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Mafic dikes are generally emplaced in extensional tectonic settings and provide key information regarding deep mantle processes and sources. The Bangong-Nujiang suture zone was formed by the collision of the Qiangtang and Lhasa terranes and experienced intense magmatism during the Early Cretaceous. However, the deep mantle processes and mechanisms involved in this magmatic flare-up (ca. 115 Ma) in the collisional belt remain controversial because of the lack of evidence for coeval mafic magmatism. Here, we present detailed petrological, geochronological, geochemical, and Sr-Nd-Hf-O isotope data for the newly discovered hypersthene-bearing mafic dikes in the Baingoin area in the middle-eastern parts of the Bangong-Nujiang suture zone, central Tibet. Secondary ion mass spectroscopy (SIMS) zircon U-Pb dating showed that the mafic dikes were emplaced during 120−115 Ma. These mafic rocks are characterized by variable MgO contents (2.7−5.2 wt%) and Mg# values (38.5−52.8), slight enrichment in light rare earth elements (REEs; [La/Yb]N = 7.5−8.1), relatively flat heavy REE patterns ([Gd/Yb]N = 1.75−1.84), and negative Eu, Ta, Nb, and Ti anomalies. The dikes also have relatively low initial 87Sr/86Sr ratios (0.7060−0.7062) and negative εNd(t) (−2.2 to −1.6) and positive εHf(t) (+2.5 to +3.6) values, and variable zircon εHf(t) (−2.2 to +7.2) and slightly elevated zircon δ18O (5.6‰−7.0‰) values. These geochemical characteristics indicate that the mafic dikes were derived from an enriched lithospheric mantle source. However, compared with coeval magmatic rocks, the mafic dikes have relatively high εNd(t) and εHf(t) values, indicating that they contain a depleted mantle component. The mafic dikes contain clinopyroxene and orthopyroxene (i.e., hypersthene), indicative of derivation from a high-temperature magma source. Clinopyroxene-melt thermobarometry yielded a temperature range of 1167−1213 °C, further supporting the involvement of a high-temperature asthenospheric component. Therefore, we suggest that the parental magmas of the Nakoulai mafic dikes were probably generated by the interaction between the asthenospheric mantle and overlying metasomatized lithospheric mantle. Combined with data from nearby Cretaceous magmatic rocks and sedimentary rocks, we suggest that the mafic dikes were generated in a postcollisional setting caused by upwelling of asthenospheric mantle owing to slab breakoff beneath the Bangong-Nujiang suture zone. Slab breakoff played a key role in the crust-mantle interactions and the onset of the magmatic flare-up in the middle-eastern parts of the Bangong-Nujiang suture zone.

Supplementary figures, Analytical methods, and Analytical data.

Subduction erosion is important for crustal material recycling and is widespread in modern active convergent margins. However, such a process is rarely identified in fossil convergent systems, which casts doubt on the importance of subduction erosion through the geological record. We report on ca. 155 Ma Kangqiong (pluton) intrusive rocks of a Mesozoic magmatic arc in the southern Qiangtang terrane, central Tibet. These rocks mainly consist of trondhjemites and tonalites and are similar to slab-derived adakites with mantle-like zircon oxygen isotope compositions (δ18O = 5.2‰–5.6‰), they display more evolved Sr-Nd isotopes and higher Th/ La relative to mid-oceanic ridge basalts from the Bangong-Nujiang suture, and they contain abundant amphibole and biotite. These characteristics indicate magma generation via H2O- fluxed melting of eroded forearc crust debris with subducted oceanic crust at 1.5–2.5 GPa and 700–800 °C. In addition, the intrusions are exposed

Subduction of Indian continental lithosphere during the Asia-India collision played an important role in the formation and evolution of the Himalaya-Tibetan orogen. However, the geometry of early Indian continental subduction remains debated. Given that the Indian continent is characterized by enriched isotope ratios (87Sr/86Sr > 0.730, εNd(t) < −10), relative to those in subducted oceanic materials (87Sr/86Sr < 0.704, εNd(t) ≈ +8), changes in the composition of magmatic rocks with time, in particular their radiogenic isotope ratios, is used to constrain the timing and nature of continental subduction. This study reports the field relations, zircon U-Pb ages and geochemical composition of a syn-collisional batholith that crosscuts the central Indus-Yarlung Zangbu suture in the Saga area of southern Tibet. Zircon U/Pb ages for the batholith mainly range from 50 to 46 Ma. Samples from the Lopu Range batholith have enriched zircon Hf (εHf(t) = −0.4 to −8.6) and whole rock 87Sr/86Sri = 0.7094–0.7121 and εNd(t) = −7.3 to −9.8, suggesting that they were derived from a mixture of juvenile Gangdese and isotopically enriched Indian crustal materials. This result indicates that subduction of Indian crustal rocks occurred before 50 Ma in the central Himalaya. The geochemical composition and distribution of high volume ca. 51 Ma magmatism in the Gangdese belt, combined with thermal models of the subduction zone, suggests a steepening of the subducted Indian continental lithosphere occurred between the onset of India-Asia collision (59 Ma) and 46 Ma in the central-eastern Himalaya.

The petrogenesis of biotite granites, which may be metaluminous or peraluminous in composition, is a subject of debate. In this study, we present new zircon U-Pb geochronology and O-Hf isotopic, and whole-rock major and trace element, and Sr-Nd isotopic data for biotite granites in the Langla–Laqinpu area of northern Lhasa Terrane, central Tibet. The rocks are distributed along the eastern segment of the Bangong–Nujiang Tethys Ocean suture, and were emplaced during the late Early Cretaceous (ca.119 Ma). The biotite granites are peraluminous, and have high SiO2 (67.5–72.4 wt%) and low MgO (0.57–1.20 wt%) and CaO (2.36–4.38 wt%) contents with variable K2O/Na2O ratios (0.77–1.32), and show geochemical affinity with the upper-continental crust, e.g., enrichment of Rb, Th, U, K and Pb, depletion of Nb, Ta, Ti, P, Eu, and Sr. They are characterized by relatively high initial 87Sr/86Sr ratios ((87Sr/86Sr)i = 0.7098–0.7137) and low eNd(t) values (−8.4 to −10.3), and high zircon δ18O values (8.29–13.47‰) and variable eHf(t) values (−0.02 to −21.36), indicating they were derived through partial melting of a crustal source consisting of metagreywackes with or without minor metaigneous rocks. Taking into account all available regional geological data, we suggest that the Bangong–Nujiang Tethys Ocean may undergo diachronous closure–although the eastern segment may have been closed by the late Early Cretaceous, its western and western–middle segments may still have been at least partially open and active at that time. The Langla–Laqinpu biotite granites were probably generated in post-collisional setting, following slab break-off after closure of the Bangong–Nujiang Tethys Ocean.

Amphibole is thought to be a key control on the differentiation of arc magmas but the fractionation of this mineral remains enigmatic because it is rarely present in erupted lavas. This study presents detailed petrological, mineralogical, and geochronological data for newly identified Late Triassic (217–215 Ma) mafic intrusive rocks from the Gangdese arc of southern Tibet. These gabbros host an amphibole-rich cumulate enclave and clinopyroxene crystal clots, including two mineral assemblages in chemical disequilibrium: (1) amphibole and Type-1 clinopyroxene within the enclave and clots; and (2) small crystals of Type-2 clinopyroxene, plagioclase, and biotite within the host. Textural and geochemical evidence indicate that the enclave and clots represent captured fragments of amphibole- and clinopyroxene-dominated lower crustal crystal mushes, respectively, whereas small host crystals formed by the shallow crystallization of evolved melts extracted from these crystal mushes. The compositional variations between the two types of clinopyroxene also reveal this melt segregation process. Amphibole with similar rare earth element patterns to associated Type-1 clinopyroxene inclusions suggest that the former formed through peritectic reactions consuming clinopyroxene. Enhanced amphibole fractionation may also have occurred as a result of the presence of high-density clinopyroxene inclusions. This indicates that the fractionation of amphibole together with precursory clinopyroxene inclusions within the deep crust controls the early chemical evolution of mafic arc magmas, a process that is consistent with the geochemical variations in lavas from three other active arc volcanoes. The associated cumulates can efficiently delaminate back into the mantle, ultimately leading to the generation of SiO2-rich continental crustal material.

Incompatibility group C (IncC) plasmids have received attention due to their broad host range and because they harbor key antibiotic resistance genes. Because these resistance genes can spread from food-producing animals to human, the proliferation of these plasmids represents a public health risk. In this study, a total of 20 IncC plasmids were collected from food-producing animals in China, and characterized by Oxford Nanopore Technologies (ONT) long-read sequencing. Based on four key differences of the IncC backbone, 4 IncC plasmids were classified as type 1, 15 were classified as type 1/2 hybrid, and one was classified as type 2. The 15 type 1/2 hybrids were further divided into 13 type 1/2a and 2 type 1/2b, based on sequence differences arising from different homologous recombination events between type 1 and type 2 IncC backbones. Genome comparison of accessory resistance modules showed that different IncC plasmids exhibited various phenotypes via loss and gain of diverse modules, mainly within the blaCMY-carrying region, and two antibiotic resistance islands designated ARI-A and ARI-B. Interestingly, in addition to insertion and deletion events, IS26 or IS1294-mediated large sequence inversions were found in the IncC genome of the 4 type1/2a plasmids, suggesting that insertion sequence (IS)-mediated rearrangements also promote the diversity of the IncC genome. This study provides insight into the structural diversification and multidrug resistance of IncC plasmids identified from food-producing animals in China.

A-type granites have been the focus of considerable research due to their distinctive major- and trace-element signatures and tectonic significance. However, their petrogenesis, magmatic source and tectonic setting remain controversial, particularly for aluminous A-type granites. The earliest Cretaceous (ca. 140 Ma) Comei granite in the eastern Tethyan Himalaya is associated with coeval oceanic island basalt (OIB)-type mafic lava, and has A-type granite geochemical characteristics including high 10,000 × Ga/Al (up to 6), FeOtotal/MgO (4.6–6.1) and (Na2O + K2O)/Al2O3 (0.50–0.61) ratios but low CaO (0.6–1.6 wt%) and Na2O (1.8–2.6 wt%) contents. The Comei granite also has variable peraluminous compositions (A/CNK = 1.00–1.36) along with zircon δ18O, εNd(t) and initial 87Sr/86Sr values of 8.2‰ to 9.3‰, − 13.0 to − 12.4 and 0.7238 to 0.7295, respectively. This range of compositions can be interpreted as the interaction between high-temperature upwelling OIB type basaltic magmas and a shallow crustal (< 5 kbar) metapelitic source. The Comei granite and coeval OIB type basaltic rock could represent the earliest stage (145–140 Ma) of a large igneous event in eastern Tethyan Himalaya, which may well have been triggered by pre-breakup lithospheric extension prior to the arrival of the Kerguelen plume head.

High-silica granites are common in collisional orogenic belts. However, the petrogenesis of such granites and the geodynamic processes associated with their emplacement are debated. In this study, we present zircon U–Pb ages and Hf isotopes, and whole-rock geochemical and Sr–Nd isotopic compositions for biotite granites from the Jiang Co area, in the Bangong–Nujiang suture zone, central Tibet. Zircon U–Pb dating reveals that the Jiang Co granites were emplaced during the late Early Cretaceous (ca.114 Ma). These granites are characterized by high and variable SiO2 (69.7–78.2 wt%) and K2O (4.7–8.4 wt%), and low MgO (0.09–1.25 wt%) and P2O5 (

The nature and pre‐Cenozoic evolution history of crust in southern Lhasa, which is crucial for our understanding of Indo‐Asian continental collision and Tibetan uplift during the Cenozoic, remains controversial due to a “missing” pre‐Mesozoic magmatic record. In this contribution, we report petrological and geochemical data for newly identified Paleozoic bimodal magmatism in the Zhengga area of southern Tibet. The magmatism comprises Late Devonian‐Early Carboniferous (366–353 Ma) amphibolite and two‐mica gneissic granite. The protoliths of the Zhengga amphibolite were gabbro and diorite with low SiO2 and high MgO, Cr, and Ni contents with high eNd(t) values of +3.3 to +8.0, variable and positive zircon eHf(t) of +0.9 to +11.2, and low zircon δ18O of 5.7 ± 0.2‰. These protoliths are proposed to have formed by decompression melting of asthenosphere during intracontinental back‐arc extension. In contrast, the granite has relatively high SiO2 and low MgO contents with much lower eNd(t) of −8.6 to −7.3, variable and negative zircon eHf(t) of −10.4 to −1.3, and high zircon δ18O of 9.4 ± 0.2‰ values and was most likely derived from an ancient metasedimentary source. This magma subsequently underwent recharge with minor amounts mafic magma followed by fractional crystallization of K‐feldspar in middle‐upper crust (~10–20 km) magma chambers. Using our new data, in combination with Nd‐Hf isotopes, we present the first comprehensive picture of crustal evolution in southern Lhasa. The southern Lhasa sub‐block is likely to have been a microcontinent that underwent extensive Phanerozoic crustal reworking and growth, rather than a Mesozoic‐Early Tertiary juvenile accretionary arc terrane.

Crustal reworking in the collisional zones is commonly considered as an important process to result in continental crust differentiation and maturation. However, the reworking mechanism remains unclear. Here, a combined study of zircon SIMS U–Pb age, whole-rock major and trace element, Sr–Nd–Hf and zircon Hf–O isotopic geochemistry was carried out for the Duoma–Namuqie (DM–NMQ) granite porphyry intrusions, including DM, NMQ I, II and III intrusions, in southern Qiangtang, central Tibet. Zircon SIMS U–Pb dating yielded ages of 79–76 Ma, suggesting that they were formed in the later stage of Late Cretaceous. The DM granite porphyries are metaluminous to peraluminous with slightly low SiO2 (69.2–71.4 wt%) and high MgO (0.67–0.79 wt%) contents. They are depleted in high-field-strength elements (HFSEs) and enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs), and show weakly negative Eu anomalies. The NMQ III granite porphyries show similar elemental features to the DM granite porphyries, but have relatively high SiO2 (69.8–72.2 wt%) and low MgO (0.25–0.28 wt%) contents. Both of them belong to I-type granites. The NMQ I and II granite porphyries are relatively differentiated with high SiO2 (76.4–77.9 wt%), low MgO (0.11–0.16 wt%) contents, and significantly negative Eu anomalies. Extremely low LREE contents and notable REE tetrad effect can be observed in the NMQ II granite porphyries. The NMQ I and II intrusions are fractionated I-type granites. The whole-rock Sr–Nd–Hf and zircon Hf–O isotope data exhibit an enriched trend from the DM granite porphyries ((87Sr/86Sr)i = 0.7049–0.7050, eNd(t) = 1.2–1.6, eHf(t)whole-rock = 9.9–12.0, eHf(t)zircon = 7.4–11.5, δ18O = 6.2–7.1‰) to the NMQ III granite porphyry ((87Sr/86Sr)i = 0.7058–0.7067, eNd(t) = −0.9 to −1.1, eHf(t)whole-rock = 7.0–7.4, eHf(t)zircon = 2.7–9.5, δ18O = 7.2–7.6‰) to the NMQ I and II granite porphyries (eNd(t) = −3.0 to −4.3, eHf(t)whole-rock = 5.3–6.6, eHf(t)zircon = 1.5–7.4, δ18O = 6.6–9.2‰). We suggest that the DM–NMQ granite porphyries were mainly derived by partial melting of the juvenile mafic lower crust with variable volumes of ancient crustal components involved in their magma sources. The way in which these granite porphyries were formed provides evidence for the crustal differentiation and maturation in a post-collisional extensional setting triggered by the far-field rollback of the subducted Neo-Tethys oceanic slab

Arc magmas are generated by complex geological processes in subduction settings. Due to the complexity of source materials and geological processes, the genesis of arc magmatic rocks can be difficult to disentangle. Here, we report on diorites from the Kenama area of the middle-eastern part of the Bangong–Nujiang suture zone in central Tibet. New SIMS and LA–ICP–MS zircon U Pb dating for three diorite samples indicates that they crystallized during the early Late Jurassic (ca. 161 Ma). The diorites can be divided into two groups based on whole-rock major element compositions and mineralogical characteristics: Group I diorites with relatively low SiO2 (47.6–53.4 wt%), and high MgO (4.97–9.10 wt%) and amphibole contents (50–54 vol%); and Group II diorites with slightly higher SiO2 (56.9–59.5 wt%), and low MgO (2.9–3.8 wt%) and amphibole contents (25–30 vol%). The Group I diorites exhibit relative enrichment in light rare earth element (LREE) ((La/Yb)N = 5.7–10.5) with slightly negative Eu anomalies, and are characterized by enrichment of large ion lithophile elements (LILEs; K, Rb, Ba, Th, and U), the depletion of high field strength elements (HFSEs; Nb, Ta, Zr, Hf, and Ti). The Group I diorites have relatively high initial 87Sr/86Sr ratios (0.7073–0.7094), variably negative eNd(t) values(−10.3 to −5.9), negative zircon eHf(t) values (−14.8 to–4.4), and slightly elevated δ18O values (6.5‰–7.3‰). The Group II diorites show similar trace element characteristics to Group I. They also have high initial 87Sr/86Sr ratios (0.7083–0.7087), uniformly negative eNd(t) values (−9.5 to −9.0), negative zircon eHf(t) values (−10.3 to −4.2), and elevated δ18O values (6.6‰–7.5‰). Amphiboles from Group I and Group II diorites have low Al2O3 contents (3.6–9.9 wt% and 5.6–8.5 wt%, respectively), and formed at similar P–T conditions (751–871 °C and 69–226 MPa and 745–832 °C and 77–162 MPa, respectively). On primitive mantle-normalized spider diagrams, these low-Al amphibole grains have slightly convex upward REE patterns with distinctly negative anomalies in Pb, Sr, Eu, Zr, Hf, and Ti, suggesting that amphiboles from both groups crystallized from the similar arc magmas after plagioclase and magnetite crystallization. These mineralogical, geochemical and isotopic characteristics suggest that both groups of Kenama diorites probably originated from an enriched lithospheric mantle metasomatized by subducted oceanic sediment-derived melts. Their parental magmas may have similar geochemical characteristics and underwent varying degrees of accumulation and fractional crystallization. The Group I diorites were likely generated by accumulation of amphibole and fractional crystallization of olivine, clinopyroxene, and plagioclase from mafic magmas, and the Group II diorites were formed by the fractional crystallization of clinopyroxene and plagioclase from mafic magmas that were geochemically similar to the Group I diorites. In combination with regional geology, in particular adjacent ophiolites, high-magnesian andesitic rocks and Cretaceous sedimentary rocks, we conclude that all of the Kenama diorites were probably generated in an early Late Jurassic arc setting related to the subduction of the Bangong–Nujiang Tethys oceanic lithosphere.

The South China Block (SCB) is considered to have undergone extensive reworking of continental crust. However, the mechanisms of this crustal reworking are unclear. Here, we report on Late Jurassic (162–155 Ma) two-mica granites and associated diorites and syenite porphyries from the Huolushan–Longyandong area of Guangzhou City, southeastern China. The two-mica granites have high SiO2 contents (69.6–73.6 wt%) and weakly peraluminous to strongly peraluminous compositions. These rocks have enriched Sr–Nd–Hf isotopic compositions ((87Sr/86Sr)i = 0.7094–0.7145; eNd(t) = −10.5 to −9.3; eHf(t) = −12.7 to −4.2). The Huolushan two-mica granites have variable zircon O isotopic compositions (δ18O = 6.8‰–10.4‰), whereas the Longyandong two-mica granites have homogeneous compositions (δ18O = 8.6‰–9.9‰). The Huolushan syenite porphyries have moderate SiO2 (59.6–60.1 wt%) and high alkaline (K2O + Na2O = 9.4–9.8 wt%) contents. Their Sr–Nd–Hf–O isotopic compositions ((87Sr/86Sr)i = 0.7105–0.7119; eNd(t) = −9.9 to −9.8; eHf(t) = −14.1 to −5.9; δ18O = 6.5‰–10.6‰) are similar to those of the Huolushan two-mica granites. The Huolushan diorites have moderate SiO2 contents (59.9–60.4 wt%) and are high-K calc-alkaline and metaluminous with Mg# values of 43.2–43.8. Their Sr Nd isotopic compositions ((87Sr/86Sr)i = 0.7106–0.7109, eNd(t) = −8.8 to −8.6) are less enriched than those of the two-mica granites and syenite porphyries. In addition, the diorites have high zircon δ18O values (7.8‰–8.9‰) and a wide range of zircon eHf(t) values (−13.4 to −5.6). We propose that the Huolushan two-mica granites were derived from a metagreywacke-dominated hybridized source with minor juvenile crustal rocks and that the Longyandong two-mica granites were generated by partial melting of metagreywackes. The Huolushan syenite porphyries were formed by the mixing of metasedimentary-rock-derived felsic magmas and minor enriched-mantle-derived alkaline magmas. The Huolushan diorites were most likely derived by partial melting of mafic lower crust, with the dioritic magmas undergoing assimilation and fractional crystallization (AFC) during ascent. All of these intrusive rocks were likely formed in an extensional intraplate setting. The mantle-derived magmas, which could have been triggered by lithospheric extension, underplated the middle–lower crust and provided heat for crustal reworking and materials for late Mesozoic crustal growth.