Search Results (113)

A-type granites represent high-temperature, highly differentiated felsic magmas formed in post-collisional and intraplate tectonic settings. While whole-rock geochemistry constrains bulk melt evolution, zircon trace element systematics provide higher-resolution insights into crystallization conditions, including temperature, oxidation state, and differentiation intensity. This study integrates whole-rock geochemical data with zircon trace element analyses to evaluate the extent to which zircon records magmatic evolution in Neoproterozoic A-type granites from Sinai, Egypt. Whole-rock compositions define a high-silica, ferroan differentiation trend characterized by enrichment in high-field-strength elements (HFSE) and pronounced negative Ba–Sr–Ti anomalies, indicating advanced fractional crystallization. Zircon trace element patterns exhibit strong heavy rare earth element (HREE) enrichment (Yb up to 1757 ppm), systematically negative Eu anomalies (mean Eu/Eu* = 0.32), and elevated Hf concentrations (up to 14,453 ppm; mean = 4763 ppm), reflecting progressive melt differentiation. Ti-in-zircon thermometry yields crystallization temperatures ranging from 562 °C to 1384 °C. However, most values cluster between 757 °C and 872 °C (mean ≈ 837 °C), indicating sustained high-temperature magmatic conditions. The broader temperature range likely reflects analytical uncertainties, assumptions in Ti activity, and possible outliers. Positive Ce anomalies indicate moderately oxidized crystallization environments. Systematic relationships among zircon Hf, Eu/Eu*, Yb/Gd, Th/U, and Ti-in-zircon temperatures demonstrate a strong coupling between zircon chemistry and whole-rock differentiation trends. These relationships are supported by statistically significant correlations, indicating that zircon trace element systematics provide a robust, semi-quantitative framework for interpreting melt evolution, while preserving independent constraints on temperature and redox state. Full article

The formation of tectonic–magmatic–sedimentary processes during the Permian in the Beishan region represents a highly debated research topic along the southern margin of the Central Asian Orogenic Belt and even globally: does it mark the final subduction and amalgamation of the Paleo-Asian Ocean, or does it instead represent rifting superimposed upon an earlier orogen? New field observations combined with geochemical analyses reveal that the Liuyuan area is dominated by Early Permian basalts, associated with a rifting sedimentary sequence. During the Mid–Late Permian, gabbro–rhyolite associations were emplaced, accompanied by minor lacustrine sedimentation. The late stage was characterized by minor granitic intrusions or dikes with adakitic affinities, culminating in the emplacement of lamprophyre dikes. The basalts and gabbros in the Liuyuan area display mantle-derived geochemical signatures, with compositions intermediate between MORB and OIB. The exposed Permian basalt–rhyolite bimodal magmatic suite represents a genetically integrated rift-related rock series. Geochemical data from the Ordovician granites and schists within the belt reveal adakitic characteristics, implying that the Permian granitic rocks largely represent remelting products of these early granitic and schistose protoliths. Collectively, the lithological characteristics and magmatic associations clearly demonstrate that the tectonic setting during the Early Permian corresponded to a post-collisional extensional environment superimposed upon the early Paleozoic orogenic belt (Caledonian Huitongshan ophiolite–arc accretionary orogen), which subsequently underwent tectonic inversion to form the present-day orogenic structure. This paper proposes a theoretical model wherein the bimodal magmatic suite was generated by the upwelling of enriched asthenospheric mantle material, providing the driving mechanism for rifting. It formed within a post-collisional extensional environment developed over a complex pre-existing orogenic belt and was subsequently inverted, forming the current tectonic belt—a typical intracontinental Pyrenees-type orogeny. Full article

The Mesozoic dykes in the Xingcheng area of western Liaoning Province in China were investigated through an integrated study involving zircon U–Pb geochronology, whole-rock geochemistry, and zircon Hf isotopic compositions to elucidate their emplacement phases, petrogenesis, and tectonic setting. The dykes are classified into two groups: felsic (granite porphyry, granite aplite) and mafic (diabase, lamprophyre). Emplacement occurred in four discrete phases: Late Triassic (229–212 Ma), Early Jurassic (ca. 179 Ma), Late Jurassic (162–152 Ma), and Early Cretaceous (133–102 Ma). The felsic dykes are characterized by high SiO₂ and alkali contents, low TFeO and MgO abundances, and belong to the high-K calc-alkaline I-type granite series. The mafic dykes exhibit low SiO₂, elevated MgO, and high Na₂O contents, displaying both alkaline and calc-alkaline affinities. Both dyke suites are consistently enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), and depleted in heavy rare earth elements (HREEs) and high field-strength elements (HFSEs). Zircon ε_Hf(t) values for the felsic dykes range from −22.3 to −7.4, corresponding to two-stage model ages (T_DM2) of 2613–1729 Ma, indicating derivation from partial melting of Neoarchean to Paleoproterozoic crustal material. Late Jurassic mafic dykes yield ε_Hf(t) values between −27.8 and −20.2, consistent with an origin from partial melting of enriched lithospheric mantle. In contrast, Early Cretaceous mafic dykes display a bimodal ε_Hf(t) distribution (−12.9 to −9.5 and +4.3 to +8.4), suggesting a predominant enriched mantle source with variable inputs from depleted mantle components. Integrated with regional tectonic reconstructions, the data indicate that the Xingcheng area evolved within a post-collisional extensional regime following the amalgamation of the North China Craton and the Central Asian Orogenic Belt during the Late Triassic. The Jurassic magmatic pulses are attributed to an active continental margin setting associated with subduction of the Paleo-Pacific Plate, whereas the Early Cretaceous phase reflects regional extension triggered by rollback of the subducting Paleo-Pacific slab. Full article

Baixintan is a magmatic Ni–Cu sulfide deposit discovered in the central Tuwu–Yandong porphyry Cu belt of the Eastern Tianshan Orogen (ETO) of NW China in 2016. It is in close proximity (~5 km) to the Tuwu Cu deposit, the largest Carboniferous porphyry Cu deposit (~336 Ma) in Xinjiang. The Baixintan Ni–Cu ore is characterized by a high Cu/Ni ratio, but the reason for it remains unclear. To resolve this question, we present petrographic, geochronological, whole-rock geochemical, and S, Pb, Cu, and Lu–Hf isotopic data. Ore-related hornblende olivine websterite (HOW) and hornblende olivine gabbro (HOG) were emplaced at 296.6 ± 1.1 Ma and 289.7 ± 1.2 Ma, respectively, which were formed in an Early Permian post-collisional extensional setting. Whole-rock Pb and zircon Lu–Hf isotopes suggest that the parental magmas were predominantly mantle-derived. The Baixintan HOW and HOG contain abundant hornblende and are enriched in LILEs and LREEs but depleted in HFSEs, suggesting subduction-related metasomatism in their magma source. The sulfide (chalcopyrite, pyrrhotite, and pentlandite) δ³⁴S values cluster around 0‰ (–0.13 to 0.11, n = 11), and the chalcopyrite has uniformly negative but variable δ⁶⁵Cu values (–0.96 to –0.13, n = 6), which suggest that the ore-forming materials were mainly derived from the subduction-metasomatized mantle. Olivine Ni contents are significantly lower than those crystallized under sulfide-unsaturated conditions, implying that olivine fractional crystallization was an important trigger for sulfide melt segregation at Baixintan. Baixintan is the only known magmatic Ni–Cu sulfide deposit in the ETO that shares a Cu-preconcentrated, metasomatized mantle source with a giant porphyry Cu system. Copper pre-enrichment in the magma source may be the main factor for the relatively high Cu/Ni ratio observed in the Baixintan deposit. Full article

The Oligocene–Miocene magmatic rocks extensively developed in the Gangdese magmatic belt are key records of the post-collisional tectono-magmatic evolution of the Tibetan Plateau. In this study, petrological, zircon U-Pb geochronological, zircon Hf isotopic and whole-rock geochemical investigations were carried out on two granitic porphyry stocks exposed in the Chunzhe area of the middle Gangdese belt. LA-ICPMS zircon U-Pb dating, cathodoluminescence (CL) images and trace element characteristics indicate that the granitic porphyries were emplaced at 11.8 ± 0.2 Ma (MSWD = 1.1) and 11.5 ± 0.1 Ma (MSWD = 1.2), with a small number of zircon grains yielding ²⁰⁶Pb/²³⁸U ages of 51.1~59.5 Ma, 29.8 Ma and 19.4~12.2 Ma, which are interpreted as inherited or captured zircon components. The analyzed samples are monzogranite porphyries composed mainly of quartz, plagioclase and alkali feldspar, with variable secondary white mica/sericite. In whole-rock composition, they display high-K calc-alkaline and weakly peraluminous characteristics. These rocks are enriched in large-ion lithophile elements (LILEs) such as Ba, Sr and Rb, and relatively depleted in Nb-Ta-Ti as well as Cr and Ni. They show light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion, with distinctly high chondrite-normalized La/Yb ratios (31.05~71.25) and Sr/Y ratios (35.90~49.07), and a positive correlation between the LREE/HREE ratio and La content, indicating robust adakite-like trace element characteristics. Zircon εHf(t) values of the Miocene magmatic rocks range from −4.44 to 2.41, corresponding to two-stage Hf model ages of 1380~944 Ma, suggesting that the magmas were mainly derived from juvenile continental crust materials with the addition of a small amount of ancient continental crust materials. Combined with the regional geological setting, the Chunzhe Miocene granitic porphyries were most likely generated by partial melting of the thickened lower crust in the Gangdese belt during the late stage of Oligocene–Miocene post-collisional magmatism; local lower-crustal delamination may also have contributed, although this is not uniquely constrained by the present dataset. Full article

An integrated Visible–Near-Infrared to Shortwave Infrared spectroscopy (VNIR–SWIR spectral), mineralogical, and geochemical study was conducted on the Shadan Au–Cu porphyry–epithermal system in the eastern Lut Block, Iran, to characterize hydrothermal alteration zonation and classify alteration–lithological units. Thirty-eight representative samples were analyzed by reflectance spectroscopy (0.35–2.50 µm), petrography, XRD (X-ray Diffraction), X-ray fluorescence (XRF), and Inductively Coupled Plasma Mass Spectrometry (ICP–MS). Quantitative continuum-removal processing identified diagnostic absorption features near 0.90, 1.40, 1.90, 2.17, 2.20, 2.33, and 2.50 µm, corresponding to Fe³⁺, Al–OH, H₂O, and CO₃ absorptions. Seven alteration–lithological groups (G₁–G₇) were defined and verified by XRD and petrography, representing illite–smectic–kaolinite (argillic), alunite–dickite (advanced argillic), quartz–silicified, Fe-oxide, oxidized argillic, chlorite–epidote (propylitic), and carbonate–iron vein assemblages. Whole-rock geochemical data reveal coherent enrichments of Al₂O₃–K₂O in clay-dominant zones, Fe₂O₃ in oxide-rich areas, and CaO–MgO in carbonate-bearing assemblages. Spectral and geochemical integration delineates a vertically and laterally zoned system evolving from acidic to neutral–oxidizing conditions, typical of low-sulfidation epithermal overprints on porphyry-style magmatic centers. This multidisciplinary framework demonstrates the value of combining VNIR–SWIR spectroscopy with mineralogical and geochemical constraints for vectoring and classification of alteration systems in post-collisional volcanic belts. Full article

The West Kunlun represents one of the largest and most economically significant rare metal metallogenic belts in NW China. The newly discovered Dahongliutandong Li deposit is the first Li deposit identified within the Permian Huangyangling Group in this region, and its discovery has important implications for regional lithium exploration. In this study, whole-rock major and trace-element geochemistry and cassiterite U–Pb isotope data from both Li-poor and Li-rich pegmatites of the Dahongliutandong deposit were analyzed to constrain the mineralization age and tectonic setting. Geochemically, the pegmatites are characterized by high SiO₂ (70.57–78.50 wt%), low TiO₂, MnO, and MgO (<0.2 wt%), and strongly peraluminous signatures (A/CNK = 1.45–1.95). They exhibit coherent chondrite-normalized REE patterns with LREE enrichment and negative Eu anomalies (Eu/Eu* = 0.03–0.77), along with consistent enrichment in LILEs (e.g., Rb, U, K) and depletion in HFSEs (e.g., Nb, Ti) on primitive mantle-normalized spider diagrams, suggesting a common magmatic source or evolutionary path. Cassiterite U–Pb dating yielded consistent lower-intercept ages of 208 ± 11 Ma (MSWD = 0.86) for Li-poor pegmatites and 206 ± 5 Ma (MSWD = 1.7) for Li-rich pegmatites, both indicating Late Triassic mineralization. Combined with regional geology, these data suggest that Li mineralization was likely related to post-collisional extension following the closure of the Paleo-Tethys Ocean. This study provides new insights into regional rare metal mineralization in the West Kunlun orogenic belt. Full article

The Arganaty Massif in the Eastern Balkhash region (Kazakhstan) is located in a key sector of the Central Asian Orogenic Belt, but its petrogenesis and relationship to neighboring Late Palaeozoic intrusions remain poorly constrained. This study presents the first U–Pb zircon age and whole-rock geochemical data for the Arganaty granites, combined with a comparison with massifs of the Northern Balkhash region and Alatau Mountains (East Kazakhstan and Western Xinjiang, NW China). The Arganaty granites have a concordant U–Pb age of 281.5 ± 2.1 Ma. They are high-K calc-alkaline, metaluminous to slightly peraluminous I-type granites with low Mg# (0.22–0.33) and Nb/Ta ratios (10.2–17.3). Geochemical comparison indicates close affinity to the Lepsy complex intrusions and eastern plutons of Alatau mountains, rather than to the Katbar complex of Northern Balkhash. The new age and geochemical data show that the Arganaty granites formed in a post-collisional setting after the closure of the Junggar–Balkhash Ocean. Their mixed crust–mantle signature and depth estimates (~30 km) are consistent with lower crustal melting triggered by slab break-off. These results clarify the post-collisional magmatic evolution of the region and contribute to the understanding of Late Palaeozoic crustal growth in the CAOB. Full article

The Middle Tonian tectonic setting of the Jiangnan Orogen, South China, remains intensely debated, and is centered on two competing models: subduction–collision versus mantle plume. This study addresses this critical knowledge gap through an integrated, multi-proxy investigation of the Middle Tonian Fanjingshan Group. This region preserves a continuous volcano-sedimentary and magmatic record, offering key insights into the orogen’s full lifecycle. To test these hypotheses, we employed a synthesis of geological survey, sediment provenance analysis, detrital zircon U-Pb geochronology of clastic rocks to determine sediment provenance and basin evolution, and petrogenetic study of coeval magmatic suites (pillow lava, mafic–ultramafic sills, and granitoids) to evaluate their magmatic processes and tectonic setting. Analysis of 1736 detrital zircon U-Pb ages from Middle Tonian strata reveals a four-stage provenance evolution: (1) SW Yangtze sources in a passive margin basin before 870 Ma; (2) bidirectional sources in an 870–835 Ma arc-derived basin; (3) syn-collisional detritus during 835–820 Ma amalgamation; and (4) post-collisional and northern Yangtze inputs in an 800 Ma rifting basin. Geochemical data from ~845–840 Ma basalts and coeval sills reveal calc-alkaline affinities and marked subduction-fluid signatures. Their calculated mantle potential temperature (1404 °C) is significantly lower than that expected for plume-derived melts (1570 °C), which is consistent with melting in a subduction-modified mantle wedge, supporting a continental rear-arc basin setting. The ~845–832 Ma mafic–ultramafic sills exhibit symmetrical geochemical zoning and two-stage emplacement, recording sustained magma recharge in the rear-arc basin. Furthermore, the ~830 Ma Fanjingshan granite is identified as a crust-derived, syn-collisional S-type granite. Synthesizing these findings, we demonstrate that the sedimentary and magmatic records collectively point to plate margin setting. A four-stage tectonic model is suggested: (1) pre-870 Ma passive margin without significant magmatic activity; (2) 870–835 Ma continental arc development at an active continental margin; (3) 835–820 Ma Yangtze–Cathaysia collision; and (4) post-820 Ma post-orogenic rifting. This work provides a robust regional case study, demonstrating that integrating records of deep magmatic processes with coeval shifts in sedimentary provenance and basin architecture is essential to reconstruct the complete evolution of ancient orogens. Full article

The Tawenchahanxi mining area, situated in the southeastern Qimantagh region of the East Kunlun Orogenic Belt, hosts a skarn-type Fe–polymetallic deposit associated with acidic granitic intrusions. Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating yields ages of 233.3 ± 1.2 to 234.3 ± 1.1 Ma for a granodiorite and 397.7 ± 1.4 Ma for a quartz porphyry, indicating two magmatic intrusive events during the Early Devonian and Late Triassic. The Early Devonian quartz porphyry is characterized by high ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ (72.39%–74.04%), high total alkalis (7.81%–7.83%), high TFeO (>1.0%) and high crystallization temperatures (~865 °C), together with low CaO (1.64%–1.70%) and MgO (0.61–0.65%), which are all consistent with A-type granite affinity. The granodiorite exhibits aluminum saturation index (A/CNK) values of 0.67–1.07 (metaluminous to weakly peraluminous) and belongs to the high-K calc-alkaline series. It exhibits moderate negative Eu anomalies (δEu = 0.71–0.83), and zircon saturation temperatures of ~748 °C, collectively indicative of I-type granite affinity. Both rock suites display depletion in Nb, Ta, and Sr and enrichment in Rb and LREEs. Zircon Hf isotopic data show εHf(t) values of −0.64 to 0.57 for the quartz porphyry and −4.37 to −1.06 for the granodiorite, indicating derivation primarily from partial melting of ancient crust with variable mantle contributions. These intrusions formed during post-collisional extensional (Early Paleozoic) and collisional to post-collisional (Late Paleozoic–Early Mesozoic) stages, respectively, associated with mantle magma underplating and crust–mantle mixing. Such processes formed the material basis for the polymetallic mineralization in the Tawenchahanxi district by providing Fe–Cu–Pb–Zn and other ore-forming elements from deeper crust. Full article

The Himalayan metallogenic belt is a globally significant province for leucogranites and pegmatites. Recent exploration has yielded major breakthroughs in the exploration of pegmatite-type Li-Be-Nb-Ta rare-metal deposits within its eastern segment. Discoveries such as the Qiongjiagang and Lhozhag deposits underscore the region’s substantial mineralization potential. In contrast, the western Himalayan segment remains comparatively underexplored. This study presents the geology and geochronology of the newly identified Zhaguopu Li-Be-Nb-Ta deposit in the Gyirong area, providing critical new insights. The deposit is centered on the Gyirong granite dome, which features a core of tourmaline-bearing leucogranite surrounded by a peripheral zone of beryl-bearing pegmatites and vein- to lens-shaped spodumene pegmatites, all hosted within metamorphosed sandstone, slate, and marble. The largest individual spodumene pegmatite vein exceeds 400 m in length, with thicknesses ranging from 0.5 to 4 m and a cumulative thickness surpassing 50 m. Principal ore minerals include spodumene, beryl, and columbite-group minerals. U-Pb geochronology of zircon, monazite, and columbite-group minerals from the leucogranite and pegmatite units constrains the rare-metal mineralization to a tight interval of 25–23 Ma, contemporaneous with the Qiongjiagang and Lhozhag deposits. Whole-rock geochemical data define a coherent fractional crystallization sequence from tourmaline granite through beryl pegmatite to spodumene pegmatite, characterized by increasing SiO₂ and peraluminosity, and extreme depletion in Ba, Sr, Eu and Nb/Ta ratios. This geochemical trend underscores the critical role of extreme magmatic differentiation in rare-metal enrichment. Field relationships and these coeval ages strongly support a genetic model in which the mineralized pegmatites originated from the extreme fractional crystallization of a common, cogenetic magmatic suite. The timing of this mineralization event correlates precisely with the post-collisional extension of the Himalayan orogen and the activity of the Southern Tibet Detachment System. We conclude that the interplay between this large-scale tectonism and magmatic differentiation is the fundamental driver for rare-metal enrichment. The discovery of the Zhaguopu deposit highlights the significant and previously underestimated potential for major pegmatite-type rare-metal deposits in the western Himalayan belt. Full article

The southern Central Asian Orogenic Belt (CAOB) underwent a major Early Paleozoic tectonic transition, yet its timing and mechanisms remain unclear. We present zircon U-Pb-Hf, whole-rock geochemical, and Sr–Nd isotopic data for newly identified Early Silurian (ca. 439–431 Ma) granitoids from the Liuyuan area of the southern Beishan Orogenic Belt. These high-silica, high-K calc-alkaline intrusions not only show arc-like trace-element patterns but also display elevated Ga/Al ratios and enriched Sr–Nd isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.7158–0.7189; ε_Nd(t) = −4.6 to −3.9), consistent with aluminous A₂-type granites derived mainly from ancient crust. Their heterogeneous zircon ε_Hf(t) values (−6.3 to +3.7) suggest a minor, localized input from mantle-derived mafic magmas superimposed on the dominant crustal signature. Integrating regional metamorphic constraints, we interpret this magmatism to have formed during the transition from oceanic subduction to incipient collision/continent involvement and subsequent post-subduction extension, plausibly triggered by slab break-off at the slab root (ocean–continent transition). Slab-window-related asthenospheric inflow and localized thermal perturbation could have promoted high-temperature crustal melting and facilitated Early Silurian crustal reworking in the southern CAOB. Full article

Post-collisional Cu-Au-Ni-Co-Pt-Pd-Sc porphyry [Duck Creek porphyry system (DCPS)] with overlying Au-Te-Bi-W-HRE epithermal mineralisation [Highway epithermal system (HES)] has been discovered in the core of the Mitakoodi anticline, southwest of Cloncurry. Xenotime and monazite geochronology indicate mineralisation occurred between ~1490 and 1530 Ma. Host rock lithologies show widespread potassic and/or propylitic to phyllic alteration. Paragenesis of porphyry sulphides indicates early crystallisation of pyrite, followed by chalcopyrite, with bornite forming by hydrothermal alteration of chalcopyrite. Cu sulphides also show the effect of supergene oxidation alteration with rims of covellite, digenite and chalcocite. Redox conditions deduced from the V/Sc systematics indicate that the DCPS contains both highly oxidised (typical of porphyries) and reduced lithologies, typical of plume-generated tholeiitic and alkaline suites. Ni/Te and Cu/Te systematics plot within the fields defined by epithermal and porphyry deposits. Duck Creek chalcophile and highly siderophile element (Cu, MgO and Pd) systematics resemble data from porphyry mineral systems, at Cadia, Bingham Canyon, Grasberg, Skouries, Kalmakyr, Elaisite, Assarel and Medet. SAM geophysical inversion models suggest the presence of an extensive porphyry system below the HES. A progressive increase in molar Cu/Au ratios with depth from the HES to the DCPS supports this conclusion. Three metal sources contributed to the linked DCPS-HES viz., tholeiitic ferrogabbro, potassic ultramafic to mafic system and an Fe and Ca-rich alkaline system. The latter two imparted non-crustal superchondritic Nb/Ta ratios that are characteristic of many deposits in the eastern Mount Isa Block. The associated tholeiite and alkaline magmatism reflect mantle plume upwelling through a palaeo-slab window that had accreted below the eastern flank of the North Australian craton following west-verging collision by the Numil Terrane. Discovery of this linked mineral system provides a new paradigm for mineral exploration in the region. Full article

The Late Cretaceous to Paleocene magmatic evolution along the southern margin of the Lhasa Terrane records a critical transition from oceanic subduction to continental collision, yet its western segment remains underexplored. This study presents integrated petrographic, zircon U–Pb geochronological, zircon Hf isotopic, whole-rock geochemical, and Sr–Nd isotopic data for three distinct phases of intermediate to felsic intrusions from the Qiuwo area in the western segment of the southern Lhasa terrane. The results reveal three distinct magmatic pulses: an early granodiorite emplaced at 89.9 ± 0.75 Ma, followed by a diorite crystallizing at 68.6 ± 0.56 Ma, and a late-stage granodiorite forming at 56.75 ± 0.43 Ma. All three rock units are metaluminous to weakly peraluminous (A/CNK < 1.1), sodic (Na₂O > 3.2 wt.%), and dominated by amphibole, with zircon saturation temperatures of 737–786 °C, consistent with I-type granitoid affinity. All units are metaluminous (A/CNK = 0.92–1.00), calc-alkaline to high-K calc-alkaline, and enriched in LILE (K, Th, Rb) while depleted in HFSE (Nb, Ta, P, Ti), with moderate ΣREE (81–130 ppm), elevated (La/Yb)_N (9.3–15.8), and negative Eu anomalies (δEu = 0.70–0.89). The early granodiorite is Na-rich (Na₂O/K₂O = 1.6), whereas the Paleocene granodiorite shows elevated K₂O (3.2 wt.%) and reduced Na₂O/K₂O (~1.0), reflecting progressive crustal thickening and increasing magmatic differentiation. Zr and Hf are relatively enriched, and Sr/Y ratios decrease from 39 to 21, consistent with evolving magmatic conditions from deeper crustal melting in the Late Cretaceous to shallower, more evolved sources in the Paleocene. Zircon Hf isotopes reveal consistently positive εHf(t) values (+10.4 to +4.9), indicating derivation from juvenile basaltic lower crust. Sr–Nd isotopic data further demonstrate a systematic evolution: εNd(t) decreases from +2.7 to −0.1, while (⁸⁷Sr/⁸⁶Sr)_i increases from 0.7044 to 0.7055, reflecting progressive incorporation of ancient crustal components into the magma source from the early Late Cretaceous to the Paleocene. These findings indicate that the Qiuwo intrusions formed by partial melting of a juvenile basaltic lower crust, with increasing crustal contamination during ascent and emplacement. The temporal progression of magmatism—spanning the waning stages of Neo-Tethyan subduction to the initial India–Eurasia collision (~55 Ma)—supports a model in which slab breakoff and lithospheric delamination triggered decompression melting of the lower crust, while assimilation of older crustal materials intensified as the continental collision progressed. This work provides key geochemical evidence for the transition from arc to post-collisional magmatism in the western Gangdese belt and refines the timing and mechanism of crustal growth in southern Tibet. Full article

The voluminous Mesozoic volcanic rocks developed in the Great Xing’an Range, northeastern China, have received extensive attention in recent decades. However, the timing and petrogenesis, as well as the related geodynamic processes of the Late Mesozoic volcanism, are still controversial. In this paper, we present the whole-rock geochemistry and zircon U–Pb ages for the Late Mesozoic volcanic rocks from the western part of the central Great Xing’an Range, which provide considerable insights into the geodynamic setting of the region. The zircon U-Pb dating results indicate that two main episodes of volcanism occurred in the central Great Xing’an Range, including in the Late Jurassic (ca. 147 Ma) and Early Cretaceous (ca. 142–125 Ma). These Late Mesozoic volcanic rocks display similar geochemical compositions, which are mainly intermediate–felsic, alkaline, peraluminous to metaluminous, enriched in large ion lithophile elements and light rare earth elements, and depleted in high-field-strength elements, indicating arc affinities in the subduction zone. The trace element compositions suggest that the magmatism was related to a post-collisional extensional environment. Combined with the spatial distribution and temporal migration of the Mesozoic magmatic events in the whole northeastern China region, we propose that these Late Jurassic–Early Cretaceous volcanic rocks formed in a continental arc setting, which was mainly related to the rollback of the subducted Paleo-Pacific oceanic plate. Full article