Search Results (809)

We present ID-TIMS U-Pb single zircon ages and major and trace element data for granitoid plutons from the Imorona–Itsindro and Kiangara suites in central Madagascar, in order to constrain the timing of igneous emplacement and investigate the petrogenesis and tectonic settings of these Neoproterozoic plutons. A U-Pb crystallization age of 779 ± 7 Ma was determined from an Imorona–Itsindro intrusion, while a Kiangara intrusion yields 777 ± 4 Ma, older than previously reported. The identical U-Pb ages suggest contemporaneous emplacement of some Kiangara and Imorona–Itsindro intrusions. Elemental data indicate that the two suites display trace element patterns similar to those of arc-type magmas. Some distinct geochemical features are apparent between these two suites. The Imorona–Itsindro sample displays I-type affinity with low REE abundances, whereas the Kiangara samples exhibit A-type signatures with higher REE contents. We suggest that the elemental differences between A-type and I-type reflect the contamination of mantle-derived magma by lower and upper crustal rocks, respectively. We suggest that the coeval A-type and I-type granitoids in central Madagascar were generated in a subduction system associated with slab rollback and back-arc extension like extension. The compositional diversity in these Neoproterozoic plutons reflects the evolution of the tectonic regime within a single geodynamic environment, similar to that proposed for plutons in other Precambrian and younger terranes. Full article

The origin of intermediate rocks within large igneous provinces (LIPs), which often exhibit a bimodal compositional distribution, remains poorly understood. To investigate the petrogenesis of such intermediate magmas within the Early Cretaceous Tethyan Himalaya igneous province in Tibet, we present a comprehensive study of zircon U–Pb geochronology, whole-rock geochemistry, and Nd isotopes for the tonalites from the Zhegucuo area. Zircon U–Pb dating yields a crystallization age of 130.81 ± 0.55 Ma. The rocks exhibit low Mg# and compatible element contents, indicating significant fractional crystallization of ferromagnesian minerals, plagioclase, and accessory minerals. Their homogeneous, near-chondritic ε_Nd(t) values (−0.34 to +0.01) preclude significant crustal contamination. Based on field relationships, geochemistry, and isotopic evidence, we conclude that the Zhegucuo tonalites were generated by extensive fractional crystallization of basaltic magmas. FC3MS and FCKANTMS systematics reveal a peridotitic component in the mantle source of the Zhegucuo mafic rocks. The exceptionally high values of these proxies of the Zhegucuo tonalites are attributed to extensive fractional crystallization of evolved magmas. Full article

The early crustal evolution of microcontinental fragments in the Central Asian Orogenic Belt remains poorly constrained. Among these fragments, the Erguna Block records extensive Neoproterozoic magmatism that provides key constraints on its tectono-magmatic development in relation to the Rodinia supercontinent cycle. To furthering constrain the Neoproterozoic magmatic evolution of the Erguna Block, an integrated investigation combining petrography, zircon U-Pb and Lu-Hf isotopic analyses, whole-rock geochemistry, and Sr-Nd isotope data was carried out on the newly recognized Fengshuishan intrusion in northern Alongshan. Zircon U-Pb ages of 810 ± 5 Ma and 807 ± 4 Ma were obtained from granitic samples, while the dioritic sample gave an age of 773 ± 2 Ma, representing a major Neoproterozoic magmatic episode. The 810–807 Ma granites show positive zircon εHf(t) (+0.09 to +12.1) and whole-rock εNd(t) (+0.50 to +1.77), suggesting derivation mainly from partial melting of Mesoproterozoic juvenile crust with minor contribution from mantle-derived materials. In contrast, ca. 773 Ma gabbroic diorite exhibits εHf(t) values of −1.23 to +4.3 and an εNd(t) value of +1.33, implying a contribution from an enriched mantle source. These Fengshuishan igneous rocks show A-type geochemical signatures, enriched in Rb, Th, and Pb but depleted in Ba, Sr, and Eu. Integrating these data with regional geological evidence, we infer that the Fengshuishan intrusion formed in an intraplate extensional regime, recording an important phase of crust–mantle interaction during the Neoproterozoic. These results expand the record of Neoproterozoic igneous rocks in the Erguna Block and offer new constraints on its role within the Rodinia supercontinent. Full article

Hainan Island has experienced a superposition of multiple phases of tectonic movements and magmatic activities, leading to numerous controversies regarding the genesis, spatiotemporal distribution, and tectonic setting of its Yanshanian granites. Accurately determining the characteristics of magmatic rocks during this period is crucial for clarifying the regional tectonic evolution. This study focuses on Diaoluoshan granite in the southeastern part of Hainan Island. Through petrological, mineralogical, zircon U-Pb geochronological, and geochemical analyses, it aims to identify the genetic type, formation age, and magma source properties of this pluton, thereby revealing the Late Yanshanian tectonic setting of Hainan Island. The results show that the zircon U-Pb dating of Diaoluoshan granite yields an age of 102.5 ± 2.8Ma, indicating its formation in the late Early Cretaceous. This granite is a high-K calc-alkaline I-type granite, with silica (SiO₂) content ranging from 63.9% to 77.3%. The pluton exhibits significant negative anomalies of Ta, Nb, P, and Ti, as well as relatively obvious positive anomalies of Rb, Th, U, and K. The biotite in the granite has a magnesium oxide (MgO) content ranging from 12.84% to 13.13%, showing characteristics of crust–mantle material mixing. The magma of this pluton was derived from the partial melting of the lower continental crust mixed with the uprising and underplating mantle mafic magmas, driven by the subduction of the Paleo-Pacific Plate and its slab rollback. This study confirms that during the Late Yanshanian, Hainan Island was in an extensional rift environment driven by the subduction of the Paleo-Pacific Plate and its slab rollback, but without a well-developed volcanic front. It provides key geological evidence for the study of Yanshanian tectono-magmatic evolution in South China. Full article

The Khanbogd-Erdene region in southern Mongolia is a globally important copper–polymetallic metallogenic province, hosting large to super-large deposits, such as Oyu Tolgoi and Tsagaan Suvarga. The area experiences frequent tectonic–magmatic activity, particularly Late Paleozoic subduction-related magmatism, which controls the occurrence of large-scale copper–polymetallic mineralization. This study focuses on the Late Paleozoic granitic intrusive rocks in the Khanbogd-Erdene region of southern Mongolia. Using LA-ICP-MS and SHRIMP dating techniques, precise zircon U–Pb ages were obtained for 10 samples. A total of 209 zircon grains from these 10 intrusive rocks were analyzed, with most cathodoluminescence (CL) images of zircon grains showing distinct oscillatory zoning. Th/U ratios ranging from 0.11 to 2.92 indicate they are magmatic. The younger group of granitic rocks yielded ages between 260.2 ± 1.2 Ma and 286.6 ± 0.9 Ma, indicating an Early Permian geological age. The other seven samples yielded older ages between 315.9 ± 1.8 Ma and 340.9 ± 0.9 Ma, indicating a Carboniferous geological age. These large-scale Carboniferous to Early Permian intrusive rocks in the Khanbogd-Erdene region are products of tectonic–magmatic activity during specific stages of crustal evolution. The findings provide reliable chronological data for regional tectonic–magmatic activity and offer new evidence for constraining the timing of the Variscan orogeny in southern Mongolia. Full article

The development of the continental crust during the Archean era is one of the key issues of geoscience. Determining the geological nature of the Archean terrane of the southern Liaoning Province (SLP) is fundamental to decipher the tectonic framework of the eastern North China Craton (NCC) from the late Neoarchean to Paleoproterozoic. The Archean assemblage of the SLP is composed of metabasalt, deformed diorite, TTG, and granite. Zircon U-Pb and Lu-Hf data constrain that the metabasalt formed at 2.52 Ga and was metamorphosed at 2.49 Ga. Dioritic rocks, TTG (tonalite-trondhjemite-granodiorite) and granite formed between 2.53 and 2.48 Ga. More than 85% of analyzed zircon grains yield ε_Hf(t) values intermediate between coeval CHUR and depleted mantle (DM). Their single-stage (T_DM) Hf model ages are dominantly between 2.90 and 2.58 Ga with a peak at 2.76–2.66 Ga, suggesting that the Archean assemblages of the SLP were derived from short-lived crustal sources with limited contributions from older materials. Geochemistry and zircon Lu-Hf systems indicate that these metamafic rocks have N-MORB and island arc-like tholeiitic affinities. Similar basaltic associations were identified from the Wutai greenstone belt. Intra-oceanic subduction and back arc basin extension can be ascribed to the generation of associated MORB-like and arc-related basalt. Along with the closure of the SLP back arc basin, an unknown terrane accreted to the south of the Longgang block at the end of the Neoarchean. Full article

Determining the timing of hidden faults that terminate beneath the subsurface remains a significant challenge. For this contribution, seismic fault interpretation, fracture diagenesis analysis, and U-Pb dating of fracture cements are integrated to constrain the activity of hidden thrust faults in the southeastern Sichuan Basin. The results show that the EW- and NW-trending hidden thrust faults developed in the Permian, while the NE-trending faults have inherited later fault activity till the Cenozoic. The hidden thrust fault propagates upward from the top of the Upper Permian to the Lower Triassic strata. Fault inversion within the Permian is firstly identified by the thickness variation between the two fault walls. Core-based fracture diagenesis analysis indicates that multiple fractures and associated dissolution porosity developed within the tight matrix reservoir. In situ U-Pb dating of fracture cements yields ages of 247.4 ± 2 Ma and 234.8 ± 9.1 Ma, indicating that the hidden fault activity predates the Early Triassic. The absence of strata, evidence of structural uplift, and fault inversion collectively suggest that the first faulting in the eastern Sichuan Basin occurred at the end of the Middle Permian. The findings highlight that fracture–cave reservoir along the hidden thrust fault zone has been controlled by the coupling of the fracturing and karstification at the end of the Middle Permian, and is the key target for high gas production. Full article

The Yangtze Block provides a natural window into the tectonic evolution of Precambrian continental crusts. The Julin Group is a dominant Precambrian stratigraphic unit in the southwestern block, the depositional age of which is still poorly constrained. The lowest sequence of this group, the Pudeng Formation, is primarily composed of mica-quartz schists and quartzites intruded by a biotite monzogranite. LA–ICP–MS zircon U-Pb ages of biotite monzogranite and detrital zircons constrain the deposition of the Julin Group to between 1099 and 1052 Ma. Geochemical compositions of the mica-quartz schists and quartzites display high δCe, ΣREE, Th/Sc, and Th/U, along with low δEu, La/Sc, Ce/Th, and Al₂O₃/(Al₂O₃ + Fe₂O₃) ratios, indicating their derivation from felsic volcanic protoliths in a passive continental margin setting. The detrital zircons show distinct age peaks at 2.5, 1.85, and 1.6 Ga, with their source regions primarily located along the western and northern Yangtze Block. Integrating the magmatic records within the Yangtze Block with the ages and ε_Hf(t) values of detrital zircons indicates that the tectonic setting of the western Yangtze Block evolved from a subduction-related arc at ~2.5 Ga to an orogenic belt at ~1.86 Ga and subsequently to intracontinental extensional (rift) environments at ~1.6 Ga and ~1.2 Ga. This evolution reflects the geodynamic transition from the Arrowsmith orogeny to the assembly and development of the Columbia and Rodinia supercontinents. Full article

The Yanlinsi gold deposit, located in the middle section of the Jiangnan Orogenic Belt, is one of the typical gold deposits in northeastern Hunan Province. Diabase dikes are exposed by underground workings and drill holes in the mining area. The dikes strike NW and cut the NE-trending gold ore body. To investigate the petrogenetic age, characteristics of the magmatic source area, and tectonic setting of the diabase dikes in the Yanlinsi gold mining area, northeastern Hunan, and to determine the mineralization age of the deposit, in this paper, diabase dike LA-ICP-MS zircon U-Pb dating, whole-rock geochemistry, and gold-bearing quartz vein LA-ICP-MS zircon U-Pb dating were studied. The results of LA-ICP-MS zircon U-Pb dating indicate that the diabase was emplaced at an age of 219.5 Ma, belonging to the late Indosinian. The investigated diabase dikes are characterized by low SiO₂ (43.68%–46.55%), high MgO (7.78%–9.84%), and high Mg# (65.0–68.7) values, belonging to the alkaline basalt series with high potassium. The chondrite-normalized REEs patterns show highly fractionated LREEs and HREEs ((La/Yb)_N = 11.21–14.82), and the primitive mantle-normalized spider patterns show enrichment in large ion lithophile elements (e.g., Rb, Ba, K and Sr) and relative depletion in high field strength elements (e.g., Nb, Ta, and P), similar to those of ocean island-like basalt (OIB). Rock geochemical characteristics indicate that the magma of the Yanlinsi diabase was formed by partial melting of the enriched mantle (EM II), with the source region being spinel-garnet lherzolite. The degree of partial melting was approximately 10%–15%, and the assimilation and contamination with continental crustal materials were weak. Meanwhile, weak fractional crystallization of olivine, clinopyroxene, and apatite occurred during the magma evolution process. On the basis of a synthesis of previous research results, it is concluded that the Yanlinsi diabase formed in an extensional tectonic setting after intracontinental collisional orogeny. The LA-ICP-MS U-Pb age of hydrothermal zircons from quartz veins in the main mineralization stage of the Yanlinsi gold deposit is 421.9 ± 1.5 Ma. Combined with the cross-cutting relationships between mafic dikes and gold veins (ore bodies), it is determined that the main mineralization stage of the deposit formed during the Caledonian Period. Full article

The Gangdese Belt is sandwiched between the Yarlung–Zangbo Suture Zone (YZSZ) and the Bangong–Nujiang Suture Zone (BNSZ), and witnessed large-scale magmatic activity during the Early Cretaceous period. Currently, controversies remain regarding the petrogenetic mechanism and tectonic setting of the Early Cretaceous magmatism in the eastern Gangdese Belt. To clarify these controversies, this study conducted systematic petrogeochemical analysis on the Ranwu pluton in the eastern Gangdese Belt. The results show that the main rock types of the Ranwu pluton are monzogranite and granodiorite. The LA-ICP-MS zircon U-Pb ages of the monzogranite (sample CZTW1105) and granodiorite (sample CZTW2051) are 116.3 ± 0.5 Ma and 114.6 ± 0.6 Ma, respectively, collectively indicating that the Ranwu pluton formed during the Early Cretaceous period. The results of in situ zircon Hf isotope analysis show that the εHf(t) values range from −5.0 to 0.5, with corresponding Hf crustal model ages (T_DMC) of 1139–1494 Ma. The Ranwu pluton belongs to the high-K calc-alkaline series and is classified as I-type granite. Combined with geochemical characteristics and tectonic setting discrimination diagrams, it is determined that the granites of this period have geochemical signatures of post-collisional granites and formed in a tectonic setting during the transition from a compressional to an extensional regime. The occurrence of Early Cretaceous post-collisional granites marks the end of the main orogenic stage in the Bangong–Nujiang Suture Zone, and the Gangdese Belt has since transitioned into a tectonic environment of the post-orogenic extensional stage. Full article

The Nakexiuma area in the East Kunlun Orogen Belt hosts two spatially distinct mineralization systems: uranium-molybdenum (U-Mo) in schist and granitoid, and tungsten-molybdenum (W-Mo) in skarn and granitoid. To clarify their genetic relationship, we conducted U-Pb dating and trace element analyses on zircon, garnet, and uraninite. Zircon from granitoids yields a crystallization age of 250 ± 2.3 Ma, followed by W-Mo mineralization at 245 ± 2.1 Ma (garnet) and U-Mo mineralization at 235 ± 9 Ma (uraninite), indicating a prolonged magmatic-hydrothermal history spanning approximately 15 million years. Trace element data reveal a shift in fluid chemistry over time: Skarn garnets show high W contents, suggesting oxidizing, high-temperature fluids; uraninite displays REE depletion and negative Eu anomalies, precipitated from oxidizing fluids encountering a reducing environment. We propose that the W, U, and Mo mineralization in Nakexiuma is the result of this long-lived magmatic-hydrothermal system. The spatial separation of these mineralization systems is attributed to a multi-stage process involving host rock lithology and fluid redox evolution. Early oxidizing fluids from granitoids metasomatized carbonates to form W-Mo mineralization skarn. Later, meteoric water influx increased oxygen fugacity, generating U-rich, highly oxidizing fluids that precipitated uraninite and molybdenite upon interaction with the reducing meta-mafic rocks. These results highlight the roles of lithology and fluid chemistry in controlling spatially separated mineralization within the same system. Furthermore, they expand the Early Mesozoic metallogenic spectrum of the East Kunlun Belt, providing a refined model for polymetallic ore formation in a post-collisional extensional setting. Full article

The Wushan Loess, situated in the Yangtze Three Gorges region of China, represents the southernmost aeolian loess deposit in China and provides critical insights into Late Pleistocene paleoenvironmental conditions and East Asian monsoon dynamics. Despite its significance, the genesis and provenance of this unique loess deposit remain controversial. This study employs an integrated multi-proxy approach combining detrital zircon U-Pb geochronology, optically stimulated luminescence (OSL) dating, and detailed grain size analysis to systematically investigate the provenance and depositional mechanisms of the Wushan Loess. Three representative loess–paleosol profiles (Gaotang-GT, Badong-BD, and Zigui-ZG) were analyzed, yielding 17 OSL ages, 729 grain size measurements, and approximately 420 analyses per profile were conducted, yielding 1189 valid ages (GT 406, BD 391, ZG 402). OSL chronology constrains the deposition period to 18–103 ka (Marine Isotope Stages 2–5), coinciding with enhanced East Asian winter monsoon activity during the Last Glacial period. Grain size analysis reveals a dominant silt fraction (modal size: 20–25 μm) characteristic of aeolian transport, with coarse silt (20–63 μm) averaging 47.1% and fine silt (<20 μm) averaging 44.2% of the sediments. Detrital zircon U-Pb age spectra exhibit consistent major peaks at 200–220 Ma, 450–500 Ma, 720–780 Ma, and 1800–1850 Ma across all profiles. Kernel Density Estimation (KDE) and Multi-Dimensional Scaling (MDS) analyses indicate a mixed provenance model. Non-negative least squares (NNLS) unmixing confirms this quantitative source apportionment., dominated by proximal contributions from the upper Yangtze River basin (including the Three Gorges area and Sichuan Basin, ~65%–70%), supplemented by distal dust input from the Loess Plateau and northern Chinese deserts (~30%–35%). This study establishes for the first time a proximal-dominated provenance model for the Wushan Loess, providing new evidence for understanding southern Chinese loess formation mechanisms and Late Pleistocene East Asian monsoon evolution. Full article

The Apuseni-Banat-Timok-Srednogorie Metallogenic Belt is one of the most important polymetallic metallogenic belts in the western segment of the Tethys, where numerous porphyry-type, skarn-type, and epithermal deposits are developed. However, scholars have noted a lack of systematic chronological and geochemical studies of andesites within this belt. Furthermore, the metallodynamic mechanisms controlling mineralization—such as oceanic plate exhumation and plate tearing—remain controversial. To complement the available research, this study focuses on andesites from the Čukaru Peki area in Serbia and integrates zircon U-Pb dating, molybdenite Re-Os isotopic analysis, and whole-rock geochemical analysis. The results reveal that plagioclase andesitic breccia and fine-grained plagioclase amphibole andesite were emplaced during the Late Cretaceous. Consistently, the molybdenite isochron age (81.46 ± 0.60 Ma, MSWD = 1.30) constrains the mineralization event to the same period. Both rock types exhibit geochemical signatures typical of island arc volcanic rocks, characterized by high SiO₂ contents and low Al₂O₃, MgO, and TiO₂ contents, as well as pronounced fractionation between light and heavy rare earth elements (LREEs and HREEs). The magma source is the mantle wedge metasomatized by fluid-rich melts derived from the dehydration of the subducted oceanic crust. Additionally, the primary magma produced by partial melting of this metasomatized mantle wedge assimilated and was contaminated by continental crustal material predating the Vardar Ocean’s closure during its ascent. Our findings suggest that the regional andesites are products of the exhumation of the Vardar Ocean. This study aims to provide a theoretical foundation for mineral exploration in the Timok ore cluster and, simultaneously, support the identification of ore prospecting targets in andesite alteration zones. Full article

Introduction: Trace metals can negatively impact biological functions and brain development. Cognitive and neurobehavioral disorders in children are poorly documented in Haut-Katanga Province, an area with significant and multiple exposures to trace metals that can lead to the exacerbation of cognitive and behavioral disorders. Objective: This study aimed to characterize the behavior of schoolchildren linked to their cognitive performance in urban and rural environments. Methods: A cross-sectional pilot study was conducted on 52 schoolchildren aged 6 to 11 (22 from rural areas presumed less exposed to metals and 30 from Lubumbashi, DRC). This study employed NEPSY-II tests, the Strengths and Difficulties Questionnaire (SDQ-Tutor), ENA 2020 software and trace metal spectrometry assays. Statistical tests were carried out with SPSS-20 and Stata-18. Results: Our findings revealed a correlation between children’s malnutrition and low mother’s education. The “total difficulties score” was more prevalent in rural areas (73%) compared to urban settings (37%) p < 0.05), in contrast to the “negative impact of difficulties” (59% versus 57%, p > 0.05). Urban children demonstrated superior cognitive performance, particularly in “facial affect recognition” (8 versus 4, p = 0.013) and “inhibitory control” (6.5 versus 3, p = 0.032). As-U(urine), Cd-B(blood), Hg-B, Mo-U, Ni-U, Pb-U, Pb-B and Sb-U were elevated compared to references. In general, urban areas had higher metal levels than rural areas. Blood and urine metals showed a complex and significant relationship with behavioral difficulties or cognitive performance. Conclusions: The observed behavioral issues, cognitive performance deficits and their association with nutritional deficiencies and trace metal exposure suggest a multifactorial neurodevelopmental origin. These findings highlight the need for further research in the region. Full article

The Dazhuyuan Formation (northern Guizhou) is the host stratum for bauxite deposits and enriched with critical metals like Li. We investigated sedimentary processes of the formation using detrital zircon geochronology and whole-rock geochemistry. From bottom to top, the formation comprises iron-rich claystone (IC), clastic bauxite (CB), massive bauxite (MB; where Li is enriched (1555–4210 ppm)), and clastic claystone (CC). From lower part to upper part of the formation, the sedimentary environment becomes more reducing, transitioning from continental to marine–continental facies. The P₁d exhibit rare-earth-element (REE) distributions similar to the Hanjiadian Formation. The Hanjiadian Formation detrital-zircon U–Pb ages reach ~960 and ~760 Ma; the IC and CB layers show similar results. The dominant peak of detrital-zircon ages for the MB and CC layers occurs at ~960 Ma, while the ~760-Ma dominant peak disappears. Numerous zircons are aged 1030–1150 Ma, which substantially diverges from the Hanjiadian Formation. All layers exhibit different REE distributions and detrital-zircon age distributions than the Huanglong Formation, indicating that the formation is the primary source for the Dazhuyuan Formation. The MB and CC layers receive contributions from other sources. Full article