Lithos最新文献

{"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}

{"title":"Multi-stage evolution of the lithospheric mantle beneath the Hessian Depression (Germany): Peridotite xenoliths from Stöpfling","authors":"Jacek Puziewicz ,&nbsp;Sonja Aulbach ,&nbsp;Mary-Alix Kaczmarek ,&nbsp;Theodoros Ntaflos ,&nbsp;Magdalena Matusiak-Małek ,&nbsp;Małgorzata Ziobro-Mikrut ,&nbsp;Axel Gerdes","doi":"10.1016/j.lithos.2024.107908","DOIUrl":"10.1016/j.lithos.2024.107908","url":null,"abstract":"<div><div>The Hessian Depression in Germany is the northern continuation of the Upper Rhine Graben, from which it is separated by the Vogelsberg volcanic region. Abundant Cenozoic basaltic eruptions locally brought mantle xenoliths to the surface. The legacy suite of 15 ultramafic xenoliths from the Stöpfling quarry has been studied in detail to decipher nature and evolution of this fragment of European mantle lithosphere.</div><div>The xenolith suite comprises harzburgites, clinopyroxene-poor lherzolites and clinopyroxene-rich lherzolites. One of the xenoliths is a harzburgite hosting a centimetric olivine websterite layer. Olivine contains 90.1–91.5 % forsterite, 0.39–0.43 wt%. NiO, 120–500 μg/g Ca. Orthopyroxene (0.10–0.18 atoms of Al per formula unit, pfu), has Mg/(Mg + Fe), Mg#, of 0.90–0.92, similar to that of olivine. Clinopyroxene (0.12–0.25 atoms Al pfu; Mg# 0.90–0.95). Rare Earth Elements (REE) and trace-element patterns are highly variable, but all are enriched in light REE relative to medium/heavy REE. Spinel Cr/(Cr + Al) varies from 17 to 46. The ⁸⁷Sr/⁸⁶Sr ratios measured in situ in clinopyroxene vary from 0.703969(± 37 1σ) to 0.708615(± 149 1σ) and are in part heterogenous at the scale of individual samples and grains.</div><div>The peridotites typically have well defined olivine-orthopyroxene or olivine-only crystal preferred orientation, whereas clinopyroxene (or clinopyroxene and orthopyroxene) is oriented independently in most of the rocks. This is taken to reflect secondary clinopyroxene addition to an originally refractory harzburgite protolith. The latter is still preserved in two harzburgites with highly depleted compositions and low clinopyroxene modal abundances. Melt depletion recorded in the most depleted harzburgites was followed by carbonatitic metasomatism, whereas other harzburgites and clinopyroxene-poor lherzolites were metasomatized by carbonated silicate or alkaline silicate melts. The clinopyroxene-rich lherzolites preserved relics of MORB-like refertilization, overprinted by alkaline metasomatism analogous to that affecting the rest of the rocks.</div><div>The two-pyroxene equilibration temperatures (940–1050 °C) mostly show excellent agreement between Fe<img>Mg and REE-based thermometers. This suggests chemical and thermal equilibration after clinopyroxene addition and shows that Stöpfling xenoliths sample a rather narrow ∼8 km depth interval of the mantle lithosphere. The Stöpfling mantle profile probably records two-stage tectono-metasomatic evolution, comprising (1) mantle lithosphere upwelling and melting during flattening of the Variscan orogen root due to late orogenic collapse followed by thermal re-equilibration, and (2) further local lithosphere thinning during Alpine rifting, accompanied by multiple local chromatographic-style metasomatic episodes that culminated in volcanism as well as xenolith entrainment and transport to the surface.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107908"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161959","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":"Revisiting the high temperature Darongshan-Shiwandashan granitoids in the South China: A response to slab tearing associated with diachronous collision between Indochina and South China blocks","authors":"Yu-Fan Yue ,&nbsp;Xiao-Ping Xia ,&nbsp;Pengfei Li ,&nbsp;Bin He ,&nbsp;Touping Peng ,&nbsp;Min Sun ,&nbsp;Jian Xu ,&nbsp;M.P. Manu Prasanth","doi":"10.1016/j.lithos.2024.107898","DOIUrl":"10.1016/j.lithos.2024.107898","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Darongshan-Shiwandashan granite belt (DSGB) is composed of S-type granites and granodiorite intrusions, which are characterized by high- or ultrahigh-temperature cordierite, orthopyroxene, and granulite xenoliths. The petrogenesis of these plutons is a subject of debate, and a thorough overview of regional tectonic evolution and geochemistry is still absent despite the numerous research conducted in this granite belt. This study is a comprehensive overview of geochronology, whole-rock major-trace elements, Sr&lt;img&gt;Nd isotopes, and zircon Hf&lt;img&gt;O isotopes in the DSGB, focusing on their petrogenesis and tectonic setting of formation. The geochronological data indicates that DSGB granitoids emplaced at ca. 250 Ma, with a southwestward-younging trend. Moreover, mineral assemblages of cordierite + orthopyroxene suggest that the DSGB was formed in a high-temperature (∼850 °C) and low-pressure (3.7–6 kbar) tectonic setting. Three main plutons (Darongshan, Jiuzhou, and Taima) of the DSGB exhibit distinctly different compositions. The Darongshan and Taima granitoids display high silica (SiO&lt;sub&gt;2&lt;/sub&gt; = 68.65–78.10 wt%), low-maficity (FeO + MgO = 1.97–7.28 wt%), along with negative whole-rock ε&lt;sub&gt;Nd&lt;/sub&gt;(t) values (−13.9 to −9.7) and elevated initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr values (0.71638 to 0.73165). The Jiuzhou granitoids, on the other hand, exhibit relatively low silica (SiO&lt;sub&gt;2&lt;/sub&gt; = 63.90–72.72 wt%) and high maficity (FeO + MgO = 3.03–9.88 wt%), with largely overlapping but relatively high ε&lt;sub&gt;Nd&lt;/sub&gt;(t) values ranging from −12.9 to −9.9 and lower initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr values from 0.71453 to 0.72401. Two-component mixing model results indicate these different compositions represent varying degrees of mixing between crust- and mantle-derived magmas, with 0–10 %, 0–20 % and 20–40 % basaltic melts involved for Taima, Darongshan and Jiuzhou plutons, respectively. The subducting slab tearing, induced by the diachronous collision between the South China Block (SCB) and Indochina Block (ICB), provide the most feasible interpretation for the petrogenesis and spatio-temporal geochemical pattern of the granitic rocks in the DSGB. The onset of the diachronous collision initiated at the Hainan-Yunkai massif, southwest of SCB, while the Tethys Ocean still existed in the northwest (Nanpanjiang area), causing notable disparities in the convergence velocities of the subducting ocean slab. The heterogeneous stresses resulting from the different subduction rates were accommodated by bending and tearing of the subducting slab. Then, ultrahigh-temperature basaltic melts derived from the decompression melting of the lithospheric mantle facilitated the melting of metasedimentary rocks, which resulted in the formation of high-temperature S-type granitoids. The Jiuzhou pluton, located at the center of slab tearing, received more mantle contributions than the Darongshan and the Taima plutons, which are emplaced away from th","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107898"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161055","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 ca. 470 Ma continental margin arc volcanism in the Cathaysia Block interior: Constrains on the geodynamic process of the early Paleozoic orogeny in South China","authors":"Longming Li ,&nbsp;Fan Xiao ,&nbsp;Xilin Zhao ,&nbsp;Guangfu Xing ,&nbsp;Yan Zhou","doi":"10.1016/j.lithos.2024.107928","DOIUrl":"10.1016/j.lithos.2024.107928","url":null,"abstract":"<div><div>Due to the lack of evidence related to oceanic subduction, it has been debated whether the early Paleozoic orogeny in South China Block belongs to an intracontinental orogeny or a subduction-collision orogeny. To better understand the nature and geodynamic processes of this orogeny, we conducted geochronological, geochemical, and isotopic studies on pyroclastic rocks, including crystal tuffs and sedimentary volcanic breccias, which outcrop in the Zhenghe area of the Cathaysia Block. The crystal tuffs have experienced strong chloritization and have high FeO^t (25–31.3 wt%) and high Cr (60.7–143 ppm) and Ni (33.8–93.6 ppm) contents. Immobile elements indicate that the crystal tuffs are products of basic-intermediate volcanism. SIMS and LA-ICP-MS U<img>Pb dating show that the crystal tuffs were erupted during 471–465 Ma. The crystal tuffs exhibit positive zircon <em>ε</em>_Hf(t) (+7.8 to +14.2) and low δ¹⁸O values (5.05 to 5.89 ‰), suggesting that they were derived from depleted mantle. They exhibit subduction-related geochemical signatures, with enrichment in Th but depletion in Nb and Ta. Additionally, high U/Yb and low Nb/Yb values of the zircons suggest that the crystal tuffs were generated in a continental arc environment. The interlayered sedimentary volcanic breccias are products of intermediate-acidic volcanism. They share similar geochemical characteristics with the crystal tuffs, including zircon U<img>Pb ages (<em>ca.</em> 467 Ma), whole-rock trace element patterns, zircon CL images, zircon <em>ε</em>_Hf(t) values (+ 9.9 to +13.3) and zircon trace element ratios, implying that the two types of volcanic rocks originated from similar sources or were genetically related. Notably, the presence of few continental clastic materials in these pyroclastic rocks provides evidence that the volcanic arc was situated offshore from the continent. The identification of the <em>ca.</em> 470 Ma continental margin arc volcanism in the Zhenghe-Dapu fault, along with the previously discovered <em>ca.</em> 520 Ma MOR-type ophiolite in the same fault, and the widespread presence of late-Ordovician to early-Devonian igneous activities and Silurian high-grade metamorphism in the Cathaysia Block, supports that the early Paleozoic orogeny in South China was a subduction-collision orogeny, with the Zhenghe-Dapu fault serving as a suture zone. Consequently, it is believed that this orogeny resulted from the collision between the West Cathaysia Block and either the East Cathaysia Block or the northern margin of Gondwana. The geodynamic process involved the initiation of oceanic plate subduction during the middle Ordovician, transitioning to continent-continent collision by the middle Silurian, and concluding with post-orogenic collapse from the late Silurian to early Devonian.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107928"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161966","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}