Lithos最新文献

{"title":"Be–Nb–Ta mineralization in granites: An example from the Nyalam area in the Himalayan belt, southern Tibet","authors":"Li-E Gao ,&nbsp;Lingsen Zeng ,&nbsp;Linghao Zhao ,&nbsp;Lilong Yan ,&nbsp;Yinglong Di ,&nbsp;Guangxu Li ,&nbsp;Yaying Wang ,&nbsp;Rui Wang ,&nbsp;Li Wang","doi":"10.1016/j.lithos.2025.108224","DOIUrl":"10.1016/j.lithos.2025.108224","url":null,"abstract":"<div><div>In the Himalayan orogenic belt, numerous Cenozoic granites are enriched in rare metals, and three giant rare metal deposits have been discovered. However, the mechanisms responsible for rare metal enrichment and mineralization remain poorly understood. In the Nyalam area, a suite of granites intruding the Southern Tibet Detachment System have high rare metal contents (100–284 ppm Be, 24–117 ppm Nb, 15–102 ppm Ta). Zircon U<img>Pb analyses revealed that these granites formed ca. 17.3 Ma. Compared with barren granites in nearby areas, the rare metal-rich granites are characterized by (1) higher Na₂O and MnO contents and lower TiO₂ and MgO contents; (2) higher Rb and Rb/Sr values but lower Sr and Ba contents; (3) lower REE contents, nearly flat REE patterns and pronounced negative Eu anomalies; (4) higher Be, Nb, Ta, Rb, Cs, Ga, and Tl contents but lower B contents; and (5) lower ⁸⁷Sr/⁸⁶Sr(t) and ε_Nd(t) values. Significantly, when Nb/Ta &lt; 5 and Zr/Hf &lt; 20, melt structures undergo changes characterized by increasing M/F ratios (network formers/modifiers). These geochemical compositional variations between the two types of granites imply the combined effects of fractional crystallization and hydrothermal alteration but ultimately derived from melt structural changes. Depolymerization reduces melt viscosity and increases Nb<img>Ta solubility, thereby enhancing the efficiency of fractional crystallization and facilitating rare metal enrichment.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108224"},"PeriodicalIF":2.5,"publicationDate":"2025-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of the Late Cretaceous–Paleogene I- and A-type granite association from the Gyeongsang Basin, southeastern Korean Peninsula","authors":"Hyun-Ok Choi ,&nbsp;Sung Hi Choi","doi":"10.1016/j.lithos.2025.108220","DOIUrl":"10.1016/j.lithos.2025.108220","url":null,"abstract":"<div><div>Rare highly fractionated A-type granites are spatially associated with Late Cretaceous–Paleogene I-type granitoids in southeastern Korea. We present new zircon U-Pb ages and Hf isotopic compositions and whole-rock geochemical and Sr–Nd–Pb isotopic data for Late Cretaceous–Paleogene granitoids that crop out in the Gyeongsang Basin, SE Korea, to constrain their origin and the genetic relationship between the I- and A-type granites. The samples can be divided into three groups: (1) I-type low-silica granitoids (SiO₂ = 61–65 wt%), (2) I-type high-silica granites (SiO₂ = 71–78 wt%), and (3) A-type alkali feldspar granites (SiO₂ = 77–82 wt%). SHRIMP zircon U-Pb dating yields ages of 77–52 Ma for the I-type granites and 55–53 Ma for the A-type granites. Both I- and A-type granitoids have juvenile whole-rock Sr–Nd–Pb and zircon Hf isotopic compositions that are distinct from those of the Precambrian basement in the Yeongnam Massif. The I-type granitoids were most likely produced by adding &lt;15 % of ancient-crust-derived melts to the magma derived from juvenile Paleozoic crust. In contrast to the I-type granitoids, the A-type granites are characterized by high SiO₂ and heavy rare earth element contents and large negative Ba, Sr and Eu anomalies. We propose that the A-type granites were produced by partial melting of dehydrated charnockitic rocks in the middle–lower crust. Both the I- and A-type granitoids were emplaced during crustal extension induced by rollback of the subducting paleo-Pacific plate. Starting during the Early Cretaceous, a retreating arc system led to increased extension, lithospheric thinning, and underplating of mantle-derived magmas. This caused the heat-flux melting of both juvenile and ancient basement rocks, leaving dehydrated charnockitic material above the I-type source. During the late stages of the Late Cretaceous magmatism, the charnockitized crustal rocks melted at high temperatures, leading to the formation of the A-type granites.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108220"},"PeriodicalIF":2.5,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144890538","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":"Fe-Cu separation in skarn deposits: Insights from magmatic and hydrothermal titanite","authors":"Fang-Yue Wang ,&nbsp;Xian Liang ,&nbsp;Long Zhang ,&nbsp;Tao-Fa Zhou ,&nbsp;Yu Fan ,&nbsp;Xian-Zheng Guo ,&nbsp;Yong-Hong Guo ,&nbsp;Jun-Wu Zhang","doi":"10.1016/j.lithos.2025.108218","DOIUrl":"10.1016/j.lithos.2025.108218","url":null,"abstract":"<div><div>Iron (Fe) and copper (Cu) mineralization often coexist in skarn deposits, but they can also occur as independent deposits. Skarn Fe and Cu mineralization in the Yueshan ore field (Eastern China) is associated with the Cretaceous diorite intrusions. Notably, while these deposits exhibit comparable iron reserves, their copper endowments vary greatly. However, the main factors controlling the Fe-Cu separation remain poorly understood. This study investigates U-Pb geochronology and chemistry of magmatic and hydrothermal titanite from the Anqing Cu-Fe (Fe: 39 Mt, @45.19%; Cu: 0.5 Mt, @1.29%) and Zhuchong Fe-(Cu) (Fe: 51 Mt, @50.10%; Cu: 0.05 Mt, @1.15%) deposits in the ore field. The U-Pb ages of the magmatic titanite from the Zhuchong and Anqing deposits were 139.6 ± 2.2 Ma (1σ, n = 30, MSWD = 0.7) and 139.6 ± 0.6 Ma (1σ, n = 35, MSWD = 1.4), respectively. The hydrothermal titanite U-Pb ages were 137.0 ± 0.5 Ma (1σ, n = 29, MSWD = 2.7) for Zhuchong and 137.9 ± 1.1 Ma (1σ, n = 26, MSWD = 2.1) for Anqing, showing consistent ages across both deposits. The in<em>-situ</em> Nd isotope (ε_Nd(t)) of titanite from Zhuchong Fe deposit decreased from -7.6 in magmatic to -8.0 in hydrothermal stages, suggesting some contamination of evaporite-rich wall rocks during the hydrothermal process. Nevertheless, the mean titanite ε_Nd(t) from the Anqing deposit remains constant at -7.0 from magmatic to hydrothermal stages and was higher than that from the Zhuchong deposit, implying less crustal material involvement during the emplacement of the Anqing pluton. The magmatic titanite from the Zhuchong deposit has higher levels of Sn, Ga, Fe, lower δEu, Sr/Y, and La/Yb, and similar F and Cu contents compared to those from the Anqing deposit. This suggests that the Zhuchong magma had a higher oxygen fugacity, was relatively water-poor, and exhibited a similar Cu ore-forming potential to that of the skarn Cu deposit. Compared to the Anqing hydrothermal titanite, the Zhuchong hydrothermal titanite had significantly higher F, high field strength elements (HFSE), and extremely high Nb/Ta (∼115) but relatively lower Cu content and La/Yb. The high F and low Cu in Zhuchong hydrothermal titanite suggest that the hydrothermal fluids in Zhuchong may have experienced extensive fluid exsolution and migration of CuCl^- components, ultimately resulting in the formation of shallow vein-type copper ore bodies surrounding the Yueshan pluton. Our findings suggest that Fe-Cu fractionation in skarn deposits could be attributed to fluid exsolution during magma emplacement. Titanite proves to be a valuable tool for elucidating magmatic-hydrothermal processes.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108218"},"PeriodicalIF":2.5,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866189","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":"Generation of andesitic–dacitic magmas by open-system progressive melting of the middle crust in Rishiri Volcano, northern Japan","authors":"Hanai Kawara ,&nbsp;Miku Matsumoto ,&nbsp;Takeshi Kuritani","doi":"10.1016/j.lithos.2025.108221","DOIUrl":"10.1016/j.lithos.2025.108221","url":null,"abstract":"<div><div>Understanding the genesis of andesite and dacite magmas in subduction zones is important because their compositions are similar to the average composition of the continental crust and they have higher potential for violent eruptions than mafic magmas. In this study, we conducted a petrological and geochemical analysis of Rishiri-Wankonosawa (Rs-Wn) pumices that erupted explosively from Rishiri Volcano, located at the rear of the Kuril Arc, to understand the origin of the voluminous andesitic–dacitic magmas. The main volume of pumices has relatively homogeneous whole-rock compositions (66.0 to 67.7 wt% SiO₂); however, those ejected in the later stage of the eruption are less differentiated and show wide compositional variations (59.0 to 64.5 wt% SiO₂). The Sr, Nd, and Pb isotopic ratios of the pumices vary systematically with the SiO₂ content. We demonstrate that the tightly curved whole-rock compositional trends of the Rs-Wn pumices in geochemical variation diagrams cannot have been produced by assimilation and fractional crystallization of mafic magmas; rather, the compositional variations were established by open-system melting of the middle crust, that is, progressive partial melting of the crustal source into which there was a continuous influx of mafic melts. Partial melting of the middle crust was caused by heating due to the emplacement of hot mafic melts, and some of the mafic melts were supplied to the melting region. The partial melts then accumulated to form a zoned magma reservoir at a depth of ∼400 MPa, from which heterogeneous magmas ascended and erupted explosively. At Rishiri, andesite–dacite suites with different geochemical features have occurred at least three times since 50 ka. Through a comparison of the generation processes for these suites, it is suggested that the origin of the Rs-Wn magmas resulted essentially from the emplacement of hot mafic magmas in the thermally mature middle crust.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108221"},"PeriodicalIF":2.5,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841075","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":"Spatiotemporal distribution of Mesozoic A-type granites and numerical modeling reveal episodic and progressive lithospheric extension in SE China","authors":"Sheng-Di Zhou ,&nbsp;Xiao-Lei Wang ,&nbsp;De-Hong Du ,&nbsp;Benjun Wu ,&nbsp;Xisheng Xu ,&nbsp;Zeng-Qian Hou","doi":"10.1016/j.lithos.2025.108214","DOIUrl":"10.1016/j.lithos.2025.108214","url":null,"abstract":"<div><div>The Late Mesozoic tectonic evolution to the west side of Pacific Ocean in SE China is an enigmatic issue and important to compare with the magmatism and mineralization to the east side in North America. However, it is hotly debated on the distribution of a large scale of felsic magmatism and associated W<img>Sn polymetallic mineralization in the wide (&gt;1000 km) inland area of SE China. To avoid the complexity in shaping the high-silica granites in SE China, here we focus on A-type granites that are commonly free of debate in petrogenesis and lack comprehensive research. We present the spatiotemporal distribution of Mesozoic A-type granites in SE China based on a geological map-based compilation of available geochemical and geochronological data. The refined spatiotemporal distribution of the Jurassic-Cretaceous A-type granites in SE China can be further illustrated by numerical modeling of geodynamics, indicating an episodic and progressive lithospheric extension by a long-term subduction and episodic rollback of the Paleo-Pacific Plate. This study builds the strong correlation of granite formation and deep geodynamic processes in the wide inland area to the west of the Paleo-Pacific Plate.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108214"},"PeriodicalIF":2.5,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866187","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":"Provenance of the Late Triassic-Early Jurassic Gano bauxite deposit in Alborz Orogen, Northern Iran: A multi-proxy geochronological approach by detrital zircon and rutile","authors":"Jintao Zhou ,&nbsp;Maryam Khosravi ,&nbsp;Wenchao Yu ,&nbsp;Guangyan Zhou ,&nbsp;Hao Deng","doi":"10.1016/j.lithos.2025.108219","DOIUrl":"10.1016/j.lithos.2025.108219","url":null,"abstract":"<div><div>A significant Eo-Cimmerian unconformity developed during the Late Triassic-Early Jurassic in the Alborz Orogen, Iran, resulting in the formation of bauxite on the surface of carbonate rocks. Provenance analysis of such bauxite can help understand the Tethyan tectonic evolution, but strong geochemical weathering eliminates most geochemical information for source tracing. The multiproxy geochronology method is emerging for bauxite provenance studies and remains unexplored in Iran. Here, we supplemented a multi-proxy approach (detrital zircon and rutile) with zircon trace elements, Hf isotopes, and machine learning methods to constrain the provenance of Gano bauxite in the Alborz Orogen. New data present a dominant zircon age cluster (250–200 Ma), indicating magmatic provenance from the Alborz Orogen. The Semi-supervised Random Forest algorithm indicates a transition from S-type to A-type granites as detrital zircon sources. This shift correlates with the initial collision of the Central Iran and Eurasia blocks, likely occurring during the Late Triassic Carnian stage (≥ ∼231 Ma). Two rutile age groups (1100–500 Ma and 500–400 Ma) indicate local recycled basement contributions. These two types of provenance were deposited in a foreland basin and underwent bauxitization in the Late Triassic-Early Jurassic. Zircon and rutile U<img>Pb ages in Gano bauxite show a young, near-unimodal zircon age spectrum with several older rutile age fractions, reflecting provenance fertility imbalance in the active continental margin. The application of detrital zircon alone for bauxite provenance analysis in active continental margins is constrained. Employing diverse detrital accessory minerals could better clarify the complex origins.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108219"},"PeriodicalIF":2.5,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144826506","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":"Errors of the garnet-orthopyroxene-olivine oxybarometers","authors":"Chun-Ming Wu,&nbsp;Hui C.G. Zhang","doi":"10.1016/j.lithos.2025.108212","DOIUrl":"10.1016/j.lithos.2025.108212","url":null,"abstract":"<div><div>The errors in rebuilding the experimental oxygen fugacity (expressed as its common logarithm, log<em>f</em>O₂) of the Stagno et al. (2013, <em>Nature</em>, 493: 84–88) garnet-orthopyroxene-olivine oxybarometer are within ±1.2 log units and this oxybarometer is relatively the most precise one among the six different versions, although experimental data are not sufficient. If we adopt ferric iron contents of the related phases estimated by charge balance method, the computed log<em>f</em>O₂ values were erroneously increased to &gt; + 0.5 log units for all the oxybarometers compared to those determined by direct experimental measuring methods of ferric iron contents. Input pressure-temperature (<em>P-T</em>) errors of +3 kbar/+70 °C or − 3 kbar/−70 °C may propagate to log<em>f</em>O₂ errors of +0.48 ∼ +1.60 log units or − 0.52 ∼ −1.31 log units, respectively, for the oxybarometers. Application of the garnet-orthopyroxene-olivine oxybarometers does need direct measurement of ferric contents of the phases, such as Mössbauer spectroscopy, synchrotron Fe-edge X-ray absorption near edge structure spectroscopy (XANES) or flank method.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108212"},"PeriodicalIF":2.5,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144829088","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":"Paleo-Asian Ocean subduction-related multiple mantle metasomatism: Constraints from in-situ SrMg isotopes of mantle xenoliths in the Xing-Meng orogenic belt","authors":"Xudao Liu ,&nbsp;Kaizhang Yu ,&nbsp;Yongsheng Liu ,&nbsp;Zhicheng Liu ,&nbsp;Chunfei Chen ,&nbsp;Jie Lin ,&nbsp;Ao Yang ,&nbsp;Xi Zhu ,&nbsp;Zhaochu Hu","doi":"10.1016/j.lithos.2025.108217","DOIUrl":"10.1016/j.lithos.2025.108217","url":null,"abstract":"<div><div>Subduction-induced metasomatism profoundly modifies the chemical composition and physical state of lithospheric mantle. However, overprint of multiple mantle metasomatism impedes the identification of metasomatic agents and understanding of mantle dynamics. Here, in-situ major and trace elements, and Sr<img>Mg isotopes of mantle xenoliths from the Abaga alkali basalts are conducted to decipher multiple mantle metasomatism and evaluate its impact on lithospheric mantle transformation. Based on mineral assemblages and chemistry, these mantle xenoliths classify into four groups. The clinopyroxenes in Group I peridotite exhibit light rare earth element (LREE) depletion, high Ti/Eu (3468–6386), low ⁸⁷Sr/⁸⁶Sr (0.7023–0.7029) and normal mantle-like δ²⁶Mg (−0.11 ‰ to −0.26 ‰), indicating a depleted mantle source. The clinopyroxenes in Group I pyroxenite also exhibit similar REE patterns, Ti/Eu (3792–5208) and δ²⁶Mg (−0.19 ‰ to −0.26 ‰) to those in Group I peridotite. In contrast, the clinopyroxenes in Group II peridotite exhibit LREE enrichment, high field strength elements depletion (HFSE, such as Nb, Ta, and Ti) and low Ti/Eu (2324–3301), signifying that the mantle underwent carbonate metasomatism. Most of them display high ⁸⁷Sr/⁸⁶Sr (0.7032–0.7036) and low δ²⁶Mg (−0.32 ‰ to −0.42 ‰), suggesting that the carbonate melts originated from the subducted carbonate sediments. While some clinopyroxenes in Group II peridotite show relatively higher U/Nb (0.12–0.39) and higher δ²⁶Mg (−0.09 ‰ to −0.27 ‰), reflecting an early-stage fluid metasomatism. Most clinopyroxenes in Group II pyroxenite present LREE enrichment, HFSE depletion, high Ti/Eu (4435–6177), and high Dy/Yb (2.04–3.70), signatures consistent with silicate melt metasomatism. Their Cr₂O₃ and TiO₂ contents further correspond to those generated by peridotite-silicate melt reactions, implying that those pyroxenites resulted from the reaction between eclogite-derived silicate melts and peridotite. Paradoxically, those clinopyroxenes exhibit high ⁸⁷Sr/⁸⁶Sr (0.7036–0.7045) and low δ²⁶Mg (−0.31 ‰ to −0.46 ‰), suggesting that the metasomatic agent retained subducted carbonate signatures. We suggest light Mg isotopes originate from “ghost carbonate”, where silicate melts preserve recycled carbonate’s isotopic fingerprint after carbonate component loss. Considering the tectonic setting and geophysical evidence, Paleo-Asian Ocean subduction-induced fluid/melt-peridotite reactions result in the transformation of the lithospheric mantle beneath the eastern Xing-Meng orogenic belt.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108217"},"PeriodicalIF":2.5,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866188","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":"Iranian Neo-Tethyan magmas as a significant CO2 source during the Middle Eocene Climatic Optimum","authors":"Lea Ostorero ,&nbsp;Rosario Esposito ,&nbsp;Pierre Bouilhol ,&nbsp;Paolo Ballato ,&nbsp;Veleda Astarte Müller ,&nbsp;Maria Luce Frezzotti ,&nbsp;Pietro Sternai","doi":"10.1016/j.lithos.2025.108216","DOIUrl":"10.1016/j.lithos.2025.108216","url":null,"abstract":"<div><div>CO₂ emissions from magmatic arcs can affect the atmosphere composition, thereby driving long-term global climate changes. Early Cenozoic climate trends are generally associated with changes in global silicate weathering related to Neo-Tethyan geodynamics, but the likely climatic effects of changes in degassing from Neo-Tethyan magmatic arcs have been poorly quantified. Here, we characterize the petrography and provide the first measures of the volatile content (CO₂, H₂O, F, Cl, and S) of pre-eruptive melts based on glassy, bubble-bearing and reheated melt inclusions within plagioclase and clinopyroxene crystals in Early Cenozoic trachyandesites from the Alborz and Tabriz regions (Iran). CO₂ concentrations in these melt inclusions reach up to 6733 ppm, thus providing a minimum estimate of the total amount of CO₂ degassed from Iranian magmas during the middle-late Eocene of 1.01 × 10¹⁹ (± 4.04 × 10¹⁷) g CO₂, with a total C flux released of 0.306 (± 0.012) Mt. C/yr, which is within the carbon imbalance predictions estimated based on other proxies. Our measures validate earlier hypotheses that magmatic CO₂ degassing from the targeted igneous provinces contributed to the Middle Eocene Climatic Optimum. Further measurements of the volatiles content of Neo-Tethyan magmas are thus critical to assess the drivers of Early Cenozoic climate trends and understand the global volatile cycling over geological timescales.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108216"},"PeriodicalIF":2.5,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144826328","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":"Spatial distribution and chemical characteristics of bastnäsite and monazite provide insights into the Bayan Obo deposit, the world's largest rare earth element mineralization","authors":"Jin Wang ,&nbsp;Lin Li ,&nbsp;M. Santosh ,&nbsp;Guo-Ying Yan ,&nbsp;Jun-Feng Shen ,&nbsp;Mao-Wen Yuan ,&nbsp;Masroor Alam ,&nbsp;Zhao-Jing Wang ,&nbsp;Sheng-Rong Li","doi":"10.1016/j.lithos.2025.108215","DOIUrl":"10.1016/j.lithos.2025.108215","url":null,"abstract":"<div><div>Bastnäsite and monazite are the main carriers of thorium (Th) and rare earth elements (REEs) in Bayan Obo, the world's largest REE deposit. Understanding the spatial distribution of their chemical compositions is crucial for deciphering mineralization processes and improving resource utilization. Meanwhile, the precise mechanisms by which Th enters the lattice of these minerals remain poorly understood. Petrographic studies reveal that bastnäsite and monazite predominantly occur as fine-grained (&lt;50 μm) aggregates, classified into three distinct paragenetic types: associated only with dolomite (Bsn/Mnz-I), associated with fluorite (Bsn/Mnz-II), and associated with alkali silicate minerals (Bsn/Mnz-III). Th⁴⁺ enters the lattice of all types of bastnäsite through Th⁴⁺+(Ca, Ba)²⁺ → 2ΣREE³⁺. In contrast, monazite exhibits distinct Th⁴⁺ incorporation mechanisms depending on its type. Specifically, Th⁴⁺ is incorporated in Mnz-I exclusively through cheralite substitution (Th⁴⁺ + Ca²⁺ → 2REE³⁺), while in Mnz-II and Mnz-III, it involves cheralite (Th⁴⁺+Ca²⁺ → 2REE³⁺) and huttonite (Th⁴⁺+Si⁴⁺ → REE³⁺+P⁵⁺) substitutions. Our data also show that the chemical composition of bastnäsite and monazite within the Main Orebody is highly heterogeneous, exhibiting a tendency towards enrichment in La₂O₃ and Pr₂O₃ and depletion in ThO₂ and Nd₂O₃ from the deep eastern part to the shallow western part of the Main Orebody. Based on the metallogenic temperature, mineralized materials, and REE migration characteristics, it is inferred that the ore-forming hydrothermal fluids originate from the eastern depths of the Main Orebody and subsequently migrate upwards towards the western domain.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"514 ","pages":"Article 108215"},"PeriodicalIF":2.5,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866190","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}