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Orogenic peridotite is an important component of orogenic belts and retains crucial information on mantle magmatic activity, slab subduction, and melt or fluid metasomatism. To determine the source of the mantle‐derived parental magma of the peridotite and to investigate the metasomatism that it experienced, we undertook an integrated study of the petrography, whole‐rock major‐ and trace‐element compositions, in situ zircon U‐Pb geochronology, and mineral major‐and trace‐element compositions of an early Paleozoic ultramafic complex in the North Wulan area of North Qaidam. The Halihatu ultramafic–mafic complex is composed of dunite, pyroxene peridotite, and gabbro, which are characteristic of Alaskan‐type complexes. The dunite yields a weighted mean 206Pb/238U age of 479 ± 5 Ma (MSWD = 0.7), which reflects the age of the metasomatism rather than the crystallization age of the ultramafic magma. The peridotites have high Mg# (89.8–91.8) and Cr contents (2419–5190 ppm), low Al2O3 (0.20–1.68 wt%) and Ni (289–1012 ppm) contents, and high olivine Fo contents (87–91), suggesting a large degree (∼15%–22%) of partial melting of lithospheric ultramafic rocks followed by variable degrees of fractional crystallization of olivine and pyroxene. This is consistent with estimates of 15%–22.3% partial melting calculated using the Cr# of spinel crystals and with the low Yb (0.04–0.33 ppm) and Y (0.72–1.29 ppm) contents of clinopyroxene crystals. Whole‐rock trace‐element patterns show enrichment in large ion lithophile elements and depletion in high field strength elements, along with high Al2O3 (2.10–6.47 wt%) and low TiO2 (0.01–0.21 wt%) contents of clinopyroxene crystals, suggesting an arc magma cumulate trend. These features, along with the high olivine Fo contents (87–91 ppm), imply that the Halihatu peridotite is an Alaskan‐type crustal cumulates derived from Mg‐rich hydrous basaltic melts. The high estimated fO2 (FMQ +1.97 to FMQ +3.81) further supports the idea that they formed in an arc setting. The Ni/Co and Ni/Mn ratios and cumulate textures of the olivine, quenched boundaries between mafic and felsic melts, and the occurrence of tremolite and phlogopite reflect interactions between the Halihatu peridotite and injected silicate and carbonatitic melts in the lower crust. Therefore, we propose a new cumulate‐infiltration model for the petrogenesis of Alaskan‐type ultramafic complexes, which improves our understanding of the nature of Alaskan‐type continental arc root. [ABSTRACT FROM AUTHOR]

The metamorphism of the Central Qilian Block in the northeastern Tibetan Plateau records a complete tectonic history of the Qilian Orogen. Here, results of structural measurements, geochronological data, and thermobarometry for metamorphic rocks in the Central Qilian Block were presented, which trace the tectonic evolution of the Qilian Orogen. New U–Pb dating of detrital zircon from one paragneiss shows a main age population between c. 1500 and c. 1250 Ma, with the youngest age of 1085 Ma. This unit was intruded by an orthogneiss which has a U–Pb weighted mean age of 920 ± 18 Ma. Together with c. 1200–1000 Ma ages from inherited zircon cores in amphibolites, these results indicate that the protoliths of the Huangyuan Group were formed during the Mesoproterozoic and Neoproterozoic. Rims of these zircons obtain tightly constrained and concordant ages ranging from c. 459 to c. 427 Ma, with a weighted mean age of c. 450 Ma. Phase equilibrium modelling and conventional thermobarometry jointly indicate high‐temperature/medium‐pressure HT–MP metamorphism along a clockwise pressure–temperature (P–T) path at c. 450 Ma, passing through prograde conditions of 7.8–8.0 kbar and 620–650°C to peak conditions of ~7 kbar and ~780–800°C. Together with documented widespread metamorphism, magmatism, and ductile shear belts, these new results reassert that the Central Qilian Block experienced a three‐stage tectono‐metamorphic evolution during the Early Palaeozoic and the HT–MP metamorphism of Huangyuan Group was developed by a continental collision geodynamic setting with coeval mafic and granitic magmatism. [ABSTRACT FROM AUTHOR]

A Mesoproterozoic granite covering about 5 km2 is firstly recognized in the Zhusileng area, which is located between the northern Alxa Block and the South Gobi microcontinent. New geochronological data from this area provide new insight for understanding the Precambrian crustal evolution of the middle segment of the southern Central Asian Orogenic Belt (CAOB). Based on the crystal shapes, internal textures, and high Th/U ratios, the zircons from this Mesoproterozoic granite are interpreted as magmatic origin. Meanwhile, LA‐ICP‐MS zircon U–Pb dating shows that it was emplaced at 1458 ± 7.5 Ma. Published geochronological data and Sr–Nd isotopic compositions of igneous rocks from the Zhusileng area and its vicinity are also compiled in this study. The Late Palaeozoic granitoids from the Zhusileng area have strongly negative εNd(t) values (−0.1 to −10.8), high (87Sr/86Sr)i (0.69657–0.73423) and old Nd model ages (0.9–1.8 Ga), suggesting the existence of Precambrian microcontinent in the Zhusileng area. Furthermore, the statistical analysis (or isotopic mapping) of Sr–Nd isotopic compositions of Palaeozoic granitoids from the middle segment of the southern CAOB also displays similar εNd(t) values and relatively old Nd model ages along the Hanshan Block, Zhusileng, Tsaggan Uul terrane, and Hutag Uul terrane. Therefore, we propose that those units may share a common basement during Mesoproterozoic to Early Neoproterozoic. [ABSTRACT FROM AUTHOR]

With the fast growth of nanotechnology, the usage of nuclear materials is becoming increasingly widespread, and the exposure of people, plants, and fauna to nanomaterials has become unavoidable. As scaffolds of biomaterials, nanomaterials are widely used in tissue engineering because of their good biocompatibility, noncytotoxicity, and noninflammatory reaction. In this paper, the tissue engineering properties of nanomaterials and their performance evaluation for repairing sports ligament injuries in dance sports were investigated. Sports ligament injury is a common sports disease, and ligament injury has a very serious impact on sports performance and sports life of athletes. In this paper, we takes football as an example, establishes a human body model of tendon-bone repair after anterior cruciate ligament reconstruction, evaluated the effect of injectable rhBMP-2 nanocontrolled release capsule on ligament bone tunnel interface repair, and evaluated from the scientific and biomechanical point of view. In addition, human ligament research and rabbit ligament supplementary experiment were carried out. In the study of human ligament, we selected 30 patients with unilateral polyarticular ligament injury caused by sports dance as the research subjects and randomly divided them into control group, experimental group, and blank group. The experimental group underwent the repair and reconstruction of rhBMP-2 nanocontrolled release capsule ligament. The results of human ligament study showed that the injectable rhBMP-2 nanocontrolled release capsules showed positive staining and uniform staining for ligament repair. The stiffness of the tender bony temple junction was 11.73%, 15.65%, and 50.59% greater in the test group than in the control group at 2, 4, and 8 weeks postoperatively, respectively. [ABSTRACT FROM AUTHOR]

The Early Cretaceous represents a peak period of the North China Craton (NCC) destruction. A comprehensive analysis of crustal deformation during this period can reveal processes and dynamics of the destruction. The peak destruction of the NCC was associated with intense extension whose representative deformation products are metamorphic core complexes (MCCs), extensional domes and rifted basins. These MCCs occurred along both northern and southern margins of the NCC, and resulted from synchronous extension and magmatism, showing difference from the typical orogen-type MCCs in many aspects. The MCCs of the Early Cretaceous were replaced by extensional domes under relatively weak extension and uplift. In contrast to a major depression-type basin of the Early Cretaceous in the western NCC, rifted basins of the same age in the eastern NCC appeared as medium- to small-scale ones extensively. In the eastern NCC, the rifted basins north of the Bohai Bay are characterized by a feature similar to an active rift whereas those south of the Bohai present similarity to a passive rift. Various sorts of extensional structures developed during the peak destruction indicate a stable stress state of NE-SE extension over the entire central to eastern NCC, consistent with the plate margin-driven stress field. Spatial distribution of the extensional structures presents an 1800 km wide back-arc extension region in the central to eastern NCC, consistent with the Paleo-Pacific slab rollback model following flat subduction. Temporal-spatial variation of initial extension and volcanic activity during the peak period also supports the rollback model right after the flat oceanic slab. The crustal deformation evolution demonstrates that the peak destruction of the NCC took place after the B-episode compression of the Yanshan Movement of the earliest Early Cretaceous and terminated with onset of the C-episode compression of the earliest Late Cretaceous. [ABSTRACT FROM AUTHOR]

As the remnant of the South Qilian Ocean, the South Qilian suture zone recorded abundant information on the Cambrian–Ordovician subduction history of the southern branch of the Proto-Tethyan Ocean. However, the closure timing of the South Qilian Ocean and subsequent collision are poorly constrained. In this study, we report early Silurian (433–435 Ma) U–Pb ages of felsic subvolcanic rocks from Lianhuashan, Ayishan and Shihuiyao of the Lajishan district within the South Qilian suture zone. They intruded the Late Ordovician – Silurian sedimentary or Late Ordovician volcanic rocks and have high SiO2 (61.43–73.06 wt%), Sr/Y ratios with significant different rare earth elements (REEs) and trace-element spider diagrams, and Sr–Nd isotopic compositions, probably implying that they were formed through distinctly different generation mechanisms. Geochemistry of the Lianhuashan dacites reveals compositions typical of adakitic rocks derived from partial melting of lower crust in a thickened setting. The Ayishan dacites were derived from partial melting of crustal materials with the involvement of minor peridotite mantle, and the Shihuiyao rhyolites were derived from partial melting of felsic crust. The similar geochemical characteristics of coeval post-collisional igneous rocks in the Central Qilian and South Qilian blocks indicates that the lower Silurian subvolcanic rocks were generated in a thickened crust of post-collisional setting. Considering their intrusive contacts with Late Ordovician – Silurian retro-foreland basin and Late Ordovician collisional volcanic rocks, we propose that the South Qilian suture zone was at a transitional stage from collisional to post-collisional during the early Silurian Period. [ABSTRACT FROM AUTHOR]

Intensive mid‐Neoproterozoic magmatism is the salient feature of the Yangtze Block, preserving abundant information about crustal reworking and growth. Zircon U–Pb–Lu–Hf isotope analysis was performed on material from the Feidong Complex (FDC) and Zhangbaling Group (ZBLG) of the Zhangbaling Uplift, in order to determine the age and magmatic source of the Neoproterozoic igneous rocks as well as the detrital provenance for the sedimentary rocks, to further provide important data for understanding the mid‐Neoproterozoic crustal evolution of the Northeast Yangtze Block. The amphibolite and gneissic granites in the Feidong Complex (FDC) gave similar protolith ages of 782–776 Ma. The synmagmatic zircons exhibited variable negative ∊Hf(t) values of –26.9 to –8.3. Early (ca. 2.4 Ga) to late Paleoproterozoic (ca. 2.0–1.9 Ga) inherited zircons were found in the gneissic monzogranite, with negative ∊Hf(t) values of –11.2 to –7.2, indicating strong reworking of the ancient crustal materials of the Northeast Yangtze Block. Whereas the amphibolites represent minor crustal growth through emplacement of continental rifting‐related mafic magmas. The quartz–keratophyres in the Xileng Formation of the ZBLG in contrast systematically yield young protolith crystallization ages of 754–727 Ma with high ∊Hf(t) values of –2.0 to +5.6, indicating their derivation from the reworking of juvenile crustal materials. The detrital zircons from the metasiltstone in the Beijiangjun Formation yield variable 206Pb/238U ages (871–644 Ma) with a peak age at 741 ± 11 Ma and ∊Hf(t) values of –4.3 to +5.3, which is consistent with those of the Xileng Formation, but distinct from the FDC, indicating that the provenance of the metasiltstone is primarily the underlying Xileng Formation. The mid‐Neoproterozoic igneous and sedimentary rocks of the Zhangbaling Uplift were products from continental rifting zones along the northern margin of the Yangtze Block, situated in different positions from the Susong Complex and the Haizhou Group. The transition from ancient to juvenile crustal sources for felsic magmatic rocks is attributed to gradually increased crustal extension during continental rifting. [ABSTRACT FROM AUTHOR]

The Ayishan Group in the Lajishan area is sandwiched between the South Qilian Belt and the Qilian Block, which is transitionally interpreted to represent the products of the post‐collision setting or the continental marginal arc during the Early Ordovician or Silurian and is associated with the evolution of the Proto‐Tethyan Ocean. While the detailed information about the age, geochemistry, and tectonic setting of the Ayishan Group is lacking, our geological mapping and analyses demonstrates that the Ayishan Group consists of andesites, rhyolites, ignimbrites, sandstones, and conglomerates, which unconformably overlies the Cambrian–Ordovician arc‐ophiolite complex. Zircon U–Pb dating of the rhyolites demonstrated that the Ayishan Group formed between 447 and 442 Ma and is Late Ordovician. Geochemical analyses demonstrated that rhyolites have high and variable SiO2 contents of 69.6–76.5 wt% and an aluminium saturation index (A/CNK) of 0.85–1.45, belonging to calc‐alkaline to high K calc‐alkaline series. They are subdivided into two subtypes of high‐Sr/Y rhyolites (HSRs) and normal rhyolites (NRs) based on the geochemical characteristics. The HSRs show lower total rare earth elements (34.77–62.78 ppm), lower Yb (0.19–0.21 ppm) and Y (1.77–1.99 ppm) contents, and relatively higher Sr contents (159–193 ppm), compared with NRs, and with positive Eu anomalies. Both subtypes exhibit extremely high whole‐rock δ18O values of 12.63–13.21‰, but various initial 87Sr/86Sr ratios and εNd(t) values, indicating a dominant origin of terrigenous sediments and the HSRs exhibit a more terrestrial composition than the NRs. Various magma sources further caused the assorted residual phase leading to the different geochemistry between the HSRs and the NRs. Combined with the previous data, these results imply that the rhyolites of the Ayishan Group were produced in the process of the amalgamation of the Qilian Block with the Qaidam Block during the Late Ordovician, which further indicated that the Proto‐Tethyan Ocean closed 450 Ma ago. [ABSTRACT FROM AUTHOR]

Purpose: Bioremediation is widely considered the most desirable procedure for remediation of oil-contaminated soil. Few studies have focused on the relationships among microbial community, functional genes of biodegradation, and geochemical processes during field bioremediation, which provide crucial information for bioremediation. Methods: In the current study, the microbial community and functional genes related to hydrocarbon and nitrogen metabolism, combined with the soil physico-chemical properties, were used to diagnose a set of bioremediation experiments, including bioaugmentation, biostimulation, and phytoremediation, at the field scale. Result: The results showed that the added nutrients stimulated a variety of microorganisms, including hydrocarbon degradation bacteria and nitrogen metabolism microorganisms. The functional genes reflected the possibility of aerobic denitrification in the field, which may be helpful in biodegradation. Biostimulation was found to be the most suitable of the studied bioremediation methods in the field. Conclusion: We offer a feasible approach to obtain useful bioremediation information and assist with the development of appropriate remediation procedures. The findings improve our knowledge of the interactions between microorganisms and edaphic parameters. [ABSTRACT FROM AUTHOR]

The compositions and ages of the sediments within retro or foreland basins that are formed and preserved adjacent to collisional orogens can reflect the nature of colliding tectonic elements. The nonmarine Yaoshuiquan and Huabaoshan formations in the South Qilian belt on the NE Tibetan Plateau deposited within a retro‐foreland basin setting during latest Ordovician to Late Silurian time in response to arc‐continent collision. Detritus derivation from a Cambro‐Ordovician arc‐ophiolite complex contains mixed 530‐480 Ma oceanic‐crust together with contributions from a 479‐450 Ma continental‐arc early in development of the basin. The Cambrian arc‐accretionary system and Central Qilian block united to form the basement of a continental arc at ~450 Ma, and both then contributed sediments to the Lianhuashan‐Huabaoshan basin. After the Hualong complex accreted to the north, a broad Andean‐type margin developed along the southern margin of the Central Qilian block from 450 to 440 Ma. These processes generated a wider basin that received detritus from both the south and the north. Consumption of the Proto‐Tethyan Ocean ended with collision between the Qaidam and Hualong blocks, which led to mass wasting of detritus from the Andean‐type igneous rocks and both blocks with the basin from 440 to 420 Ma. Key Points: The Yaoshuiquan and Huabaoshan formations of the Qilian Orogen record alluvial deposition in a retro‐foreland basinThe retro‐foreland basin formed in response to collision of the Qaidam block and an Andean‐type arc between 440 and 420 MaVoluminous detritus shed from a Cambrian‐age arc‐ophiolite complex, micro‐continental block, and Andean‐type margin [ABSTRACT FROM AUTHOR]

The Qilian Orogen in the northern margin of the Tibetan Plateau is the northernmost of the Tethyan domain. Abundant ophiolites record the closure of an early Tethyan ocean and amalgamations between micro-continents of North China, Qaidam, and Tarim. The Muli arc–ophiolite complex in the western segment of the South Qilian belt represents remnants of the Proto-Tethyan oceanic lithosphere. It comprises serpentinite, dunite, cumulate gabbro, basalt, plagiogranite, and chert, which are in tectonic contact with Upper Ordovician turbidites. Basalts have typical subduction-related calc-alkaline geochemical affinity, representing portions of an island arc. Geochemical results for plagiogranites and spinels from serpentinite indicate that the Muli arc–ophiolite complex represents a super-subduction zone (SSZ)-type ophiolite. U–Pb zircon data indicate formation associated with southward subduction of the Proto-Tethys Ocean during a short interval between 539 and 522 Ma. Results of petrology, geochemistry, and zircon U–Pb dating demonstrate that granitoids intruded into this complex are Middle to Late Ordovician (470–450 Ma) products of subduction-related arc magmatism. Voluminous Late Ordovician–Early Silurian rocks include deep-water marine siliciclastic and volcaniclastic turbidites and abundant volcanic arc rocks located to the south of the Muli arc–ophiolite complex, whereas fluvial coarse-grained sandstones and conglomerates unconformably overlie the Cambrian–Middle Ordovician ophiolite–arc systems in the eastern South Qilian belt. This indicates that closure of the Proto-Tethys Ocean was diachronous during the early Paleozoic. [ABSTRACT FROM AUTHOR]

The early Palaeozoic South Qilian–North Qaidam orogenic belt in northwestern China records a nearly complete history of early‐stage long‐lived oceanic subduction–accretion followed by late‐stage continental collision. Most previous studies have focused on low dT/dP metamorphism (HP–UHP) in this belt whereas the paired high dT/dP belt in the hinterland has received little attention. In this contribution, phase equilibrium modelling is combined with zircon petrochronology to determine the P–T–t evolution of granulites in the North Wulan gneiss complex in the high dT/dP hinterland of the South Qilian–North Qaidam orogen. Granulites record a clockwise P–T path with near‐peak temperatures of ~800–900°C at 5.5–7 kbar. Peak metamorphism was followed by high‐T decompression. Zircon petrochronology reveals protracted zircon growth from c. 474 to 446 Ma during the high‐T portion of the P–T path. High dT/dP metamorphism in the North Wulan gneiss complex was likely the result of heat transfer from the underlying hot asthenosphere and minor coeval magmatism in an arc–back‐arc system during slab retreat and roll‐back of the South Qilian oceanic plate. Broadly contemporaneous but slightly younger HP–UHP metamorphism in the foreland of the South Qilian–North Qaidam orogenic belt indicates that the region records an early Palaeozoic paired metamorphic belt. This early Palaeozoic paired metamorphic belt provides a detailed example of dual thermal regimes in a modern‐style orogenic system that can be applied to understanding the time‐scales and P–T conditions of high dT/dP metamorphism that accompany subduction in Phanerozoic and Precambrian orogenic belts. [ABSTRACT FROM AUTHOR]

The continental arc and intraplate magmatic rocks occur widely within the Altun-Qilian-North Qaidam (AQNQ) region of NW China and play a key role in reconstructing the assembly and dispersal history of micro-continental blocks within a complex orogenic system. In the South Qilian belt, amphibolites from the Hualong Complex can be subdivided into four types based on their lithologies, ages, and tectonic affinities. Type I is characterized by garnet and Proterozoic detrital zircons, indicating a metasedimentary origin. Type II and IV amphibolites are tholeiitic and calc-alkaline, respectively, and characterized by enrichment in LREES, Th, U, and Ba, accompanied by depletion in Nb and Ta, indicating a continental arc setting on an active continental margin. Type III is alkaline with ocean island basalt affinity and considered to have intraplate, rift-related origins. SHRIMP U-Pb dating and previous studies suggest that type II, III, and IV amphiboltes are formed at 1126 Ma, 882 Ma, and 470 Ma, respectively, which corresponds to 1126-895 Ma continental arc magmatism, 882-580 Ma rifted-related magmatism, and 522-440 Ma continental arc magmatism within the AQNQ. The three episodes of magmatism further demonstrate the processes of assembly and breakup of the Proterozoic supercontinent Rodinia and reassembly of the Altun-Qilian-North Qaidam orogenic belt. [ABSTRACT FROM AUTHOR]

Abstract: The Lajishan ophiolite complex in the Qilian Orogen is one of several ophiolites situated between the Qaidam and North China blocks that record episodic closure of the Proto‐Tethyan Ocean. Detailed field relations and geochemical and geochronological studies are critical to unraveling the tectonic processes responsible for an extensive period of intraoceanic subduction that produced juvenile ophiolite/island arc terranes, which were obducted onto continental margins during ocean closure. The Lajishankou ophiolite complex crops out along the northern margin of the South Qilian belt and was thrust over a Neoproterozoic‐Ordovician passive margin sequence that was deposited upon the Proterozoic Central Qilian block. The mafic rocks in Lajishankou ophiolite complex are the most abundant slices and can be categorized into three distinct groups based on petrological, geochemical, and geochronological characteristics: massive island arc tholeiites, 509‐Ma back‐arc dolerite dykes, and 491‐Ma pillow basaltic and dolerite slices that are of seamount origin in a back‐arc basin. These results, together with spatial relationships, indicate that the Cambrian island arc rocks, ophiolite complex, and accretionary complex developed between 530 and 480 Ma as a single, intraoceanic arc‐basin system as a result of south directed subduction of the Proto‐Tethyan Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. Final continental amalgamation involved continental collision of the Central Qilian block with the Qaidam block during the Late Ordovician. This model solves the long‐lasting discussion on the emplacement of the Lajishan ophiolite and contributes to an improved understanding of multiple accretionary and collisional processes in the Qilian Orogen. [ABSTRACT FROM AUTHOR]

The Qilian orogenic belt, as an important component of the central orogenic system, can be divided into three tectonic units from north to south: the North Qilian tectonic belt, the Central Qilian tectonic belt and the South Qilian tectonic belt. The Lajishan ophiolitic mélange zone is an important part of the South Qilian tectonic belt. The study of the formation age and tectonic attributes of the different rock units in the Lajishan is of great significance for reconstructing the tectonic evolution of the south Qilian tectonics belt and the Proto‐Tethys Ocean. The Ayishan formation is an important unit of the Lajishan mélange belt, but its stratigraphic age and formation environment are still not constrained, which limits the reconstruction of the early Palaeozoic tectonic evolution of the South Qilian tectonic belt and the closure time of the Proto‐Tethys Ocean. In recent years, a set of rock assemblages consisting of andesite, rhyolite, sandstone and pebbly sandstone have been identified in the Ayishan formation exposed in the Lajishan through detailed geological mapping in the field. They are in fault contact with the underlying ophiolite mélange. Regionally, a volcano‐sedimentary succession consisting of andesite, rhyolite, volcanic breccia, and volcaniclastic sandstone nonconformably overlies the Cambrian arc‐accretionarycomplex system in the Ayishan area. These rocks were originally assigned to the Ayishan formation and attributed an Early Ordovician age (BGMRQP, 1964, 1991). Our rhyolite samples from the Ayishan formation yielded a weighted mean 206Pb/238U age of 447 Ma using zircon U‐Pb dating, which can be interpreted as the eruption age of the volcanic rocks. These volcanic rock assemblages are distributed in sandstone, pebbled sandstone and conglomerate in the form of interlayers. Therefore, the zircon U‐Pb age of the volcanic rocks can constrain the age of Ayishan formation that it should belong to the late Ordovician rather than early Ordovician. Additionally, we propose that the Ayishan rhyolites were formed in collision‐related tectonic setting based on the geochemistry of the rhyolites, which means the initial continental collision between the Central Qilian block and the Qaidam block occurred at least in the Late Ordovician. Ayishan formation are in fault contact with the Cambrian Donggoumeikuang complex in the south. The Donggoumeikuang complex represents a Cambrian introceanic subduction system that formed in response to subduction of the Proto‐Tethyan Ocean (Yan et al., 2015; Fu et al., 2018). At 450 to 420 Ma, the Proto‐Tethyan Ocean closed and the Qaidam block collided against the central Qilian tectonics belt. Voluminous 450–440 Ma I‐type and S‐type granites (Yan et al., 2015; Tung et al., 2016) that straddle the Central and South Qilian belts formed a broad Andean‐type continental margin (Yan et al., 2019), which indicates that the transition from oceanic subduction to continental subduction occurred in 450–440Ma. At 440–420 Ma, the syncollisional and postcollisional granitoids extensively developed, accompanied by high‐pressure granulite‐facies metamorphism and anatexis in the South Qilian belt and the Qaidam block (Yu et al., 2014; Yan et al., 2015; Fu et al., 2018; Li et al., 2018). [ABSTRACT FROM AUTHOR]

Slab breakoff originally denotes the detachment of dense subducted oceanic slab from the light subducted continental slab, which is driven by opposing buoyancy forces during continental collision (Davies and von Blanckenburg, 1995; von Blanckenburg and Davies, 1995). The breakoff of subducted oceanic slab can induce the upwelling of sub‐slab asthenosphere through the slab window, and then heat the overriding lithospheric mantle resulting in the melting of its fertile layer within the metasomatic mantle wedge. The decompression partial melting of uprising asthenospheric mantle commonly produce mafic magma with depleted MORB‐like geochemical signatures (Davies and von Blanckenburg, 1995; Cole et al., 2006; Wang et al., 2018), whereas the partial melting of enriched lithospheric mantle will produce mafic magma with alkaline, calc‐alkaline or ultrapotassic features (von Blanckenburg and Davies, 1995). These mafic magmas rise into overlying lower crust and trigger crustal melting to generate the granitic magma. The North Qaidam tectonic belt (NQTB) records the evolutionary process of the South Qilian Ocean from subduction to closure. The subduction of oceanic and continental lithosphere to mantle depths is proven by the identification of oceanic‐type and continental‐type eclogites enclosed in crustal metapelite and gneiss from the North Qaidam tectonic belt (Song et al., 2006; Zhang et al., 2008; Zhang et al., 2010; Zhang et al., 2017). However, details of this process are not exactly constrained, in particularly, the closure timing of South Qilian Ocean. The study of characteristic mafic magmatism, combined with the previous studies of ultra‐high pressure metamorphism, give us an excellent opportunity to trace the detailed processes associated with the transition from oceanic subduction to continental subduction, and assess the feasibility of slab breakoff in the North Qaidam tectonic belt. In this contribution, an integrated study of petrology, geochemistry, geochronology and Sr‐Nd‐Hf isotopes is performed on the mafic igneous rocks from Chahanhe area in the North Wulan gneiss complex. These mafic igneous rocks can be divided into two groups, namely, arc‐like type and E‐MORB type based on their trace element patterns. Arc‐like mafic rocks (441–428 Ma) were characterized by enrichment of light rare earth elements (LREEs), large ion lithophile elements (LILEs) and depletion of heavy rare earth elements (HREEs), high field strength elements (HFSEs). Combined with variable zircon ∊Hf(t) values of −6.17 to +1.58, it is suggested that arc‐like mafic rocks are predominantly derived from the partial melting of the enriched lithospheric mantle, and minor juvenile materials have contributed to their sources. The E‐MORB mafic rocks (440 Ma) exhibit relatively flatted REE patterns and positive ∊Nd(t) values of +1.63 to +4.28, but high (87Sr/86Sr)i ratios of 0.706825 to 0.708979, indicting a derivation from partial melting of asthenospheric mantle, with involvement of enriched components probably derived from ambient lithospheric mantle or stagnant subducted oceanic crust. Collectively, it is proposed that the break‐off of the subducted South Qilian oceanic slab triggered the decompression melting of asthenospheric mantle, and the upwelling of asthenosphere provided heat and induced partial melting of the enriched lithospheric mantle and pre‐existing crust, resulting in generation of arc‐like mafic rocks and widespread granites. [ABSTRACT FROM AUTHOR]

The Qilian orogenic belt, as an important component of the central orogenic system, can be divided into three tectonic units from north to south: the North Qilian tectonic belt, the Central Qilian tectonic belt and the South Qilian tectonic belt. The Lajishan ophiolitic mélange zone is an important part of the South Qilian tectonic belt. The study of the formation age and tectonic attributes of the different rock units in the Lajishan is of great significance for reconstructing the tectonic evolution of the south Qilian tectonics belt and the Proto‐Tethys Ocean. The Ayishan formation is an important unit of the Lajishan mélange belt, but its stratigraphic age and formation environment are still not constrained, which limits the reconstruction of the early Palaeozoic tectonic evolution of the South Qilian tectonic belt and the closure time of the Proto‐Tethys Ocean. In recent years, a set of rock assemblages consisting of andesite, rhyolite, sandstone and pebbly sandstone have been identified in the Ayishan formation exposed in the Lajishan through detailed geological mapping in the field. They are in fault contact with the underlying ophiolite mélange. Regionally, a volcano‐sedimentary succession consisting of andesite, rhyolite, volcanic breccia, and volcaniclastic sandstone nonconformably overlies the Cambrian arc‐accretionarycomplex system in the Ayishan area. These rocks were originally assigned to the Ayishan formation and attributed an Early Ordovician age (BGMRQP, 1964, 1991). Our rhyolite samples from the Ayishan formation yielded a weighted mean 206Pb/238U age of 447 Ma using zircon U‐Pb dating, which can be interpreted as the eruption age of the volcanic rocks. These volcanic rock assemblages are distributed in sandstone, pebbled sandstone and conglomerate in the form of interlayers. Therefore, the zircon U‐Pb age of the volcanic rocks can constrain the age of Ayishan formation that it should belong to the late Ordovician rather than early Ordovician. Additionally, we propose that the Ayishan rhyolites were formed in collision‐related tectonic setting based on the geochemistry of the rhyolites, which means the initial continental collision between the Central Qilian block and the Qaidam block occurred at least in the Late Ordovician. Ayishan formation are in fault contact with the Cambrian Donggoumeikuang complex in the south. The Donggoumeikuang complex represents a Cambrian introceanic subduction system that formed in response to subduction of the Proto‐Tethyan Ocean (Yan et al., 2015; Fu et al., 2018). At 450 to 420 Ma, the Proto‐Tethyan Ocean closed and the Qaidam block collided against the central Qilian tectonics belt. Voluminous 450–440 Ma I‐type and S‐type granites (Yan et al., 2015; Tung et al., 2016) that straddle the Central and South Qilian belts formed a broad Andean‐type continental margin (Yan et al., 2019), which indicates that the transition from oceanic subduction to continental subduction occurred in 450–440Ma. At 440–420 Ma, the syncollisional and postcollisional granitoids extensively developed, accompanied by high‐pressure granulite‐facies metamorphism and anatexis in the South Qilian belt and the Qaidam block (Yu et al., 2014; Yan et al., 2015; Fu et al., 2018; Li et al., 2018). [ABSTRACT FROM AUTHOR]

Slab breakoff originally denotes the detachment of dense subducted oceanic slab from the light subducted continental slab, which is driven by opposing buoyancy forces during continental collision (Davies and von Blanckenburg, 1995; von Blanckenburg and Davies, 1995). The breakoff of subducted oceanic slab can induce the upwelling of sub‐slab asthenosphere through the slab window, and then heat the overriding lithospheric mantle resulting in the melting of its fertile layer within the metasomatic mantle wedge. The decompression partial melting of uprising asthenospheric mantle commonly produce mafic magma with depleted MORB‐like geochemical signatures (Davies and von Blanckenburg, 1995; Cole et al., 2006; Wang et al., 2018), whereas the partial melting of enriched lithospheric mantle will produce mafic magma with alkaline, calc‐alkaline or ultrapotassic features (von Blanckenburg and Davies, 1995). These mafic magmas rise into overlying lower crust and trigger crustal melting to generate the granitic magma. The North Qaidam tectonic belt (NQTB) records the evolutionary process of the South Qilian Ocean from subduction to closure. The subduction of oceanic and continental lithosphere to mantle depths is proven by the identification of oceanic‐type and continental‐type eclogites enclosed in crustal metapelite and gneiss from the North Qaidam tectonic belt (Song et al., 2006; Zhang et al., 2008; Zhang et al., 2010; Zhang et al., 2017). However, details of this process are not exactly constrained, in particularly, the closure timing of South Qilian Ocean. The study of characteristic mafic magmatism, combined with the previous studies of ultra‐high pressure metamorphism, give us an excellent opportunity to trace the detailed processes associated with the transition from oceanic subduction to continental subduction, and assess the feasibility of slab breakoff in the North Qaidam tectonic belt. In this contribution, an integrated study of petrology, geochemistry, geochronology and Sr‐Nd‐Hf isotopes is performed on the mafic igneous rocks from Chahanhe area in the North Wulan gneiss complex. These mafic igneous rocks can be divided into two groups, namely, arc‐like type and E‐MORB type based on their trace element patterns. Arc‐like mafic rocks (441–428 Ma) were characterized by enrichment of light rare earth elements (LREEs), large ion lithophile elements (LILEs) and depletion of heavy rare earth elements (HREEs), high field strength elements (HFSEs). Combined with variable zircon ∊Hf(t) values of −6.17 to +1.58, it is suggested that arc‐like mafic rocks are predominantly derived from the partial melting of the enriched lithospheric mantle, and minor juvenile materials have contributed to their sources. The E‐MORB mafic rocks (440 Ma) exhibit relatively flatted REE patterns and positive ∊Nd(t) values of +1.63 to +4.28, but high (87Sr/86Sr)i ratios of 0.706825 to 0.708979, indicting a derivation from partial melting of asthenospheric mantle, with involvement of enriched components probably derived from ambient lithospheric mantle or stagnant subducted oceanic crust. Collectively, it is proposed that the break‐off of the subducted South Qilian oceanic slab triggered the decompression melting of asthenospheric mantle, and the upwelling of asthenosphere provided heat and induced partial melting of the enriched lithospheric mantle and pre‐existing crust, resulting in generation of arc‐like mafic rocks and widespread granites. [ABSTRACT FROM AUTHOR]

Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite40Ar/39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield40Ar/39Ar plateau ages of 192.5±0.7 Ma, 189.7 ± 0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process. [ABSTRACT FROM AUTHOR]

Two phases of sinistral strike-slip ductile shear belts occur on the eastern margin of the Dabie orogenic belt. A muscovite 40Ar/39Ar plateau age of 128 Ma was obtained from mylonite in the later ductile shear zone. Three muscovite samples separated from mylonites of 3 localities in the earlier ductile shear belts yield 40Ar/39Ar plateau ages of 192.5±0.7 Ma, 189.7±0.6 Ma and 188.7±0.7 Ma, respectively. They are interpreted as cooling ages of the earlier sinistral strike-slip deformation. It is suggested that left-lateral displacement of the Tan-Lu fault zone started in a late stage of the collision orogeny in the Dabie-Sulu orogenic belt between the North and South China plates. Therefore, the earlier Tan-Lu fault zone was syn-orogenic strike-slip tectonics. The fault zone was used again for sinistral displacement during tectonic activities of peri-Pacific regime in Early Cretaceous. It is proposed that the fault zone occurred as a transform fault during the orogenic process. [ABSTRACT FROM AUTHOR]

The Qilian orogenic belt is the northernmost orogen of the Tethyan domain and connects the Altaids to the north. It contains an assembly of Precambrian micro‐continental fragments, early Paleozoic island arcs, accretionary complexes, ophiolites, forearc and backarc basins, and high‐pressure (HP) metamorphic rocks, indicating a long history of accretionary processes. Spatially, this orogen is adjacent to the Tarim, Qaidam, and North China blocks, which also extends into accretionary orogenic belts to the east and SW such as the Qinling and Kunlun belts. Abundant ophiolites in this orogen record the closure of an early Tethyan Ocean and amalgamations between micro‐continents of North China, Qaidam, and Tarim. Thus, the ages and tectonic settings of these ophiolites within this belt provide important information regarding evolution of the Proto‐Tethys Ocean and assembly of micro‐continental blocks, which aids understanding of the spatial and temporal relationship of this orogen within the Tethyan realm. Dismembered ophiolites sporadically crop out along the northern margin of the South Qilian belt, and, from east to west, are locally referred to as the Lajishan, Gangcha, Muli, and Dadaoerji ophiolites. Much attention had been paid to these ophiolites, and several competing models for the tectonic evolution of this belt have been suggested. Considerable disagreement remains in respect of the temporal and spatial framework of the Qilian Orogen and details such as timing of subduction (s) and associated polarities, early collision events, and final closure of oceanic basins. In particular, the formation age and tectonic setting of Muli arc‐ophiolite complex remains unknown, which limits understanding of the tectonics of the South Qilian belt and the history of the Proto‐Tethys Ocean. The Muli arc‐ophiolite complex is distributed over 20 km2 west of the township of Muli in the western segment of the South Qilian Belt and consists of serpentinite, dunite, cumulate gabbro, basalt, plagiogranite, and chert. Field mapping results demonstrate that these units have been largely destroyed by faulting and generally occur as blocks/slices. They are tectonically interlayered with Upper Ordovician – Lower Silurian siliciclastic turbidite. Arc‐ophiolite rocks are intruded by 470–450 Ma subduction‐related granitoid plutons and are unconformably overlain by shallow marine to non‐marine sediments of Permian‐Jurassic age. Basalts show typical subduction‐related calc‐alkaline geochemical affinity, representing portions of an island arc. Geochemical results for plagiogranites and spinels from serpentinite demonstrate that the Muli arc‐ophiolite complex represents a super‐subduction zone (SSZ)‐type ophiolite. U‐Pb zircon data indicate formation associated with southward subduction of the Proto‐Tethyan Ocean during a short interval between 539–522 Ma. Voluminous Late Ordovician ‐ Early Silurian deep‐water marine siliciclastic and volcaniclastic turbidites and volcanic arc rocks are exposed to the south of the Muli arc‐ophiolite complex, whereas fluvial coarse‐grained sandstones and conglomerates unconformably overlie the Cambrian‐Middle Ordovician ophiolite‐arc systems in the eastern South Qilian Belt. These indicate that closure of the Proto‐Tethys Ocean was diachronous during the early Paleozoic. [ABSTRACT FROM AUTHOR]

The Qilian orogenic belt is the northernmost orogen of the Tethyan domain and connects the Altaids to the north. It contains an assembly of Precambrian micro‐continental fragments, early Paleozoic island arcs, accretionary complexes, ophiolites, forearc and backarc basins, and high‐pressure (HP) metamorphic rocks, indicating a long history of accretionary processes. Spatially, this orogen is adjacent to the Tarim, Qaidam, and North China blocks, which also extends into accretionary orogenic belts to the east and SW such as the Qinling and Kunlun belts. Abundant ophiolites in this orogen record the closure of an early Tethyan Ocean and amalgamations between micro‐continents of North China, Qaidam, and Tarim. Thus, the ages and tectonic settings of these ophiolites within this belt provide important information regarding evolution of the Proto‐Tethys Ocean and assembly of micro‐continental blocks, which aids understanding of the spatial and temporal relationship of this orogen within the Tethyan realm. Dismembered ophiolites sporadically crop out along the northern margin of the South Qilian belt, and, from east to west, are locally referred to as the Lajishan, Gangcha, Muli, and Dadaoerji ophiolites. Much attention had been paid to these ophiolites, and several competing models for the tectonic evolution of this belt have been suggested. Considerable disagreement remains in respect of the temporal and spatial framework of the Qilian Orogen and details such as timing of subduction (s) and associated polarities, early collision events, and final closure of oceanic basins. In particular, the formation age and tectonic setting of Muli arc‐ophiolite complex remains unknown, which limits understanding of the tectonics of the South Qilian belt and the history of the Proto‐Tethys Ocean. The Muli arc‐ophiolite complex is distributed over 20 km2 west of the township of Muli in the western segment of the South Qilian Belt and consists of serpentinite, dunite, cumulate gabbro, basalt, plagiogranite, and chert. Field mapping results demonstrate that these units have been largely destroyed by faulting and generally occur as blocks/slices. They are tectonically interlayered with Upper Ordovician – Lower Silurian siliciclastic turbidite. Arc‐ophiolite rocks are intruded by 470–450 Ma subduction‐related granitoid plutons and are unconformably overlain by shallow marine to non‐marine sediments of Permian‐Jurassic age. Basalts show typical subduction‐related calc‐alkaline geochemical affinity, representing portions of an island arc. Geochemical results for plagiogranites and spinels from serpentinite demonstrate that the Muli arc‐ophiolite complex represents a super‐subduction zone (SSZ)‐type ophiolite. U‐Pb zircon data indicate formation associated with southward subduction of the Proto‐Tethyan Ocean during a short interval between 539–522 Ma. Voluminous Late Ordovician ‐ Early Silurian deep‐water marine siliciclastic and volcaniclastic turbidites and volcanic arc rocks are exposed to the south of the Muli arc‐ophiolite complex, whereas fluvial coarse‐grained sandstones and conglomerates unconformably overlie the Cambrian‐Middle Ordovician ophiolite‐arc systems in the eastern South Qilian Belt. These indicate that closure of the Proto‐Tethys Ocean was diachronous during the early Paleozoic. [ABSTRACT FROM AUTHOR]

In petroleum-contaminated aquifers, biodegradation is always associated with various types of microbial metabolism. It can be classified as autotrophic (such as methanogenic and other carbon fixation) and heterotrophic (such as nitrate/sulfate reduction and hydrocarbon consumption) metabolism. For each metabolic type, there are several key genes encoding the reaction enzymes, which can be identified by metagenomics analysis. Based on this principle, in an abnormally low dissolved inorganic carbon (DIC) petroleum-contaminated aquifer in North China, nine groundwater samples were collected along the groundwater flow, and metagenomics analysis was used to discover biodegradation related metabolism by key genes. The major new finding is that autotrophic metabolism was revealed, and, more usefully, we attempt to explain the reasons for abnormally low DIC. The results show that the methanogenesis gene, Mcr, was undetected but more carbon fixation genes than nitrate reduction and sulfate genes were found. This suggests that there may be a considerable number of autotrophic microorganisms that cause the phenomenon of low concentration of dissolved inorganic carbon in contaminated areas. The metagenomics data also revealed that most heterotrophic, sulfate, and nitrate reduction genes in the aquifer were assimilatory sulfate and dissimilatory nitrate reduction genes. Although there was limited dissolved oxygen, aerobic degrading genes AlkB and Cdo were more abundant than anaerobic degrading genes AssA and BssA. The metagenomics information can enrich our microorganic knowledge about petroleum-contaminated aquifers and provide basic data for further bioremediation. [ABSTRACT FROM AUTHOR]

The Qilian orogen along the NE edge of the Tibet‐Qinghai Plateau records the evolution of Proto‐Tethyan Ocean that closed through subduction along the southern margin of the North China block during the Early Paleozoic. The South Qilian belt is the southern unit of this orogen and dominated by Cambrian‐Ordovician volcano‐sedimentary rocks and Neoproteozoic Hualong complex that contains similar rock assemblages of the Central Qilian block. Our recent geological mapping and petrologic results demonstrate that volcano‐sedimentary rocks show typical rock assembles of a Cambrian‐early Ordovician arc‐trench system in Lajishan Mts. along the northern margin of the Hualong Complex. Island arc rocks including basalt, andesite, dacite, rhyolite, and breccia is in fault contact with ophiolite complex consisting of mantle peridotite, serpentinite, gabbro, dolerite, plagiogranite, and basalt. Accretionary complexes are tectonically separated from the ophiolite‐arc rocks, with various rock assemblages spatially. They consist of pillow basalt, basalt breccia, tuff, chert, and limestone blocks with a seamount origin within the scaly shale in Dingmaoshan and Donggoumeikuang areas, and basalt, chert, and sandstone blocks within muddy shale matrix and mélange at Lajishankou area. Abundant radiolarians occur in red chert, and trilobite, brachiopod, and coral fossils occur within Dingmaoshan limestone blocks. Although partial basalt or chert blocks are highly disrupted, duplex, thrust fault, rootless intrafolial fold, tight fold, and penetrative foliation are well‐developed at Donggoumeikuang area. Spatially, accretionary complexes lie structurally beneath ophiolite complex and above the turbidites of the Central Qilian block. Ophiolite and accretionary complexes are also overlapped by late Ordovician molasse deposits sourced from Cambrian arc‐trench system and the Central Qilian block. These observations demonstrate that a Cambrian‐early Ordovician trench‐arc system within the South Qilian belt formed during the early Paleozoic southward subduction of the South Qilian Ocean collided with the Central Qilian block prior to the late Ordovician. [ABSTRACT FROM AUTHOR]

Many ophiolite complexes like those of Oman and New Caledonia represent fragments of ancient oceanic crust and upper mantle generated at supra‐subduction zone environments and have been obducted onto the adjacent rifted continental margin together with the accretionary complexes and intra‐oceanic arcs. The Lajishan ophiolite complexes in the Qilian orogenic belt along the NE edge of the Tibet‐Qinghai Plateau are one of several ophiolites situated to the south of the Central Qilian block. Our geological mapping and petrological investigations suggest that the Lajishankou ophiolite complex consists of serpentinite, wehrlite, pyroxenite, gabbro, dolerite, and pillow and massive basalts that occur in a series of elongate fault‐bounded slices. An accretionary complex composed mainly of basalt, radiolarian chert, sandstone, mudstone, and mélange lies structurally beneath the ophiolite complex. The Lajishankou ophiolite complex and accretionary complex were emplaced onto the Qingshipo Formation of the Central Qilian block which shows features typical of turbidites deposited in a deep‐water environment of passive continental margin. Our geochemical and geochronological studies indicate that the mafic rocks in the Lajishankou ophiolite complex can be categorized into three distinct groups: massive island arc tholeiites, 509 Ma back‐arc dolerite dykes, and 491 Ma pillow basaltic and dolerite slices that are of seamount origin in a back‐arc basin. The ophiolite and accretionary complex constitute a Cambrian‐early Ordovician trench‐arc system within the South Qilian belt during the early Paleozoic southward subduction of the South Qilian Ocean prior to Early Ordovician obduction of this system onto the Central Qilian block. [ABSTRACT FROM AUTHOR]