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Several mantle peridotite massifs crop out along the northern margin of the South Qilian belt, but their origin remains controversial. The Xigou peridotite massif is the largest one within the Lajishan ophiolite belt and mainly consists of lherzolite, harzburgite, and serpentinized dunite, in association with anorthosite, amphibolite, dolerite dikes, and pillow basalt. Lherzolites show typical features of relatively fertile abyssal peridotites, with iron-rich olivine, Al-spinel, and aluminous pyroxene. Harzburgites and serpentinized dunites are characterized by U-shaped rare earth element patterns and low Pd-group platinum-group elements resembling the geochemical features of suprasubduction peridotites. Spinel Cr#'s (Cr/(Cr+Al)) range from 0.38 in harzburgite to 0.75 in dunite. The progressive increase in spinel Cr#'s is related to changing melt compositions from mid-ocean ridge basalt (MORB) like to boninitic during subduction initiation. The Xigou suprasubduction peridotites, MORB-like mafic rocks, and boninites probably constitute an incomplete forearc crust-mantle section. The abyssal lherzolite preserved in the forearc region might represent older oceanic lithosphere or younger fertile mantle residue along a trench-fracture zone intersection with a transform fault. Therefore, we suggest that the intraoceanic subduction of the Proto-Tethyan Ocean may have begun no later than 535 Ma, before the development of the Lajishan intraoceanic arc-trench system.

The tectonic setting of Mesozoic magmatic complexes in the northeastern margin of the Tibet plateau is disputed, and hence gives rise to uncertainty concerning the tectonic evolution of the northeastern Tibet Plateau and the timing of the closure of the Palaeo-Tethys ocean. The Gangcha complex is typical of these complexes, consisting of andesite, dacite, gabbro, gabbroic diorite, granodiorite, quartz diorite, and diorite with typical chemical traits of continental margin arc rocks. Andesite, gabbroic diorite, and mineralization-associated potassic-altered diorite yield weighted mean 206Pb/238U ages of 242.1±1.2 Ma, 243.8±1.0 Ma and 234.0±0.6 Ma respectively. Zircon εHf(t) for magmatic grains ranges from -3.5 to +5.7, interpreted to demonstrate that the Gangcha complex contains crustally contaminated mantle magmas. Inherited zircons in the complex yield similar U-Pb ages (777-310 Ma) to the A'nyemaqen composite ophiolite assemblage with εHf(t) of -17.4 to +11.6. This suggests that components of this older ophiolite melted and contributed to the Gangcha complex magmas. Hence the Gangcha complex is considered to have formed as a continental margin arc in northeastern Tibet by northward subduction during consumption of the Palaeo-Tethys ocean. Regionally, it corresponds to the arc magmatism along the eastern and western Kunlun sutures to the west and the Mianlue suture to the east.

We have examined the Triassic sediments in the west Qinling terrane, northeastern Tibet. These sediments consist mainly of flysch and shallow-sea and fluvial deposits with abundant lithic and heavy mineral detritus, sandwiched between and overlying Late Paleozoic and Early-Middle Triassic ophiolitic mélanges. Volcanic and metamorphic detritus dominates the lithic component of Lower Triassic sandstones accompanied by high Cr-spinel, pyroxene, and magnetite contents, indicating a mixed ophiolite and metamorphic source. Detrital mineral geochemistry further suggests that ophiolitic, high-grade metamorphic, basic, and intermediate-acidic igneous rocks must have been exposed and deeply eroded in their source area. Abundances of zircon, rutile, garnet, tourmaline, and epidote are greater in the Middle Triassic samples, and granitic and volcanic sources are the major contributors of detrital clasts. Considering these new observations on sedimentary petrography and detrital heavy mineral geochemistry, along with published data on paleocurrents, detrital zircon U-Pb ages, sedimentary facies, and regional magmatism, we suggest that these Triassic sediments represent the sedimentary fill of a forearc basin that overlies a late Paleozoic ophiolitic complex. A south-facing Andean-type convergent continental margin system developed along the southern margin of the North China block during the Triassic, in response to northward subduction of the Paleotethyan Ocean.

The North Qaidam tectonic belt is characterized by the development of high-pressure to ultrahigh-pressure eclogite formed during deep subduction of the continental lithosphere. However, the tectonic processes that occurred prior to continental collision/subduction are relatively poorly studied and this leads to controversy over the evolutionary history of the North Qaidam tectonic belt. In this contribution, we present an integrated study of field observations, petrography, geochronology, and geochemistry (whole-rock major elements, trace elements, and Sr–Nd isotopes as well as zircon Lu–Hf isotopes) of continental arc mafic rocks in the North Wulan metamorphic complex to track Proto-Tethyan oceanic subduction and the nature of metasomatism of the mantle wedge. Zircon U–Pb geochronology demonstrates that continental arc mafic rocks crystallized at ca. 483–472 Ma. Mafic intrusions are enriched in light rare earth elements and large ion lithophile elements but are depleted in high field strength elements; these are typical features of arc-related magmatic rocks. They have relatively radiogenic Sr–Nd–Hf isotope compositions, with relatively high initial 87Sr/86Sr ratios of 0.710363 to 0.719404, low εNdt values of -7.77 to -2.30, variable zircon εHft values ranging from -8 to +2.8, and the single-stage Hf model ages of ca. 1.4–1.0 Ga. These features suggest that the mafic intrusions were sourced from ancient subcontinental mantle that was modified by subducted oceanic slab-derived components. The modified mantle source was generated by the interaction between subcontinental lithospheric mantle peridotite in the overlying mantle wedge and hydrous fluid and felsic melt that were derived from a subducted oceanic slab and seafloor sediments with ancient terrestrial origin in the rutile stability field. Crust-mantle interaction transferred the subducted crustal geochemical signatures to the mantle source during subduction of the Proto-Tethyan oceanic lithosphere. Retreat and rollback of the Proto-Tethyan oceanic slab triggered asthenosphere upwelling and the partial melting of metasomatized and enriched fertile lithospheric mantle to form continental arc mafic magmas in the North Qaidam tectonic belt. Combined with the coeval LP-HT metamorphism, the North Wulan metamorphic complex records the early Paleozoic tectonic evolution of a continental arc-back-arc system, and these continental arc mafic rocks record the subduction of the Proto-Tethyan oceanic lithosphere.

The possibility that the Proto‐Tethys Ocean may have undergone intra‐oceanic subduction during ocean closure remains poorly constrained due to a lack of geological evidence for a mature intra‐oceanic arc. Here we present new geochemical and geochronological data for potential arc‐related volcanic rocks adjacent to the accretionary complex and forearc basin in the North Qaidam collisional belt, northern Tibetan Plateau. The volcanic rocks are dominated by foliated basalt, andesite, tuff, and minor dacite with zircon U‐Pb ages ranging from 517 to 497 Ma. They show distinctive geochemical characteristics and can be subdivided into three groups: island‐arc intermediate‐basic volcanic rocks, back‐arc basin basalts (BABB), and dacites with intra‐oceanic arc affinity. The island‐arc volcanic rocks have variable εNd(t) values (+1.6 to +7.5) that decrease northward and were generated by partial melting of depleted mantle wedge modified by hydrous fluid and sediment melt. The BABBs have high εNd(t) values (+5.3 to +6.6) and formed through the melting of MORB‐like mantle, whereas the nearby dacites have positive εNd(t) values (+1.9 to +3.6) similar to the surrounding island‐arc volcanic rocks and were derived from partial melting of intra‐oceanic arc crust as a result of BABB underplating. Integrated analysis of the spatial‐temporal distribution of these volcanic rocks and the reconstructed intra‐oceanic arc‐trench system confirms the existence of the earliest Phanerozoic intra‐oceanic arc formed in response to north‐directed intra‐oceanic subduction. This unrecognized subduction of the Proto‐Tethys Ocean in the North Qaidam belt initiated at ca. 530 Ma, matured ca. 520 Ma, and terminated by ca. 480 Ma. Plain Language Summary Closure of an ocean basin is achieved through subduction of oceanic lithosphere at a continental margin or in an intra‐oceanic setting. Identification and structure of subduction‐related magmatic rocks are critical for fully understanding the complex processes associated with ocean closure and the paleotectonic framework. Geological mapping and geochemical analyses of the Tanjianshan Group in the North Qaidam collisional belt, northern Tibetan Plateau were undertaken. Results demonstrate the presence of relics of the earliest Phanerozoic intra‐oceanic arc and an associated complete arc‐trench system, generated by previously unrecognized intra‐oceanic subduction far from microcontinents that are now adjacent. This study reveals the entire evolution of a missing intra‐oceanic subduction system within the Proto‐Tethys Ocean, which started ca. 530 Ma, matured ca. 520 Ma and ended ca. 480 Ma. Key Points Relics of the earliest Phanerozoic intra‐oceanic arc discovered in North Qaidam collisional belt Proto‐Tethys Ocean in North Qaidam belt experienced north‐directed intra‐oceanic subduction Intra‐oceanic subduction started at ca. 530 Ma and lasted until ca. 480 Ma

To develop a structured, rich media digital paper authoring tool with an object-based model that enables interactive, playable, and convertible functions.We propose Dpaper to organize the content (text, data, rich media, etc.) of dissertation papers as XML and HTML5 files by means of digital objects and digital templates.Dpaper provides a structured-paper editorial platform for the authors of PhDs to organize research materials and to generate various digital paper objects that are playable and reusable. The PhD papers are represented as Web pages and structured XML files, which are marked with semantic tags.The proposed tool only provides access to a limited number of digital objects. For instance, the tool cannot create equations and graphs, and typesetting is not yet flexible compared to MS Word.The Dpaper tool is designed to break through the patterns of unstructured content organization of traditional papers, and makes the paper accessible for not only reading but for exploitation as data, where the document can be extractable and reusable. As a result, Dpaper can make the digital publishing of dissertation texts more flexible and efficient, and their data more assessable.The Dpaper tool solves the challenge of making a paper structured and object-based in the stage of authoring, and has practical values for semantic publishing.

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.

Most porphyry Cu deposits are formed in magmatic arc settings, but some occur in non-arc environments, such as intracontinental settings. The petrogenesis of fertile magmas for porphyry Cu deposits formed in intracontinental settings is still ambiguous. To address this issue, we performed an integrated study of the late Mesozoic porphyry Cu deposits in the South Qinling Orogenic Belt. Zircon U–Pb ages indicate that these late Mesozoic porphyry Cu deposits were formed at 149–142 Ma, in a postcollisional intracontinental setting. εNd(t) (− 4.5 to − 2.7), initial 87Sr/86Sr (0.7046 to 0.7084), and zircon εHf(t) values (− 3.8 to + 2.2) of the late Mesozoic ore-forming and barren rocks suggest that both originate from Meso-Neoproterozoic juvenile lower crust. Whole-rock geochemical and isotopic characteristics indicate that the ore-forming rocks could be formed by the delamination of thickened juvenile lower crust or by the reaction of mantle with normal juvenile lower crust. The barren rocks could be formed by the partial melting of thickened or normal juvenile lower crust. Whole-rock petrochemistry and reversed anorthite contents and Sr isotope data of zoned plagioclase crystals indicate that the mafic magma was recharged into the ore-forming magma chamber. Due to the injection of mafic magma, the ore-forming rocks obtained higher oxygen fugacity, volatiles, water, sulfur, and Cu contents than the barren rocks. According to the regional tectonic evolution, the late Mesozoic porphyry Cu deposits in the South Qinling Orogenic Belt were formed in an extensional environment due to transformation of the tectonic regime. Large-scale lithospheric extension caused asthenospheric mantle upwelling and crust-mantle interaction, providing the crucial metallogenic conditions. Moreover, the injection of mantle-derived mafic magma into the normal magma is a key factor in the formation of the late Mesozoic porphyry Cu deposits in the SQB and similar porphyry systems in an intracontinental setting.

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.

All-perovskite tandem solar cells provide high power conversion efficiency at a low cost 1 – 4 . Rapid efficiency improvement in small-area (<0.1 cm 2 ) tandem solar cells has been primarily driven by advances in low-bandgap (approximately 1.25 eV) perovskite bottom subcells 5 – 7 . However, unsolved issues remain for wide-bandgap (> 1.75 eV) perovskite top subcells 8 , which at present have large voltage and fill factor losses, particularly for large-area (>1 cm 2 ) tandem solar cells. Here we develop a self-assembled monolayer of (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid as a hole-selective layer for wide-bandgap perovskite solar cells, which facilitates subsequent growth of high-quality wide-bandgap perovskite over a large area with suppressed interfacial non-radiative recombination, enabling efficient hole extraction. By integrating (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid in devices, we demonstrate a high open-circuit voltage ( V OC ) of 1.31 V in a 1.77-eV perovskite solar cell, corresponding to a very low V OC deficit of 0.46 V (with respect to the bandgap). With these wide-bandgap perovskite subcells, we report 27.0% (26.4% certified stabilized) monolithic all-perovskite tandem solar cells with an aperture area of 1.044 cm 2 . The certified tandem cell shows an outstanding combination of a high V OC of 2.12 V and a fill factor of 82.6%. Our demonstration of the large-area tandem solar cells with high certified efficiency is a key step towards scaling up all-perovskite tandem photovoltaic technology. A self-assembled monolayer of (4-(7 H -dibenzo[ c,g ]carbazol-7-yl)butyl)phosphonic acid is integrated in wide-bandgap perovskite solar cells, which enables a high power conversion efficiency and low open-circuit voltage deficiency, as well as efficient centimetre-scale all-perovskite tandem solar cells.