Lithos最新文献

{"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}

{"title":"Identifying ore-forming magma and tectonic setting of the Tongshan porphyry Cu deposit, NE China: Evidence from zircon trace elements and U–Pb–Hf isotopes","authors":"Chenglin Bai ,&nbsp;Guiqing Xie ,&nbsp;Jie Chen ,&nbsp;Wei Li ,&nbsp;Tianqi Wang","doi":"10.1016/j.lithos.2025.108157","DOIUrl":"10.1016/j.lithos.2025.108157","url":null,"abstract":"<div><div>The Tongshan deposit is the largest porphyry Cu deposit in northeast China, which has the characteristics of complex metallogenic system formed by multiple overprinted mineralization events. Recently, the successful exploration of concealed orebodies and intrusions at Tongshan revealed various intrusive rocks in the mining area. However, the complex magmatic controls on the mineralization and the tectonic setting at Tongshan are still controversial. This paper reports the zircon geochemistry and U–Pb–Hf isotopic data from granodiorite porphyry, granodiorite, and dacite porphyry samples in the Tongshan deposit. Our new zircon U-Pb ages show that the newly discovered granodiorite porphyry dikes from drill hole ZK16–1 yield an age of 472.2 ± 1.1 Ma (<em>n</em> = 25, MSWD = 0.25). A comparative analysis of zircon geochemistry data from the granodiorite porphyry with previously studied fertile and barren intrusions at Tongshan reveals distinct geochemical signatures. Zircon crystallization temperatures for the granodiorite porphyry range from 663° to 742 °C, as calculated by the zircon Ti thermometer. The granodiorite porphyry samples exhibit relatively higher zircon Δ_FMQ (0.70 ± 0.29) and Eu/Eu* values (0.52–0.73) compared to the barren intrusions at Tongshan, suggesting differences in magma oxidation states. Zircon Hf isotopic compositions show positive zircon ɛ_Hf(<em>t</em>) values for the Ordovician granodiorite porphyry (+11.3 to +14.7, <em>n</em> = 15) and the Triassic suites (+3.4 to +13.2 for granodiorite and +6.7 to +12.5 for dacite porphyry, <em>n</em> = 30). The Ordovician granodiorite porphyry originated from mantle-derived magmas with high ɛ_Hf(<em>t</em>) values, while the Triassic dacite porphyry and granodiorite resulted from the mixing of juvenile mantle materials with pre-existing crustal rocks, as evidenced by their broad ɛ_Hf(<em>t</em>) values. Integration of zircon geochemistry and tectonic setting indicates that the Ordovician and Triassic ore-forming intrusions were formed in a subduction-related continental arc setting. Therefore, we proposed a genetic model for Tongshan, in which the Paleo-Asian Ocean and the Mongol-Okhotsk Ocean tectonic systems contributed to the two significant periods of intrusions and mineralization, respectively.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108157"},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144338625","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":"Fluid activity in continental subduction zones: Insights from barium isotopes of ultrahigh-pressure jadeite quartzites in Dabie orogen","authors":"Anxia Chen ,&nbsp;Huimin Yu ,&nbsp;Wangye Li ,&nbsp;Xiao-Ying Gao ,&nbsp;Hao Hu","doi":"10.1016/j.lithos.2025.108153","DOIUrl":"10.1016/j.lithos.2025.108153","url":null,"abstract":"<div><div>Fluid activity during deep continental subduction and exhumation plays a critical role in crust-mantle geochemical recycling. However, the origins and scales of fluid activity in continental subduction zones remain poorly constrained. Barium (Ba) isotopes exhibit significant fractionation during fluid-related processes, providing a powerful tool for tracing fluid sources and quantifying fluid-rock interactions. Coesite-bearing jadeite quartzites from the Dabie orogen in east-central China are unique ultrahigh-pressure metamorphic rocks recording extensive fluid-rock interactions during deep continental subduction. The protolith of the jadeite quartzites is a suite of ca. 2.0 Ga granitic rocks that underwent simple physical weathering and proximal accumulation. In this study, we analyzed Ba isotope compositions of these coesite-bearing jadeite quartzites and compared them with ca. 2.0 Ga granitic rocks to investigate fluid activity in continental subduction zones. The jadeite quartzites display a wide range of Ba isotope compositions (δ^138/134Ba = −0.50 to 0.11 ‰), generally lower than those of the ca. 2.0 Ga granitic rocks (−0.07 to 0.29 ‰), albeit with minor overlap. Ba isotope compositions of the jadeite quartzites correlate well with Ba contents and other fluid-mobile elements (e.g., K, Rb, Cs, and Sr), indicating significant fluid activity during their formation. Furthermore, using a Rayleigh fractionation model, we constrained the Ba isotope fractionation factor to a range of 0.10 to 0.15 ‰ (Δ^138/134Ba_f_luid-rock) during fluid-rock interaction. Considering the widespread occurrence of jadeite quartzites, fluid activity is quantitatively significant in continental subduction zones. Such fluids critically facilitate partial melting and crust-mantle interactions in subduction zones.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108153"},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144338626","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":"On the significance of thermal histories of ophiolitic and abyssal peridotites","authors":"By Nicholas Dygert ,&nbsp;Max Jansen","doi":"10.1016/j.lithos.2025.108152","DOIUrl":"10.1016/j.lithos.2025.108152","url":null,"abstract":"&lt;div&gt;&lt;div&gt;To understand the geologic significance of their thermal histories, we assessed temperatures and cooling rates recorded by peridotites from abyssal and ophiolitic geologic settings compiled from the literature, and provided by new analyses of peridotites from Masirah, a mid-ocean ridge type ophiolite with a thin but complete igneous crust. Peridotites dredged or drilled from the seafloor at amagmatic or magma starved spreading centers, core complexes, transform faults, and a tectonic window exposing mantle lithosphere formed beneath the East Pacific Rise (Hess Deep) constitute what we refer to as the abyssal peridotites. We additionally consider a smaller number of peridotites recovered from forearc settings. We evaluate temperatures from a rare earth element (REE)-based thermometer sensitive to high temperature cooling, and major element thermometers sensitive to lower temperature subsolidus cooling. Recovered cooling rates are compared to results of simple heat conduction models, which may be used to contextualize the sample-determined thermal histories. Cooling rates within a body conductively cooling into a cold thermal boundary vary as a function of temperature and distance to the boundary, i.e., the conductive cooling lengthscale. Analysis of cooling rates of Masirah peridotites suggests the lower crust and uppermost mantle at Masirah were conductively cooled, and the overlying extrusive crust was hydrothermally cooled. This result is consistent with interpretations of spatial variations in cooling rate from another paleo-spreading center with a thin crustal section, but contrasts with observations from paleo-spreading centers with thick crustal sections, which suggest hydrothermal cooling of the lithosphere to the crust-mantle boundary and conductive cooling of the underlying mantle. Among the global dataset, ophiolitic peridotites record lower temperatures than abyssal peridotites through lower temperature intervals. The significance of a temperature recovered by a thermometer for a sample’s thermal history depends on grain size. We assessed grain sizes reported in our own samples and a literature compilation and found no statistically significant bias between ophiolitic and abyssal settings, such that the lower temperatures recorded by ophiolitic peridotites demonstrate that the ophiolites cooled more slowly than the abyssal peridotites. In the context of conductive cooling models, this difference can be interpreted as reflecting differences in conductive cooling lengthscales between the settings, with ophiolites cooling over lengthscales of hundreds of m to &gt;ten km, and abyssal peridotites cooling over shorter lengthscales compressed by their advection through the geotherm. Crustal sections present at many ophiolites may have restricted the depth of hydrothermal circulation in some cases, producing thicker conductive cooling regimes than magma-starved abyssal settings, and/or the ease of sampling deeper parts of the mantle ","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108152"},"PeriodicalIF":2.9,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517923","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 sheared garnet peridotite mantle xenolith from the Delitzsch Carbonatite Complex, Germany - Evidence for thickened Cretaceous lithosphere beneath Central Europe","authors":"Tobias Röper ,&nbsp;Yannick Bussweiler ,&nbsp;Max Hellers ,&nbsp;Frank Möckel ,&nbsp;Frank Wombacher ,&nbsp;Carsten Münker","doi":"10.1016/j.lithos.2025.108156","DOIUrl":"10.1016/j.lithos.2025.108156","url":null,"abstract":"<div><div>Sheared garnet peridotites occur in the deep lithosphere and record processes of deformation, melt interaction, and metasomatism along the lithosphere-asthenosphere boundary (LAB). While sheared peridotites are typically found in kimberlites and related volcanic rocks within cratonic settings, this study reports on an exceptionally fresh occurrence found in an ultramafic lamprophyre (UML) from the Delitzsch Carbonatite Complex (DCC) in Saxony, Germany. The xenolith was emplaced during the main magmatic activity, previously dated to between 72 and 83 Ma during the late Cretaceous period. The xenolith contains porphyroclasts of garnet, clinopyroxene and orthopyroxene in a fine-grained matrix of olivine, and thus classifies as garnet-lherzolite. Evidence of deformation and metasomatism is recorded in its mosaic to fluidal mosaic texture, characterized by olivine neoblasts, elongated garnet grains, and reaction rims around garnet (kelyphite) and clinopyroxene (spongy rims). The xenolith represents a relatively fertile mantle composition with magnesium numbers (Mg# = Mg/[Mg + Fe²⁺] × 100) of 89.4 for olivines and clinopyroxenes, 90.8 for orthopyroxenes and 82.6 for garnets. Measured trace element compositions suggest high temperature interaction with primitive, fertile melts, as shown by an enrichment of middle rare earth elements (MREE) as well as high field strength elements (HFSE) such as Ti. Reconstructed P-T conditions indicate equilibration at 61.1 ± 5.1 kbar and 1330 ± 23 °C. The corresponding depth of ∼190 km is substantially deeper than the depth of the modern LAB at 120-140 km. This not only establishes the sheared garnet peridotite xenolith as the deepest sample ever recorded from Germany but also has significant implications for mantle dynamics beneath the Mesozoic Central European crust. The sheared garnet peridotite provides evidence of the destabilization and destruction (e.g., by delamination) of a formerly thick lithosphere at least beneath Eastern Germany and possibly beneath Central Europe. Such thick, craton-like lithosphere could have originally underlain the Bohemian Massif and extended to the NW at upper mantle depth.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"512 ","pages":"Article 108156"},"PeriodicalIF":2.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144330173","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}