Lithos最新文献

{"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}

{"title":"Recycling of terrigenous sediments recorded in late Permian-early Triassic Fe-rich intrusions from Yunkai Massif, South China","authors":"Yaqian Wen ,&nbsp;Feng Guo ,&nbsp;Liang Zhao ,&nbsp;Feng Zhang ,&nbsp;Xin Huang ,&nbsp;Melesse Alemayehu","doi":"10.1016/j.lithos.2024.107809","DOIUrl":"10.1016/j.lithos.2024.107809","url":null,"abstract":"<div><div>The origin of Fe-rich intrusion remains debatable regarding the respective role of magmatic evolution and Fe enrichment in the source. Here, we report detailed mineral and bulk-rock geochemistry of Permian-Triassic (251–250 Ma) mafic intrusions from the Tengxian area in Yunkai Massif, South China. These rocks consist of hornblende norites, show Fe-rich affinities with high FeO*(FeO* = FeOt / (FeOt + MgO) in weight ratio, &gt;0.8, based on total iron oxide in the rock), and exhibit significant enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) but depletion in Sr and high field strength elements (HFSEs), resembling subduction-related magmas. In addition, they show remarkable features that include very high δ¹⁸O values in zircon (δ¹⁸O = 8.8–10.6 ‰) and apatite (δ¹⁸O = 8.7–10.8 ‰), and extremely enriched Sr<img>Pb [e.g. ⁸⁷Sr/⁸⁶Sr(i) = 0.7181–0.7196, ²⁰⁷Pb/²⁰⁴Pb(i) = 15.77–15.78, ²⁰⁸Pb/²⁰⁴Pb(i) = 38.95–39.05] and nonradiogenic Nd<img>Hf isotopic compositions [e.g. ε_Nd(t) = −11.1 ∼ − 10.1, ε_Hf(t) = −8.8 ∼ −7.3] in bulk rocks. These characteristics distinguish the Tengxian norites from modern arc basalts and subduction-related magmas in the Paleo-Pacific Tectonic Domain. Instead, they are isotopically similar to Cenozoic Tibetan and Mediterranean potassic to ultrapotassic rocks in the Tethys Tectonic Domain. Regardless of variable influence by orthopyroxene and plagioclase accumulation, the intrinsically low SiO₂ and high FeOt and Fe/Mn ratios in these rocks were likely attributed to significant contribution of a Fe-rich mantle component such as Si-poor pyroxenite, which might have formed through crystal accumulation of mafic magmas at mantle conditions. The highly evolved Sr-Nd-Pb-Hf isotopic signatures and very high δ¹⁸O values in zircon and apatite required substantial (10–20 %) involvement of recycled crust in the mantle source. The combined mineral and bulk-rock geochemical data suggest that the parental magmas for the Tengxian norites originated from a metasomatized mantle wedge through addition of terrigenous sediment-derived melt following the subduction of Paleo-Tethys Ocean beneath the Yunkai Massif.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107809"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162021","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":"Remnants of a Jurassic marginal sea plate in the Meso-Tethyan Ocean revealed by multi-stage magmatism in the Lagkorco ophiolite, Central Tibet","authors":"Wei-Qi Zhang ,&nbsp;Chuan-Zhou Liu ,&nbsp;Tong Liu ,&nbsp;Chang Zhang ,&nbsp;Xiao-Ni Li ,&nbsp;Zhen-Yu Zhang ,&nbsp;Zhen Zhang ,&nbsp;Yin-Zheng Lin","doi":"10.1016/j.lithos.2024.107895","DOIUrl":"10.1016/j.lithos.2024.107895","url":null,"abstract":"<div><div>The formation of marginal sea plate, through multi-stage arc rupture and back-arc spreading, is a fundamental process in mature intra-ocean convergent plate margins. Identifying remnants of ancient marginal sea microplates within suture zones is crucial for unraveling the evolution of ancient ocean basins, although it presents significant challenges. In this study, we present new zircon and titanite U<img>Pb ages, along with Sr-Nd-Fe isotopic compositions, for a suite of well-characterized cumulates from the Lagkorco ophiolite which represents remnants of the Bangong-Nujiang Meso-Tethyan oceanic lithosphere. Our integrated dataset, combined with previous findings, reveals three distinct magmatic phases within the Lagkorco ophiolite: i) Unit A: early Jurassic (∼184 Ma) amphibolite-facies mafic-felsic complex, ii) Unit B1: early Jurassic (187–192 Ma) oceanic lithosphere, and iii) Unit B2: middle Jurassic (160–170 Ma) oceanic lithosphere. Geochemical data from Unit B1 cumulates indicate a damp (∼1 % H₂O) but arc-like parental magma. These cumulates exhibit more enriched Sr<img>Nd isotopes compared to mid-ocean ridge basalts and typical island arc basalts. Unit B1 cumulates exhibit clinopyroxene Fe isotopes (δ⁵⁶Fe = −0.06 − +0.01) lighter than mid-ocean ridge cumulate clinopyroxene (δ⁵⁶Fe = +0.02 − +0.05). These data indicate that the Unit B1 cumulates originated from a subduction-modified depleted mantle mixed with minor sediments. Combining our results with previously published data, we propose that the parental magmas for both Unit B1 and Unit B2 were damp but arc-like, which aligns with the repeated re-melting of previously depleted sub-arc mantle during episodic back-arc spreading. Our interpretation suggests two-stage back-arc spreading (Unit B1 and Unit B2) and at least one episode of arc magmatism (Unit A) between 192 and 160 Ma. These results imply the existence of a Jurassic marginal sea plate, akin to the present-day Philippine Sea plate, within the Meso-Tethyan Ocean, which was likely later subducted beneath the Qiangtang continent.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107895"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161070","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":"Sources of alkaline and tholeiitic basaltic magmas of Changbaishan volcanic area (Northeastern China)","authors":"O.A. Andreeva ,&nbsp;V.M. Savatenkov ,&nbsp;V.V. Yarmolyuk ,&nbsp;I.A. Andreeva ,&nbsp;J.-Q. Ji ,&nbsp;X. Zhou ,&nbsp;J. Zhou","doi":"10.1016/j.lithos.2024.107940","DOIUrl":"10.1016/j.lithos.2024.107940","url":null,"abstract":"<div><div>Changbaishan volcanic area (China-North Korea) is located on the margin of the Eurasian continent within the large Cenozoic intraplate province of Central and Eastern Asia. Two large volcanoes Wangtian'e and Changbaishan of the area are situated 30 km from each other in Northeastern China. Basalts of Wangtian'e volcano belong to the tholeiitic rock series as well as basalts of Changbaishan volcano belong to the alkaline one. In this paper we use data on chemical and isotopic (Pb, Sr, Nd) composition of tholeiitic and alkaline basalts to reconstruct magmatic sources that participated in the tholeiitic and alkaline rock formation. Isotopic and geochemical features of tholeiitic and alkaline basalts of the Changbaishan volcanic area indicate the participation of three different sources in their formation. The formation of tholeiitic and alkaline melts of the Changbaishan volcanic area occurred within the mechanical asthenosphere-lithosphere boundary layer at a depth of 30–75 km in two stages. The first stage corresponds to the melting of supra-subduction peridotite of the lithospheric mantle and eclogite lenses resulted in the formation of tholeiitic melts that formed Wangtian'e volcano. As the eclogite was exhausted, the resulting tholeiitic melt reacted with fertilized mantle peridotite producting pyroxenite source. The second stage corresponds to the partial melting of pyroxenite together with peridotite of the asthenospheric mantle, which led to the appearance of alkali-basaltic melts that participated in the formation of Changbaishan volcano.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107940"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161969","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":"Boron isotopic characterization of ophiolitic serpentinites from Atlin terrane, Canadian Cordillera","authors":"Adina Bogatu ,&nbsp;Loïc Labrousse ,&nbsp;Céline Martin ,&nbsp;Alexandre Zagorevski ,&nbsp;Jean H. Bédard ,&nbsp;Alain Tremblay","doi":"10.1016/j.lithos.2024.107922","DOIUrl":"10.1016/j.lithos.2024.107922","url":null,"abstract":"<div><div>Atlin terrane ophiolites (Canadian Cordillera) exhibit non-Penrose pseudostratigraphy, with extensive serpentinites at the interface between upper crust and mantle. Petrography, Raman spectroscopy, electron probe microanalyzer (EPMA) and in-situ boron (δ¹¹B) isotopic analysis of serpentinites from Squanga Lake and Union Mt. ophiolites of Atlin terrane, identified four distinct phases of serpentine growth. Phase I (δ¹¹B = +1.6 ± 1 ‰ to +12.9 ± 1.3 ‰) and Ia (δ¹¹B = −5.7 ± 1.1 ‰ to +1.8 ± 1.1 ‰) serpentines have δ¹¹B signatures suggestive of seawater input, possibly along a detachment during oceanic core complex formation. These have up to 9 wt% FeO_tot concentrations, suggestive of primary mesh and bastite after ultramafic minerals. Phase I δ¹¹B values are typical of serpentinized ophiolite (−5.7 ‰ to +25 ‰). Phase II antigorite (δ¹¹B = −13.5 ± 0.8 ‰ to −6.3 ± 1.9 ‰; with propagated 1 S.E. error) and phase III fibrous chrysotile (δ¹¹B = −10.0 ± 2.5 ‰ to −2.7 ± 0.7 ‰) have strong negative δ¹¹B values distinct from phase I/Ia values. Phase II and III serpentines formed during listvenite alteration, coeval with Jurassic thrust imbrication of ophiolitic units and post-obduction plutonism and might be resulted from sediment-derived fluids. While δ¹¹B values of phase II antigorite align perfectly with those obtained from Dalayee Lake sediment (−14.6 ± 0.6 ‰ to −7.7 ± 2.1 ‰), the less negative δ¹¹B values of phase III chrysotile might indicate fluid evolution during exhumation. Phase IV antigorite flakes (δ¹¹B = −1.9 ± 1.4 ‰ to +1.5 ± 0.9 ‰) overprint phase II &amp; III serpentines and might be related to post-obduction plutonism. These have lowest FeO_tot values (&lt;2.3 wt%), compatible with multiple re-crystallisation pulses of Union Mt. antigorite.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107922"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143162011","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 igneous rocks in the Qinfang belt: Implications for spatio-temporal framework of Paleo-Tethys","authors":"Yue Qin ,&nbsp;Yun Zhou ,&nbsp;Xijun Liu ,&nbsp;Yongshan Zhao ,&nbsp;Zhenglin Li ,&nbsp;Liya Yang ,&nbsp;Chen Li ,&nbsp;Yongfeng Cai","doi":"10.1016/j.lithos.2024.107900","DOIUrl":"10.1016/j.lithos.2024.107900","url":null,"abstract":"<div><div>The formation and evolution of the Paleo-Tethys is well documented in Southeast Asia. The Qinfang tectonic belt in the South China Block contains numerous granitic and volcanic rocks; however, the timing of their formation remains unconstrained. In this study, a spatiotemporal framework for the Paleo-Tethys is proposed based on a comprehensive analysis of zircon U<img>Pb geochronological and geochemical data of the Indosinian igneous rocks in the Qinfang tectonic belt. Geochronological results showed that the granitic and volcanic rocks had zircon U<img>Pb ages of 252–245 Ma, indicating that contemporaneous granitic and volcanic activities occurred in the belt. The granite samples belonged to the peraluminous high-K calc-alkaline-shoshonitic series of rocks and showed geochemical signatures similar to those of the S-type granite. Their formation is related to the evolution of the Paleo-Tethys with the parental magma of the rocks likely derived by partial melting of crustal materials that differentiation by fractional crystallization. Combined with regional geological data, this suggests that the Indosinian magmatic assemblages, geochemical characteristics, and sedimentary sequences in the Qinfang tectonic belt are consistent with those in the Jinshajiang, Ailaoshan, and Hainan Island regions. This indicates that these regions belong to the Paleo-Tethyan tectonic domain during the Indosinian, and that the Qinfang tectonic belt likely represents a branched ocean basin of the Paleo-Tethys.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107900"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161064","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 and geodynamic mechanism of Early Miocene post-collisional ultrapotassic rocks in the eastern Lhasa Terrane, southern Tibet","authors":"Chenyuan Hua ,&nbsp;Feng Huang ,&nbsp;Song Zhang ,&nbsp;Haiyan Fan ,&nbsp;Yunchuan Zeng ,&nbsp;Mingjian Li ,&nbsp;Shuo Wang ,&nbsp;Xi Chen ,&nbsp;Jing Hu ,&nbsp;Jifeng Xu","doi":"10.1016/j.lithos.2024.107931","DOIUrl":"10.1016/j.lithos.2024.107931","url":null,"abstract":"<div><div>Post-collisional ultrapotassic volcanic rocks (UPVRs) in the Tethyan domain archive crucial information about the composition and evolution of the lithospheric mantle, offering valuable insights into deep geodynamic processes. The Tibetan Plateau, particularly the Lhasa Terrane in its southern part, remains a subject of debate regarding the genesis and geodynamic mechanisms of the UPVRs. This study investigates geochronology, mineralogy, and whole-rock geochemistry of the UPVRs in the Majiang area of Lhasa Terrane, southern Tibet. Zircon U<img>Pb dating reveals that these rocks formed at ca. 21 Ma. Petrologically, the Majiang volcanic rocks are classified as trachyandesites, while geochemically they qualify as ultrapotassic rocks (characterized by K₂O &gt; 3 wt%, MgO &gt; 3 wt% and K₂O/Na₂O &gt; 2). They exhibit a broad range of SiO₂ contents (45.85–57.94 wt%) and high Mg# values (57.7–72.3). Elevated trace element concentrations, marked by enrichment in large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs), suggest a mantle source influenced by fluid/melt interactions. The presence of phlogopite phenocrysts in the Majiang UPVRs suggests high magma temperatures (1116 ± 15 °C) and low crystallization pressures (1.3 ± 0.3 GPa). Trace element geochemical modeling indicates that the Majiang UPVRs likely originate from a garnet stable mantle domain and experience rapid magma ascent after their formation. The Majiang UPVRs exhibit high Th/U (8.97–19.08) and Th/La (2.27–2.45) ratios, low Hf/Sm (0.52–0.64) ratios, and enriched Sr<img>Nd isotopes (⁸⁷Sr/⁸⁶Sr_i = 0.717286–0.721658, ε_Nd(t) = −9.55 - -9.28). These geochemical signatures suggest derivation from an enriched lithospheric mantle metasomatized by oceanic sediments. Integration of published data reveals that the UPVRs in both the eastern and western Lhasa Terrane share close geochemical affinities, suggesting a common mantle source. However, limited UPVR exposures in the eastern Lhasa Terrane and slightly more depleted Sr<img>Nd isotopes in the Majiang UPVRs compared to those in the western Lhasa Terrane imply distinct Miocene geodynamic processes. Lithospheric convective thinning caused by post-collisional extension and mantle upwelling likely occurred more extensively in the eastern Lhasa Terrane. This process may have led to the gradual replacement of ancient lithospheric mantle by juvenile material in the east, contrasting with the more localized effects in the western Lhasa Terrane.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107931"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161623","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 mid-Cretaceous Hohonu Batholith (South Island, New Zealand): Identifying magmatic sources and processes during onset of crustal extension","authors":"Robert Bolhar ,&nbsp;Stephen D Weaver ,&nbsp;Rose Turnbull ,&nbsp;Tod E Waight ,&nbsp;Martin J Whitehouse ,&nbsp;Roland Maas ,&nbsp;Uwe Ring","doi":"10.1016/j.lithos.2024.107847","DOIUrl":"10.1016/j.lithos.2024.107847","url":null,"abstract":"<div><div>The Hohonu Batholith is an aggregation of mostly mid-Cretaceous granitoid plutons on the West Coast of the South Island of New Zealand emplaced during a transitional period between subduction-related compression and continental lithospheric extension. This study reports an integrated dataset, comprising in-situ U-Pb, O and Hf isotope compositions and REE, Ti and other trace and major elements (Zr-Hf, Th-U) for zircons extracted from four representative plutons within the batholith. Our results provide detailed insight into the protracted thermal, chronological and geochemical histories. LA-ICPMS U-Pb zircon ages indicate a primary episode of magma genesis and emplacement from 107 to 113 Ma, confirming published SIMS dating. However, a younger previously unrecognized age population of ∼91–96 Ma is identified, primarily (although not exclusively) in zircon rims. This younger age event coincides with the timing of protracted lithospheric extension and crustal thinning of the Zealandia continent. The cryptic younger zircon ages suggest that Hohonu granitoids experienced a partial thermal overprint (accompanied by Pb loss) mostly recorded in rims. Differences in bulk rock geochemistry between plutons are inferred to reflect variable conditions of partial melting controlled by source mineralogy and H₂O content. Isotope and trace element compositions, along with Ti-thermometry, measured on the same micro-volume of CL-imaged zircons, are used to test if source characteristics were imparted from melt to minerals in zircon-saturated silicic systems. Similarities are revealed in the zircon record of the selected plutonic rocks, confirming their broadly consanguineous relationship and the fundamental role of open-system behaviour, involving hybridization or assimilation between mantle-derived (or juvenile mafic) and crustal-derived components, as previously inferred from whole rock Nd-Sr isotope systematics. However, intra-sample decoupling of zircon O-Hf isotope systematics may also be linked to residual source unmixing. This possibility, in addition to mafic recharge, may have obscured melt source compositional characteristics, and hence zircon REE appear as unsuitable fingerprints of source(s) and conditions of partial melting in this granitoid system. Simple compositional and thermal magma evolution trends appear punctuated by episodes of mafic recharge, presumably during lithospheric thinning.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107847"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161624","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}