Chemie Der Erde-Geochemistry最新文献

{"title":"Geochemistry and geochronology of high-K metaluminous (I-type) Cambrian Guwahati granites from Shillong Plateau, Northeast India: Insight into petrogenesis involving peritectic assemblage entrainment (PAE) model","authors":"Dimple Doley ,&nbsp;Gautam Sarma ,&nbsp;Balen Bhagabaty ,&nbsp;Santosh Kumar ,&nbsp;Pritom Borah","doi":"10.1016/j.chemer.2025.126325","DOIUrl":"10.1016/j.chemer.2025.126325","url":null,"abstract":"<div><div>The peritectic assemblage entrainment (PAE) model effectively explains variations in Fe, Mg, Ti, and Ca, as well as positive correlations of Ti and Ca with increased maficity [molar (Fe + Mg)] in mafic I-type granitic melts. This study analyzes the whole-rock elemental geochemistry and zircon U-Pb-Hf isotopes of newly identified Ordovician to Cambrian mafic-enriched I-type granites from the Guwahati region of the Shillong Plateau, northeastern India. The key geochemical features include positive correlations between Ti and maficity, along with V, Ca, and P, while molar A/CNK and maficity demonstrate a negative correlation. These patterns suggest the granites formed from the incongruent melting of hydrous ferromagnesian minerals in the crust, incorporating a peritectic assemblage of plagioclase, Fe<img>Ti oxides, and clinopyroxene. The U<img>Pb zircon ages of 523 ± 4.94–473 ± 3.5 Ma demonstrate the emplacement age of the Guwahati granites. Zircon Hf isotopic analysis indicates a two-stage model age (T_DM2) of 2095–2036 Ma with negative εHf(t) values between −10.66 and − 8.47. This suggests a significant contribution from Paleoproterozoic continental crust in the formation of the 473 ± 3.5 Ma Ordovician granitic magma. In comparison, the Cambrian granites, dated around 523 to 502 Ma with weighted mean ²⁰⁶Pb/²³⁸U age of 513 ± 36 Ma, exhibit a slightly higher T_DM2 of 2098–2092 Ma and show exclusively negative εHf(t) values, ranging from −9.95 to −9.63. These findings indicate a consistent involvement of ancient crustal sources in both granite types. Consequently, it can be concluded that the Ordovician and Cambrian Guwahati granites share notable similarities in their model ages and εHf(t) values, reflecting common geological processes underlying their formation. Overall, the Guwahati granites (523–473 Ma) are linked to Pan-African tectonic activity associated with Ordovician-Cambrian arc magmatism and the tectono-thermal events following the collision of India, Australia, and Antarctica during the assembly of the Eastern Gondwana Landmasses. This process involved the melting of Paleoproterozoic basement crustal rocks.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126325"},"PeriodicalIF":2.9,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144906834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 granitic pegmatite from the Lianyunshan complex, South China: Insights from apatite and muscovite chemistry","authors":"Yunfei Zhang ,&nbsp;Lei Liu ,&nbsp;Heng Liu ,&nbsp;Ming Huang ,&nbsp;Guofeng Xu ,&nbsp;Hongyu Liu ,&nbsp;Shuangshuang Wang ,&nbsp;Zhilin Wen ,&nbsp;Baoliang Huang","doi":"10.1016/j.chemer.2025.126323","DOIUrl":"10.1016/j.chemer.2025.126323","url":null,"abstract":"<div><div>The Jiangnan Orogenic Belt (JOB) in the Northeastern Hunan Province (NHP), the one of the most significant regions for rare metal mineral resources in South China Block (SCB). It is renowned for abundant Li-Be-Nb-Ta granitic pegmatite deposits, However, the magmatic process of the Lianyunshan pegmatites remain poorly understood. This study focuses on various lithologies of the Lianyunshan complex pluton and pegmatite through zircon LA-ICP-MS U<img>Pb dating, whole-rock major and trace element geochemistry, and in situ trace element analyses of muscovite and apatite. These experiments offer unique insights into the mechanisms driving lithium-enriched pegmatite formation in this region. We elucidated the genesis of pegmatite and the relationship between Li-rich pegmatite and granite in Lianyunshan region. Zircon U<img>Pb dating yielded the concordia ages of 147.4 ± 0.69 Ma for biotite monzonitic granite, 145.5 ± 0.73 Ma and 144.0 ± 1.3 Ma for two-mica monzonitic granite, respectively. The whole rock geochemical analyses reveal that granites and pegmatites exhibit obvious characteristic of fractional crystallization. In situ trace element analysis for muscovite reveal Rb, Cs, Ta concentrations increase progressively but the ration of Nb/Ta, Li/Rb, K/Cs, and K/Rb decrease in sequence of BMG → TMG → pegmatite→spodumene pegmatite in Lianyunshan region. These trends indicate varying degrees of fractional crystallization, with pegmatites and spodumene pegmatites representing more evolved magmatic differentiation products. Fractional crystallization simulation using muscovite compositions supports a rayleigh fractionation process, wherein the initial granitic melt progressively evolved to form TMG, pegmatites, and ultimately spodumene pegmatites. Apatite can be divided into magmatic and hydrothermal types, both identified as fluorapatite. The rare earth element (REE) distribution patterns of apatite are consistent with whole-rock trends. However, apatite from spodumene pegmatites and some other pegmatites exhibit anomalous REE patterns. From BMG → TMG → pegmatites to spodumene pegmatites, Sr content (23–617 ppm) in apatite decreases while REE content increases (1001–3159 ppm). Apatite in TMG, and pegmatites share similar trace element characteristics, consistent with the fractionation trends observed in muscovite modeling. Apatite from pegmatites with relative lower SiO₂ content (65–70 wt%) show reduced REE concentrations and significantly elevated Eu/Eu* (0.01–0.7) and La/Yb (0.1–26) ratios. This suggests that pegmatite formation involved plagioclase decomposition and separation crystallization of HREE-enriched minerals.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126323"},"PeriodicalIF":2.9,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144890509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 vanadium (V) enrichment in Azıtepe (Alaşehir-Manisa) meta-gabbroic rocks in Menderes massif (Western Turkiye)","authors":"Naside Merve Sutcu ,&nbsp;Zeynep Doner ,&nbsp;Mustafa Kumral ,&nbsp;Ali Tugcan Unluer ,&nbsp;Emin Ciftci","doi":"10.1016/j.chemer.2025.126321","DOIUrl":"10.1016/j.chemer.2025.126321","url":null,"abstract":"<div><div>The Azıtepe meta-gabbroic intrusions, located in Alaşehir, Manisa (western Turkiye), represent part of the Late Neoproterozoic gabbroic bodies that emplaced along the northern margin of Gondwana within the central Menderes Massif, and host Fe-Ti-(V) oxide mineralization. These gabbroic intrusions generally originated from a tholeiitic mantle source, and have minimal evidence of crustal contamination, as indicated by high Nb/U (30–166.7) and Nb/Th (9.37–58.3) ratios, along with low Pb concentrations. However, the mechanisms governing vanadium (V) enrichment in such Fe–Ti–(V) systems, particularly the role of metamorphic overprinting in V redistribution, remain poorly understood. This study aims to determine the processes responsible for V enrichment in Fe–Ti–(V) oxide minerals within the Azıtepe meta-gabbroic intrusion by evaluating V partitioning and mineral hosts in relation to magmatic and metamorphic controls. The ore mineral paragenesis includes Ti-magnetite, magnetite, ilmenite, rutile, hematite, goethite, pyrite, chalcopyrite, and pyrrhotite. In this study, V mineralization is observed in oxide minerals such as magnetite, Ti-magnetite which are influenced by both magmatic crystallization and subsequent metamorphic alteration. The Azıtepe meta-gabbroic rocks generally show enrichments in Fe₂O₃_(t) (10.2 to 18.5 wt%) and TiO₂ (2.04 to 6.50 wt%). The V concentrations of the studied rocks range from 355 to 473 ppm in meta-gabbros while varying between 217 and 628 ppm in amphibolites. EPMA (Electron probe microanalysis) data indicate that V is preferentially incorporated into magnetite rather than ilmenite in meta-gabbros and garnet-free amphibolites, likely due to its compatible ionic radius and charge relative to Fe³⁺, a behavior that supports its preferential partitioning into magnetite under moderate to high fO₂ conditions. The formation conditions of magnetite–ilmenite pairs in meta-gabbro and amphibolite samples from the study area were evaluated using EPMA-derived equilibrium data processed through the MagMin_PT software, and its application was extended to metamorphic samples in this study. The studied samples' log <em>f</em>O2 values (−13.7 to −28.1) may be pointed out moderately to strongly reducing conditions with textural context guiding interpretation. In garnet-bearing amphibolites, however, variations in metamorphic conditions (P, T, <em>f</em>O₂) and/or hydrothermal alteration may have mobilized previously magnetite-hosted V, facilitating its redistribution into silicate minerals such as garnet, chlorite, and clinozoisite. These results suggest that V enrichment in the Azıtepe meta-gabbroic rocks is primarily controlled by magmatic processes under moderately oxidizing conditions, with secondary redistribution during metamorphism, highlighting the potential of such intrusions as significant sources of Fe–Ti–V mineralization in post-collisional tectonic settings.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126321"},"PeriodicalIF":2.9,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144827512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 rift related marginal basalts from the Asal-Ghoubbet rift area, Republic of Djibouti: Implications for magma genesis and mantle source characteristics","authors":"Awaleh Djama Iltireh ,&nbsp;Yusuf Kağan Kadıoğlu ,&nbsp;Yavuz Özdemir ,&nbsp;Mohamed Osman Awaleh ,&nbsp;Jalludin Mohamed","doi":"10.1016/j.chemer.2025.126322","DOIUrl":"10.1016/j.chemer.2025.126322","url":null,"abstract":"<div><div>This research investigates the Marginal basalts in the Asal-Ghoubbet rift, a poorly understood geological feature, with the aim of clarifying magma sources and identifying the mantle reservoir responsible for forming basaltic rocks in the region. The study involved analysing major geochemical elements, rare earth elements and radiogenic isotopes of Sr, Nd and Pb from basalt samples collected in the Marginal basalts of the rift. Additionally, the mineral composition of plagioclase, olivine, pyroxene and Fe<img>Ti oxides was examined using electron probe microanalysis (EPMA) on polished thin sections. Geochemical results indicate a tholeiitic composition for the Marginal basalts, with evidence of fractional crystallization driven initially by clinopyroxene and olivine, followed by plagioclase crystallization. Thermobarometric and MELTS modelling estimated magma storage depths ranging from the Moho to the upper crust. The basalt is slightly enriched in light rare earth elements (LREEs) and depleted in Heavy Rare Earth Elements (HREEs), similar to the characteristics of enriched Mid-Ocean Ridge Basalt (<em>E</em>-MORB) and Ocean Island Basalt (OIB). Isotopic data of Sr and Nd reveal sources that vary between the high μ mantle source (HIMU) and the dominant prevalent mantle source (PREMA). Furthermore, Pb isotopic signatures suggest an influence from an enriched mantle (EM) component, plotting between the EMI and EMII mantle reservoirs fields. Forward-melting modelling and isotopic evidence suggest that the Afar mantle plume is a significant contributor to the magma source of Marginal basalts in the Asal-Ghoubbet rift. Overall, the study enhances understanding of the magma plumbing system in this area, elucidating the process governing magma chamber evolution and the nature of the mantle reservoirs that generated these basaltic rocks.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126322"},"PeriodicalIF":2.9,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metamorphism and aqueous alteration of the unusual CY carbonaceous chondrite Northwest Africa 4757","authors":"Marina A. Ivanova ,&nbsp;Maria G. Krzhizhanovskaya ,&nbsp;Sergey N. Britvin","doi":"10.1016/j.chemer.2025.126319","DOIUrl":"10.1016/j.chemer.2025.126319","url":null,"abstract":"<div><div>The first CY chondrite from the Northwest Africa region was studied (NWA 4757). It is a small (5 g) fine-grained monomict microbreccia consisting of abundant matrix (∼95 vol%) and rare pseudomorphic chondrules (up to 200 μm). The meteorite has main characteristics of CY chondrites. The oxygen isotopic composition of NWA 4757 is ¹⁶O-poor (δ¹⁸O = 23.83, δ¹⁷O = 12.84, Δ¹⁷O = 0.45 to δ¹⁸O = 26.96, δ¹⁷O = 14.50, Δ¹⁷O = 0.48 ± 0.03) which is the heaviest among other CY chondrites. NWA 4757 contains abundant sulfides (∼20 vol%) and its bulk chemical composition is enriched in sulfur compared to CM chondrites like most other CY chondrites except for Dhofar 225 and Dhofar 735.</div><div>NWA 4747 was affected by very intensive aqueous alteration corresponding to petrologic type 1.0 before it was affected by thermal metamorphism. Only a few grains of unaltered olivine (Fa10) survived in NWA 4757. In contrast to other CYs, troilite from NWA 4757 are Mn-rich. The matrix is divided into light and dark types in texture and composition. The light matrix is Ca-rich, and Fe-poor compared to the dark matrix. The dehydrated phyllosilicates had serpentine composition with a low saponite content like CY2s. The presence of high-Ni metal and sulfides, chromite and ilmenite and absence of magnetite indicate that under equilibrium conditions, the redox state of the alteration system in the NWA 4757 parent body did not exceed the fugacity of the iron-wustite buffer.</div><div>After aqueous alteration NWA 4757 experienced intensive thermal metamorphism resulting in a low H₂O (1.9 wt%) compared to usual CI and CM chondrites. The Fourier Transform Infrared (FT-IR) spectroscopy of the matrices of NWA 4757 and Mighei (CM2) showed that the NWA 4757 matrix is dominated by Fe-rich fine-grained olivine. According to a classification system for thermally metamorphosed hydrated carbonaceous chondrites based on X-ray Powder Diffraction (XRD) data, NWA 4757 is characterized by heating stage IV (&gt;750 °C) like CY2s. Since calcite (and even dolomite) survived metamorphism, it should indicate that the peak temperature was not higher than 800 °C. Thus, NWA 4757 is the first CY chondrite of thermal stage IV (CY2) which had properties of extremely altered CM1 chondrite before metamorphism and suggestively should be CY2-m1.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126319"},"PeriodicalIF":2.9,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144767027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal and irradiation history of lunar meteorites by the 40Ar/39Ar technique: Dhofar 025, 309, 730, 733, 1442, Northwest Africa 6888, and Sayh al Uhaymir 449","authors":"M. Trieloff ,&nbsp;E.V. Korochantseva ,&nbsp;A.I. Buikin ,&nbsp;J. Hopp ,&nbsp;A.V. Korochantsev","doi":"10.1016/j.chemer.2025.126318","DOIUrl":"10.1016/j.chemer.2025.126318","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We performed high-resolution &lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar dating of a suite of lunar meteorites from hot deserts: Dhofar 025, 309, 730, 733, 1442, Northwest Africa 6888, and Sayh al Uhaymir 449. The identification of terrestrial and lunar trapped argon components via isochrons allowed us to identify in situ radiogenic argon and to obtain proper chronological information. The last total reset ages of all studied samples are in the range of 3.1 to 4.2 Ga, coeval with the intense cratering period on the Moon and mare volcanism. Only Northwest Africa 6888 was totally reset &lt;2.5 Ga ago. The most deeply buried breccia Dhofar 733 has the oldest age of 4.23 ± 0.04 Ga within this series of meteorites. Dhofar 733, 1442, and NWA 6888 were furthermore affected by recent impact events ≤1 Ga. All meteorites were irradiated by galactic cosmic rays on the surface of the Moon for several up to hundreds of Ma. A simple irradiation history is revealed for only one meteorite Dhofar 733 delivered to Earth within ~0.5 Ma. The comparison of exposure ages, solar argon abundances and partial loss of cosmogenic and radiogenic argon of lunar breccias indicates that long surface residence enhances accumulation of solar wind implanted &lt;sup&gt;36&lt;/sup&gt;Ar but also diffusive gas loss, most likely by surface thermal effects as solar and/or impact heating.&lt;/div&gt;&lt;div&gt;The surficial regolith breccias Dhofar 025, 1442, NWA 6888, SaU 449 contain lunar trapped argon with &lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;36&lt;/sup&gt;Ar ratios varying from 6 to 15, while the deep-derived breccia Dhofar 730 contains argon with (&lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;36&lt;/sup&gt;Ar)&lt;sub&gt;trapped&lt;/sub&gt; ratio of 81. This could indicate that the composition of trapped argon in lunar meteorites may depend on rock layering depth. We suggest that the final capture of gases happens during sintering and agglutination along grain boundaries caused by thermal processes accompanying shock-induced compaction. Dhofar 1442 contains two distinct lunar trapped argon components with (&lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;36&lt;/sup&gt;Ar)&lt;sub&gt;trapped&lt;/sub&gt; ratios of 14.58 ± 0.28 and 5.5 ± 0.7 indicating that lunar meteorites may contain more than one extraterrestrial trapped component incorporated during different thermal events.&lt;/div&gt;&lt;div&gt;Our new &lt;sup&gt;40&lt;/sup&gt;Ar/&lt;sup&gt;39&lt;/sup&gt;Ar ages of lunar meteorites significantly increase the number of high- resolution plateau age spectra, providing more compelling evidence of geochronologically meaningful pre 3.9 Ga ages. The different age distribution when compared to Apollo samples that were frequently dominated by Imbrium ejecta may be related to the fact that lunar meteorites provide a more random and thus complete sampling of the lunar surface, encompassing ejecta of older large basins, thereby favoring scenarios of more continuous or episodic pre 3.9 Ga bombardments. A possible scenario leading to episodic small body disturbances and bombardments involves close stellar encounters within the massive stellar cluster in which the","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126318"},"PeriodicalIF":2.6,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144685852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metamorphic evolution of south Indian granulites: New insights from in-situ U-Pb dating and Nd-Hf isotope fingerprinting of zircon, titanite, monazite, and apatite","authors":"J. Amal Dev,&nbsp;J.K. Tomson","doi":"10.1016/j.chemer.2025.126317","DOIUrl":"10.1016/j.chemer.2025.126317","url":null,"abstract":"<div><div>The Precambrian Southern Granulite Terrane (SGT) of south India is well known for the preservation of high to ultrahigh-temperature granulite facies metamorphic rocks, with their formation linked to the assembly of the East Gondwana supercontinent. Although the timing and duration of this Himalayan-scale collisional orogeny is well characterized, the peak to post-peak evolutionary history of these granulitic rocks is poorly understood. This study attempts to characterize the peak to post-peak metamorphic evolutionary history of south Indian granulites using in-situ accessory mineral geochronology and isotopic fingerprinting of a metapyroxenite sample collected from the central part of SGT. U<img>Pb dating of zircon and monazite from the sample constrains the timing of peak metamorphism at 560–550 Ma, while the timing of fluid activity and cooling was characterized using titanite (557 ± 2 Ma) and apatite (410 ± 3 Ma) dating. U<img>Pb ages recovered from available accessory phases, together with temperature estimates from trace element thermometry and closure temperature estimates, suggest variable and slow cooling rates for the studied granulite. On the other hand, Hf<img>Nd isotopic fingerprinting of zircon and titanite points to the involvement of slab-derived materials during peak metamorphism, providing new evidence for melt/fluid-assisted metamorphism in the area.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126317"},"PeriodicalIF":2.6,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144662248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biotite geochemical fingerprints deciphering magma evolution and compositional diversity of the concentric Zhongchuan Batholith, West Qinling, China","authors":"Zhihui Wang ,&nbsp;Fan Yang ,&nbsp;Feifan Xu ,&nbsp;Leon Bagas ,&nbsp;Cun Zhang ,&nbsp;Zengsheng Li ,&nbsp;Weidong Ren","doi":"10.1016/j.chemer.2025.126315","DOIUrl":"10.1016/j.chemer.2025.126315","url":null,"abstract":"<div><div>Compositional diversity is a common feature of plutons and a frequent topic in earth science publications. The Zhongchuan Batholith, a composite body in the West Qinling Orogen of central China, provides an important example for understanding compositional variations and the genesis of different granitic phases. The batholith consists of three annular rings (medium-coarse grained porphyritic biotite granite, medium grained phenocryst-bearing biotite granite, and medium-fine grained biotite granite) from the outer to inner rings. Biotite is the most common ferromagnesian mineral in diverse granitic phases of the batholith and can serve as key indicators for the geochemical characteristics of the granites and their compositional variations. In this study, we present major and trace element geochemistry of biotite to constrain the physico-chemical conditions and petrogenesis of the various granitic phases in the batholith. Microstructural and alteration studies of biotite from the different granitic phases reveal features consistent with magmatic biotite. The major elements of the biotites indicate crystallisation temperatures of approximately 778 °C, 755 °C, and 726 °C for the outer, intermediate, and inner rings, respectively. These temperatures correspond to pressures of ~210 MPa (7.5 km), 390 MPa (14 km), and 440 MPa (16 km). The observed changes in crystallisation temperatures and pressures are consistent with the evolution of multi-stage and differentiated magma. The oxygen fugacity of biotite varies from −16 to −12, indicating a high magma oxygen fugacity. Major and trace elements of biotite further attest that the batholith is classified as I-type granite, derived from crust-mantle mixing, with a greater contribution of mantle-derived materials in the outer ring. The compositional diversity of the batholith is attributed to high-degree magma mixing without fractional crystallisation during magma evolution.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126315"},"PeriodicalIF":2.6,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144588008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 to Early Cretaceous mafic to felsic magmatism reveals the coupled processes of crustal growth and thinning in Southeast China","authors":"Yulin Wang ,&nbsp;Jinbao Yang ,&nbsp;Xijun Liu ,&nbsp;Hongxia Yu ,&nbsp;Zhenglin Li ,&nbsp;Tengpeng Li ,&nbsp;Zhenzhen Xu ,&nbsp;Yiting Yuan","doi":"10.1016/j.chemer.2025.126314","DOIUrl":"10.1016/j.chemer.2025.126314","url":null,"abstract":"<div><div>The study investigates the petrogenesis, deep magmatic processes, and tectono-magmatic evolution of Late Jurassic to Early Cretaceous mafic-felsic igneous rocks from the Guangdong-Fujian border area in Southeast China, using detailed field, petrographic observation, zircon U-Pb geochronology, Hf isotopes geochemistry, bulk-rock major-trace elements and Sr-Nd isotope geochemistry. Zircon U-Pb dating reveals three distinct magmatic activities. The Late Jurassic (ca. 152 Ma) granitoids, identified as fractionated both I-type and A-type granites, exhibit low ε_Hf (t) (−8.3 to −1.9) values and enriched Sr-Nd isotopes that are consistent with melting of psammitic sources. The Late Cretaceous complex (ca. 105 Ma) with initial ⁸⁷Sr/⁸⁶Sr ratios (0.7059 to 0.7067) and ε_Nd (t) values (−4.0 to −2.9), together with relatively high ε_Hf (t) values (−5.6 to 1.4), suggesting binary mixing of melts from psammitic and basaltic sources. The Cenozoic mafic rocks display varied ⁸⁷Sr/⁸⁶Sr ratios (0.7048 and 0.7096) and positive ε_Nd (t) values (4.0 and 1.0), indicating an asthenospheric mantle source. Fractional crystallization played a key role in the magmatic evolution of the rocks. The Late Jurassic magmatism may indicate that Southeast China was primarily under a setting of lithospheric extension since 152 Ma, driven by slab rollback. The Late Cretaceous magmatism reflects large-scale lithospheric extension and thinning, triggered by a change in the subduction direction of the Palaeo-Pacific slab from oblique to parallel with the continental margin. Our data suggest that the rollback of the subducted Palaeo-Pacific slab in the Guangdong-Fujian border region created a back-arc extensional setting, leading to substantial crustal thinning. The extension-induced melting of the middle to lower crust, combined with mantle-derived basaltic magma underplating, were primary drivers of granitoid magmatism in Southeast China during the Late Jurassic to Early Cretaceous. In the extensional environment, crustal growth and thinning were interconnected, forming a unified geological process.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126314"},"PeriodicalIF":2.6,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geology, mineralogy, geochemistry and Sr-Nd-Pb isotopic composition of the ultrapotassic rocks and associated shoshonites of Kef Hahouner (Northeastern Algeria): New data and geodynamic implications","authors":"Mohamed Yacine Laghouag ,&nbsp;Moulley Charaf Chabou ,&nbsp;Gaston Godard ,&nbsp;Riccardo Avanzinelli ,&nbsp;Martina Casalini ,&nbsp;Rabah Laouar ,&nbsp;Carlos J. Garrido","doi":"10.1016/j.chemer.2025.126313","DOIUrl":"10.1016/j.chemer.2025.126313","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The association of ultrapotassic rocks and shoshonites is common in the Alpine-Mediterranean region, with the exception of the Maghrebide Chain of Northern Africa, where only two small outcrops of ultrapotassic rocks have been documented. This study reports detailed field observations and new data on the petrology, mineral chemistry, whole-rock geochemistry and Sr-Nd-Pb isotopic compositions of the volcanic ultrapotassic rocks and shoshonites of the Kef Hahouner region (Northeastern Algeria). The results indicate that these rocks are composed of an association of ultrapotassic rocks that outcrop at the base of a lava flow sequence, and shoshonites that constitute shallow volcanic intrusions and the upper part of the abovementioned lava flow pile. The ultrapotassic rocks are K&lt;sub&gt;2&lt;/sub&gt;O-rich, with K&lt;sub&gt;2&lt;/sub&gt;O/Na&lt;sub&gt;2&lt;/sub&gt;O &gt; 2, high Mg# (Mg/(Mg + Fe&lt;sup&gt;2+&lt;/sup&gt;) = 0.70–0.72), and high Ni (∼173 μg.g&lt;sup&gt;−1&lt;/sup&gt; [ppm]) and Cr contents (∼392 μg.g&lt;sup&gt;−1&lt;/sup&gt;). They are strongly enriched in LREE and extremely enriched in Th and LILE (Rb, Ba, Sr), with respect to High Field Strenght Elements (Ta, Nb, and Ti), showing an orogenic-type pattern. Shoshonites display lower K&lt;sub&gt;2&lt;/sub&gt;O and higher Na&lt;sub&gt;2&lt;/sub&gt;O and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; contents compared to the ultrapotassic facies. However, these rocks have similar trace and rare earth element (REE) patterns to those observed in the ultrapotassic rocks, albeit with slightly lower LILE and MREE contents. The initial &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr values range from 0.706101 to 0.709500, and &lt;sup&gt;143&lt;/sup&gt;Nd/&lt;sup&gt;144&lt;/sup&gt;Nd from 0.512246 to 0.512438, while the lead isotope ratios vary between 18.538 and 18.571 for &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb, 15.649 to 15.657 for &lt;sup&gt;207&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb, and 39.806 to 39.998 for &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb. Ultrapotassic rocks exhibit higher &lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr, &lt;sup&gt;206&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb, &lt;sup&gt;208&lt;/sup&gt;Pb/&lt;sup&gt;204&lt;/sup&gt;Pb and lower &lt;sup&gt;143&lt;/sup&gt;Nd/&lt;sup&gt;144&lt;/sup&gt;Nd than shoshonites. The two volcanic suites most likely result from the increasing partial melting of the metasomatised mantle source in which the ambient mantle component dilutes the alkaline-rich component derived from the partial melting of the sole vein, explaining the transition from ultrapotassic to shoshonite magma. Compared to the North-African Cenozoic magmatic belt, the Kef Hahouner ultrapotassic and shoshonitic lithologies are unique and have no equivalent among the entire belt. We, therefore, propose a geodynamic model in which the subduction of the African continental margin beneath the Kabylian domain and its break-off during the Tortonian times caused the strong metasomatic episode in the source region, resulting in the formation and emplacement of the ultrapotassic rocks and shoshonites in the region. The observed Kef Hahouner–Djebel Debar fault may represent the surface expression of the tear fault related to the southern ed","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126313"},"PeriodicalIF":2.6,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144338443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}