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Mafic granulite, garnet peridotite, and garnet pyroxenite occurred as slices or lenses within dominant felsic granulite, and they together constitute a high‐pressure metamorphic terrane in the Bashiwake unit, South Altyn Tagh, Northern Tibet, China. Previous studies focused on the metamorphic evolution, and geothermobarometry results indicated that the mafic granulite has experienced high pressure/(ultra‐)high temperature (HP/(U)HT) metamorphism, followed by a medium pressure (MP) granulite‐facies overprint. However, the nature and petrogenesis of the mafic granulite in the dominant felsic granulite are poorly known. Combining the previous geothermobarometry results with the petrographic observations, mineral chemistry, and pseudosection modelling in this study, at least four stages were suggested for the metamorphic evolution of the mafic granulites in the South Altyn Tagh, including the eclogite‐facies stage (3–4 GPa, 910–1000°C), high pressure–ultrahigh temperature (HP–UHT) metamorphism, an isothermal decompression, and subsequent MP granulite‐facies overprint. The U–Pb dating of zircons yielded two age clusters: one age cluster at ca. 500 Ma, representing the retrograde age of HP–UHT metamorphism after the eclogite‐facies stage, and another age cluster of ca. 900 Ma that represented the age of the protolith for the mafic granulite. This indicated that the protolith of the mafic granulite was formed in the early Neoproterozoic and then was taken to extreme temperatures and pressures during the early Palaeozoic orogenic event. The elemental abundances of the mafic granulites in the Bashiwake area clearly indicated that they were higher in FeO and TiO2, but were significantly lower in MgO, Cr, and Ni than those of associated garnet peridotites/pyroxenites, and they showed LREE‐enriched patterns with slightly positive Eu anomalies. Sr–Nd isotopic data suggested a basaltic magmatic origin with crust contamination for the protolith of the mafic granulite. Integrating these results together with previous studies, we suggest that the mafic granulites were derived from the basaltic magma intrusion in the continental crust during the Neoproterozoic and subsequently suffered a common HP/UHT metamorphism with felsic crust rocks in the early Palaeozoic (ca. 500 Ma) after the eclogite‐facies metamorphism related to the continental collision (>500 Ma). [ABSTRACT FROM AUTHOR]

Deciphering the geodynamic evolution and compositions of the Earth's mantle is crucial for understanding the origin and evolution of the Earth, however, the original geodynamic setting and significance of tectonically emplaced mantle in ancient orogens is always ambiguous. Orogenic garnet peridotites can shed light on the understanding of upper mantle petrology and the tectonic processes that operate at convergent plate boundaries. Petrographical evidence and P-T conditions of two contrasting types of orogenic garnet peridotites in the South Altun–North Qaidam (SAT–NQD) HP/UHP metamorphic belt suggest that they experienced a notably different geological history. Geochemical characteristics show that the garnet peridotites in the Bashiwake unit represent ultramafic complexes emplaced into the continental crust before subduction, while those in the Luliangshan unit originate from the mantle wedge above a deep subduction zone. Sr Nd isotopes for the two contrasting ultramafic rocks indicate that both have been modified either by mantle metasomatism or crustal contamination. The distinct petrochemical and isotopic characteristics of these contrasting orogenic garnet peridotite types demonstrate spatio-temporal variation in the tectonothermal-evolution of the SAT–NQD HP/UHP orogen. • There are two contrasting garnet peridotite types in the SAT–NQD HP/UHP belt. • These garnet peridotites record distinct initial tectonic settings and evolution. • They have been modified either by mantle metasomatism or crustal contamination. [ABSTRACT FROM AUTHOR]

Abstract Carbonatitic magmatism in subduction zones provides extremely valuable information on the cycling, behavior and storage of deep carbon within the Earth. It may also shed light on insights into crust-mantle interaction and mantle metasomatism within subduction zones. Origin of carbonatite has long been debated: all hypotheses need to reflect the different mineral assemblages and geochemical compositions of carbonatites and their diverse tectonic settings. Here we present a petrological, geochronological, geochemical and isotopic study of carbonatite bodies associated with orogenic peridotites, which occur as stocks or dykes with widths of tens to hundreds of meters in the Luliangshan region, North Qaidam, northern Tibet, China. On the basis of modal olivine (Ol) content, the studied samples were subdivided into two groups: Ol-poor carbonatite and Ol-rich carbonatite. Zircon grains from the Ol-poor carbonatite show detrital features, and yield a wide age spectrum between 400 Ma and 1000 Ma with a pronounced peak at ca. 410–430 Ma. By contrast, oscillatory zoned zircons and inherited cores show two relatively small Neoproterozoic age peaks at ca. 920 and 830 Ma. Zircon grains from the Ol-rich carbonatite sample are also distributed in a wide spectrum between 400 and 1000 Ma, with a pronounced peak at ca. 440 Ma and a slightly inferior peak at ca. 410 Ma. The oscillatory zoned zircons and inherited cores exhibit a smaller Neoproterozoic age peak at ca. 740 Ma. The pronounced peaks ranging from 430 to 410 Ma are consistent with the deep subduction and mantle metasomatic events recorded in associated ultramafic rocks. Both groups of carbonatites are characterized by enrichment of light rare earth elements (LREEs) with high (La/Yb) N values and pronounced negative Eu anomalies. They show high 87Sr/86Sr values (0.708156–0.709004), low 143Nd/144Nd values (0.511932–0.512013) and high δ18O V-SMOW values (+17.9 to +21.3‰). This geochemical and isotopic evidence suggests that these carbonatites were derived from remobilized sedimentary carbonate rocks. We propose that the primary carbonatite magma was formed by partial melting of sedimentary carbonates with mantle contributions. Sedimentary carbonates were subducted into the shallow upper mantle where they melted and formed diapirs that moved upwards through the hot mantle wedge. The case presented provides a rare example of carbonatite originating from sedimentary carbonates with mantle contributions and relevant information on the mantle metasomatism within a subduction zone. Highlights • Geochemistry data indicate a sedimentary carbonate origin with mantle contribution. • Sedimentary carbonate formed diapirs that moved upwards through the mantle wedge. • The carbonatitic melt reacted with mantle peridotite to form the carbonatites. [ABSTRACT FROM AUTHOR]

Garnet peridotite, garnet pyroxenite, mafic granulite and dominant felsic granulite constitute a high-pressure/high-temperature (HP/HT) metamorphic terrane in the south Altyn Tagh, North Tibet (China). Garnet peridotite and associated garnet pyroxenite occur as slices or lenses within high pressure felsic granulite. Previous studies indicate that garnet peridotite experienced the peak HP/HT metamorphism, followed by a medium pressure granulite-facies overprint. However, the origin of the garnet peridotite and associated garnet pyroxenite remains controversial. In this contribution, we present new zircon U–Pb and Hf isotopic data and whole-rock major, trace element and Sr–Nd isotopic data for the representative garnet peridotites and associated garnet pyroxenites. SHRIMP U–Pb dating on the inherited (magmatic) zircons from the garnet peridotites gave an U–Pb age of ca. 780 Ma, which is interpreted as the age of the ultramafic magma crystallization. The metamorphic zircons yield an age of ca. 500 Ma, which is consistent with the Sm–Nd isochron age of 493 ± 24 Ma for whole rock, garnet and clinoproxene from a garnet pyroxenite, representing the timing of peak metamorphism. The Baishiwake garnet peridotites and garnet pyroxenites show relatively high contents in Fe 2 O 3 , TiO 2 , P 2 O 5 , Nb, Zr, and Y, but significantly low MgO, Cr, A1 2 O 3 and Ni contents. They possess enriched LREE, nearly flat HREE, slightly positive Eu anomaly and weak negative anomalies in Nb and Ti. The relatively high 87 Sr/ 86 Sr ratios (0.707–0.710) and low 143 Nd/ 144 Nd ratios (0.5123–0.5124) imply a possible crust contamination prior to HP metamorphism. Integrating these data together with previous studies, we suggest that the Bashiwake garnet peridotites and associated garnet pyroxenites were derived from mantle-derived magmas which intruded into the continental crust during the Neoproterozoic and then experienced a common HP/HT metamorphism with felsic crustal rocks in the Early Paleozoic (ca. 500 Ma). [ABSTRACT FROM AUTHOR]

Kyanite eclogites can provide insights into global orogenic processes within subduction-collision zones. Here we present an integrated study of the petrography, mineral chemistry, zircon U-Pb geochronology, and whole-rock geochemistry of granulitized kyanite eclogites from South Altyn Tagh, located at the northern margin of the Qinghai-Tibet plateau, China. Our results suggest that the rocks experienced eclogite-facies metamorphism (27–37 kbar, 1030–1068 °C), followed by a high pressure-ultra-high temperature (HP-UHT) stage (17–20 kbar, 945–1033 °C), isothermal decompression, and a medium pressure-(ultra)-high temperature (MP-(U)HT) (10–12 kbar, 810–950 °C) granulite-facies overprint. Zircon U-Pb dating yielded a weighted mean U-Pb age of ca. 500 Ma for the metamorphic domains, which is interpreted as the timing of HP-UHT metamorphism. In contrast, the age of ca. 800 Ma recorded by the inherited cores of zircon grains is considered to represent the protolith formation age. High Al 2 O 3 and CaO and relatively low MgO and FeO contents, LREE enrichment and nearly flat HREE patterns, and enriched Sr-Nd isotopic compositions suggest that the protoliths of the granulitized kyanite eclogites were likely derived from an enriched mantle source affected by crustal contamination. These results, together with previous research on these associations suggested that the protoliths of granulitized kyanite eclogites and associated garnet peridotite in the Bashiwake area are derived from mafic-ultramafic intrusions composed of plagioclase-rich gabbroic rocks and olivine-rich cumulates. These mafic-ultramafic intrusions were possibly generated by plume-induced melting related to the rifting of the Rodinia supercontinent during the Neoproterozoic, and were later subjected to early Paleozoic metamorphism. The geodynamic model proposed envisages continental subduction followed by relamination of felsic and mafic-ultramafic associations at the base of the lower crust, which were subsequently exhumed, forming diapir-like bodies. Our results, combined with those from previous studies, not only provide insights into the processes of continental collision to exhumation, but also provide significant constraints on the geotectonic processes leading to the formation of HP rocks within subduction-collision orogens. • The U-Pb dating of metamorphic zircons at ca. 500 Ma represented the HP-UHT stage. • The distinct metamorphic events were documented by Y+REEs concentrations in the garnet grain. • REE-based thermobarometer suggests the granulitized kyanite eclogite has recorded the UHP metamorphism. • A tectonic model of subduction-relamination is proposed for the geodynamic evolution of the granulite-peridotite unit. [ABSTRACT FROM AUTHOR]

The granulitized eclogites from the Luliangshan terrane of the North Qaidam UHP metamorphic belt occur as lenses within pelitic gneisses and orthogneisses. Combined petrologic data and phase equilibrium modeling indicate a multi-stage metamorphic history of the granulitized eclogites: (1) an earlier eclogite facies metamorphism (P>18.5 kbar, T> 830 °C) is deduced from omphacite relics in the matrix and rare omphacite inclusions within garnet. The possible assemblage is garnet+omphacite+rutile+ quartz; (2) the early stage of high pressure granulite facies assemblages (garnet+clinopyroxene+ plagioclase+rutile+quartz+liquid) developed in the early decompression process has a P-T regime of 17.5 kbar and 852–858 °C, constrained by plagioclase and clinopyroxene inclusions in garnet. The late stage of high pressure granulite assemblages (garnet+clinopyroxene+amphibole+plagioclase+rutile+quartz+liquid) records an isothermal decompression process with the pressure successively declining from 17.5 to 14.7 kbar and to 11.3 kbar at 858 °C; (3) the later medium pressure granulite facies assemblage (garnet+ orthopyroxene+ clinopyroxene+amphibole+plagioclase+ilmenite+liquid+quartz) indicates a drop in pressure and rise in temperature at P-T conditions of 7.6–7.7 kbar and 878–883 °C; (4) retrogressive amphibolite facies stage, which is represented by amphibole+plagioclase kelyphitic rims around garnet, formed under conditions of <5 kbar and <650 °C. The preservation of medium pressure granulite facies assemblage and the garnet composition feature constrain a following isobaric cooling path during late exhumation. This process suggests a clockwise P-T path and indicates that the granulitized eclogites record a high grade "Barrovian" metamorphic overprint at the middle-lower crust during exhumation. The present data show that the Luliangshan terrane is a "hot" HP-UHP terrane. [ABSTRACT FROM AUTHOR]

The Amdo microcontinent which separates the Qiangtang terrane to the north and the Lhasa terrane to the south is a key terrane for reconstructing the tectonic evolution of Central Tibet. We report the new finding of retrograde eclogites within the Amdo microcontinent in this study. The eclogites are characterized by peak metamorphic mineral assemblages of garnet, omphacite, rutile and quartz and underwent a four‐stage metamorphic evolution, including a peak eclogite facies stage (M1) at ~20–24 kbar and 580–620°C, followed by an HP granulite facies decompression stage (M2) at ~13–15 kbar and 750–780°C, a subsequent MP‐UHT granulite facies heating stage (M3) at 8–10 kbar and >840°C and a final amphibolite facies retrogression (M4) at 5.3–6.0 kbar and 560–580°C. The eclogites exhibit rare earth element distribution patterns and trace element abundances similar to those of N‐MORB and arc‐related volcanics, with depleted whole‐rock εNd(t) values of 3.4 to 4.2, and are inferred to have formed in a back‐arc basin tectonic setting. Zircon and rutile U–Pb dating yields a protolith age of 226 ± 5 Ma, a peak eclogite facies metamorphic age of 190 ± 1 Ma, an HP granulite facies metamorphic age of 179 ± 1 Ma and an amphibolite facies retrograde age of 172 ± 1 Ma. The clockwise P–T–t paths and the oceanic protolith signature of retrograde eclogites suggest that part of the back arc basin was subducted to depths of ~80 km. Tectonic erosion associated with the subduction of the Amdo microcontinent beneath the Tethys Ocean accounts for the deep subduction of the back‐arc basin and the absence of arc magmatic rocks in the northern Amdo microcontinent. [ABSTRACT FROM AUTHOR]

316L stainless steel (SS) is the key raw material for the preparation of high-performance oil and gas pipelines, but even 316L with excellent properties will be attacked by sulfate-reducing bacteria (SRB) corrosion. Excellent antibacterial effects have been obtained in other SS systems by doping antibacterial elements. However, the current research on the preparation of antibacterial 316L SS is not comprehensive, and the quantitative analysis of the antibacterial mechanism and doping elements is still unclear. In this paper, the SS with Cu and Ce added were prepared by vacuum induction melting. Then the homogenization treatment combined with hot rolling was used to improve the structure segregation and mechanical properties. Further, the weight loss tests and electrochemical tests were conducted to evaluate the corrosion resistance of SS, the corrosion products and morphology were analysed, and the deformation structure was characterized to clarify the corrosion mechanism of the modified SS and quantify the doping elements. The results indicate that the microstructure after homogenization is mainly austenite, and with the increase of Ce content, the Ce-rich phase segregates. The inhibitory effect of Cu on SRB can be explained by the destructive effect of Cu ions on cell membranes. On this basis, adding a low content of Ce element can increase the permeability of the SRB cell wall and further enhance the attack effect of Cu ions on the cell membrane. The corrosion behavior of alloys shows the deformation structure dependence, with crystal defects and segregation increasing the corrosion rate. The optimal addition amount of Ce is 0.18 wt%, and the strength and elongation of SS are 511.18 MPa and 108.2%, respectively. • 316L with excellent comprehensive properties were obtained by hot rolling and homogenization. • The composite addition of Cu and Ce elements shows obvious synergistic antibacterial effect. • The addition of Ce exceeding 0.18 wt% causes segregation and reduces corrosion resistance. • The tensile strength and elongation of SS after homogenization with 0.18 wt% Ce content reached 566.55 MPa and 100.15%. [ABSTRACT FROM AUTHOR]

The early Mesozoic evolution of the Lhasa terrane, which represents a major component of the Himalayan–Tibetan orogen, remains highly controversial. In particular, geological units and events documented either side of the eastern Himalayan syntaxis (EHS) are poorly correlated. Here, we report new petrological, geochemical and geochronological data for cogenetic peraluminous S-type granites and metamorphic rocks (gneiss and schist) from the Motuo–Bomi–Chayu region of the eastern Lhasa terrane, located on the eastern flank of the EHS. Zircon U–Pb dating indicates that these units record both Late Triassic magmatic (216–206 Ma) and metamorphic (209–198 Ma) episodes. The granites were derived from a Paleoproterozoic crustal source with negative zircon εHf(t) values (–5·5 to –16·6) and TDM2 model ages of 1·51–1·99 Ga, and are interpreted to have formed by crustal anatexis of nearby metasediments during collisional orogeny and crustal thickening. The gneisses and schists experienced similar upper amphibolite-facies peak metamorphism and associated partial melting, followed by decompressional cooling and retrograde metamorphism. These rocks were buried to lower-crustal depths and then exhumed to the surface in a collisional orogenic setting during plate convergence. From comparison of these data with those for other metamorphic belts with similar grades and ages, and association of coeval granitic magmatism widespread in the central–east Lhasa terrane, we propose that the studied cogenetic magmatism and metamorphism in the Motuo–Bomi–Chayu region records Late Triassic accretion of the North Lhasa and South Lhasa terranes, which represents the first evidence of the Paleo-Tethys Ocean closure in this part of Asia. These data provide new constraints on the spatial and temporal evolution of the Paleo-Tethyan Wilson Cycle and provide a 'missing link' to correlate the geology and tectonic history of the Lhasa terrane continental crust on either side of the EHS. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Phase equilibrium modelings combined with petrographic observations yield an approximate UHP P–T condition of the Yuka metapelites. • Eclogites and its country rocks in the Yuka area commonly underwent UHP metamorphism. • Two eclogites were possibly derived from different depths in the subduction zone that were subsequently juxtaposed during late exhumation. Abstract As the products of early Paleozoic continental collision, widespread eclogite facies rocks crop out in the Yuka terrane, western North Qaidam Mountains, NW China. Eclogites commonly reach ultrahigh pressure (UHP) metamorphic conditions. However, whether the associated metapelitic rocks also experience UHP metamorphism has not been thoroughly elucidated to date. In this contribution, we chose two eclogite samples and one metapelite sample to investigate their metamorphic evolution. Combining with petrographic observation and P–T pseudosections, similar clockwise P–T paths with peak stages at 25–34 kbar, 580–633 °C were obtained for eclogites and metapelites. Eclogite ZM871 records a prograde metamorphic condition at 21.6 kbar/552 °C, defined by the assemblage garnet + omphacite + epidote + lawsonite + talc (+quartz + phengite + rutile) and a peak metamorphic condition at 34.0 kbar/633 °C by the assemblage garnet + omphacite + lawsonite + talc (+coesite + phengite + rutile). Eclogite ZM641 records a prograde metamorphic condition at 21.5 kbar/520 °C, defined by the assemblage garnet + omphacite + glaucophane + lawsonite (+quartz + phengite + rutile) and a peak condition at 30 kbar/616 °C by the assemblage garnet + omphacite + lawsonite + talc (+quartz + phengite + rutile). Metapelite ZM8–1 records a prograde metamorphic condition at 18.2 kbar/530 °C defined by the assemblage garnet + chloritoid + chlorite (+quartz + phengite + rutile), a peak condition at 25 kbar/580 °C by the assemblage garnet + kyanite + chloritoid (+quartz + phengite + rutile), and a retrograde condition at 16.2 kbar/595–598 °C by the assemblage garnet + kyanite + chloritoid + chlorite (+quartz + phengite + rutile). Combined with previous data from orthogneiss and impure marble in the Yuka terrane, which also recorded UHP metamorphic conditions, the Yuka eclogite–bearing unit commonly underwent UHP metamorphism, although further investigation is warranted to verify whether the Yuka unit represents a single coherent UHP metamorphic terrane or a collage of different UHP metamorphic slices. [ABSTRACT FROM AUTHOR]

Highlights • Grenvillian orogeny of Rodinia in Oulongbuluke Block systematically investigated. • Metabasite, augen granitic gneiss, paragneiss ages of 1132 ± 33, 1118 ± 9, 1124 ± 12 Ma. • Peak metamorphic P-T conditions of 4.8–5.8 kbar and 652–700 °C. • Metabasites resemble the geochemical characteristics of Andean arc magmatism. • Oulongbuluke Block likely temporarily connected to Qilian Block and Tarim Craton. Abstract A systematic petrologic, geochemical, and zircon U-Pb and Lu-Hf isotopic investigation of an ∼1.1 Ga arc magmatism and metamorphism was studied to evaluate the Grenvillian orogeny and assembly of Rodinia in the Oulongbuluke Block in NW China. The peak metamorphic P-T conditions of the paragneiss were restricted to 4.8–5.8 kbar and 652–700 °C based on P-T pseudosection and conventional geothermobarometry. Zircon U-Pb ages of 1132 ± 33 Ma, 1118 ± 9 Ma, and 1124 ± 12 Ma were determined for the metabasite, augen granitic gneiss, and paragneiss, respectively, indicating magmatic intrusion and a metamorphism event in the late Mesoproterozoic. The metabasites exhibited enrichment of light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) and depletion of heavy rare earth elements (HREEs) and high-field-strength elements (HFSEs), resembling the geochemical characteristics of Andean arc magmatism. The whole-rock geochemistry and in-situ zircon ε Hf (t) values of 4.3 and 11.2 suggested that the protolithic mafic magma originated from a subduction-modified lithospheric mantle. The low zircon ε Hf (t) values of −5.2 and −0.5 also suggested that the calc-alkaline augen granitic gneisses were derived from the partial melting of a late Paleoproterozoic crustal source. The ∼1.1 Ga arc-related magmatism and metamorphism in the Oulongbuluke Block indicated the occurence of a tectonic-thermal event in an Andean-type active continental margin in the late Mesoproterozoic. In this regard, the Oulongbuluke Block was likely temporarily connected to the Qilian Block and Tarim Craton, forming a single continuous block with similar Grenville age during the late Mesoproterozoic to early Neoproterozoic (1.1–0.9 Ga). [ABSTRACT FROM AUTHOR]

The Early Mesozoic granitoids in the east-central Tibet are the key to understand the tectonic evolution of the Tibetan Plateau. In this study, three stages of Early Mesozoic granitic magmatism were indicated by LA-ICP-MS zircon U-Pb dating on 14 samples. The Early Triassic (248-243 Ma) and the Late Triassic (213-208 Ma) were distributed in the North Qiangtang terrane, and the Early Jurassic (ca. 187 Ma) occurred in the Tongka and Jiayuqiao blocks. The Late Triassic and Early Jurassic granitoids show similar negative zircon εHf(t) values (− 5.5 to − 16.6) with TDM2 model ages of 1.60-2.28 Ga, suggesting a Paleoproterozoic crustal source, whereas the Early Triassic granitoids have zircon εHf(t) values from − 3.4 to + 5.3 with TDM2 model ages of 0.94-1.50 Ga, indicating a Mesoproterozoic crustal source. Based on the whole-rock geochemical data, we suggest that the Early Triassic rocks from the North Qiangtang terrane include I- and S-type granites and the Late Triassic rocks are S-type granites, which were related to the northward subduction of the Longmu Tso-Shuanghu-Dingqing Paleo-Tethys Ocean and subsequent collision between the North Qiangtang terrane and Tongka block, respectively. The Early Jurassic granitoids from the Tongka and Jiayuqiao blocks also included both I- and S-type granites and were probably generated in an arc-related setting during the northward subduction of the Bangong-Nujiang Tethys Ocean. Therefore, we suggest a collision-accretion model that attributes the Early Mesozoic tectonic-magmatic event to the sequential multistage subduction and collision in the east of central Tibet. [ABSTRACT FROM AUTHOR]

The correlation between dike density and regional‐scale mineralization indicates a fundamental criterion for ore‐forming process. Here, a novel dike distribution density method is formulated for evaluating this correlation and exploring mine targets quantitatively. Three parameters (dike density, dike orientation scatter degree and dike fractal dimension) are proposed to express the degree of irregularity and complexity of dike distribution patterns. This method is applied to the South Alatao Mountains area (China), where the dike swarms show regionally well‐developed density gradients and the mineral deposits are spatially associated with abundant dike swarms. On the basis of this quantitative dike distribution density method, 60% of the deposit targets are delineated in this area. This result indicates that the method is an effective quantification tool for prospecting mine targets. The dike distribution density method is applicable for areas where abundant regional‐scale dike swarms and mineralization occur. It should be considered as an effective and complimentary technique for the common mine prospectivity analysis. [ABSTRACT FROM AUTHOR]

In the northern West Qinling orogen (WQO), granulite-facies metamorphic rocks are recognized within the Qinling Complex. These rocks are composed of amphibole-bearing two-pyroxene granulite and garnet-sillimanite gneiss with widespread migmatitization. We investigate three granulite-facies samples and one leucosome sample from the Qinling Complex, which are suitable for U-Pb analyses of zircon and monazite. SHRIMP and LA-ICPMS U-Pb age dating of zircon and monazite from two pelitic granulites provides weighted mean ages of 430±4 Ma (MSWD=0.88) and 433±4 Ma (MSWD=0.27), respectively. Based on the petrographic characteristics and zircon CL imagery, we postulated a ca. 430 Ma metamorphic timing for the pelitic granulites. LA-ICPMS zircon U-Pb data from an amphibole two-pyroxene granulite sample reports two weighted mean age groups: 424±3 Ma (MSWD=0.45) and 402±3 Ma (MSWD=1.4), which were interpreted as granulite-facies metamorphic and retrograde ages, respectively. LA-ICPMS U-Pb dating of zircons from the leucosome sample yields a weighted mean age of 426±2 Ma (MSWD=0.3), which is interpreted as the crystallization age of the leucosome. These data indicate that the West QOB experienced early Paleozoic granulite-facies metamorphism and anatexis similar to the East QOB. However, it remains unclear whether the early Paleozoic granulite facies metamorphism resulted from an arc setting created by the northward subduction of the Shangdan ocean or from a continental collisional orogenic event. [ABSTRACT FROM AUTHOR]

The Oulongbuluke Block, which is located in the northeastern margin of the Tibet Plateau, has traditionally been considered to be a fragment of the Tarim Craton. Here we present a systematic petrologic, geochemical, and zircon U-Pb and Hf isotopic investigation on mafic granulite and migmatite in the Oulongbuluke Block. The mafic granulite is mainly composed of clinopyroxene, orthopyroxene, plagioclase, amphibole and quartz, with peak metamorphic P-T contions of 6.5–8.8 kbar, 745–770 °C. Macroscopic and microscopic observations provide strong evidence for in situ partial melting of the felsic gneiss involving breakdown of biotite within the Oulongbuluke Block. The Pl-rich leucosomes with positive Eu anomalies and higher Sr contents were generated as the early-formed feldspar cumulate, and the Kfs-rich pegmatite with negative Eu anomalies and lower Sr contents may represent percolating fractionated melt that was trapped during cooling. Zircon U–Pb dating and Hf isotopic analyses on the mafic granulite and migmatite of the Oulongbuluke Block reveal two distinct age populations: the early Paleoproterozoic (∼2.37 Ga) and late Paleoproterozoic (1.93–1.92 Ga). The ∼2.37 Ga magmatic zircon cores of the migmatite have ε Hf (t) values between −4.3 and 0.4, with two-stage Hf model ages (T DMC ) mainly between 2.82 Ga and 3.05 Ga. The age of 1.93–1.92 Ga obtained from the mafic granulite and migmatite is interpreted as the age of Late Paleoproterozoic metamorphism and anatexis. Most of the 1.93–1.92 Ga metamorphic and anatectic zircons have significantly lower 176 Lu/ 177 Hf ratios but higher 176 Hf/ 177 Hf (t) values than the inherited magmatic zircon cores, which demonstrates that both the zircon U–Pb and Lu–Hf isotope compositions were significantly reset during metamorphism and anatexis. The late Paleoproterozoic metamorphic and anatectic event coincided with global orogenic events that are recorded in many continental fragments, which suggests their link to the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

Plagioclase-rich leucosomes and K-feldspar--rich veins are widely distributed within retrogressed eclogite in the Xitieshan area of the North Qaidam ultrahigh-pressure metamorphic terrane, western China. In this contribution, a combined study of petrology, zircon internal structure, zircon U-Pb age, zircon trace-element composition, whole-rock geochemistry, and Sr-Nd isotopes in plagioclase-rich leucosomes and K-feldspar--rich veins provides insight into the nature and timing of partial melting in these rocks. Petrological evidence for partial melting is provided by elongated, highly cuspate feldspars, quartz along grain boundaries (e.g., muscovite, garnet, and clinopyroxene), and felsic veinlets composed of quartz and feldspar along the boundaries of garnet, clinopyroxene, and clinopyroxene-plagioclase symplectite in the metabasite. Whole-rock geochemistry suggests that the plagioclase-rich leucosomes have lower contents of both rare earth elements (REEs) and high field strength elements (HFSEs) but higher large ion lithophile elements (LILEs; e.g., Rb, Ba, K, Sr, and Pb) than the metabasite hosts. The plagioclase-rich leucosomes may be divided into two subgroups according to their distinct REE patterns: (1) higher total REE content with or without weak negative Eu anomalies, and (2) lower total REE content with conspicuous positive Eu anomalies. The Eu-rich group also shows higher Sr content than those in the Eu-poor group. However, the K-feldspar--rich veins show higher REE, HFSE, and LILE concentrations than the plagioclase-rich leucosomes and metabasites. The inherited cores of K-feldspar--rich veins are of typical magmatic origin (oscillatory zoning with high Th/U ratios, enriched heavy [H] REEs, and negative Eu anomalies), yielding 206Pb/238U ages ranging from 904 ± 8 Ma to 915 ± 28 Ma. The zircon cores of plagioclase-rich leucosomes and mantles of K-feldspar--rich veins exhibit no zoning or weak zoning, with flat HREE patterns and no negative Eu anomalies, and they contain mineral inclusions of garnet and clinopyroxene, implying that these zircon domains were formed during an episode of eclogite-facies metamorphism with 206Pb/238U ages ranging from 444 ± 10 Ma to 452 ± 9 Ma. Internal textures and mineral inclusions (quartz, plagioclase, and K-feldspar) and trace-element systematics (steep HREE patterns with negative Eu anomalies and low Th/U ratios) of the zircon rims from plagioclase-rich leucosomes and K-feldspar--rich veins are similar to anatectic zircon. These anatectic zircon domains yielded 206Pb/238U ages ranging from 430 ± 10 Ma to 440 ± 12 Ma, and 406 ± 12 Ma to 430 ± 13 Ma, respectively. An integrated study of petrology, geochronology, and geochemistry demonstrated that the metabasites of the North Qaidam ultrahigh-pressure terrane likely experienced initial partial melting with plagioclase-rich leucosome formation under eclogite-facies conditions and partial melt crystallization during the granulite-facies stage, triggered by dehydration melting involving zoisite and rare muscovite. The K-feldspar--rich veins within the metabasites may be the result of injected melts that were derived from partial melting of nearby gneisses. [ABSTRACT FROM AUTHOR]

The petrogenesis and geodynamic implications of the early Paleozoic adakitic rocks in the North Qilian orogenic belt remain topics of debate. In this study, petrology, zircon U–Pb age and Lu–Hf isotopic composition, whole-rock geochemistry and Sr–Nd isotopes were carried on both low-Mg and high-Mg adakitic rocks from the North Qilian orogenic belt. These results will provide significant constraints on the evolution of the North Qilian orogenic belt. In general, the low-Mg adakitic granites mainly consist of plagioclase (50–55%), alkali feldspar (20–25%), quartz (20–25%) and biotite (5%). In contrast, the high-Mg adakitic granodiorites are generally composed of alkali feldspar (30–35%), plagioclase (30–45%), quartz (20–25%) and amphibole (∼10%). The low-Mg adakitic granitoids (446–457 Ma) are characterized by high SiO 2 (69–72 wt.%), low Mg # (39–42) and low Cr and Ni contents. However, the high-Mg adakitic granitoids (430–431 Ma) have relatively lower SiO 2 (65–66 wt.%), higher Mg # (50–59) and higher Cr and Ni contents. The low-Mg adakitic rocks have high initial 87 Sr/ 86 Sr ratios (0.7068–0.7080), negative ε Nd ( t ) (−2.3 to −3.3) and ε Hf ( t ) values (−6.8 to 1.9) with old zircon Hf model ages (1.2–1.6 Ga). However, the high-Mg adakitic rocks show lower initial 87 Sr/ 86 Sr ratios (0.7044–0.7066), higher ε Nd ( t ) (−1.8 to 3.0) and positive ε Hf ( t ) values (2.3–7.7) with younger zircon Hf model ages (0.9–1.1 Ga). These results suggest that the low-Mg rocks were generated by partial melting of thickened crust, whereas the high-Mg rocks were derived from anatexis of delaminated lower crust, which subsequently interacted with mantle magma upon ascent. The data obtained in this study provide significant information about the geological and tectonic processes after the closure of the Qilian Ocean. The continent–continent collision and thickening probably occurred during 440–467 Ma with formation of low-Mg adakitic rocks; and the transition of the tectonic regime from compression to extension probably occurred at ∼430 Ma with formation of high-Mg adakitic rocks. [ABSTRACT FROM AUTHOR]

HP mafic and felsic adakitic granulite bodies in the Dulan area of the North Qaidam ultrahigh-pressure (UHP) terrane record high-pressure (HP) granulite-facies metamorphism and anatexis and provide temporal and tectonic constraints on deep subduction of continental crust and its subsequent exhumation. Mafic HP granulite components dominate the main outcrop and preserve features diagnostic of anatexis and locally may be described as migmatite. The HP mafic granulites comprise garnet, clinopyroxene, plagioclase and quartz. The felsic granulite (leucosome) is mainly composed of K-feldspar+plagioclase+quartz+kyanite+garnet. Detailed zircon U–Pb and amphibole Ar–Ar geochronology, combined with trace element geochemistry, indicate peak metamorphism for the mafic HP granulite at 434±3 to 435±3Ma and peak metamorphism and partial melting for the felsic HP granulite at 433±5 to 438±4Ma, which overlaps the ages of UHP metamorphism for adjacent eclogite (430–446Ma). 40Ar/39Ar amphibole ages of 423 to 432Ma represent amphibolite-facies retrograde metamorphism and indicate rapid cooling during exhumation of the HP granulite bodies. Our geochronological data, combined with field relationships, petrology and geochemistry suggest that HP granulite-facies metamorphism and the partial melting that produced adakitic melts represent the same tectonic event. In this case, the felsic HP granulites (leucosome) formed from an adakitic melt derived from partial melting of mafic HP granulite in the overriding plate in a relatively higher geothermal gradient (15–18°C/km), leaving garnet-cumulate and/or meta-ultramafic (mainly garnet pyroxenite) as the residual component. In contrast, the nearby UHP eclogite is thought to have formed in the subducted plate in a relatively lower geothermal gradient (6–10°C/km). Penecontemporaneous metamorphic ages but different geothermal gradients between HP granulites and related UHP eclogite define a possible paired metamorphic belt generated in a subduction–collision setting associated with the North Qaidam continental collisional orogeny during the Late Ordovician–Early Silurian. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report Neoproterozoic tectothermal events in the Altun–Qilian–North Qaidam region. [•] Neoproterozoic magmatism was derived from ancient igneous protolith. [•] Neoproterozoic magmatism formed in an active continental margins. [•] The Altun–Qilian–North Qaidam was connected with the Tarim and South China block. [Copyright &y& Elsevier]

The Qilian orogenic system in the northern Tibetan Plateau records the complete tectonic cycle from opening of Proto-Tethys Ocean, initial subduction, to continental subduction and collision, and extensional collapse during Neoproterozoic to Devonian. Based on a compilation of recently published high-quality data, this contribution provides an overview of the composition, distribution, nature and ages of the principal tectonic elements, including ophiolites, multiple magmatic rocks, as well as high-grade metamorphism and anatexis, with a view to trace the tectonic evolution of the Qilian orogenic system with respect to the opening, subduction, accretion and closure of Proto-Tethys Ocean. Three main suture zones resulting from amalgamation involving microcontinental blocks within the Proto-Tethys Ocean are identified in the Qilian orogenic system, including the North Qilian subduction-accretion suture (NQLS), South Qilian subduction-accretion suture (SQLS) and North Qaidam subduction-collision zone (NQDS) from north to south that sandwich the Alxa, Qilian, Oulongbuluke and Qaidam Blocks. Two contrasting types of convergent orogeny in the Early Paleozoic includes the accretionary orogeny between Alxa, Qilian and Oulongbuluke Blocks (NQLS and SQLS), and the collisional orogeny between the Oulongbuluke Block and Qaidam Block (NQDS). Both Mariana-type and Andean-type subduction systems were identified in the NQLS based on the occurrence of Early Paleozoic accretionary complexes, ophiolites, high-pressure/low temperature metamorphic rocks and arc-related volcanic rocks and intrusions. The northward subduction beneath a Mariana-type intra-oceanic subduction system is represented by the Cambrian-Ordovician island-arc related volcanic rocks, back-arc volcanic rocks and ophiolite complex, and the southward subduction of the Proto-Tethys North Qilian Ocean beneath the Qilian Block generated an Andean-type continental arc, characterized by coeval arc magmatism and high-temperature metamorphism. Although oceanic subduction-related high-pressure metamorphism has not yet been recognized, the SQLS is also a typical accretionary orogen composed of island arc rocks, back-arc magmatic assemblages, ophiolite and accretionary complexes. The NQDS is a typical collisional orogen, characterized by ultrahigh pressure pelitic/granitic gneisses intercalated with minor eclogites and garnet peridotite blocks, although the previous subduction of oceanic crust can not yet be precluded, supported by the existence oceanic-type eclogite and arc-related magmatism and high-temperature metamorphism. Integrating the geological, petrological, geochemical and geochronological evidence, we reconstruct the Neoproterozoic-Paleozoic tectonic history of the Qilian orogenic system with respect to Proto-Tethys Ocean, which includes opening of the Proto-Tethys Qilian Ocean (580-550 Ma), subduction (520-460 Ma), and closure with subsequent deep continental subduction (455-430 Ma), and multi-stage exhumation of deeply subducted continental slab (425-400 Ma), as well as final extensional collapse (400-360 Ma) [ABSTRACT FROM AUTHOR]

In this present work, a room temperature coprecipitation method for the synthesis of CaMoO 4 @SiO 2 :Ln (Eu3+, Tb3+, Dy3+) phosphors was reported. These particles were characterized using X-ray diffraction (XRD), Energy dispersive spectrometer (EDS), Fourier Transform IR spectroscopy (FTIR), scanning electron microscope (SEM), UV-visible spectrophotometer and photoluminescence (PL) respectively. The results indicated that emission intensity of SiO 2 modified samples increased by about 2 times, compared with no-silica modified samples. Multicolor phosphors were also designed by changing the lattice activators (Eu3+, Tb3+, Dy3+). To further explore its applications, the transparent photoluminescent film was developed through the incorporation of polyvinyl alcohol (PVA), and selective and sensitive detection performance on dichromate was demonstrated in detail. In addition, red emission LED devices was assembled with as-prepared phosphors. The present results provide not only the high-performance phosphors modified by silica, but also a deep explanation of the structure-property relationship of the as-prepared sample. Based on these findings, it can be foreseen that these microparticles will be applied in versatile filed. Graphical Abstract: The design of CMO:Eu3+@SiO 2 and its functional applications. Image 1 • A co-precipitation method for preparation of samples was proposed. • The emission intensity of samples increased about 2-fold after modificating by SiO 2. • The enhancement mechanism of CaMoO 4 @SiO 2 : Eu3+ was discussed in detail. • The applications in luminescent film, LED devices and Cr 2 O 7 2- probe were designed. [ABSTRACT FROM AUTHOR]

• Flower-like CaMoO 4 :Eu3+/AgBr composites were successfully synthesized. • CaMoO 4 :Eu3+/AgBr composites exhibited excellent catalytic activity for 4-NP. • CaMoO 4 :Eu3+/AgBr composites act as the luminescence sensor for 4-NP and TNP. • The sensing mechanism was the competitive absorption between CMOA and analytes. In this work, bifunctional 3D flower-like CaMoO 4 : Eu3+/AgBr composites were successfully prepared using a two-step hydrothermal process. The as-prepared samples were characterized by SEM, XRD, FT-IR and EIS technologies, and their catalytic and photoluminescence properties were investigated in detail. The results showed that flower-like CaMoO 4 : Eu3+/AgBr composites exhibited high catalytic activity for 4-nitrophenol reduction. The reduction reaction can be completed within 5 min at room temperature, and the calculated apparent rate constant is 0.607 min−1. Furthermore, CaMoO 4 : Eu3+/AgBr composites could be developed as an inorganic sensor for nitroaromatic compound assay, due to the competitive adsorption mechanism. Thus, this work provided a new thought in the design of multifunctional materials for the monitoring and removal of organic pollutants. [ABSTRACT FROM AUTHOR]

The tectono-magmatic evolution of the Bangong-Nujiang Tethyan Ocean (BNO) plays a crucial role in understanding the Tibetan Plateau accretion before the Cenozoic India-Asia collision. The microcontinents and oceanic plateau recognized recently within the BNO provide important clues for constructing the subduction process between BNO and the Qiangtang terrane. In this contribution, we provide a comprehensive overview of the multidisciplinary information from magmatism, metamorphism, stratigraphy, geochronology, geochemistry, Hf isotopic data, ophiolite suites, and paleomagnetism to gain insights into the spatially and temporally related geodynamic processes of the BNO. A compilation of geochronological data indicates that the emplacement of the diverse igneous suites occurred mainly during three stages: stage 1 (190–150 Ma), stage 2 (130–110 Ma), and stage 3 (110–70 Ma). The igneous suites, including granitoids, mafic intrusions and volcanic rocks, formed two arcuate E–W trending belts that parallel the Bangong-Nujiang suture zone and are correlated to the double sided subduction of the BNO. We infer that the BNO initially opened at ~270Ma between the Lhasa terrane and Qiangtang terrane, although the relationship between the BNO and Longmu Tso-Shuanghu paleo-Tethyan ocean is still unclear. Age data related to metamorphism, arc magmatism, supra-subduction zoneophiolites, and sedimentary strata indicate that the northward subduction of the BNO started at ~190 Ma, followed by the subduction of microcontinents beneath the Qiangtang terrane at 195 Ma. In contrast, the subsequent southward subduction of the BNO started at ~170 Ma, resulting in the opening of the Shiquanhe-Namuco ocean. As indicated by the high Mg volcanic suite, intra-ocean subduction within the BNO also occurred during 170-145Ma, possibly related to the resistance from subduction of ocean plateau and slab retreat. Based on evidence from petrology, isotope geochronology, and isotopic geochemistry, we also infer that the magmatic lull during 145-130Ma is related to the slab subduction of ocean plateau beneath the southern Qiangtang subterrane. The closure of the BNO was most likely diachronous, which started as early as Late Jurassic and continued to the late Early Cretaceous (120-110Ma). • Initial opening of BNO at ~270 Ma and northward subduction at ~190 Ma. • Southward subduction started at ~170 Ma, leading to the opening of SNO. • Ocean plateau mechanism for intra-ocean subduction of BNO and magmatic lull during 145–130 Ma. • Diachronous closure of the BNO initiated at 150 Ma and the final closure during 110–100 Ma. [ABSTRACT FROM AUTHOR]

The red emitting composite phosphors Bi 2 MoO 6 :Eu3+/C 3 N 4 were prepared via a solid-state method and characterized by different techniques like XRD, SEM, FT-IR, Raman, UV-vis DRS and PL. The effects of reaction temperature and C 3 N 4 amount on the structure and optical properties of Bi 2 MoO 6 were studied in detail. The powder X-ray diffraction patterns showed that the crystal phase structure changed with the increase of temperature. Also, the introduction of C 3 N 4 had a significant impact on photoluminescence properties, which provides a universal strategy for phosphors to improve luminescence performance. • The red emitting composite phosphors Bi 2 MoO 6 :Eu3+/C 3 N 4 are synthesized. • The emission intensity increases by about 4 times after C 3 N 4 recombination. • The enhancement mechanism of Bi 2 MoO 6 :Eu3+ is discussed in detail. [ABSTRACT FROM AUTHOR]

• The Altun block, Qilian block, North Qaidam and East Kunlun block show strong affinity in the Meso-Paleoproterozoic. • The assembly of Rodinia in AQK may start as early as 1030 Ma with a peak convergent time of ∼918 Ma. • The initial breakup of Rodinia in AQK may have started from 860 Ma until to 660 Ma with the peak time of ∼765 Ma. • The separation of AQK from the South China craton may occur until the opening up of Qilian ocean after 660 Ma. The Altun-Qilian-Kunlun Mountain (AQK), located on the northeastern margin of the Qinghai-Tibet Plateau, experienced multiple Neoproterozoic magmatic and metamorphic events which are correlated to the Rodinia supercontinent history. Here we present results from a systematic petrologic, geochemical, and zircon U Pb and Hf isotopic study on Neoproterozoic granitoids and mafic rocks from the AQK. In conjunction with a review of the available age data, we divide the early Neoproterozoic magmatism in AQK into two stages: the first stage at ca. 1030–846 Ma and the second stage at ca. 860–660 Ma. The new Lu Hf isotopic data coupled with published Lu Hf and Sm Nd results indicate that the stage 1 mafic rocks were mainly derived from a depleted mantle source with minor contamination with crustal materials or subducted sediments. The stage 2 mafic rocks were mainly derived from the depleted mantle with limited crustal contamination. Combined with whole-rock geochemical compositions and Sr Nd isotopic data, the stage 1 granitic magmas are inferred to have been derived from reworked Paleoproterozoic-Mesoproterozoic crust and the stage 2 granitoid magmas mainly came from reworked continental crust with minor mantle magma input. The AQK experienced arc magmatism in a compressional environment on an active continental margin during the late Mesoproterozoic-early Neoproterozoic (1030–846 Ma), followed by rift-related magmatism in an extensional setting in the middle to late Neoproterozoic (860–660 Ma). Similarities in basement compositions, magmatism and metamorphism between the Qilian block (QL) and surrounding blocks suggest that the AQK was with a composite block at early Neoproterozoic. The assembly of AQK started as early as 1030 Ma with peak convergence at ca. ∼918 Ma. The initial breakup might have started from 860 Ma and lasted until to 660 Ma with the peak at ca. ∼765 Ma. These timings correspond well with those of the assembly and breakup of the Neoproterozoic supercontinent Rodinia. The breakup of AQK from the South China Craton might have occurred in the late Neoproterozoic, not until the opening of the Qilian ocean at around 660 Ma. [ABSTRACT FROM AUTHOR]