M. Trieloff , E.V. Korochantseva , A.I. Buikin , J. Hopp , A.V. Korochantsev
{"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 , E.V. Korochantseva , A.I. Buikin , J. Hopp , A.V. Korochantsev","doi":"10.1016/j.chemer.2025.126318","DOIUrl":"10.1016/j.chemer.2025.126318","url":null,"abstract":"<div><div>We performed high-resolution <sup>40</sup>Ar/<sup>39</sup>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 <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 <sup>36</sup>Ar but also diffusive gas loss, most likely by surface thermal effects as solar and/or impact heating.</div><div>The surficial regolith breccias Dhofar 025, 1442, NWA 6888, SaU 449 contain lunar trapped argon with <sup>40</sup>Ar/<sup>36</sup>Ar ratios varying from 6 to 15, while the deep-derived breccia Dhofar 730 contains argon with (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> 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 (<sup>40</sup>Ar/<sup>36</sup>Ar)<sub>trapped</sub> 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.</div><div>Our new <sup>40</sup>Ar/<sup>39</sup>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, 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}
Zhihui Wang , Fan Yang , Feifan Xu , Leon Bagas , Cun Zhang , Zengsheng Li , Weidong Ren
{"title":"Biotite geochemical fingerprints deciphering magma evolution and compositional diversity of the concentric Zhongchuan Batholith, West Qinling, China","authors":"Zhihui Wang , Fan Yang , Feifan Xu , Leon Bagas , Cun Zhang , Zengsheng Li , 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}
Yulin Wang , Jinbao Yang , Xijun Liu , Hongxia Yu , Zhenglin Li , Tengpeng Li , Zhenzhen Xu , Yiting Yuan
{"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 , Jinbao Yang , Xijun Liu , Hongxia Yu , Zhenglin Li , Tengpeng Li , Zhenzhen Xu , 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<sub>Hf</sub> (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 <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.7059 to 0.7067) and ε<sub>Nd</sub> (t) values (−4.0 to −2.9), together with relatively high ε<sub>Hf</sub> (t) values (−5.6 to 1.4), suggesting binary mixing of melts from psammitic and basaltic sources. The Cenozoic mafic rocks display varied <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.7048 and 0.7096) and positive ε<sub>Nd</sub> (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}
Mohamed Yacine Laghouag , Moulley Charaf Chabou , Gaston Godard , Riccardo Avanzinelli , Martina Casalini , Rabah Laouar , Carlos J. Garrido
{"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 , Moulley Charaf Chabou , Gaston Godard , Riccardo Avanzinelli , Martina Casalini , Rabah Laouar , Carlos J. Garrido","doi":"10.1016/j.chemer.2025.126313","DOIUrl":"10.1016/j.chemer.2025.126313","url":null,"abstract":"<div><div>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<sub>2</sub>O-rich, with K<sub>2</sub>O/Na<sub>2</sub>O > 2, high Mg# (Mg/(Mg + Fe<sup>2+</sup>) = 0.70–0.72), and high Ni (∼173 μg.g<sup>−1</sup> [ppm]) and Cr contents (∼392 μg.g<sup>−1</sup>). 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<sub>2</sub>O and higher Na<sub>2</sub>O and Al<sub>2</sub>O<sub>3</sub> 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 <sup>87</sup>Sr/<sup>86</sup>Sr values range from 0.706101 to 0.709500, and <sup>143</sup>Nd/<sup>144</sup>Nd from 0.512246 to 0.512438, while the lead isotope ratios vary between 18.538 and 18.571 for <sup>206</sup>Pb/<sup>204</sup>Pb, 15.649 to 15.657 for <sup>207</sup>Pb/<sup>204</sup>Pb, and 39.806 to 39.998 for <sup>208</sup>Pb/<sup>204</sup>Pb. Ultrapotassic rocks exhibit higher <sup>87</sup>Sr/<sup>86</sup>Sr, <sup>206</sup>Pb/<sup>204</sup>Pb, <sup>208</sup>Pb/<sup>204</sup>Pb and lower <sup>143</sup>Nd/<sup>144</sup>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}
Anna Neubeck , Piotr Szymczak , Vyllinniskii Cameron , Daniel Buczko , Magnus Ivarsson
{"title":"Mixed fluid processes in FeMn dendrite formation and associated carbon and nickel isotope fractionation","authors":"Anna Neubeck , Piotr Szymczak , Vyllinniskii Cameron , Daniel Buczko , Magnus Ivarsson","doi":"10.1016/j.chemer.2025.126303","DOIUrl":"10.1016/j.chemer.2025.126303","url":null,"abstract":"<div><div>Dendritic iron- and/or manganese-rich microstructures, often referred to as “microstromatolites,” are commonly observed in carbonate veins in the deep subsurface. However, the mechanisms responsible for their formation, particularly the role of microbial processes, remain incompletely understood. One hypothesis suggests that Fe- and Mn-enriched fluids, sourced from submarine hydrothermal vents and circulating through mafic or ultramafic rocks, lead to the precipitation of manganese dendrites within open fractures. Microbial activity has been proposed as a contributing factor, particularly due to its ability to catalyze Mn<sup>2+</sup> oxidation to Mn<sup>4+</sup> at rates significantly faster than abiotic processes under ambient conditions. Such microbial mediation often results in the formation of poorly crystalline Mn oxide phases, which are commonly associated with biologically mediated oxidation. These disordered Mn oxides, frequently observed in natural settings, suggest a microbial contribution to mineral precipitation, particularly in environments where redox gradients and fluid-rock interactions are prominent. Because manganese oxides are an important sink for Ni in marine systems, stable Ni isotope analyses may offer valuable insights into their formation. Biological activity in laboratory systems is known to fractionate Ni isotopes, producing negative δ<sup>60</sup>Ni values, while abiotic interactions with Mn oxides can result in a range of isotopic signatures. In this study, we show that manganese-rich dendrites likely formed through the interplay between organic matter, oxidizing fluids and viscous serpentine muds, resulting in the fractionation of both carbon and nickel isotopes. The moderately negative δ<sup>13</sup>C and δ<sup>60</sup>Ni values, together with the presence of organic matter, suggest a mixed formation pathway involving both abiotic mineral precipitation and biologically mediated processes. One plausible mechanism involves the nucleation of Mn oxides on nanoparticulate “seeds,” which could include both abiotic particles, organic matter, microbial cells and their metabolic byproducts. Understanding the formation of Fe<img>Mn dendrites is key to interpreting the biogeochemical cycling of essential elements like iron, manganese, and nickel. Due to its redox flexibility, Mn forms highly reactive oxides that effectively scavenge trace metals such as Ni, Co, Fe, and Cu, facilitating their removal from seawater and incorporation into marine minerals. Our findings underscore the complexity of Fe<img>Mn oxide formation and point to the combined influence of abiotic fluid dynamics and microbial processes. This improves our ability to interpret geochemical signatures in both modern and ancient environments and enhances the utility of stable isotope systems in reconstructing past ocean conditions and elemental cycling.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126303"},"PeriodicalIF":2.6,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189512","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}
De-Chao Li , Xi-Jun Liu , Xiao Liu , Gang Chen , Qi Song , Hao Tian , Zheng-Lin Li , Peng-De Liu , Rong-Guo Hu
{"title":"Cambrian mid-ocean ridge basalt-like mafic rocks and associated boninites in the Dachadaban ophiolite from the North Qilian Block, northwest China: Petrogenesis and implications for back-arc extension","authors":"De-Chao Li , Xi-Jun Liu , Xiao Liu , Gang Chen , Qi Song , Hao Tian , Zheng-Lin Li , Peng-De Liu , Rong-Guo Hu","doi":"10.1016/j.chemer.2025.126301","DOIUrl":"10.1016/j.chemer.2025.126301","url":null,"abstract":"<div><div>The early Paleozoic Qilian Orogen is ideal for investigating ancient plate tectonic processes and can be divided into the north, middle, and south Qilian blocks. There is a consensus that North Qilian oceanic lithosphere was subducted northward beneath the Alxa Block. However, the details of this subduction in the North Qilian Ocean (e.g., whether an intra-oceanic back-arc basin was developed) are poorly constrained. In this study, we undertook petrological observations, zircon U<img>Pb geochronological and Hf isotopic analyses, and whole–rock and mineral major and trace element, and Sr<img>Nd isotopic analyses of the Cambrian (513–506 Ma) lower series mid-ocean ridge basalt (MORB)-like mafic rocks and upper series (503–490 Ma) boninites in the Dachadaban ophiolite in the North Qilian Block, northwest China. The lower series mafic rocks can be further divided into two types. Type 1 mafic rocks have uniform SiO<sub>2</sub> contents of 45.1–49.8 wt% and slightly enriched light rare earth element (REE) and relatively flat heavy REE patterns, similar to enriched-type MORBs. The type 2 mafic rocks and boninites have a wider range of SiO<sub>2</sub> contents of 49.3–59.2 and 48.1–56.6 wt%, respectively, and are depleted in light REEs and have relatively flat heavy REE patterns, similar to normal-type MORBs. In primitive-mantle-normalized element diagrams, the type 1 and 2 mafic rocks exhibit no or negligible Nb<img>Ta depletion, while the boninites exhibit obvious Nb<img>Ta depletion. The lower series type 1 and 2 mafic rocks have depleted whole-rock Nd (ε<sub>Nd</sub>[t] = +2.6 to +6.5) and zircon Hf (ε<sub>Hf</sub>[t] = +2.8 to +14.8) isotopic compositions, while the upper series boninites have relatively enriched Nd<img>Hf (ε<sub>Nd</sub>[t] = +2.8 to +4.7; ε<sub>Hf</sub>[t] = +3.4 to +13.6) isotopic compositions. We suggest that the lower series type 1 and 2 mafic rocks were formed by partial melting of garnet lherzolite (>70 km depth; type 1) and spinel harzburgite (<70 km; type 2) mantle sources, respectively. The upper series boninites were derived from a refractory harzburgitic mantle source that had been metasomatized by subducted-sediment-derived melts and minor slab-derived fluids. Based on these results and regional geological data, we suggest that the North Qilian Ocean experienced three stages of expansion, in the Precambrian–early Cambrian (550–520 Ma), middle–late Cambrian (513–497 Ma), and Middle–Late Ordovician (458–449 Ma). In addition, intra-oceanic subduction beneath the North Qilian Ocean and subsequent back-arc extension occurred during the middle–late Cambrian (513–490 Ma).</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126301"},"PeriodicalIF":2.6,"publicationDate":"2025-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144154683","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}
Jianjun Liu , Huan Li , Ruilin Wang , Yue Hou , Shaban Godang
{"title":"Formation process of a newly explored ion-adsorption type REE deposit in Pingtian, Guangdong, South China: A detailed profile analysis","authors":"Jianjun Liu , Huan Li , Ruilin Wang , Yue Hou , Shaban Godang","doi":"10.1016/j.chemer.2025.126302","DOIUrl":"10.1016/j.chemer.2025.126302","url":null,"abstract":"<div><div>Recently, ion-adsorption-type rare earth element (REE) deposits have been explored in Nanxiong Basin (South China), with an estimated total reserve of >100 million tons. The formation of ion-adsorption-type deposits is closely linked to the weathered crust of their parent granitic rocks. To better understand how the weathered crust influences the formation of ion-adsorption type REE deposits, this study presents detailed research on the relationship between the characteristics of the weathered crust and parent rock in Pingtian Town, Nanxiong Basin, Guangdong Province, through a detailed profile analysis. The U<img>Pb dating of zircon and apatite indicates that the parent rock (biotite monzogranite) was formed at ca. 220 Ma, which provides favorable metallogenic conditions for the formation of the weathered crust. Minerals such as monazite, zircon, apatite, and plagioclase play critical roles in the formation of the weathered crust. Monazite and plagioclase are the main controlling minerals for REE enrichment in the weathered crust. Monazite, influenced by apatite, determines the REE distribution pattern in the crust, with a particular emphasis on light rare earth elements (LREE). Zircon, being resistant to weathering, leads to the preferential enrichment of LREE in the weathered crust and limits the accumulation of heavy rare earth elements (HREE). Plagioclase, through weathering into kaolinite, provides an adsorption medium for ionized REE. In addition, trace element analysis of zircon and apatite, as well as geochemical studies on the parent rock, indicate that the parent rock belongs to a moderately differentiated granite. The degree of granite differentiation impacts REE enrichment in the weathered crust. The higher the degree of differentiation, the more ionized REE elements and adsorption media are provided, facilitating the formation of ion-adsorption type REE deposits. This highlights the importance of detailed profile geochemical analysis in revealing the genesis of ion-adsorption-type REE deposits.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126302"},"PeriodicalIF":2.6,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144154684","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}
Yanshen Liu , Zhongjie Xu , Hong Zhu , Rihui Cheng
{"title":"Sedimentary records of tectonic background transition in the eastern Guangdong Basin in the Late Early Jurassic of the South China continental margin","authors":"Yanshen Liu , Zhongjie Xu , Hong Zhu , Rihui Cheng","doi":"10.1016/j.chemer.2025.126297","DOIUrl":"10.1016/j.chemer.2025.126297","url":null,"abstract":"<div><div>The southeastern margin of the South China Block preserves sedimentary records of tectonic evolution controlled by Paleo-Pacific subduction. This study integrates sedimentological and detrital zircon U-Pb geochronological analyses of the Lower Jurassic Qiaoyuan Formation in the eastern Guangdong Basin. One Late Early Jurassic sample exhibits detrital zircon U-Pb ages ranging from 2317 to 187 Ma, with dominant age groups at 260–240 Ma and 1900–1800 Ma. In contrast, a terminal Early Jurassic sample shows age spectra of 2827–180 Ma dominated by a 200–180 Ma group, reflecting a transition from multi-peak to unimodal age distributions. Provenance analysis indicates that late Early Jurassic sediments (Member 1) were primarily sourced from the Jiangnan Orogen, Yunkai Terrane, and Hainan Island, while terminal Early Jurassic deposits (Member 3) originated predominantly from the Nanling Tectonic Belt. Comparative analysis of detrital zircon age characteristics in Mesozoic strata across the South China Block, incorporating similarity assessments, visualization methods, and crustal thickness estimations, demonstrates that the southeastern margin completed the transition from a compressional to extensional tectonic setting by approximately 180 Ma. This shift is chronologically constrained by provenance reorganization, basin structural transformation, and progressive crustal thinning, documenting the dynamic interplay between Paleo-Pacific subduction and intracontinental deformation.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126297"},"PeriodicalIF":2.6,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143931566","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}
Heng Liu , Lei Liu , Shuhab D. Khan , Yongjun Gao , Lijuan Xu , Tianyang Hu , Inkyeong Moon
{"title":"Late Neoarchean multi-stage granitoid rocks in the Dengfeng terrane, North China Craton: Petrogenesis and implications for geodynamic processes","authors":"Heng Liu , Lei Liu , Shuhab D. Khan , Yongjun Gao , Lijuan Xu , Tianyang Hu , Inkyeong Moon","doi":"10.1016/j.chemer.2025.126300","DOIUrl":"10.1016/j.chemer.2025.126300","url":null,"abstract":"<div><div>During the late Neoarchean era, the rise of K-rich granitoid rocks marked a significant geological event indicative of the maturation and stabilization of continental crust. These granitoids, emerging after tonalite-trondhjemite-granodiorite (TTG) magmatism, stirred debates over the interrelations and geodynamic implications. In this study, diverse granitoid rocks were identified in the Dengfeng terrane of the North China Craton (NCC), dating as approximately 2.63–2.50 Ga. The 2.5 Ga meta-dioritic rocks exhibit elevated MgO (2.2–7.7 wt%) and Mg<sup>#</sup> (45–69). Geochemical simulation reveals sanukitoid-like pattern, featuring highly fractionated REE compositions and depleted zircon Hf isotopes (Ɛ<sub>Hf</sub>(t) values range from +3.9 to +6.5). Apatite Nd isotopes of ε<sub>Nd</sub>(t) values ranging from −0.1 to 4.69. Meta-dioritic rocks were interpreted to be formed by partial melting of a depleted mantle source influenced by subducted slab-derived fluids. The TTG gneiss (2.63–2.52 Ga) exhibit mildly fractionated REE patterns, weakly positive Eu anomalies, lack of magmatic fractionation evidence, and high (La/Yb)<sub>N</sub> (6.94–114.9) and Sr/Y (28.6–294) ratios, indicating their formation derived from partial melting of pre-existing low-K mafic crust. The K-rich granitoids (2.56 Ga) are characterized by high K<sub>2</sub>O/Na<sub>2</sub>O ratios (0.67–1.89), low MgO content and Mg<sup>#</sup> (< 1.2 wt% and < 55, respectively). A chain of evidence including geochemical modeling, constant aluminum saturation index (ASI) values of 1.00–1.35, and zircon ε<sub>Hf</sub>(t) values ranging from +8.2 to +11.2 suggest their derivation through partial melting of tonalitic rocks. Further analysis suggests that the source for K-rich granitoids are enriched by subducted slab melts or metasedimentary rocks at various crustal depths. In terms of petrogenesis, late Neoarchean granitoid magmatism in Dengfeng terrane likely relates to subduction and accretionary orogeny. Archean active continental margins are vital for early crustal maturation and granitoid diversification during subduction and collision.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126300"},"PeriodicalIF":2.6,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144068553","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}