Lithos最新文献

{"title":"Mesozoic highly oxidized and hydrous adakitic magmatism controlling porphyry Cu mineralization in NE China: Evidence from the Baoquan deposit","authors":"Yan Cao ,&nbsp;Qihai Shu ,&nbsp;Kai Xing ,&nbsp;Jinyu Liu ,&nbsp;Xudong Niu ,&nbsp;Lijun Liu ,&nbsp;Zhonghai Zhao ,&nbsp;Yubao Yang ,&nbsp;Zhaolong Liu","doi":"10.1016/j.lithos.2025.108164","DOIUrl":"10.1016/j.lithos.2025.108164","url":null,"abstract":"<div><div>In northeastern China, Mesozoic porphyry Mo-dominated deposits are abundant but porphyry Cu deposits are rare. Investigating the mechanisms controlling the formation of the limited number of the porphyry Cu deposits is critical in understanding the regional Cu metallogeny. Here, we present geochronological and geochemical data for the Cu-mineralized and barren intrusions in the newly discovered Baoquan porphyry deposit in the northern Great Xing'an Range. Zircon U-Pb dating indicates that the mineralized quartz diorite porphyry and barren syenogranite were emplaced at ∼115 Ma and ∼312 Ma, respectively. The quartz diorite porphyry (SiO₂ = 62.7–63.9 wt%) has high alkaline contents (Na₂O + K₂O = 6.82–8.28 wt%), is enriched in LILEs (K, Rb, Ba, and Sr) and depleted in HFSEs (Th, Nb, Ta, Zr and Ti), and exhibits low initial ⁸⁷Sr/⁸⁶Sr ratios (0.7049–0.7067) and positive ε_Nd(t) values (+1.9 to +2.0), as well as positive zircon ε_Hf(t) values (+4.9 to +13.6), indicating that the parental magma was predominantly derived from the mantle, likely metasomatized by fluids derived from the subducted Paleo-Pacific slab. In contrast, the barren syenogranite (SiO₂ = 76.4–78.0 wt%) is depleted in Sr (40.6–82.4 ppm) and Ba (348–498 ppm), with high Zr + Y + Ce + Nb values (206–277 ppm), showing A-type granite affinities. The Baoquan ore-related porphyry is oxidized (ΔFMQ = +1.2 in average) as calculated using magmatic oxybarometer using trace elements in zircon, in contrast with that of the barren syenogranite with lower magmatic ΔFMQ values (+0.6 in average). The porphyry also has low Zr contents (average 151 ppm) and Sr/Zr ratios (average 7.96), consistent well with other Cu-fertile magmas. Additionally, it also displays adakitic signatures with relatively high Sr/Y ratios (78–130), low Dy/Yb ratios (1.86–2.03) and negligible Eu anomalies (Eu/Eu* = 0.79–0.96). These findings suggest that zircon and hornblende fractionation, rather than plagioclase separation, has dominated magma crystallization, further indicating a high magmatic water content. Together with previously published data for the other Cu-mineralized intrusions in NE China, it is proposed that the magmas with high oxygen fugacities and H₂O contents that have experienced high-pressure fractionation are favorable for Cu mineralization. Notably, the intrusions with such characteristics are mainly distributed in the northern Great Xing'an Range characterized by thickened Mesozoic crust, where should be prioritized for future Cu exploration.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108164"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144534804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of aquamarine-bearing granitic pegmatite: The case of Haramosh pegmatite field (northern Pakistan)","authors":"Shah Ismail ,&nbsp;Lian-Xun Wang ,&nbsp;Chang-Qian Ma ,&nbsp;Le-Guang Li ,&nbsp;Khan Hawas ,&nbsp;Yu-Xiang Zhu ,&nbsp;Alam Masroor","doi":"10.1016/j.lithos.2025.108162","DOIUrl":"10.1016/j.lithos.2025.108162","url":null,"abstract":"<div><div>The Haramosh pegmatite field in northern Pakistan is renowned for numerous granitic pegmatites, containing economically significant quantities of aquamarine, tourmaline, and topaz. This study investigates the petrogenesis of aquamarine-bearing pegmatite and its genetic relationship with the country rock (Iskere gneiss) and an adjacent intrusion (Jutial leucogranite). The studied pegmatite is composed predominantly of feldspar, quartz, muscovite and tourmaline, resembles the S-type Jutial leucogranite and shows internal zonation with gem-quality aquamarine and topaz forming in the miarolitic cavities. Zircon U<img>Pb dating yields ages of 4.3 ± 0.9 Ma for the pegmatite and 10.3 ± 0.2 Ma for the leucogranite, distinct apparently from the Iskere gneiss (1881 ± 27 Ma). Lu<img>Hf isotopic data suggest a common crustal source for the studied pegmatite and leucogranite, with εHf(t) values ranging from −35.9 to −19.7 (mean = −26.5) and − 29.5 to −24.4 (mean = −26.0), respectively. These results significantly deviated from those observed in the Iskere gneiss (−16.0 to +6.5, mean = −6.0), thereby precluding the possibility of a partial melting model of the country rock. The pegmatite, classified as LCT-type, shows high SiO₂ (71.53–77.17 wt%), Al₂O₃ (13.50–15.82 wt%), Li (14.62–224 ppm), Ta (0.01–4.51 ppm) concentrations and ASI values (1.34–2.37), with higher differentiation-index values (DI = 92–97) and lower K/Rb ratios than the leucogranite. Compositional variations of tourmaline, plagioclase and muscovite also indicate a higher degree of magma evolution in the pegmatite compared to the leucogranite. The plagioclase in the pegmatite displays a decrease in CaO content from the border to core zones, while whole rock Be concentrations exhibit an increase along this gradient, indicating a progressive enrichment of Be during magma evolution within the pegmatite dyke. Based on all results, we propose that the Haramosh aquamarine-bearing pegmatite was likely generated by magmatic fractional crystallization from a leucogranitic parent magma. The formation of aquamarine gems can be attributed to a progressive enrichment of Be during magma evolution process within the pegmatite dykes. The observed widespread occurrence of miarolitic cavities associated with aquamarine gems, coupled with the observed decrease of fluorine content in tourmaline from the pegmatite border to core zones, indicates the involvement of a magmatic volatile phase (MVP) exsolution process during the final stage of magma cooling. This process reduces the solubility of Be in the melt, thereby promoting the crystallization of aquamarine.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108162"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518017","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":"Xonotlite and pectolite in rodingites from the Samail ophiolite: Markers of reducing conditions and element transfer during peridotite-gabbro interaction","authors":"Alireza Eslami ,&nbsp;Benjamin Malvoisin ,&nbsp;Mayuko Fukuyama ,&nbsp;Marguerite Godard ,&nbsp;Yuji Ichiyama ,&nbsp;László Előd Aradi ,&nbsp;Katsuyoshi Michibayashi ,&nbsp;Zaicong Wang ,&nbsp;Ming Li ,&nbsp;Alessandro Cavallo ,&nbsp;The Oman Drilling Project Science Team","doi":"10.1016/j.lithos.2025.108160","DOIUrl":"10.1016/j.lithos.2025.108160","url":null,"abstract":"<div><div>The Oman Drilling Project cored Holes BA1B, BA3A and BA4A into serpentinized peridotites in Wadi Lawayni of the Samail ophiolite, Oman. These mantle peridotites are crosscut by numerous gabbro, olivine gabbro and clinopyroxenite dikes that are altered to calc-silicate assemblages (hydrogarnet, diopside, xonotlite, vesuvianite and pectolite), chlorite, and phlogopite. These mineralogical assemblages are typical of rodingites. Xonotlite [Ca₆Si₆O₁₇(OH)₂] and pectolite [NaCa₂Si₃O₈(OH)] forming as fibrous or acicular/radial crystals in milk-white vein-like are common in these holes. In contrast, only a few occurrences of these minerals have been reported worldwide. Bulk rock analyses indicate two types of altered dikes: chlorite-bearing dikes displaying enrichments in Mg, Fe, Mn, Ti, Cr, Ni and volatiles as well as loss of Na compared to lower crustal gabbros; and rodingitized dikes with enrichments in Ca and Na during alteration. Mass gains in chlorite-bearing dikes are consistent with intense mass transfer from peridotite to gabbroic dikes. These results are consistent with thermodynamic modelling showing a strong control of the peridotite-gabbro ratio on the mineralogy of the altered gabbro: wollastonite, pectolite, and vesuvianite present here are predicted to form in peridotite-dominated systems, whereas prehnite, epidote and pumpellyite not reported in the studied boreholes are predicted to form in gabbro-dominated systems. Fluid inclusions containing H₂ and CH₄ are observed in both primary orthopyroxene and pectolite. They indicate the presence of a carbon-rich reduced fluid during rodingitization. The xonotlite stability field calculated with thermodynamic modelling is indeed limited by carbonate formation as oxygen fugacity increases. The rodingites from Oman display numerous markers of strong fluid/rock interactions, including enrichment in mobile elements such as Na, K and Li, typically associated with seawater interaction and hydrothermal fluid transport. The presence of xonotlite, pectolite and phlogopite is consistent with the addition of external elements during rodingitization since the extent of the calculated stability fields of these minerals increases when adding Ca, Na and K to the system. High δ^44/40Ca values in chlorite-bearing dikes (1.65 ± 0.09 ‰ to 1.91 ± 0.09 ‰), rodingitized dikes (0.28 ± 0.09 ‰ to 1.25 ± 0.02 ‰) and serpentinized harzburgites (1.04 ± 0.05 ‰ to 1.64 ± 0.06 ‰) reveals mineral-fluid fractionation of Ca isotopes and/or interaction of seawater with gabbro-peridotite samples.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108160"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144513681","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":"Multistage petrogenesis and suprasubduction metasomatism of orthopyroxenites in the Ab-Bid ultramafic complex (Iran): Insights from open-system mantle melting","authors":"Mahdieh Mohammadi ,&nbsp;Hamid Ahmadipour ,&nbsp;Abbas Moradian ,&nbsp;Daniele Brunelli ,&nbsp;Reza Derakhshani","doi":"10.1016/j.lithos.2025.108163","DOIUrl":"10.1016/j.lithos.2025.108163","url":null,"abstract":"<div><div>The Ab-Bid ultramafic complex, located within the Esfandagheh–Hadji Abad ophiolite mélange in southern Iran, hosts numerous orthopyroxenite intrusions emplaced as dykes and irregular bodies within mantle peridotites. These orthopyroxenites exhibit sharp contacts with the host rocks and display cumulate textures characterized by early-crystallizing orthopyroxene and spinel, followed by intercumulus olivine and clinopyroxene. While the Ab-Bid ultramafics show textural and compositional similarities to abyssal mantle residues, they also record subtle geochemical signatures consistent with limited slab-derived metasomatism. This study presents the first detailed petrographic and geochemical dataset from orthopyroxenites in the Ab-Bid massif, including field observations, mineral chemistry, whole-rock and in-situ trace element analyses. Petrogenetic modeling of clinopyroxene trace element distributions in lherzolite, harzburgite, and orthopyroxenite supports a multistage evolutionary scenario involving open-system melting of a depleted oceanic mantle source variably modified by suprasubduction fluids. The resulting high-Mg tholeiitic melts triggered localized remelting, melt-peridotite interaction, and sequential lithological transformation across the complex. Our results indicate a genetic link among the lithological units and demonstrate that localized metasomatic processes—without the need for boninitic melt involvement—can produce high-Mg tholeiitic magmas in suprasubduction settings. These findings provide new constraints on mantle heterogeneity, melt evolution, and the complex dynamics of subduction-modified ultramafic systems within the Tethyan ophiolite belt.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108163"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502225","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":"Geochronology and geochemistry of Cenozoic magmatism in the north-western Ecuadorian Andes: the role of crustal thickness","authors":"J. Iglesias ,&nbsp;C. Witt ,&nbsp;O. Poma ,&nbsp;O. Bruguier ,&nbsp;D. Bosch ,&nbsp;V. Bosse ,&nbsp;M. Zattin ,&nbsp;M. Seyler ,&nbsp;M.J. Hernández ,&nbsp;F. Chanier ,&nbsp;O. Averbuch","doi":"10.1016/j.lithos.2025.108159","DOIUrl":"10.1016/j.lithos.2025.108159","url":null,"abstract":"<div><div>The Ecuadorian Cenozoic arc developed over autochthonous continental and accreted oceanic terrains. We reconstruct the tectono-magmatic evolution of the northernmost part of this arc using a comprehensive, multi-proxy approach that incorporates whole-rock chemistry and zircon petrochronology, including U-Pb geochronology, trace element geochemistry, and Hf-O isotopic analysis. Our results reveal two distinct magmatic periods at 41–16 Ma and 14–7 Ma. The older period is characterized by tonalitic rocks that exhibit trace element ratios, δ¹⁸O values (6.4–3 ‰), and εHf values (+17 − +12) in zircons that are indicative of highly juvenile sources, while the younger period comprises granodioritic rocks derived from a more enriched reservoir (δ¹⁸O: 8.2–5.8 ‰ and εHf: +13 − +7). The older magmas formed within the amphibole stability field in a moderately thick crust (∼ 35 km), while the younger magmas were generated within the garnet stability field in thickened crust (∼60 km). The transition from intermediate crustal thickness and juvenile settings to a thicker crust and more enriched settings occurred at around 14 Ma. This shift was most likely related to the arrival of the young (and buoyant) Nazca plate at the South American margin, which would have resulted in the shallowing of the subduction angle, increased compressional stresses, and facilitated melting of an evolved oceanic crust. This study highlights the utility of zircon petrochronology in unraveling the crustal-scale evolution of Cordilleran arcs, providing valuable insights into the dynamic processes that control continental growth and orogeny.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108159"},"PeriodicalIF":2.9,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144614875","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":"Late Triassic ultrahigh-temperature mafic granulite from the North Dabie terrane, Central China","authors":"Heng-Cong Lei ,&nbsp;Hai-Jin Xu ,&nbsp;Hui Zhang ,&nbsp;Fei Xia ,&nbsp;Cong-Jun Yu ,&nbsp;Wang-Chao Li ,&nbsp;Liang-Peng Deng ,&nbsp;Ling Wang ,&nbsp;Jian-Bing Duan","doi":"10.1016/j.lithos.2025.108165","DOIUrl":"10.1016/j.lithos.2025.108165","url":null,"abstract":"<div><div>Ultrahigh-temperature (UHT) granulites, essential components of collisional orogens, preserve key records of orogenic geodynamics. This investigation provides a systematic examination of mafic granulites from the Dabie orogenic belt through integrated petrological and geochronological analyses. Petrographic observations and phase equilibria modeling reveal clockwise pressure-temperature (<em>P–T</em>) paths, involving an inferred middle-pressure (MP) high amphibolite–granulite-facies (M₁; 10.7–11.7 kbar and 745–810 °C) followed by decompressional heating, UHT granulite-facies metamorphism (M₂; 6.5–6.8 kbar and 938–950 °C) and subsequent cooling, amphibolite-facies stage (M₃; 3.6–4.5 kbar and 636–660 °C). In-situ zircon dating show that the granulite has a protolith age of ∼1805 Ma and underwent HP and UHT metamorphism during the Late Triassic (∼215–197 Ma; M₁–M₂), followed by amphibolite-facies retrograde metamorphism from 193 to 172 Ma (M₃). Meanwhile, zircons within the granulites document anatexis at ∼120 Ma, corresponding to orogenic collapse of the Dabie orogenic belt. We propose a metamorphic process of the mafic granulite as follows: the ∼1.8 Ga mafic rock was buried to the MP amphibolite-granulite-facies level during the Triassic continental collision orogenesis, and was heated by the upwelling asthenosphere during exhumation, leading to UHT metamorphism; and subsequently, it was chilled and retrograded to amphibolite-facies level. This study establishes critical constraints on <em>syn</em>-collisional thermal-tectonic coupling in continental collision zones, with deep thermal processes recorded by mafic granulites enhancing our understanding of the spatiotemporal evolution of orogenic events in both ancient and active mountain belts globally.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108165"},"PeriodicalIF":2.9,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The source of mafic post-collisional magmatism in the Southern Variscan domain: Insights from the Permian dyke swarms of northern Sardinia","authors":"Matteo Velicogna ,&nbsp;Andrea Boscaini ,&nbsp;Abimbola Chris Ogunyele ,&nbsp;Angelo De Min ,&nbsp;Massimo Chiaradia ,&nbsp;Mattia Bonazzi ,&nbsp;Alberto Zanetti ,&nbsp;Andrea Marzoli","doi":"10.1016/j.lithos.2025.108158","DOIUrl":"10.1016/j.lithos.2025.108158","url":null,"abstract":"<div><div>Early Permian post-collisional magmatism is widely spread in southern Europe and it is represented by both felsic and mafic occurrences. One of the best places to observe such magmatism is northern Sardinia, where felsic Late Carboniferous-Early Permian batholiths are intruded by a large number of mafic dyke swarms. This study focuses on several dykes of mafic and intermediate composition from the Gallura region (northern Sardinia, Italy) that were emplaced during the extensional event(s) related to the collapse of the Variscan orogen. Based on textural, chemical and isotopic data the dykes are divided into three groups. Group 1 and Group 3 generally show calc-alkaline affinity, moderate to high enrichment in LREE over HREE, respectively, strong enrichments in LILE, Nb and Ta negative anomalies. Group 1 samples show more radiogenic Nd and less radiogenic Sr isotopic values compared to Group 3, while the two groups show similar Pb isotopic values. Group 2 shows depleted LREE and depleted Sr<img>Nd isotopic composition, relatively close to those of MORBs. Nonetheless, the negative Nb anomaly and Pb isotopic composition clearly distinct from those of MORBs highlight the subduction signature also in dykes from this group.</div><div>Our modelling suggest that the distinctive geochemical features of the three groups are not related to closed-system fractional crystallization or to crustal assimilation, but they are the result of melting of a heterogeneous mantle source. Group 1 and 2 could have formed by melting of a peridotite at the transition of the spinel and garnet stability, with Group 1 possibly requiring a more enriched mantle composition and generally lower melting temperature. By contrast, a peridotite-pyroxenite mixture or an amphibole peridotite is the most likely source of Group 3 dykes.</div><div>The widespread coeval Early Permian mafic dykes and intrusive bodies from Southern Europe show geochemical features that are quite similar to those of northern Sardinia dykes. The comparison shows that the most common magma-types are similar to Group 1 and subordinately to Group 3 from Sardinia, suggesting that most of the mafic Early Permian post Variscan magmatism was formed by melting a mantle that was enriched during the Variscan orogeny. On the contrary, Group 2-like magmatism is very scarce in southern Europe and its more depleted compositions are probably the result of decompression melting of asthenospheric mantle with a subtle subduction signature.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108158"},"PeriodicalIF":2.9,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522067","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":"Miocene N-MORB- and OIB-type diabase dikes in the western Yarlung Tsangpo suture zone, southern Tibet: Insights into the Indian slab tearing and asthenosphere–lithosphere interaction","authors":"Jianbo Cheng ,&nbsp;Yalin Li ,&nbsp;Xianshu Dong ,&nbsp;Siqi Xiao ,&nbsp;Shuai Li ,&nbsp;Wenjun Bi ,&nbsp;Rui Zhou","doi":"10.1016/j.lithos.2025.108154","DOIUrl":"10.1016/j.lithos.2025.108154","url":null,"abstract":"<div><div>Post-collisional magmatic rocks are widely distributed in southern Tibet, and their petrogenesis can provide critical information about lithospheric-scale thermal and compositional structures. However, the deep geodynamic processes responsible for post-collisional magmatism remain ambiguous. Here, Miocene (ca. 16 Ma) diabase dikes are identified in the Dare area within the western Yarlung-Tsangpo Suture Zone (YTSZ). The Dare diabase rocks can be divided into subalkaline and alkaline series. The subalkaline diabase rocks exhibit normal mid-ocean ridge basalt (MORB)-type multi-element distribution patterns and have high positive ε_Nd(t) values (+8.23 to +8.99) and low initial ⁸⁷Sr/⁸⁶Sr (0.7059–0.7074), La_N/Yb_N (0.50–0.72), and Y/Yb (8.94–9.91) values. By contrast, the alkaline diabase rocks display oceanic island basalt (OIB)-type multi-element distribution patterns, and have low positive ε_Nd(t) (+1.17 to +1.30) and initial ⁸⁷Sr/⁸⁶Sr (0.7064–0.7067) values and high La_N/Yb_N (16.57–20.45) and Y/Yb (12.69–13.44) values. The relatively depleted Sr-Nd isotope compositions and different rare earth element ratios reveal that the subalkaline and alkaline diabase rocks were most likely derived from asthenospheric mantle sources at depths of 55–63 km in the spinel-stability field and at depths of 85–91 km in the spinel-bearing garnet-stability field, respectively. The Sr-Nd isotope models, as well as several trace element ratios (e.g., Nb/Ta, Nb/U, and Ba/Nb), further demonstrate that these asthenosphere-derived melts were contaminated to varying degrees by the overlying Zhongba lithospheric mantle and crust during their ascent and emplacement, implying significant asthenosphere–lithosphere interaction and resultant thermal perturbation beneath the western YTSZ. Based on the spatiotemporal distribution of the post-collisional magmatic rocks, the bilateral tearing of the subducted Indian slab can best account for the E–W-trending zonal distribution patterns with an eastward younging trend in the 73–89°E segment and a westward younging trend in the 90–96°E segment. In addition, the derivative longitudinal tearing and subsequent slab advancement would lead to the locally southward and northward younging trends of post-collisional magmatic rocks, respectively.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108154"},"PeriodicalIF":2.9,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144522177","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":"Mantle evolution of the nascent oceanic basin subsequent to continental breakup constrained by Mo–Sr–Nd–Hf isotopes in MORBs from the northern margin of the South China Sea","authors":"Yu-Xin Cai ,&nbsp;Xiao-Long Huang ,&nbsp;Fan Yang ,&nbsp;Yang Yu ,&nbsp;Jie Li ,&nbsp;Zhen-Min Ge","doi":"10.1016/j.lithos.2025.108151","DOIUrl":"10.1016/j.lithos.2025.108151","url":null,"abstract":"<div><div>The geochemical characteristics of the mantle during continental breakup and the initial spreading of marginal sea basins remain poorly understood. Mid-ocean ridge basalt (MORB) samples from Holes U1500B and U1503A in the northern margin of the South China Sea (N-SCS), obtained during International Ocean Discovery Program (IODP) Expeditions 367 and 368X, provide crucial insights into mantle evolution of the nascent oceanic basin subsequent to continental breakup. MORB samples from Hole U1500B, closer to the continent-ocean transition zone, exhibit higher ⁸⁷Sr/⁸⁶Sr ratios, along with lower ε_Nd and ε_Hf values compared to the depleted mantle. Additionally, their δ^98/95Mo values correlate positively with Mo/Ce and Mo/Nb ratios, indicating the influence of recycled oceanic crust (ROC) in the mantle source. In contrast, MORB samples from Hole U1503A, nearer to the oldest fossil ridge of the steady-state ocean, show a broader range of δ^98/95Mo values, higher ⁸⁷Sr/⁸⁶Sr ratios, and lower ε_Nd and ε_Hf values compared to those from Hole U1500B, due to varying extents of subcontinental lithospheric mantle (SCLM) metasomatized by terrigenous sediment input into the mantle source. The distinct trace element and Mo–Sr–Nd–Hf isotope compositions of MORBs from the two sites in the N-SCS highlight a significant transition in the mantle source of the nascent oceanic basin subsequent to continental breakup. During the initial stages of seafloor spreading in the SCS, the mantle source beneath nascent mid-ocean ridges may have been replenished with enriched components, likely derived from subduction-related processes since the Mesozoic. This study offers critical geochemical insights into the evolution of the mantle in nascent oceanic basins. The prolonged subduction led to substantial amounts of enriched components into the mantle, potentially lowering its solidus temperature, thereby facilitating rapid lithospheric rupture and extensive magmatism during the early development of the SCS.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108151"},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144470029","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":"Petrogenetic processes in alkaline magmatism in the southern Mozambique Channel","authors":"C. Berthod ,&nbsp;P. Bachèlery ,&nbsp;S. Revillon ,&nbsp;R. Doucelance ,&nbsp;F. Schiavi ,&nbsp;J.-L. Devidal ,&nbsp;E. Bou ,&nbsp;S.J. Jorry","doi":"10.1016/j.lithos.2025.108155","DOIUrl":"10.1016/j.lithos.2025.108155","url":null,"abstract":"<div><div>Whereas the northern part of the Mozambique Channel, between the eastern coast of Africa and Madagascar, is intensively studied, the southern part remains poorly investigated. The 2014 PAMELA-MOZ01 and 2015 PAMELA-MOZ04 cruises enabled us to collect volcanic rocks from the submarine flanks of the Bassas da India-Europa complex, including Bassas da India atoll, Europa Island, and Jaguar and Hall Banks. Despite significant alteration, probably due to their prolonged stay in seawater and the hydrothermal circulation they underwent, we are able to describe the main petrological and geochemical aspects of these largely unknown lavas. To achieve this, we integrated petrographic and mineralogical observations with geochemical analyses of the dredged rocks, aiming to identify the key aspects of the alteration and to characterize their petrological and geochemical properties.</div><div>The volcanism of this region is characterized by strongly silica-undersaturated alkaline magmas. Here, we demonstrate that this volcanism is marked by a bimodal magmatic activity with ultrabasic and basic compositions, and more silica-rich compositions. Using isotopic signatures and trace elements, we suggest that magmas are produced by a low degree of partial melting (1 to 5 %) of a metasomatized mantle at about 80 km depth. These mafic magmas then rise from the source to the surface via several magma storage levels, located at about 25–30 km and 15 km depth, the latter corresponding to the mantle-crust boundary as identified by geophysical methods. Fragments of zoned sanidine phenocrysts within intermediate lavas (olivine-free nephelinite or tephri-phonolite) also suggest the presence of differentiated magma reservoirs. Our observations strongly support frequent magmatic recharges, coupled with magma differentiation through olivine + clinopyroxene crystallization/assimilation, in long-lived magma reservoirs. In many respects, this volcanism has similar characteristics (nature of the source, degree of partial melting, composition of the lavas, age, and spatial distribution) to those of the Miocene to Quaternary volcanic provinces of Madagascar, the northern Mozambique Channel or the East African Rift. We propose that this volcanism might result from regional extension through the Mozambique Channel and the southern part of the East African Rift System, coupled with a thermal erosion of a mantle plume.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108155"},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480248","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}