Lithos最新文献

{"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}

{"title":"Using elastic geobarometry to unveil subduction-collision and rapid exhumation in the West Gondwana Orogen: Application to high-T/HP rocks in the NW part of the Borborema Province, NE Brazil","authors":"Felipe da Silva Aires ,&nbsp;Lucilene dos Santos ,&nbsp;Renato de Moraes ,&nbsp;Armando Lucas Souza de Oliveira ,&nbsp;Mattia Gilio ,&nbsp;André Luiz Silva Pestilho ,&nbsp;Felipe Holanda dos Santos ,&nbsp;Carlos Eduardo Maciel Cruz","doi":"10.1016/j.lithos.2024.107920","DOIUrl":"10.1016/j.lithos.2024.107920","url":null,"abstract":"<div><div>Elastic geothermobarometry is a method used to estimate pressure and temperature (<em>P-T</em>) conditions based on the residual pressure exhibited by mineral inclusions entrapped in a host. In this study, we present micro-Raman spectroscopic data for quartz inclusions in host garnet from a retrograde mafic granulite and a retrograded eclogite from the Cariré Granulite Zone and Forquilha Eclogite Zone, Ceará Central Domain, northwestern Borborema Province, northeastern Brazil. Elastic modeling using the Quartz-in-Garnet geobarometer suggests residual pressure (P_inc) values between −0.14(6) and − 0.01(6) GPa for the mafic granulite, and a range of 0.06(6) to 0.54(4) GPa for the eclogite, indicating that some inclusions are under tensile stresses (i.e., negative P_inc) while other experienced compressive stresses (i.e., positive P_inc). Isomekes built using Equations of State (EoS) for almandine garnet yield an entrapment pressure (P_trap) value of 1.35(2) GPa at 910 °C for the retrograde mafic granulite, whereas retrograded eclogite isomekes indicate a P_trap value of 1.68(6) GPa at 770 °C. These findings suggest that the volumetric response of quartz inclusions to pressure and temperature changes during exhumation to Earth's surface resulted in compressive and tensile stresses, consistent with the pressure conditions for the Forquilha and Cariré zones, as determined by conventional geothermobarometry. Compressive and tensile stresses result from decompression within the stability field of alpha-quartz. Retrograded eclogite entrapment pressure (P_trap) of 1.68(6) GPa suggests metamorphism at the base of a thickened continental crust (ca. 61 km). In contrast, the retrograde mafic granulite pressure of 1.35(2) GPa indicates peak metamorphic conditions during the collisional stage at a burial depth of ca. 49 km. The observed variability in residual pressures suggests a relatively fast exhumation for this segment of the West Gondwana Orogen.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107920"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A near-surface fine-velocity structure in the western Hoh Xil Basin revealed by first-arrival travel-time tomography from a deep seismic reflection profile","authors":"Guowei Wu ,&nbsp;Zhanwu Lu ,&nbsp;Wenhui Li ,&nbsp;Guangwen Wang ,&nbsp;Yongzhi Cheng ,&nbsp;Si Chen ,&nbsp;Yuguo Cai ,&nbsp;Guan Wang ,&nbsp;Wei Cai","doi":"10.1016/j.lithos.2024.107923","DOIUrl":"10.1016/j.lithos.2024.107923","url":null,"abstract":"<div><div>The Hoh Xil Basin (HXB) is a key site for continental sedimentation from the Late Cretaceous to the Neogene on the northern-central Tibetan Plateau and provides a record of regional tectonic activity before and after the onset of the India-Asia collision in the early Paleogene. On the basis of a deep seismic reflection profile spanning the western HXB, we used the first-arrival travel-time tomography method to study the shallow upper crustal structure beneath the area in detail. Our images revealed a high-resolution 2D P-wave velocity structure at an approximate depth of 4 km. The P-wave velocity structure constrains the shallow upper crustal tectonics of the area and allows some speculation regarding its geodynamics. P-wave velocities exceeding 4.0 km/s were observed in the widely distributed Triassic flysch deposits within the western HXB. Lateral velocity perturbations are based on P-wave velocity structure calculations and can increase the lateral resolution of the profile and accurately delineate stratigraphic boundaries across different geological ages in the shallow upper crust. During the Late Cretaceous to Early Eocene (81–50 Ma), the amount of crustal shortening within the Tanggula thrust was estimated to have been greater than 50 % throughout the HXB, reflected by the complex P-wave velocity structure of the Kangtuo Formation. During the middle Eocene to Oligocene (45–28 Ma), the Hoh Xil thrust fault and Fenghuoshan thrust fault controlled the deposition of the Suonahu Formation in the west and the Yaxicuo Formation in the east, respectively, as well as the subsequent tectonic deformation. Our results indicate that the tectonic deformation and shortening of the upper crust during this period led to crustal thickening and elevation uplift. The Neogene Wudaoliang Formation in the eastern HXB and the Quaternary sedimentary layers in the western HXB show no signs of tectonic deformation. These results indicate that the uplift of the HXB after the Neogene was unlikely to be related to upper crustal tectonic deformation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107923"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161944","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":"Cretaceous thinning of the Kaapvaal craton and diamond resorption: Key insights from a highly-deformed and metasomatized ilmenite-dunite xenolith","authors":"Catharina Heckel ,&nbsp;Alan B. Woodland ,&nbsp;Sally A. Gibson","doi":"10.1016/j.lithos.2024.107901","DOIUrl":"10.1016/j.lithos.2024.107901","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Sheared peridotite xenoliths have been entrained by kimberlites in most global cratons but typically constitute only a minor proportion of mantle xenolith suites. Nevertheless, sheared peridotites are important because they record the short-lived cycles of metasomatism, deformation and rheological weakening that occur in Earth's ancient cratonic mantle immediately prior to their entrainment. Our work is focused on a highly-deformed ilmenite-dunite entrained from the south-east margin of the Kaapvaal craton by a Late Cretaceous kimberlite from Thaba Putsoa (northern Lesotho). The compositions of olivines and ilmenites show that this dunite is enriched in Fe and Ti and not simply a fragment of highly-refractory mantle. Two populations of olivine porphyroclasts are present: (i) Olivine porphyroclasts with moderate forsterite (Fo) contents (Fo&lt;sub&gt;85&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;86&lt;/sub&gt;) and minor and trace element concentrations comparable to those in many other sheared peridotites and also Cr- and Fe-poor olivine megacrysts (Fo&lt;sub&gt;83&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;88&lt;/sub&gt;) found in kimberlites from northern Lesotho and adjacent South Africa; and (ii) olivine porphyroclasts (Fo&lt;sub&gt;78&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;79&lt;/sub&gt;) with compositions that are enriched in Mn, Zn and Ge and depleted in Ni, Ca, Cr, Al, V and Cu, and overlap with Cr-poor, Fe-rich olivine megacrysts (Fo&lt;sub&gt;78&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;82&lt;/sub&gt;). Olivine neoblasts in the sheared ilmenite-dunite xenolith reveal the full range of Fo contents (Fo&lt;sub&gt;79&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;86&lt;/sub&gt;) exhibited by the porphyroclasts whereas the orthopyroxene neoblasts have Mg# of 86.5, CaO contents of ∼1 wt% CaO and variable Ti, Al and Cr contents. Ilmenite neoblasts have variable concentrations of TiO&lt;sub&gt;2&lt;/sub&gt; (45–55 wt%), MgO (9–12 wt%), and calculated Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (2–12 wt%).&lt;/div&gt;&lt;div&gt;This sheared fragment of mantle material is relatively unique in that it experienced multiple oxidizing magmatic/metasomatic events accompanied by deformation, giving important insights into a highly-dynamic environment within the Kaapvaal craton 90 Ma ago. The olivine megacrysts are thought to have crystallized in the Kaapvaal mantle from percolating proto-kimberlite melts and their chemical similarities with the porphyroclasts in the ilmenite-dunite imply that they both crystallized from a similar melt, but the two populations of porphyroclasts were subsequently mechanically mixed during deformation and contemporaneous oxidizing, Ti-rich metasomatism. Oxidation is implied by heterogeneous V/Sc ratios in olivine porphyroclasts and neoblasts and heterogeneous Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; contents in ilmenite neoblasts. We propose that multiple proto-kimberlitic pulses were widespread in northern Lesotho during the Late Cretaceous and led to the crystallization of megacrysts, metasomatism, oxidation and deformation of the surrounding mantle wall-rock. This short-lived metasomatism-deformation cycle caused mechanic","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107901"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161066","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":"Magma evolution along detachment fault-affected ridge segments: Petrology and geochemistry of MORBs from the Tianxiu segment, Carlsberg Ridge","authors":"Hang Hu ,&nbsp;Xing Yu ,&nbsp;Xiqiu Han ,&nbsp;Jiqiang Liu ,&nbsp;Yejian Wang ,&nbsp;Zhongyan Qiu ,&nbsp;Tong Zong ,&nbsp;Honglin Li ,&nbsp;Xucheng Xu ,&nbsp;Hu He","doi":"10.1016/j.lithos.2024.107917","DOIUrl":"10.1016/j.lithos.2024.107917","url":null,"abstract":"<div><div>The interaction between mid-ocean ridge magmatism and tectonic movement is well-documented. Spreading rates, for instance, influence magma generation, while magmatic processes can, in turn, shape the structural features of the ridge, such as parallel normal fault systems and symmetrical oceanic detachment faults. However, it remains unclear whether oceanic detachment faults directly impact the evolution of magma beneath the ridge. Here, we present new petrological and geochemical data of basalts from the Tianxiu segment of the Carlsberg Ridge, an asymmetrical ridge featuring detachment faults and an active hydrothermal system. All Tianxiu basalts are classified as depleted mid-ocean ridge basalts, with consistent Sr-Nd-Pb isotopic compositions indicative of a depleted peridotite-dominated mantle source. Corrected major element data indicates that the Tianxiu segment has undergone lower degrees of melting compared to adjacent symmetrical segments (62.5–63.5°E). Crystallization pressure for the Tianxiu basalts, calculated at 3.96 kbar, is similar to that found at the TAG segment (4.03 kbar), but significantly higher than that of the adjacent symmetrical ridge segments (2.28 kbar). Pressure estimates from clinopyroxene in Tianxiu samples ranged from 0.21 to 8.71 kbar, with an average of 5 kbar, suggesting that crystallization primarily occurs within the lithospheric mantle. These results point to a magma system characterized by a narrow melting interval, with lower degrees of melting and higher crystallization pressures. We conclude that the detachment fault and associated hydrothermal system at the Tianxiu segment alter the thermal structure of the shallow lithosphere, thereby affecting the magma generation process. This study enhances our understanding of the relationship between oceanic detachment faults and mid-ocean ridge magmatism.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107917"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161071","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":"Mineral chemistry-perspective of the Kadavur gabbro-anorthosite Complex, Southern Granulite Terrane of the Indian shield: Implications to its petrogenesis in a ridge-subduction setting","authors":"Debaleena Sarkar ,&nbsp;Jyotisankar Ray ,&nbsp;Rohit Pandey ,&nbsp;Moumita Chowdhury ,&nbsp;Christian Koeberl ,&nbsp;Suresh C. Patel ,&nbsp;Desikan Ramakrishnan ,&nbsp;Aantarica Chakraborty ,&nbsp;Simran Dutta","doi":"10.1016/j.lithos.2024.107880","DOIUrl":"10.1016/j.lithos.2024.107880","url":null,"abstract":"<div><div>Mineral chemistry data of constituent silicate and oxide phases are often regarded as a useful tool for assessing the petrogenesis of mafic rocks. In view of this, the chemistry of minerals from the Kadavur gabbro-anorthosite Complex (10°35′N: 78°11′E), a magmatic intrusion in the Southern Granulite Terrane of the Indian shield, has been evaluated using several thermo-barometric methods and tectonic discrimination diagrams. The Complex represents a magmatic intrusion that consists of a highly deformed schistose gabbro-anorthosite type and an undeformed layered gabbro-anorthosite type, with local patches of pegmatoidal gabbro-anorthosite bodies. The constituent minerals in the Complex include clinopyroxene, orthopyroxene, plagioclase, amphibole, and subordinate amounts of ilmenite and magnetite. Pyroxene thermometry (clinopyroxene thermometry, orthopyroxene thermometry and two pyroxene thermometry) gives mean temperatures of ∼1060 °C for the layered gabbro- anorthosite bodies, and ∼ 1124 °C for the pegmatoidal bodies; and ∼ 1130 °C for the schistose gabbro-anorthosite. Hornblende-plagioclase and amphibole thermometry give temperatures of ∼1000–1190 °C. The co-existing oxide (magnetite-ilmenite) thermometry gives a lower temperature of ∼420 °C. The mean clinopyroxene pressure value is 17 kbar for the schistose gabbro-anorthosite, 9 kbar for the layered gabbro-anorthosite, and 11 kbar for the pegmatoid bodies. During the earlier phase of deformation associated with magmatic crystallization (responsible for schistose type), the ambient temperature and pressure of crystallization of the Complex were 955 to 1285°C at ∼17 kbar. The magma equilibrated at shallow to intermediate levels allowing for localized input of H₂O. Consideration of whole-rock geochemical data (especially immobile trace elements) indicates that parent magma was of tholeiitic and alkaline composition and later underwent fractionation. The rare earth element (REE) distribution in the schistose gabbro-anorthosite is broadly similar to that of N-MORB, while the geochemical characteristics of the layered gabbro-anorthosite resemble island arc basalt (IAB). The pegmatoidal gabbro-anorthosite bodies have a transitional affinity between both the N-MORB and IAB. The mineral chemistry and whole-rock geochemistry data suggest that the schistose gabbro-anorthosite mostly corresponds to “non orogenic” and “MORB-type” while layered gabbro-anorthosite and pegmatoid bodies correspond to an ‘orogenic’ and ‘island-arc’ setting, suggesting a clear shift from a MORB setting to an arc-setting suggesting a ridge-subduction event. The Kadavur gabbro-anorthosite Complex is analogous to other well-known Archaean gabbro-anorthosite Complexes around the world.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107880"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161622","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":"Correlating early Wuchiapingian (early Lopingian/late Permian) biotic and environmental changes with eruptive activity of the Emeishan LIP","authors":"Borhan Bagherpour ,&nbsp;Luis F. De Lena ,&nbsp;Maria Ovtcharova ,&nbsp;Dong-xun Yuan ,&nbsp;Shu-Zhong Shen ,&nbsp;Hugo Bucher ,&nbsp;Urs Schaltegger","doi":"10.1016/j.lithos.2024.107937","DOIUrl":"10.1016/j.lithos.2024.107937","url":null,"abstract":"<div><div>The volcanic activity of the Emeishan Large Igneous Province (LIP) is widely regarded as the main cause of environmental changes and the consequent biodiversity loss around the Guadalupian-Lopingian boundary (GLB). The limited number of high-precision numerical ages, as well as the scarcity of volcanic ash layers interbedded within sedimentary profiles with bio- and chemostratigraphic controls, has hampered the establishment of a temporal correlation between the Emeishan LIP and environmental and biotic changes. Here, we present new high-precision CA-ID-TIMS U<img>Pb ages and Hf isotope data from ash layers of the paleontologically dated early Wuchiapingian Mapojiao section in southern Guizhou (south China). Our data indicate that the Emeishan volcanic activity continued at least until 258.279 ± 0.065 Ma in the <em>Clarkina transcaucasica</em> conodont zone of the Wuchiapingian Stage. Based on our high-resolution Bayesian age-depth Bchron model, the calculated duration of Wuchiapingian conodont interval zones in this section are the <em>C. transcaucasica</em> Zone: 740 ± 150 kyr, <em>C. guangyuanensis</em> Zone: 195 ± 184 kyr, <em>C. leveni</em> Zone: 221 ± 162 kyr, <em>C. asymmetrica</em> Zone: 285 ± 228 kyr. Moreover, the sedimentation rate of shallow-marine bioclastic thick-bedded limestones and deep-marine radiolarian and sponge spicule-bearing thin-bedded black limestones is estimated at 10 cm/kyr and 3.84 cm/kyr, respectively. Although the GLB is not included in the studied section, our age-depth model implies that the age of the GLB is noticeably older than any currently considered GLB age. The co-occurrence of a base-level fall and drowning event, temperature rise, mantle-sourced volcanism, negative shifts in carbon and strontium isotope records, and thermal fluid activity provide a strong base to suggest two distinct phases of Emeishan volcanic activities in the mid-Capitanian and early Wuchiapingian, respectively.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107937"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161967","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":"Petrogenesis of Neoproterozoic high-K calc-alkaline granites forming large batholiths in SE Brazil: Clues from trace-element chemistry of apatite, titanite and hornblende","authors":"Valdecir de Assis Janasi,&nbsp;Lucelene Martins,&nbsp;Bárbara Bueno Toledo,&nbsp;Adriana Alves,&nbsp;Silvio Roberto Farias Vlach","doi":"10.1016/j.lithos.2024.107927","DOIUrl":"10.1016/j.lithos.2024.107927","url":null,"abstract":"<div><div>Granites may lose or gain residual melts respectively by compaction and reactive porous flow, and therefore their composition is potentially different from that of the original magmas. Consequently, the chemistry of individual minerals with well-understood textural relationships should be prioritized for inferring magma sources and crystallization conditions. We investigated the major and trace element chemistry of coexisting apatite, titanite and hornblende in thin sections of I-type high-K calc-alkaline (HKCA) granitic rocks forming two voluminous Neoproterozoic batholiths in SE Brazil. Detailed textural studies, major-element analyses by EPMA, and trace-element analyses by LA-ICPMS bring key information on magma genesis and evolution. Titanite is absent or forms thin rims in ferri-ilmenite in granites from Socorro Batholith, resulting from magmatic crystallization at higher temperatures (&gt;800 °C) compared to similar granites from the Agudos Grandes Batholith, where it occurs as large crystals preserving temperature-related zonation, reflected in decreasing LREE and Zr contents. The influence of titanite crystallization is particularly evident in the trace-element chemistry of hornblende and apatite from the Agudos Grandes granites, with one order of magnitude lower REE contents and smaller to suppressed negative Eu anomalies. Systematically higher Sr/Y (and in part also La/Yb) of hornblende, apatite and titanite from Agudos Grandes granites confirms suggestions that they equilibrated at significantly greater depths (and by inference in a thicker crust) as compared to the Socorro granites. Quantitative estimates of Sr/Y in the original melts are hampered by coprecipitation of minerals that accommodate these elements and by potential Sr diffusion, especially in apatite. However, as an early-crystallizing phase in granitic magmas, apatite trace-element composition is a precious source of petrogenetic information; in our study, it reveals that most of the volume of the Agudos Grandes granites crystallized below 800 °C (i.e., after titanite starts to crystallize) and confirms, in agreement with other proxies, that the two batholiths crystallized under oxidizing conditions (e.g., sulfur in apatite up to 800 ppm).</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107927"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162155","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}