospheric mantle. In contrast, the potassic lamprophyres, displaying relatively depleted Sr–Nd–Pb isotopes and lower MgO contents and K₂O/Na₂O ratios than the ultrapotassic lamprophyres, show high Sr/Y and low Y geochemical signatures, thereby demonstrating that they formed due to contamination of the ultrapotassic lamprophyre magma by adakitic melts. We, therefore, propose that the lamprophyres represent a new magmatic record of the Indian lithosphere, suggesting that the subduction of Indian plate beneath the Lhasa terrane was already operating at ca. 50 Ma. The data gained here in conjunction with published data further suggest that the upwelling asthenosphere associated with the Neo-Tethyan slab breakoff caused the significant melting of both mantle and crust.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107933"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162153","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":"Identification of intermediate-silicic cumulates in the Emeishan large igneous province, SW China","authors":"Kwan-Nang Pang ,&nbsp;Yang Sun ,&nbsp;Christina Yan Wang ,&nbsp;Sun-Lin Chung ,&nbsp;Hao-Yang Lee","doi":"10.1016/j.lithos.2024.107932","DOIUrl":"10.1016/j.lithos.2024.107932","url":null,"abstract":"<div><div>Geochemical signatures of crystal accumulation in silicic igneous rocks are subtle and difficult to discern. However, the presence of silicic cumulates is required to explain the formation of silicic magmas by fractionation-dominated mechanisms. In large igneous provinces, such rock records are scarce if ever reported. In this study, we document a case example of identifying intermediate-silicic cumulates in the end-Guadalupian (∼260 Ma) Emeishan large igneous province, SW China. We demonstrate that syenitic rocks associated with the Panzhihua intrusion have textures and trace element geochemistry consistent with origins involving both crystal accumulation and melt extraction. Micro-X-ray fluorescence mapping shows that the rocks are either supported by a framework of interconnected, relatively large crystals of alkali feldspar, or by a fine- to medium-grained matrix. The former has relatively low SiO₂, relatively high TiO₂, Fe₂O₃, CaO, Na₂O, Sr and Ba, and a characteristic positive Eu anomaly, whereas the latter has essentially the opposite features. All studied rocks have restricted initial Sr-Nd-Pb isotopic ratios that are similar to mafic rocks of the Panzhihua intrusion, requiring minimal contamination by the Precambrian basement of the Yangtze block. Because of delayed zircon saturation, Zr and Zr/Hf are less promising compared with Eu/Eu* and Ba in identifying cumulates in the studied rocks, a view that might hold in other intraplate magmatic systems. Our results, combined with available data, improve the current understanding of volcanic-plutonic connection concerning silicic magma types of the Emeishan large igneous province.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107932"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New age and geochemical constraints on the “Old Andesite” and Middle Miocene adakites from Pacitan, East Java, Indonesia","authors":"Lediyantje Lintjewas ,&nbsp;Yu-Ming Lai ,&nbsp;Iwan Setiawan ,&nbsp;Sun-Lin Chung ,&nbsp;Andrie Al Kautsar ,&nbsp;Hao-Yang Lee ,&nbsp;Long Xiang Quek ,&nbsp;Yoshiyuki Iizuka","doi":"10.1016/j.lithos.2025.107943","DOIUrl":"10.1016/j.lithos.2025.107943","url":null,"abstract":"<div><div>The subduction of the Indo-Australian Plate beneath the Eurasian Plate resulted in Cenozoic volcanism along the Sunda Arc, with Java Island located in its central portion. Pacitan is situated on the southern coast of East Java, where arc volcanic rocks are widely exposed and have traditionally been designated as Old Andesite, which erupted during the Eocene epoch. In this study, we present new whole-rock geochemical data, including major and trace elements, Sr<img>Nd isotopes, and zircon U<img>Pb ages and Lu<img>Hf isotopes of volcanic rocks from Pacitan. Our age data indicate that magmatism in Pacitan occurred in three stages: Late Oligocene (26.7 to 26.0 Ma), Early Miocene (∼20 Ma), and Middle Miocene (13.4 to 11.4 Ma). The first two stages comprise various lithologies (basalt-andesite-dacite-rhyolite) exhibiting low-K to median-K calc-alkaline compositions, while the third stage includes an additional rock type with adakitic geochemical affinities. We propose that the Old Andesite in Pacitan is not as old as previously believed but was active from the Late Oligocene because of the Sunda subduction initiation in this region. The Middle Miocene adakitic volcanism was attributed to the onset of ridge subduction southwest of Java Island, a key tectonic process that we assert occurred earlier than previously suggested. Consequently, we propose a new three-stage tectonomagmatic evolution model for the central segment of the Tertiary Sunda subduction system.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107943"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162010","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}