The East Kunlun-North Qaidam orogenic belt (EKO-NQO) preserves extensive magmatic records of the Proto- and Paleo-Tethys oceans, making it an ideal window for studying the Proto-Paleo-Tethys tectonic transition. Three Late Silurian-Early Devonian plutons (Hatu, Niantang, Chachaxiangka) in the EKO-NQO were selected for study. We also integrated recent high-quality geochemical and geochronological data to assess regional tectonic evolution. The ca. 415-417 Ma Hatu I-type granites in the South Kunlun Belt (SKB) are derived from partial melting of metabasalts in the middle/lower crust due to mantle-derived magma underplating, with minor juvenile crustal components input, during slab break-off and exhumation in the late-stage continental subduction. The ca. 414 Ma Hatu A-type granites (SKB) are mainly formed by dehydration melting of Paleo- to Mesoproterozoic crust, reflecting lithospheric thinning and delamination. The ca. 419-420 Ma Chachaxiangka adakite-like granites in the North Qaidam Belt (NQB) are formed through hydration melting of thickened lower crust during continental deep subduction-exhumation. The ca. 383-386 Ma Niantang A-type granites in the Aqikekulehu-Kunzhong ophiolitic melange zone (AKM) are derived from partial melting of ancient metasedimentary basement (predominantly metapelites), with minor juvenile crust input, during lithospheric delamination and thinning. Based on existing studies, we propose a three-stage evolution model for the Ordovician-Devonian Proto-Tethys orogeny in EKO-NQO: (1) Cambrian- Middle Silurian Oceanic Subduction: NQB (>450 Ma), Qimantagh Belt (QMTG), North Kunlun Belt (NKB) and SKB (>430 Ma); (2) Early Silurian-Early Devonian Slab Break-off/Exhumation: NQB (450 - 415 Ma), QMTG (430 - 410 Ma), NKB and SKB (430 - 415 Ma; SKB: western collision, eastern subduction); (3) Early-Middle Devonian Delamination: NQB, NKB and SKB (<415 Ma, SKB western segment), QMTG (<410 Ma). The Early-Middle Devonian Niantang A-type granites (A2-A1 transition) in EKO-NQO indicate a gradual shift to intraplate setting, marking both the end of the Proto-Tethys and the onset of Paleo-Tethys.

The crust-mantle magmatism is crucial for understanding the Late Paleozoic subduction and closure history of the Paleo-Asian Ocean (PAO). The tectonic evolution of the eastern PAO remains controversial, which makes the study of magmatic assemblages at the northern margin of the North China craton (NCC) essential for deciphering the evolutionary history of this region. In this study, we present petrological, geochronological, geochemical, and in situ zircon Hf isotopic data from the Early Permian basic, intermediate, and acidic intrusive rocks in the Shangyi area. Zircon U-Pb dating yielded ages of 289 Ma for the monzonite, 289 Ma for the monzogranite, and 283 Ma for the diabase. The studied monzonite is characterized by low SiO2 (57.68-64.28 wt%) content, high Al2O3 (13.54-16.42 wt%) content, and the A/CNK value ranges from 0.78 to 0.95, exhibiting characteristics of Itype granite. Coupled with variable zircon epsilon Hf(t) values of -8.03 to -11.03, this suggests that the parental magma was derived from the partial melting of amphibolite/basalt in the lower crust. The monzogranite contains high SiO2 (73.68-75.36 wt%) and Al2O3 (11.93-12.39 wt%), with lower MgO content (0.21-0.63 wt%). The zircon epsilon Hf(t) value ranges from -7.64 to -9.78, indicating its affinity with highly fractionated I-type granites formed by partial melting of greywackes in the lower crust. They are all enriched in large ion lithophile elements and light rare earth elements, and depleted in high field strength elements and heavy rare earth elements, formed in an active continental margin tectonic environment. The geochemical characteristics of the mafic microgranular enclaves, monzogabbro, and diabase indicate that they are alkaline to peralkaline rocks, formed during the southward subduction of the PAO slab beneath the northern margin of the NCC in the Early Permian. The break-off of the subducted slab induced upwelling of asthenosphere, which originated from the partial melting of garnet-spinel lherzolite in the enriched mantle. Synthesized data from this and previous studies leads us to favor a bidirectional subduction model of the PAO in the Early Permian, with the PAO not closed before the Early Permian.

Neoproterozoic magmatic rocks exposed along the margins of the Yangtze Block provide key constraints for deciphering the tectonic evolution of the South China Plate and reconstructing its paleogeographic position within Rodinia. This study presents an integrated investigation of Neoproterozoic mafic complexes from the Bikou microblock in the northwestern Yangtze Block, using petrology, zircon U-Pb geochronology, whole-rock geochemistry, and zircon Lu-Hf isotopes to elucidate their petrogenesis and tectonic implications. Results show that the Yanzibian mafic complex formed at 905-902 Ma, whereas the Cangshe mafic complex formed at 882-881 Ma. The Yanzibian mafic complex is characterized by enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs), with relative depletions in Nb, Ta, P, and Ti, exhibiting typical geochemical affnities of arc magmas. Zircon epsilon Hf(t) values range from +8.84 to +12.92, with tDM1 ages of 1097-931 Ma. High Nb/Zr ratios and relatively constant Rb/Y ratios suggest that these magmas were derived from the partial melting of a mantle wedge metasomatized by subduction-related melts. The Cangshe mafic complex exhibits slight LREE enrichment without significant negative Nb, Ta, or Ti anomalies, resembling the geochemical characteristics of enriched mid-ocean ridge basalt (E-MORB). Zircon epsilon Hf(t) values vary from +8.66 to +13.34, with tDM1 ages of 1086-905 Ma. Moderate Nb/Yb and Th/Yb ratios indicate that their petrogenesis was related to enriched asthenospheric upwelling triggered by slab rollback. Combined with previous studies, our results further support a long-lived subduction-related tectonic setting for the northwestern Yangtze Block during the early Neoproterozoic, suggesting that it occupied a marginal position within Rodinia.

East Junggar Orogenic Belt, at the northeastern margin of the Junggar Block, has favorable ore-forming conditions hosting various metallogenic systems, including magmatic Cu–Ni sulfide, skarn Cu–Mo, magmatic–hydrothermal Cu–Au, and porphyry Cu–Au deposits. The Devonian is a critical epoch for Cu–Au mineralization in the East Junggar Orogenic Belt, yet the tectonic controls on magma genesis and metal enrichment remain controversial. The adjacent Yuleken rhyolite porphyry and Jiamate monzodiorite, hosted in distinct metallogenic belts, provide an ideal opportunity to investigate the petrogenesis of Devonian ore-forming intrusions and their association with local tectonic regimes. To address these issues, we present new zircon U-Pb geochronological, whole-rock geochemical, and zircon Lu-Hf isotopic data for these two intrusions. Our results not only constrain the petrogenesis of Devonian ore-related magmas in the East Junggar but also contribute to refining the regional tectonic framework. Zircons from the Yuleken rhyolite porphyry and Jiamate monzodiorite show magmatic oscillatory zoning and high Th/U ratios (>0.1), confirming a magmatic origin. U–Pb dating yields weighted mean ages of 382.2 ± 3.3 Ma and 381.5 ± 3.6 Ma for Yuleken, and 381.6 ± 2.7 Ma for Jiamate. Zircons from the Yuleken rhyolite porphyry (εHf(t) = +8.53 to + 17.51, TDM2 = 0.28–0.83 Ga) and Jiamate monzodiorite (εHf(t) = +13.04 to + 17.05, TDM2 = 0.29–0.54 Ga) show highly positive εHf(t) values and young model ages, indicating a depleted mantle-dominated source with significant juvenile crustal input during the Late Devonian. The Yuleken rhyolite porphyry and Jiamat monzodiorite display island-arc related geochemical signatures, as evidenced by their high Al2O3 contents, enrichment in large ion lithophile elements (LILEs), and depletion in high field strength elements (HFSEs). Mineralization in both districts is structurally controlled by fault intersections and occurs as azurite-bearing quartz veinlets in the immediate wall rocks. Zircon trace-element geochemistry (Dy/Yb < 0.3, Eu/Eu* >1.2) indicates high water contents and elevated oxygen fugacities in the parental magmas, which facilitated Cu–Au mineralization. The East Junggar Orogenic Belt was situated in an island-arc setting during the Late Devonian. However, the two ore-forming intrusions have distinct petrogenetic origins: the Yuleken rhyolite porphyry was derived from mantle-derived basaltic magmas with juvenile lower crustal input, whereas the Jiamate monzodiorite (avg. Sr/Y = 39.75) originated from deep-seated fractional crystallization of mantle-derived basaltic magmas. These contrasting yet coeval processes, both linked to the same subduction system, were critical to Cu–Au mineralization in the two districts. This study provides new insights into Devonian metallogenic mechanisms and ore controls and offers a refined genetic framework for Cu–Au exploration in the East Junggar.

The Bikou Group, situated in the southern part of the Bikou microblock along the northwestern Yangtze Block, preserves extensive remnants of Tonian volcanic magmatism. However, the timing of its formation and its tectonic setting remain debated. In this study, we report a newly identified geological record of subduction initiation from the Heimulin forearc ophiolite in the Bikou microblock. The Heimulin ophiolite comprises Tonian forearc peridotites, forearc basalts (diabases), boninites, high-Mg andesites and dacites, resembling the forearc igneous sequences observed in the Izu-Bonin-Mariana (IBM) subduction zone. Forearc basalts (diabase) with zircon U-Pb ages of 841 Ma exhibit geochemical signatures similar to normal mid-ocean ridge basalts (N-MORB) but lower Ti/V ratios indicate slightly higher concentrations of fluid-mobile elements than N-MORB. In contrast, the similar to 834 Ma boninite displays more pronounced depletion in high field strength elements (HFSEs) and Heavy rare earth elements (HREEs) compared to the FABs. The high-Mg andesites (HMAs) and dacites yield zircon U-Pb ages of 833 Ma and 825 Ma, respectively. The HMAs were derived from partial melting of a mantle wedge metasomatized by melts/fluids released from a subducting oceanic slab, whereas the dacites were produced in a mature intra-oceanic arc setting through dehydration melting of mafic rocks in the middle to lower crust. The Heimulin forearc ophiolites record a magmatic evolution from less to more HFSE-depleted and LILE-enriched, similar to the magmatic evolution of the IBM forearc, reflecting progressive subduction of the oceanic slab. Inherited zircons and negative Hf isotopes indicate the presence of ribbon-like continental fragments in the Heimulin intra-oceanic arc, which may have facilitated the initiation of Tonian intra-oceanic subduction in the Heimulin Ocean. Integrated with previously published reliable data, our study provides further evidence that the northwestern Yangtze Block experienced continuous subduction-accretion processes during the Tonian, with the Yangtze Block (South China Block) likely situated on the margin of the Rodinia supercontinent.

The North Qaidam (NQ) preserves records of Paleozoic to Early Mesozoic magmatic activity and metamorphism, reflecting a complex multi-stage tectonic evolution. The Maoniushan Formation is a key stratigraphic record of the Proto- to Paleo-Tethys transition. We present petrological, zircon U-Pb geochronological, whole-rock geochemical, and Lu-Hf isotopic data for Maoniushan Formation alkaline volcanics in the Xiatuoaer area. The suite comprises basalt, basaltic andesite, and trachyte. Zircon U-Pb geochronology indicates an Early Devonian eruption age (ca. 403 - 400 Ma). Geochemically, the suite is shoshonitic, enriched in LREEs, and depleted in HREEs and HFSEs (e.g., Nb, Ta, P, Ti). Their epsilon Hf(t) values range from -11.4 to + 6.8, predominantly negative (-11.4 to -3.4), indicating a mixed mantle source dominated by enriched mantle. Petrographic and geochemical data indicate the basalts originated from low-degree partial melting of a mixed, fluid-metasomatized lithosphere mantle with a minor asthenosphere component. The trachytes resulted from mixing of mantle-derived mafic magmas and crustal-derived felsic melts. Integrated regional geological data indicate the NQ subcontinental mantle was metasomatized by slab-derived fluids during Proto-Tethys oceanic subduction. During the Early Devonian, lithosphere delamination and remote response to back-arc extension in the Paleo-Tethys main ocean (Qiangtang area) triggered partial melting of this metasomatized mantle, generating the Maoniushan Formation alkaline volcanics. This magmatic event marks the onset of extensional collapse of the southern Proto-Tethys orogenic belt in the NQ, indicating the terminal stage of its tectonic cycle. Concurrent development of a local aulacogen (initial rift) along the northern NQ indicates the initial transition into the Paleo-Tethys domain.

The Liqiao and Xianping plutons can provide crucial evidence for the collision-orogeny process of the Proto-Tethys Ocean in the western section of the North Qinling Orogen. In this study, we present petrological, zircon U-Pb geochronological, geochemical, and zircon Lu-Hf isotopic data for these plutons. Both the Liqiao and Xianping plutons are characterized as high-K, calc-alkaline, metaluminous to weakly peraluminous granites, with ages of 429 and 421 Ma, respectively. The Liqiao pluton was classified as I-type granite, displaying positive ϵHf(t) values ranging from −0.1 to +3.4, and high Mg# values from 37.86 to 48.25. We interpret this to indicate that it was generated by the partial melting of juvenile felsic lower crust, with a contribution from mantle-derived material. In contrast, the Xianping pluton exhibits lower Mg# values (20.40 to 35.11) and negative ϵHf(t) values (−18.0 to −13.9), consistent with the geochemical characteristics of highly fractionated I-type granite. This suggests that the Xianping pluton formed through the partial melting of ancient felsic crust and followed by extensive fractional crystallization. We propose that the Liqiao pluton originated in a syn-collisional setting, while the Xianping pluton formed in a post-collisional environment. Both plutons are products of the collisional orogeny between the Yangtze Block and the North Qinling Orogen, which were associated with the closure of the Wushan-Shangdan Ocean, the northern of the Proto-Tethys Ocean.

The closure of the Paleo-Asian Ocean is pivotal for deciphering Late Paleozoic-Early Mesozoic paleogeographic evolution and Pangea's assembly, yet the timing and geodynamic mechanism of the Central Asian Orogenic Belt's final closure remain highly debated. This study comprehensively analyzes petrology, geochemistry, zircon geochronology, and Hf isotopes of Early Permian-Late Triassic trachytes and Early Permian amphibolite in Shangyi (northern North China Block) to constrain its petrogenesis and geodynamics. Zircon U-Pb dating research displays that the three trachytes were formed at 274 Ma, 249 Ma, and 235 Ma, respectively. Geochemically, they are distinguished by high alkali content, FeOT/MgO, and Ga/Al ratio, low MgO, TiO2, and P2O5. They are enriched in large ion lithophile elements (e.g., Rb, Ba, and K) and light rare earth elements (e.g., La, Ce, and Sm). The zircon saturation temperatures (TZr) of the whole rock are 945 degrees C, 892 degrees C, and 883 degrees C, respectively, showing A-type granite affinity. The trachyte epsilon Hf(t) isotopes reveal that it is formed by the partial melting of the Archean-Paleoproterozoic crust materials. The amphibolite is dated at 297 Ma. The Permian amphibolite and trachyte were formed in the back-arc extensional tectonic environment caused by slab break-off during the PAO slab subduction to the northern North China Block (NCB). The Triassic trachytes were formed in the extensional stage after the collision between the NCB and the Siberian Block. Thus, the main body of East Asian blocks joined Pangea after the PAO closure in the Late Permian.

While extensive research has been conducted on the Early Palaeozoic tectonic evolution of the North Qilian Orogenic Belt, its Late Triassic tectono-magmatic history remains poorly understood. Controversies persist regarding the tectonic setting, ages and geodynamic setting of magmatic activity in the eastern North Qilian Orogenic Belt, which negative our comprehension of the region's post-collisional evolutionary processes. Clarifying these events is crucial for reconstructing the final stages of the Paleo-Tethys Ocean closure and the conjunction between the Qilian and Qinling Orogenic Belts. This study determined that the Shilijia monzogranite dyke formed during the Late Triassic (Norian), with 206Pb/238U weighted mean ages of 213.5 +/- 1.5 Ma and 214.5 +/- 2.3 Ma. Geochemically, the dyke is characterised by high SiO2 and alkali contents, low Al2O3 content, and an aluminium saturation index (A/CNK) ranging from 1.00 to 1.06. The dyke is enriched in large-ion lithophile elements (LILEs) such as Rb, and in high-field-strength elements (HFSEs) including Th and U, but depleted in Ba, Ta, Nb, Sr, P, Eu and Ti. The high-field-strength elements (Zr + Nb + Ce + Y) range from 389.70 to 622.39 ppm, while the rare earth element (REE) concentrations vary from 252.94 to 460.24 ppm, exhibiting a 'seagull-shaped' distribution pattern and indicating negative Eu anomalies. The K2O/Na2O ratio of the Shilijia monzogranite dyke ranges from 1.37 to 1.54, with F content below 1000 ppm. Biotite dominates the dark minerals, and plagioclase mineral content is relatively high. Geochemical characteristics suggest that the Shilijia monzogranite dyke formed in a post-orogenic extensional environment, marking the end of the Late Triassic North Qilian orogenic event and the closure of the Paleo-Tethys Ocean. In conjunction with regional geological information, the Shilijia dyke shares similarities with granites from the Qinling Orogenic Belt, thereby provide support for the region was transitioning from a post-orogenic to an anorogenic setting at the end of the Late Triassic.

The Qiushulin molybdenum deposit, located in the central Taihang Mountains of the North China Craton (NCC), is hosted at the contact zone between the quartz monzonite porphyry and the Neoarchean Fangli gneiss. LA-ICP-MS zircon U-Pb dating of the quartz monzonite porphyry yielded a weighted mean206Pb/238U age of 132 Ma. Combined with whole-rock geochemical characteristics, indicated that it was formed by the partial melting of mantle-derived amphibolite/basalt in the Early Cretaceous, which was caused by the subduction of the Paleo-Pacific plate (PPP) beneath the NCC and subsequent plate rollback. Re-Os dating was performed on molybdenite, obtaining two stages of metallogenic ages. The former metallogenic age is130 Ma, which is broadly consistent with the age of the quartz monzonite porphyry and comprises the first two mineralization stages: (Ⅰ) quartz pyrite, (Ⅱ) quartz polymetallic sulfides. The latter metallogenic age is 113 Ma, which comprises the last mineralization stage: (Ⅲ) quartz carbonate. The petrography, microscopic thermometry, and laser Raman results of fluid inclusions indicate that the main component of the inclusions is CO2, dominated by three-phase primary inclusions, with liquid-rich secondary inclusions also observed. The primary inclusion for stages I and II mineralization temperatures are 357–427 ℃ and 257–381 ℃, with salinities of 6.54–9.44 wt% and 2.96–11.61 wt%, respectively. The calculated capture pressures for stages I and II mineralization are 200–276 MPa and 203–248 MPa, and the ore-forming depth is about 8.34 km. H-O isotope analysis reveals that for stage I, the ranges of δDV-SMOWand δ18OH2Oare − 58.1 to − 59.0 ‰ and 5.37 to 6.07 ‰, respectively, plotting near the primary magmatic water field. For stage II, the ranges of δDV-SMOWand δ18OH2Oare − 59.4 to − 60.8 ‰ and 4.40 to 4.48 ‰, respectively, shifting towards the meteoric water line. This indicates that the ore-forming fluid was mainly primary magmatic water, and as the mineralization proceeded, meteoric water was added. Combined S-Pb isotope composition indicates that the metallic minerals are mainly derived from the mantle-lower crust. Based on the research of the Qiushulin molybdenum deposit and host rock quartz monzonite porphyry, together with previously regional tectonic-magmatic events, ore geology, and the geochronologic and isotopic data, we suggest that the Qiushulin molybdenum deposit is a typical porphyry-type deposit. Its formation is attributed to the crust-mantle magma interaction triggered by lithosphere extension and asthenosphere upwelling during the rollback of the subducted PPP beneath the NCC, accompanied by multi-stage tectonic magmatic activities and mineralization superposition.

Magmatism in continental margin arc is generally episodic, and alternatively appears with magmatic flare-up and lull. Although numerous researches are related to arc tempos, there is little understanding for the genetic mechanism of magmatism during a lull. According to the distribution characteristics of magmatic rocks in the Neo-Tethyan continental margin arc, this study selected the Late Cretaceous granitic rocks in Tengchong Block to further constrain their petrogenesis and dynamics process during lulls. The monzogranite ages in Husa area of Tengchong Block are 73 Ma, formed within the Late Cretaceous magmatic lull (85 similar to 65 Ma) at the continental margin arc related to Neo-Tethyan subduction. They are metaluminous to weakly peraluminous and calc-alkaline, with enriched Nd-Hf isotopic characteristics. These signatures reveal their sources are orthometamorphic gneisses in the Gaoligongshan Group. In addition, the continental margin arc related to the flat subduction of Neo-Tethyan slab should be compressional state during Late Cretaceous (ca. 85 similar to 65 Ma). Comparing Late Cretaceous magmatic rock assemblages, geochemical signatures, Zr saturated temperature and zoning in plagioclase with these in Early Eocene rocks during magmatic flare-up (ca. 55 similar to 50 Ma), the granitic rocks during a magmatic lull formed at a thicken crust and partial melting of gneisses induced by a long-time thermal accumulation. Therefore, the continental margin arc could form granitic magma by a long-time thermal accumulation within a thicken crust during a magmatic lull with the low mantle-derived magma flux at a local region.

The conjunction of the Qinling-Qilian Orogenic Belt is a critical area for understanding the tectonic relationship between the eastern and western sections of the Central China Orogenic Belt. It serves as an important region for studying the tectonic framework of the northern margin of the Proto-Tethys Ocean. This paper identifies a series of meta-volcanic rocks in the Fanjiaqu area of Fenggeling Town, situated in the eastern section of the North Qilian Orogenic Belt. To determine the formation age, petrogenesis, and tectonic environment of these volcanic rocks, we conducted systematic studies that include petrology, geochemistry, isotope geochronology, and zircon Lu-Hf isotope analysis. Petrographic analysis reveals that the protoliths of the meta-volcanic rocks comprise an assemblage of basalt, andesite, dacite, and rhyolite. LA-ICP-MS zircon U-Pb dating indicates that the protoliths of the meta-basaltic andesite and meta-dacite were formed at 441.9 +/- 4.1 Ma and 443.9 +/- 2.6 Ma, respectively. Geochemical characteristics show that the meta-basalt-andesite has medium SiO2 contents (47.10% to 59.64%), higher TFe2O3 and TiO2 contents, lower Cr and Ni concentrations, Mg# values ranging from 43 to 53 and La/Nb ratios between 4.53 and 5.97. In contrast, the meta-dacite and meta-rhyolite exhibit high SiO2 (67.62% to 75.18%) and Al2O3 contents, along with low TFe2O3, TiO2 and P2O5 contents, as well as Mg# values ranging from 42 to 55. Overall, the meta-volcanic rocks display notable negative Eu anomalies, with Eu/Eu* values varying from 0.76 to 0.83 for basic rocks and from 0.47 to 0.79 for acidic rocks. The meta-volcanic rocks are enriched in large-ion lithophile elements (LILE), such as Th and U, while being depleted in high-field-strength elements (HFSE) like Nb, Ta and Ti, indicating geochemical characteristics similar to those of arc magmatic rocks in subduction zones. The zircon epsilon Hf (t) values of the meta-dacite range from +4.5 to +13.1, while the two-stage model ages (TDM2) range from 1135 to 588 Ma. These characteristics suggest that the meta-basalt-andesite derived from partial melting of the mantle, metasomatised by subduction fluids, whereas the meta-dacite and meta-rhyolite are products of crust-mantle mixing. Integrating regional geological data, this study proposes that the meta-volcanic rocks in the Fenggeling area formed in a continental margin arc environment, while the eastern section of the North Qilian Orogenic Belt was in the subduction setting of back-arc oceanic crust during the Late Ordovician to Early Silurian.

The North China Craton (NCC) is considered a part of the Columbia Supercontinent, and geological records related to the convergence and breakup events of the Columbia Supercontinent have been preserved to varying degrees. The Shangyi Complex, located at the tectonic conjunction of the Khondalite Belt and the Trans-North China Orogen (TNCO) on the northern margin of the NCC, recorded the tectonic magmatic activities related to the collision orogeny of the Ordos Block and the Yinshan Block at similar to 1950 Ma and the Western and Eastern Blocks at similar to 1850 Ma respectively. The Shangyi Complex mainly comprises leucogranite, garnet granite, and gabbro. In this paper, LA-ICP-MS zircon U-Pb dating, whole rock geochemistry, and Lu-Hf isotope studies on leucogranite and garnet granite are conducted, and the ages of the zircons are 1961 +/- 20 Ma and 1873 +/- 20 Ma respectively. Geochemical characteristics show that they are all S-type granites. The results of the zircon Lu-Hf isotope show that the epsilon(Hf)(t) values of the leucogranite zircons range from -5.86 to + 5.88, with an average value of +1.11, and the two-stage model ages (T-DM2) range from 2943 Ma to 2222 Ma, which is formed by the partial melting of ancient crusts during the collision of the Yinshan Block and the Ordos Block. The epsilon(Hf)(t) values of the garnet granite zircon range from +0.86 to +2.53, with an average value of +1.50, and the two-stage model ages (T-DM2) range from 2464 Ma to 2361 Ma, which is formed by the partial melting of Paleoproterozoic crusts during the collision of the Western Block and the Eastern Block. The gabbro geochemical characteristics show that it possess alkaline rock property, which was formed by the underplating of mantle-derived magma in the postcollision extension stage after the collision of the Western and Eastern Blocks.

Numerous granitic pegmatite dikes intrude the Wuduoshan batholith in the eastern North Qinling orogen (NQ). However, the petrogenesis, interrelationships, and geodynamic setting of these granitoids and associated dikes remain poorly understood. This study investigates the Erlangchuan and Sikeshu plutons and their related dikes in the Qinling orogen, central China, through integrated petrographic, whole-rock geochemical, zircon U-Pb geochronological, and Lu-Hf isotopic analyses. Zircon U-Pb dating yielded crystallization ages of 430.8 +/- 2.0 Ma for the Erlangchuan monzogranites, 415.2 +/- 1.7 Ma for associated biotite granitic pegmatites, 416.9 +/- 2.2 Ma for associated aplite dikes, and 403.6 +/- 4.7 Ma for Sikeshu muscovite granitic pegmatites. All samples display geochemical characteristics consistent with a crustal origin, showing enrichment of large-ion lithophile elements (LILE; e.g., Rb, Th, Ba, and Cs) and depletion of high field strength elements (HFSE; e.g., Nb, Ta, and Ti). The granitic dikes exhibit higher SiO2 contents compared to their respective host plutons: the K-rich Erlangchuan monzogranites and the Na-rich, two-mica Sikeshu granites. Zircon Lu-Hf isotopic data reveal higher epsilon Hf(t) values for the Erlangchuan monzogranites (average = +2.6) compared to the associated biotite pegmatites (+2.0), aplites (+1.6), and the Sikeshu muscovite pegmatites (+0.9). The epsilon Hf(t) values of both plutons and their dikes fall between those of the Qinling Group and juvenile mafic crust, suggesting derivation from a mixed source. Variations in epsilon Hf(t) values likely reflect differing proportions of these two endmembers. The Erlangchuan monzogranites formed via partial melting of the lower crust, triggered by mafic magma underplating during Shangdan Ocean subduction. The Sikeshu two-mica granites, associated aplites, and biotite pegmatites likely formed during subsequent collision and slab break-off. Finally, the Sikeshu muscovite pegmatites may represent a later magmatic pulse related to post-collisional lithospheric delamination. Regionally, granitic pegmatites in the eastern NQ define three distinct age peaks at 437 Ma, 413 Ma, and 367 Ma. These pegmatites can be broadly classified into two series: (1) a rare metal-bearing series, predominantly located in the northern eastern NQ, enriched in Nb, Ta, Be, Rb, Li, and Cs, and characterized by negative epsilon Hf(t) values indicative of a Qinling Group source; and (2) a U-bearing series, primarily found in the southern eastern NQ, positive or slightly negative epsilon Hf(t) values, suggesting derivation from a mixed Qinling Group and juvenile crustal source.

The study area is situated in the Tianshan region,specifically within the eastern segment of the North Qilian Orogenic Belt(NQLOB).The NQLOB is a critical region for understanding oceanic closure and continental collision processes driven by the Shangdan Ocean subduction-exhu-mation,which was a segment of the Proto-Tethys Ocean during the Early Paleozoic.Despite significant research,the Early Paleozoic tectonic background and subduction-related orogenic processes,particularly in the eastern NQLOB,remain subjects of debate.This study presents significant petrographic,geochemical,and geochronologic insights into the metavolcanic rocks of the Chenjiahe Group in the eastern NQLOB.Petrographic analysis reveals that these metavolcanic rocks originated in a low-grade metamorphic setting.Zircon laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)U-Pb dating yielded ages ranging between 449.7-443.4 Ma,indicating Late Ordovi-cian formation.Geochemical signatures of felsic and inter-mediate rocks exhibit calc-alkaline to high-K calc-alkaline similarities,characterized by high light rare earth elements(LREEs),low heavy rare earth elements(HREEs),and mod-erate Eu anomalies,consistent with a continental arc set-ting.In contrast,basaltic rocks display tholeiitic features with elevated large-ion lithophile elements(LILEs),reduced high-field-strength elements(HFSEs),and weak Eu anoma-lies,suggesting an extensional environment.These findings imply that the metavolcanic rocks evolved in a continental arc-back-arc extension setting connected with the northward subduction and exhumation of the Huluhe back-arc oceanic basin.This process was likely triggered by the northward subduction and closure of the Shangdan Ocean,culminating in the Late Ordovician amalgamation of the Qilian Block and the southwestern North China Block.This study pro-vides critical insight into the tectonic development of the NQLOB and the broader Proto-Tethys Ocean dynamics at the northern periphery of the Eastern Gondwana.

The formation of early Mesozoic granitoid plutons in the Qinling Orogen is widely regarded as a result of the collision and accretion between the Yangtze Block and the South Qinling Block during the early Mesozoic, but the specific magmatic process, source composition, tectonic environment and deep dynamic background remain controversial. This study reports the petrology, zircon U–Pb geochronology, and whole-rock geochemistry of diorites from the Liuba and Qingyangyi plutons in the South Qinling, to provide new evidence for understanding the final collision tectonic evolution process of Qinling Orogenic belt. The Liuba and Qingyangyi plutons, located in the central part of the South Qinling region, are primarily composed of quartz diorite and quartz monzodiorite, respectively. The results indicate that the weighted mean crystallization ages of the quartz diorite in the Liuba pluton range from 216.1 ± 0.8 Ma to 217.1 ± 1.3 Ma, with the weighted mean crystallization ages of its MMEs being 215.4 ± 1.0 Ma. The crystallization ages of the quartz monzodiorite in the Qingyangyi pluton range from 214.6 ± 0.9 Ma to 215.4 ± 0.9 Ma, suggesting that both plutons were formed in the late Triassic. The investigated plutons are characterized as right-leaning and have weak negative Eu anomalies on the chondrite-normalized REE patterns diagram. The large ion lithophile elements (LILE) Rb, Ba, Th and K are relatively enriched, while high-field strength elements (HFSE) Nb, Ta, Ti and P are strongly depleted. The formation of numerous MMEs in the Liuba pluton is the product of magmatic mixing. The Liuba and Qingyangyi plutons are the results of crust thickening and partial melting of lower crust caused by the comprehensive late Triassic collision between the Yangtze Block and the North China Block (NCB), and are the manifestation of magmatic intrusion along the South Qinling tectonic belt in the late Triassic period.

The Cambrian period marks a crucial phase in the initial subduction of the Proto-Tethys Ocean beneath the East Kunlun Orogen. Studying the I-type granites and mafic–ultramafic rocks formed during this period can provide valuable insights into the early Paleozoic tectonic evolution of the region. This paper incorporates petrology, LA-ICP-MS zircon U-Pb geochronology, and whole-rock major and trace element data obtained from the Kekesha intrusion in the eastern section of the East Kunlun Orogen. The formation age, petrogenesis, and magmatic source region of the intrusion are revealed, and the early tectonic evolution process of the subduction of the Proto-Tethys Ocean is discussed. The Kekesha intrusion includes four main rock types: gabbro, gabbro diorite, quartz diorite, and granodiorite. The zircon U-Pb ages are 515.7 ± 7.4 Ma for gabbro, 508.9 ± 9.8 Ma for gabbro diorite, 499.6 ± 4.0 Ma for quartz diorite, and 502.3 ± 9.3 Ma and 501.6 ± 6.2 Ma for granodiorite, respectively, indicating that they were formed in the Middle Cambrian. The geochemical results indicate that the gabbro belongs to the high-Al calc-alkaline basalt series, the gabbro diorite belongs to the medium-high-K calc-alkaline basalt series, the quartz diorite belongs to the quasi-aluminous medium-high-K calc-alkaline I-type granite series, and the granodiorite belongs to the weakly peraluminous calc-alkaline I-type granite series, all of which belong to the medium-high-K calc-alkaline series that have undergone varying degrees of differentiation and contamination. Gabbro and gabbro diorite exhibit significant enrichment in light rare earth elements (LREEs), depletion in heavy rare earth elements (HREEs), and an enhanced negative anomaly in Eu (Europium). Compared to gabbro and gabbro diorite, quartz diorite and granodiorite exhibit more pronounced enrichment in LREEs, more significant depletion in HREEs, and an enhanced negative anomaly in Eu. All four rock types are enriched in large-ion lithophile elements (LILEs) such as Cs, Rb, Th, Ba, and U, and are depleted in high-field-strength elements (HFSEs) such as Nb, Ta, and Ti. This indicates that these rocks originated from the same or similar mixed mantle source regions, and that they are formed in the island-arc tectonic environment. This paper suggests that the gabbro and gabbro diorite are mainly derived from the basic magma formed by partial melting of the lithospheric mantle metasomatized by subducted slab melt in the oceanic crust subduction zone and mixed with a small amount of asthenosphere mantle material. Quartz diorite results from the crystal fractionation of basic magma and experiences crustal contamination during magmatic evolution. Granodiorite forms through the crystal fractionation of basic magma, mixed with partial melting products from quartz diorite. While the lithology of the intrusions differs, their geochemical characteristics suggest they share the same tectonic environment. Together, they record the geological processes associated with island-arc formation in the East Kunlun region, driven by the northward subduction of the Proto-Tethys Ocean during the Early Paleozoic. Based on regional tectonic evolution, it is proposed that the Proto-Tethys Ocean began subducting northward beneath the East Kunlun block from the Middle Cambrian. The Kekesha intrusion formed between 516 and 500 Ma, marking the early stages of Proto-Tethys Ocean crust subduction.