Lithos最新文献

{"title":"Calcium and iron isotope fractionation during felsic magma differentiation","authors":"Qiu-Yun Guan ,&nbsp;Jin-Xiang Li ,&nbsp;Ya-Li Sun ,&nbsp;Shi-Lei Tang ,&nbsp;Noreen J. Evans ,&nbsp;Zhao-Feng Zhang ,&nbsp;Li-Yun Zhang ,&nbsp;Fu-Long Cai ,&nbsp;Wei-Ming Fan ,&nbsp;Lin Ding","doi":"10.1016/j.lithos.2024.107893","DOIUrl":"10.1016/j.lithos.2024.107893","url":null,"abstract":"<div><div>Stable calcium (Ca) and iron (Fe) isotopes could provide a new way to investigate granite petrogenesis, and their isotope fractionation mechanisms in felsic magmas have been increasingly understood through continuous efforts in recent years. However, comprehensive Ca and Fe isotope fractionation during highly fractionated magmas is still unclear. This study presents Ca and Fe isotope data for some fractionated granites from Southern Myanmar. The δ^56/54Fe values of the less fractionated Eocene granites range from 0.11 ± 0.03 ‰ to 0.23 ± 0.04 ‰. The highly fractionated Late Cretaceous and Paleocene granites clearly exhibit 0.15 ‰ and 0.42 ‰ variations in δ^56/54Fe values, respectively. These δ^56/54Fe values are negatively correlated with those of Fe₂O_3T, TiO₂ contents and (La/Yb)_N ratios, suggesting that more evolved melts are enriched in heavy Fe isotopes, primarily as a result of fractional crystallization of Fe-rich minerals enriched in light Fe isotopes (e.g., biotite and ilmenite). Some Late Cretaceous granites with low Nb/Ta and Zr/Hf ratios display relatively low δ^56/54Fe values, which may be modified by exsolved fluids enriched in light Fe isotopes. Moreover, the δ^44/40Ca values of the Late Cretaceous, Paleocene, and Eocene granites range from 0.71 ± 0.07 ‰ to 0.90 ± 0.06 ‰, 0.62 ± 0.08 ‰ to 0.89 ± 0.06 ‰, and 0.66 ± 0.06 ‰ to 0.75 ± 0.05 ‰, respectively. Most of the studied granites have relatively consistent Ca isotopic compositions with those of the continental crust. Combined with high δ^44/40Ca values (up to 0.90 ‰), the studied granites have a weakly negative correlation between δ^44/40Ca values and Eu/Eu^⁎ ratios. This evidence suggests that fractional crystallization of plagioclase with light Ca isotopes may also be a reason for Ca isotope fractionation during felsic magma differentiation, in addition to crustal magma sources and crustal contamination. Additionally, a Late Cretaceous granite with a high (Dy/Yb)_N ratio has the lowest δ^44/40Ca value (0.52 ± 0.06 ‰), possibly reflecting the presence of residual garnet in the source. The affirmation of significant Ca and Fe isotope fractionation in highly evolved melts strengthens the utility of Fe and Ca isotopes as tracers of magma differentiation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"494 ","pages":"Article 107893"},"PeriodicalIF":2.9,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143161961","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":"Origin and evolution of sub-caldera magmatic systems before and during the caldera-forming eruptions of the Furongshan caldera, SE China","authors":"Ming-Lu Li ,&nbsp;Zhen-Yu He ,&nbsp;Tian-Yu Lu ,&nbsp;Li-Li Yan","doi":"10.1016/j.lithos.2025.107974","DOIUrl":"10.1016/j.lithos.2025.107974","url":null,"abstract":"<div><div>The formation of collapse caldera is commonly associated with large-scale eruptions of silicic magmas, where the magma reservoirs generally undergo long-term accumulation and maturation processes before the caldera-forming eruptions. However, the pre-caldera eruptions have been less documented, since such eruption products are usually concealed by subsequent collapse and filling. The Furongshan caldera in SE China preserves the records of both the pre-caldera and caldera-forming eruption products, providing vital insights into the evolution of the magmatic systems from pre-caldera to caldera-forming eruptions. The pre-caldera volcanic rocks are characterized by small-volume dacite with relatively low SiO₂ contents (64–65 wt%), while the caldera-forming volcanic rocks are relatively large-volume crystal-rich tuff with high crystal contents (35–45 vol%) and relatively high SiO₂ contents (70–78 wt%). LA-ICP-MS zircon U-Pb dating results show that the age of pre-caldera dacite is 151 ± 1 Ma, and the age of caldera-forming crystal-rich tuff is 148 ± 1–144 ± 1 Ma, which indicates a prolonged evolution of the caldera magmatic systems. Zircon trace elements of the caldera-forming crystal-rich tuff show relatively low Ti contents and Eu/Eu* ratios, consistent with relatively low magma temperatures and high magmatic differentiation. The pre-caldera dacite and the caldera-forming crystal-rich tuff further show different zircon Hf isotopic compositions, with ε_Hf(<em>t</em>) values of −8.7 to −3.5 and −14.2 to −5.5, respectively, indicating higher crustal contributions in the magma of the caldera-forming crystal-rich tuff. We suggest that from the pre-caldera to caldera-forming eruptions at the Furongshan caldera, the contribution of crustal materials in the magma systems increased, and the magmas also gradually evolved, which well recorded the maturation process of the magmatic system of caldera-forming eruption. The eruption of caldera-forming crystal-rich tuff may be related to magma recharge and associated mush rejuvenation within the magma reservoirs.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107974"},"PeriodicalIF":2.9,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143320755","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":"Laterally differential composition and dynamics of a continental collision belt: Evidence from the North Qaidam orogenic system (western China)","authors":"Hao-Qin Sun,&nbsp;Qing Xiong,&nbsp;Qiang Ma,&nbsp;Si-Yi Cao,&nbsp;Xiang Zhou,&nbsp;Hong-Kun Dai,&nbsp;Wei Wang,&nbsp;Jian-Ping Zheng","doi":"10.1016/j.lithos.2025.107968","DOIUrl":"10.1016/j.lithos.2025.107968","url":null,"abstract":"<div><div>Revealing the large-scale, along-strike variations of composition and evolution of continental collisional belts remains a challenging task. Here, we report new zircon U-Pb ages, Lu-Hf isotopes and whole-rock major elements of granitoids, combined with a synthesis of published geochemical data of magmatic rocks across the whole North Qaidam collisional orogenic system (western China). Geochemical comparison and mapping reveal a pronounced dichotomy between the eastern and western segments during the ∼460–360 Ma orogeny. We observed that the eastern magmatism was continuous, with the magma source transition from mixed mantle-crust reservoirs to a solely exhumed continental crust at ∼420–410 Ma. A gradual increase in asthenosphere-derived magmatism triggered a magmatic burst at ∼400–380 Ma, followed by the orogen-collapse-related mafic magmatism at ∼380–360 Ma. In contrast, the western segment experienced a two-phase magmatism interrupted by a hiatus at ∼400–380 Ma. The earlier phase originated mainly from the moderately evolved and fractionated felsic magmas with variable older crustal components, while the later switched to asthenosphere-sourced mafic magmatism similar to that in the east. These contrasting features suggest that a relatively flat continental slab in the west gradually attached onto the overlying plate during ∼460–400 Ma, completely shutting down the western magmatism during ∼400–380 Ma. Meanwhile, the oceanic and continental slabs in the east progressively steepened until the slab broke off at ∼400–380 Ma. The whole orogenic root was finally removed together at ∼380–360 Ma. This study shows that slab tearing and differential slab behaviors may be a common feature of convergent and collisional orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107968"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143321012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-stage continental crust maturation in accreted oceanic terranes: Evidences from granitoids in the Qinling Orogen, Central China","authors":"Yadi Zhuang ,&nbsp;Wenxiang Zhang ,&nbsp;Yujie Zhao ,&nbsp;Guangyan Zhou ,&nbsp;Yuanbao Wu","doi":"10.1016/j.lithos.2025.107969","DOIUrl":"10.1016/j.lithos.2025.107969","url":null,"abstract":"<div><div>Accreted oceanic arc terranes are crucial sites for net continental crust growth. It is intriguing how the mafic oceanic arcs can subsequently evolve into high-Si and K-rich mature continental crust. The granitoid Xizhuanghe and Dongzijie plutons display enriched geochemical composition and occur in the same oceanic arc unit of the Paleozoic Qinling orogen. They provide an ideal opportunity to reveal the mechanism for transforming mafic oceanic arcs to continental crust. The Xizhuanghe and Dongzijie granites have zircon U<img>Pb ages of ca. 460 Ma and 454 Ma, respectively, after the collision between the Erlangping and North Qinling units. Geochemically, both of them display low Mg# (38.9–45.4 vs. 18.9–43.4) values and arc-type trace element distribution patterns. According to the different K₂O/Na₂O ratios, the Xizhuanghe pluton is relatively sodic I-type granites, while the Dongzijie pluton belongs to typical potassic species. They are characterized by depleted Sr-Nd-Hf compositions (Xizhuanghe: ⁸⁷Sr/⁸⁶Sr_i = 0.704171–0.704692, ε_Nd(t) = +1.68 ∼ +2.23, zircon ε_Hf(t) = +5.9 ∼ +9.8; Dongzijie: ⁸⁷Sr/⁸⁶Sr_i = 0.694356–0.705627, ε_Nd(t) = −0.94 ∼ +1.37, zircon ε_Hf(t) = +8.1 ∼ +11.9) and zircon δ¹⁸O values (Xizhuanghe: 4.31–5.15 ‰; Dongzijie: 3.30–5.19 ‰) lower than those of normal mantle zircon, indicating that the mafic precursors of the two plutons might be the Erlangping lower oceanic crust, which might be heterogeneously modified in a supra-subduction zone and have experienced high-temperature hydrothermally alteration with seawater. We suggest that the Xizhuanghe pluton can directly be produced by partial melting of such mafic oceanic crust, while the Dongzijie pluton needs additional fractionation process: dehydration melting of sodic felsic rocks generated by partial melting of the enriched lower oceanic crust. Our finding highlights the significance of the enriched oceanic crust and multi-stage differentiation within oceanic arc crust plays an important role for progressively crust maturation in accretionary orogens.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107969"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143320149","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 Jurassic high-silica granites in the interior and coastal South China and their tectonic implication","authors":"Tianxing Bai,&nbsp;Xin Qian,&nbsp;Chengshi Gan,&nbsp;Yuejun Wang","doi":"10.1016/j.lithos.2025.107971","DOIUrl":"10.1016/j.lithos.2025.107971","url":null,"abstract":"<div><div>The South China Block is predominantly influenced by the Paleo-Pacific dynamic domain during the Late Mesozoic, resulting in the formation of volcanic-intrusive complexes along the interior and coastal regions, which provide significant insights into magmatic evolution and geodynamic processes. This paper presents new zircon ages and geochemical data for the Late Jurassic granites in Zhuhai and its surrounding islands. The inland granites from Zhuhai (163–159 Ma) consist of biotite granites and two-mica granites with (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.70901–0.70993, ε_Nd (t) values from −10.1 to −8.9, and ε_Hf (t) values from −12.5 to −4.2. In contrast, the island biotite granites form Wanshan and Dong'ao islands (155–150 Ma) exhibit lower (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.70418–0.70722, higher ε_Nd (t) values from −7.0 to −6.1, and ε_Hf (t) values from −8.5 to −2.0 than inland granites. The two groups share similar (²⁰⁶Pb/²⁰⁴Pb)_i ratios of 17.95–18.96, (²⁰⁷Pb/²⁰⁴Pb)_i ratios of 15.72–15.76, and (²⁰⁸Pb/²⁰⁴Pb)_i ratios of 38.53–39.16. Geochemical characteristics indicate that the inland granites formed from the partial melting of Paleoproterozoic crustal metasedimentary rocks, while the island granites were derived from a mixed source region of ancient metaigneous rocks with a juvenile crustal component. Subsequent extreme crystallization and amalgamation formed granitic plutons. Our study, together with geological observations and previous data, suggests that the Late Jurassic magmatism in the interior and coastal regions of the southeastern South China Block likely corresponds to western and eastern sides of Cathaysia and formed in response to the far-field effects of the subduction of the Paleo-Pacific Plate beneath the Eurasia.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107971"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377377","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":"An appraisal on crustal growth and reworking in collisional high-temperature granites: The Neoproterozoic Serra dos Órgãos batholith, Central Ribeira belt, SE Brazil","authors":"Clarisse Monteiro Fernandes ,&nbsp;Julio Cezar Mendes ,&nbsp;Patrícia Anselmo Duffles Teixeira","doi":"10.1016/j.lithos.2025.107973","DOIUrl":"10.1016/j.lithos.2025.107973","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Pan-African/Brasiliano orogeny, the result of the West-Gondwana assembly from the Neoproterozoic to the Early Paleozoic, culminated in a widespread, long-lived Ediacaran to Cambro-Ordovician granite production event at the Araçuaí-Ribeira Orogenic System. Collisional granitoids were emplaced along an interval wider than 100 m.y., following three subduction-accretion episodes. The Serra dos Órgãos batholith is the main granitoid intrusion emplaced during the &lt;em&gt;syn&lt;/em&gt;-collisional episode at the Central Ribeira belt, southeastern Brazil. The integration of Nd–Sr–Hf isotopes and mineral chemistry data were employed to constrain the physical-chemical conditions concerning this intrusion and host rocks, along with potential sources. For this purpose, sensu stricto granites from Serra dos Órgãos batholith and the surrounding Sumidouro Leucogneiss were examined. Zircon and whole-rock isotopic signatures reveal distinct multi-component inheritance in both the intrusion and the country rocks. The Sumidouro Leucogneiss recorded diverse zircon populations of igneous origin, with juvenile to crustal Nd–Sr–Hf isotopic signatures in a large range of geochronological ages (200 m.y. interval), an evidence of zircon preservation in disequilibrium melting situations. The Sumidouro Leucogneiss must be the result of partial melting of multiple sources, behaving as a temporal archive of past events preceding the collision. Conversely, the Serra dos Órgãos batholith records a more mature, crustal signature, presenting a main zircon population interpreted as autocrystic (ca. 590 Ma), and minor inheritance given by an antecrystic population (ca. 610–620 Ma). The less spanned geochronological ages, more homogeneous Nd–Sr–Hf isotopic signatures, and the discrete preservation of an antecrystic zircon population are evidence of early zircon crystallization from a homogeneous source undergoing disequilibrium melting. An even older, ca. 1.9 Ga inherited/xenocrystic zircon population recorded in both the intrusion and the surrounding leucogneisses is also a piece of evidence of zircon preservation in disequilibrium melting situations. Zircon saturation and Ti-in-zircon temperatures strongly suggest thermal disequilibrium between relict zircon and magmas, consistent with the presence of antecrystic and inherited/xenocrystic zircon populations, previously distinguished by isotopic and U&lt;img&gt;Pb criteria. Ti-in-zircon thermometry suggests early crystallization temperatures for zircon precipitation, while biotite geothermometry yields near-&lt;em&gt;solidus&lt;/em&gt;, late crystallization temperatures for the Serra dos Órgãos batholith. REE-in-zircon oxybarometry suggests &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt; around FMQ conditions for the intrusion, contrasting with more oxidized &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt; conditions for the country rocks. The evidence indicates that the studied sensu stricto granites were formed by water-undersaturated melting of crustal protoliths at temperatures up to 840 ","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107973"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143207830","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":"Detrital zircon chronology of the Guryong Group, the eastern part of the Gyeonggi Massif, Korea: Implication for the Late Paleozoic pre-collisional evolution in the Korean Peninsula","authors":"Ji Wan Jeong ,&nbsp;Nobuhiko Nakano ,&nbsp;Tatsuro Adachi ,&nbsp;Kenta Kawaguchi","doi":"10.1016/j.lithos.2025.107972","DOIUrl":"10.1016/j.lithos.2025.107972","url":null,"abstract":"<div><div>The tectonic evolution of the Korean Peninsula during the Middle to Late Paleozoic remains a subject of debate due to sparse evidence. The Guryong Group—a metamorphosed sedimentary formation located in the Odesan area of the Gyeonggi Massif—is reported to have been deposited during the Middle Paleozoic and subsequently underwent Permo–Triassic collision-related metamorphism. Therefore, the Guryong Group is crucial for understanding the Paleozoic tectono-thermal history of the region. In this study, we performed comprehensive zircon U-Pb dating and Lu-Hf isotope analysis coupled with geochemical investigations of the metasedimentary rocks of the Guryong Group and its surrounding rocks of the Gyeonggi Massif. Our aim is to determine the timing of deposition and tectonic settings, thereby elucidating the Paleozoic tectono-thermal evolution of the Korean Peninsula. The detrital zircon age distributions in the metasedimentary rocks from the western Guryong Group include clusters of ca. 1899–1616 Ma (8 %), 998–723 Ma (11 %), 537–419 Ma (10 %), and 418–307 Ma (56 %), with the youngest detrital zircons dating between 344 and 307 Ma. In contrast, calc-silicate rocks from the eastern Guryong Group exhibit different age patterns of ca. 1958–1830 Ma (20 %), 1522–1427 Ma (8 %), 1398–1200 Ma (17 %), 1194–1001 Ma (17 %), and 850–720 Ma (23 %), and a main age peak of ca. 749 Ma. Additionally, three biotite gneisses and one quartzite from the eastern Guryong Group show age clusters of ca. 3361–3187 Ma (7 %), 2778–2500 Ma (19 %), 2494–2414 Ma (24 %), 2382–2200 Ma (24 %), 2186–2002 Ma (15 %), and 1927–1826 Ma (6 %), with no Paleozoic detrital zircons. These results suggest that parts of the Guryong Group were deposited at different times from the western part, similar to paragneisses in the Gyeonggi Massif. The newly identified Carboniferous metasedimentary rocks, with the youngest detrital zircons dated to 344–307 Ma, contain 56 % of detrital zircons aged between 418 and 307 Ma. This suggests that Devonian to Carboniferous magmatic rocks were the major source to form the Carboniferous sedimentary rocks of the Guryong Group. The whole-rock chemical analyses of metasedimentary rocks in the western Guryong Group reveal a consistent pattern characterized by enrichment in light rare-earth elements (REEs) and notable depletion in Nb-Ta. The ε_Hf(t) values of zircon grains dated to the Devonian are negative (ranging from −6.67 to −18.13), suggesting that these Devonian magmatic rocks originated from the reworking of the Precambrian basement of the Gyeonggi Massif. This study supports the hypothesis that extensive arc magmatism occurred in the Odesan area during the Devonian to Carboniferous periods prior to the Permo–Triassic continental collision, possibly representing the easternmost extension of Paleozoic arc magmatism occurring along the southern margin of the North China Craton.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107972"},"PeriodicalIF":2.9,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143321011","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 metasomatism by subducted Indian continental crust: Evidence from post-collisional basaltic ultrapotassic rocks in southern Tibetan plateau","authors":"Miao-Yan Zhang ,&nbsp;Lu-Lu Hao ,&nbsp;Yue Qi ,&nbsp;Qiang Wang ,&nbsp;Andrew C. Kerr ,&nbsp;Lin Ma ,&nbsp;Cheng-Cheng Huang ,&nbsp;Gang-Jian Wei ,&nbsp;Jie Li ,&nbsp;Jin-Long Ma ,&nbsp;Qi-Wei Li ,&nbsp;Zi-Long Wang ,&nbsp;Tong-Yu Huang ,&nbsp;Yu-Chen Yang","doi":"10.1016/j.lithos.2025.107966","DOIUrl":"10.1016/j.lithos.2025.107966","url":null,"abstract":"<div><div>At continental collisional zones, the continental crust is known to subduct, penetrating the deep lithospheric mantle and undergoing partial melting. However, the extent to which these melts can effectively alter, or metasomatize, the overlying mantle remains a contentious issue. This debate is especially pronounced in the Cenozoic Himalayan-southern Tibet collisional orogen. The complexity arises from the fact that previous research has predominantly concentrated on the post-collisional intermediate ultrapotassic rocks. However, these rocks could have originated either from the subducted Indian continental crust through a process of mantle assimilation or from mélange rocks, thereby primarily reflecting crustal recycling rather than mantle metasomatism by subducted continental crust. In this study, we shift our focus to the less-well-studied post-collisional basaltic ultrapotassic rocks (BUPRs) from the Sailipu region in the Lhasa block of southern Tibet. Our aim is to evaluate the characteristics of the orogenic mantle and the dynamics of crust-mantle interactions. In this study we report major and trace elements and Sr-Nd-Pb-Mo-B isotopes for these Miocene post-collisional BUPRs. The rocks are typically characterized by alkaline affinity, arc-like trace element distribution patterns, and enriched Sr-Nd-Pb isotopes, which point to their derivation from an enriched mantle source. Moreover, the Mo<img>B isotope ratios of these BUPRs - δ^98/95Mo ranging from −0.85 ‰ to −0.27 ‰ and δ¹¹B from −20.2 ‰ to −14.4 ‰ - are notably lower than those found in Mid-Ocean Ridge Basalts (MORBs) and arc lavas. Instead, they are similar to the isotopic compositions of basalts associated with continental subduction, as well as intermediate ultrapotassic rocks from western Anatolia and the Lhasa block, and the gneisses and schists of the Himalayas. These similarities strongly suggest the input of subducted Indian continental crust to the mantle source for these rocks. In conclusion, our study supports the metasomatism of the mantle beneath southern Tibet by subducted Indian continental crust. These results show that continental subduction zones, much like their oceanic counterparts, are key regions for mantle metasomatism, and thus expands our understanding of the geological processes at work in these dynamic areas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"498 ","pages":"Article 107966"},"PeriodicalIF":2.9,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143360222","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":"P-T evolution and refined UPb geochronology of the giant eclogite layer of the Cabo Ortegal Complex (NW Iberian Massif)","authors":"I. Novo-Fernández ,&nbsp;R. Albert ,&nbsp;R. Arenas ,&nbsp;J.I. Gil Ibarguchi ,&nbsp;S. Sánchez Martínez ,&nbsp;A. Gerdes ,&nbsp;R. Díez Fernández ,&nbsp;A. Beranoaguirre ,&nbsp;A. Garcia-Casco","doi":"10.1016/j.lithos.2025.107952","DOIUrl":"10.1016/j.lithos.2025.107952","url":null,"abstract":"<div><div>In the Cabo Ortegal Complex (NW Iberian Massif), a 20 km long and 700 m thick layer of eclogites constitutes one of the world's largest outcrops of this type of rocks. It belongs to the Upper Allochthon, a terrane that represents the remnants of a Cambrian peri-Gondwanan fore-arc basin that was involved in the Variscan collision. In this layer, three types of eclogites are differentiated according to their mineralogy and bulk composition: the common, the ferrotitaniferous, and the Al-Mg-rich eclogites. This work studies the three types of eclogites via thermodynamic modelling. The ferric content of the bulk composition during the metamorphic peak is analyzed, the results demonstrating a strong influence on the metamorphic paragenesis in two of the three types. Isochemical equilibrium phase diagrams in the MnNCKFMASTHO system indicate metamorphic peak conditions of c. 23–25 kbar at c. 750–800 °C prior to a decompression up to c. 16–20 kbar. U<img>Pb dating in zircon crystals (LA-ICP-MS) from an eclogite yields an age of c. 390 Ma for the high-P metamorphism. All this indicates deep subduction of the peri-Gondwanan realm at the onset of the Variscan Orogeny during Early Devonian. The results are used to discuss the stacking of units that constitute the Upper Allochthon and envisage the processes that contributed to their exhumation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107952"},"PeriodicalIF":2.9,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143319886","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":"Legacy of mantle fabrics preserved within heavily serpentinized peridotites in Hole BA3A cores of the Oman Drilling Project","authors":"Katsuyoshi Michibayashi ,&nbsp;Yuki Kakihata ,&nbsp;Itsuki Natsume ,&nbsp;Takeo Okuwaki ,&nbsp;Marguerite Godard ,&nbsp;Peter Kelemen ,&nbsp;The Oman Drilling Project Science Team","doi":"10.1016/j.lithos.2025.107970","DOIUrl":"10.1016/j.lithos.2025.107970","url":null,"abstract":"<div><div>Crystallographic preferred orientations (CPO) of olivine within natural peridotites are commonly expressed by pole figures for the [100], [010], and [001] axes, and they can be categorized into six well-known crystal fabric types: A, B, C, D, E, and AG. In this paper, we have studied olivine crystal fabrics preserved within serpentinized peridotites in Hole BA3A cores from the Wadi Tayin mantle section of the Samail ophiolite in the Sultanate of Oman, drilled by the ICDP Oman Drilling Project (OmanDP) as part of the Multi-Borehole Observatory (MBO). Hole BA3A cores mostly consist of serpentinized harzburgites with small proportions of thin serpentinized dunitic and mafic layers. Quarter slabs were obtained from Hole BA3A cores, from parts of the core in which the degree of serpentinization was slightly lower than the range of the average through the whole core (70–96 %). The mineral phases and crystal orientations in each polished thin section were analyzed using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) system. EBSD mapping and data processing were then performed to reveal the original CPO of mantle olivine, based on the orientation of relict grains of olivine in surrounding serpentine that retain the legacy of mantle fabrics. As a result, we found that olivine CPOs in Hole BA3A cores were mostly characterized by A to D type fabrics typical of steeply oriented, late, relatively low temperature mantle shear zones in the Samail ophiolite, as opposed to A to AG type fabrics typical of high-T asthenospheric mantle textures. However, Hole BA3A cores preserve foliations subparallel to the crust-mantle boundary like some of the high temperature fabrics. This implies that the olivine fabric transition could have occurred during continued deformation at progressively lower temperature until mantle flow ceased within the lithospheric mantle.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"496 ","pages":"Article 107970"},"PeriodicalIF":2.9,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143320469","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}