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Multiparametric magnetic resonance imaging (MRI) is widely used in breast cancer screening. Accurate prediction of the axillary lymph nodes metastasis (ALNM) is essential for breast cancer surgery and treatment. However, there is no mature and effective discerning method for ALNM based on multiparametric MRI.To evaluate the ALNM using T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), and diffusion-weighted imaging (DWI) sequences, respectively, and construct a quantitative ALNM discerning model of integrated multiparametric MRI.Retrospective.Three-hundred forty-eight breast cancer patients, 163 with ALNM (99.39% females), and 185 without ALNM (100% females). The dataset was randomly divided into the training set (315 cases) and the testing set (33 cases).1.5 T; T1WI (VIBRANT), T2WI (FSE), and DWI (echo planar imaging [EPI]).The lesion region of interest images were cropped and sent to a pretrained ResNet50 network. Then, the results of different sequences were sent to a classifier for ensemble learning to construct the ALNM model of multiparametric MRI.Performance indicators such as accuracy, the receiver operating characteristic (ROC) curve, and the area under the ROC curve (AUC) were calculated. Student's t-test, chi-square test, Fisher's exact test, and Delong test were performed, and P 0.05 was considered statistically significant.T2WI performed the best among the three sequences, and achieved the accuracy and AUC of 0.933/0.989 in the testing set. Compared to T1WI with the accuracy and AUC of 0.691/0.806, the increase is significant. While compared to DWI with the accuracy and AUC of 0.800/0.910, the improvement is not significant (P = 0.126). After integrating three sequences, the accuracy and AUC improved to 0.970 and 0.996.T2WI performed better than DWI and T1WI in discerning ALNM in this breast cancer dataset. The proposed quantitative model of integrated multiparametric MRI could effectively help the ALNM diagnosis.1 TECHNICAL EFFICACY STAGE: 2.

Through the numerical simulation of the internal flow field of the thrust bearing, the distribution of the oil membrane pressure field was calculated using the CFD software Fluent. The effect made by inclination angle and rotor speed on the thrust bearing performance was analyzed. The results show that the inclination angle has a strong impact in pumped storage units. Only when the inclination of the circular direction reaches a certain value, with the increase of the circular inclination, the bearing capacity of the oil film gradually increases, and the pressure center moves to the oil outlet. With the increase of the rotor speed, the bearing capacity of the oil film gradually increases, and the pressure center remains unchanged. Therefore, in the limit of the minimum oil film thickness, running at large inclination angles and rotor speed can improve the performance.

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag2O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag2O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min−1, which is 27.4- and 15.6-times higher than those of ZnS and Ag2O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag2O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag2O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag2O composite is promising in degrading organic pollutants in water.

The water-guide bearing lubricating oil system of pumped storage unit is prone to oil dumping and oil spillage during the start-up of the unit, which seriously threatens the safe and stable operation of the unit. In this study, a three-dimensional unsteady numerical simulation is performed to investigate the causes of oil dumping and oil spillage of a water-guide bearing lubricating oil system of a pumped storage power plant unit based on the VOF (volume of fluid) multiphase flow model and Realizable k-ε model. The unsteady flow characteristics inside the rotating oil basin and pump-type Pitot tube during the start-up process are analyzed. The results demonstrate that the change of the external characteristics of the lubricating oil system can be divided into two stages, the initial formation process of the lubricating oil flow and the stable circulation process of the lubricating oil flow. In the initial formation process, the pressure inside the rotating basin is uniformly distributed in the circumferential direction, and a high-pressure zone is generated near the inlet of the pump-type Pitot tube, driving the lubricant flow to the stationary basin above; in the stable flow cycle process, the internal lubricant flow velocity gradually decreases along the radius direction, and a large vortex zone appears behind the pump-type Pitot tube and at the inlet of it. This phenomenon leads to the lubricating oil pressure here to be lower than the saturation vaporization pressure, which may trigger lubricating oil atomization and then overflow from the seal ring. This study is committed to provide theoretical analysis and engineering reference for the investigation of the causes of oil dumping and oil spillage in the lube oil system of water guide bearings of pumped storage units.

The veins in the mantle wedge peridotite can record the activity of slab-derived melt/fluid, which is the reflection of the material circulation between crust and mantle. A red-corundum-bearing vein is present in the Rai–Iz ultramafic rocks in the Polar Urals, Russia. The ultramafic rocks are harzburgite and dunite, and the red corundum-bearing rocks consist of phlogopite, paragonite, oligoclase, red corundum, and chromian spinel. Red corundum occurs as prophyroblasts or fine grains that contain 92–98 wt% Al2O3 and 2–7 wt% Cr2O3. Chromian spinel has Cr# values ([100Cr/ (Cr + Al)] atomic ratio) of 46–78. Oligoclase is characterized by An values of 20–30. Phlogopite is Ba-rich (BaO = 0.8–2.7 wt%) and paragonite is Sr-rich (SrO = 0.8–2.3 wt%). Zircons from the oligoclasite show oscillatory zoning and Th/U values of

Mobile laser scanning (MLS) systems are often used to efficiently acquire reference data covering a large-scale scene. The terrestrial laser scanner (TLS) can easily collect high point density data of local scene. Localization of static TLS scans in mobile mapping point clouds can afford detailed geographic information for many specific tasks especially in autonomous driving and robotics. However, large-scale MLS reference data often have a huge amount of data and many similar scene data, significant differences may exist between MLS and TLS data. To overcome these challenges, this paper presents a novel deep neural network-based localization method in urban environment, divided by place recognition and pose refinement. Firstly, simple, reliable primitives, cylinder-like features were extracted to describe the global features of a local urban scene. Then, a probabilistic framework is applied to estimate a similarity between TLS and MLS data, under a stable decision-making strategy. Based on the results of a place recognition, we design a patch-based convolution neural network (CNN) (point-based CNN is used as kernel) for pose refinement. The input data unit is the batch consisting of several patches. One patch goes through three main blocks: feature extraction block (FEB), the patch correspondence search block and the pose estimation block. Finally, a global refinement was proposed to tune the predicted transformation parameters to realize localization. The research aim is to find the most similar scene of MLS reference data compared with the local TLS scan, and accurately estimate the transformation matrix between them. To evaluate the performance, comprehensive experiments were carried out. The experiments demonstrate that the proposed method has good performance in terms of efficiency, i.e., the runtime of processing a million points is 5 s, robustness, i.e., the success rate of place recognition is 100% in the experiments, accuracy, i.e., the mean rotation and translation error is (0.24 deg, 0.88 m) and (0.03 deg, 0.06 m) on TU Delft campus and Shanghai urban datasets, respectively, and outperformed some commonly used methods (e.g., iterative closest point (ICP), coherent point drift (CPD), random sample consensus (RANSAC)-based method).

Heritage documentation is implemented by digitally recording historical artifacts for the conservation and protection of these cultural heritage objects. As efficient spatial data acquisition tools, laser scanners have been widely used to collect highly accurate three-dimensional (3D) point clouds without damaging the original structure and the environment. To ensure the integrity and quality of the collected data, field inspection (i.e., on-spot checking the data quality) should be carried out to determine the need for additional measurements (i.e., extra laser scanning for areas with quality issues such as data missing and quality degradation). To facilitate inspection of all collected point clouds, especially checking the quality issues in overlaps between adjacent scans, all scans should be registered together. Thus, a point cloud registration method that is able to register scans fast and robustly is required. To fulfill the aim, this study proposes an efficient probabilistic registration for free-form cultural heritage objects by integrating the proposed principal direction descriptor and curve constraints. We developed a novel shape descriptor based on a local frame of principal directions. Within the frame, its density and distance feature images were generated to describe the shape of the local surface. We then embedded the descriptor into a probabilistic framework to reject ambiguous matches. Spatial curves were integrated as constraints to delimit the solution space. Finally, a multi-view registration was used to refine the position and orientation of each scan for the field inspection. Comprehensive experiments show that the proposed method was able to perform well in terms of rotation error, translation error, robustness, and runtime and outperformed some commonly used approaches.

The Wenquan ultramafic rocks, located in the East Kunlun Orogenic belt in the northeastern part of the Qinghai-Tibet Plateau, consist of dunite, wehrlite, olivine-clinopyroxenite and clinopyroxenite, and exhibit cumulate textures. Olivine from dunite has high Fo (forsterite, 90.0–91.8 wt%) and NiO content (0.15–0.42 wt%). Cr-spinels from all of the rocks in this suite are characterized by high Cr# (100×[Cr/(Cr + Al)], 67–91), low Mg# (100×[Mg/(Mg + Fe2+)], 17–35) and low TiO2 contents (mostly 80) and low-CaO (

Although deep carbon recycling plays an important role in the atmospheric CO2 budget and climate changes through geological time, the precise mechanisms remain poorly understood. Since recycled sedimentary carbonate through plate subduction is the main light-δ26Mg reservoir within deep-Earth, Mg isotope variation in mantle-derived melts provides a novel perspective when investigating deep carbon cycling. Here, we show that the Late Cretaceous and Cenozoic continental basalts from 13 regions covering the whole of eastern China have low δ26Mg isotopic compositions, while the Early Cretaceous basalts from the same area and the island arc basalts from circum-Pacific subduction zones have mantle-like or heavy Mg isotopic characteristics. Thus, a large-scale mantle low δ26Mg anomaly in eastern China has been delineated, suggesting the contribution of sedimentary carbonates recycled into the upper mantle, but limited into the lower mantle. This large-scale spatial and temporal variation of Mg isotopes in the mantle places severe constraints on deep carbon recycling via oceanic subduction.

Ophiolitic chromitites in the eastern sector of the Alpine-Himalayan and Polar Ural orogenic belts preserve evidence of formation under ultra-high-pressure (UHP), deep mantle conditions. The textural and compositional characteristics of microscopic and submicroscopic inclusions in magnesiochromite from the Ray-Iz ophiolites are considered as clues of their complex evolutionary history. Bulk-rock platinum-group-element (PGE) compositions of refractory and metallurgical chromitite ores (102–309 ppb) with generally IPGE>PPGE are consistent with supra-subduction zone (SSZ) metasomatism. The abundant unusual UHP phases (e.g., micro-diamonds, moissanite, coesite…etc.), together with clinopyroxene lamellae, and globular silicate inclusions in the Cr-spinel are seen as indications of deep mantle recycling of the mantle section of the Ray-Iz ophiolites. The calculated fO2 values for dunite and chromitite (+1.17 to +4.16, generally above the FMQ buffer) are in line with interaction of mid-ocean ridge (MOR) or back-arc ophiolites with oxidized, Mg-rich silicic (boninitic) melts in a SSZ environment.

New major, trace and rare earth element (REE) data, and Sr-Nd isotopic compositions of jadeitite and REE-Hf-O isotopic compositions of zircon in jadeitite of the Syum-Keu ultramafic complex of the Polar Urals are used to constrain its origin and source. The jadeitites have high contents of Na 2 O (12.80–14.56 wt%), Al 2 O 3 (20.30–23.81 wt%), SiO 2 (58.47–59.50 wt%), and are enriched in Sr, Ba, Zr, Hf and depleted in Nb relative to primitive mantle values. Chondrite-normalized REE patterns of the jadeitite display weakly U-shaped distribution patterns, with La N /Yb N ratios of 0.82–2.42, and very weak positive Eu anomalies (δEu = 1.2–1.6). The initial Sr isotopic compositions of the jadeitite range from 0.704000 to 0.703519 ( t = 368 Ma), and the initial Nd-isotope ratios (e Nd = +0.77 to +5.61) differ from those of ancient ocean water, oceanic sediments and eclogite, metagranite, and metasediments in the nearby Marun-Keu complex. Zircons from the jadeitite have variable REE contents (37–587 ppm) and are enriched in HREE, with La CN /Yb CN ratios ranging from 0.001 to 0.01, and Lu CN /Gd CN ratios ranging from 10 to 83. Cerium shows positive anomalies with Ce/Ce* values ranging from 2.8 to 72, and δEu from 0.53 to 1.02. The 176 Hf/ 177 Hf ratios of the zircons range from 0.282708 to 0.283017, with initial Hf isotope compositions ranging from 6.5 to 17.4. These characteristics resemble those of zircons from depleted mantle-derived magmas. The δ 18 O isotope compositions of the zircons range from 5.03‰ to 6.04‰, with an averaged value of 5.45 ± 0.11‰, similar to those of mantle rocks, suggesting that the zircons were acquired from precursor igneous rocks, and then transported and reworked by fluids from the subducting slab. Our new results show that the jadeitite was precipitated from material mainly produced by fluid interaction with mafic-ultramafic rocks in a subduction zone environment.

Knowing the protoliths of eclogites is important to understanding the nature and process of orogeny. It has been debated whether the eclogites of the Marun-Keu complex, Russian Polar Urals represent a fragment of metamorphosed oceanic crust or a fragment of metamorphosed continental crust. Here, we focus on eclogites from the garnet- peridotite-eclogite unit in the complex at the Mica Hill. The eclogites have high MgO contents (mostly greater than 8 wt%) and Mg# (Mg/[Mg + Fe2+] = 0.7–0.8), their Al2O3 contents vary from 16 wt% to 26 wt%, and CaO contents vary from 10 wt% to 15 wt%, respectively. TiO2 contents less than 0.5 wt% and a large variation of chromium concentrations (282–1745 ppm). The eclogites are enriched in the light rare earths (LREE), have positive Eu anomalies (δEu = 1.0–2.3), and varying eNd (t) from −3 to +2. Such geochemical features are evidence that the protoliths of these eclogites are troctolite and gabbro, which may have formed in a rift environment of a continental margin. Using the SHRIMP method to date zircons two groups of ages were obtained: 500–490 Ma and 370–360 Ma, respectively. The older population is interpreted as protolith formation age while the later population is interpreted as the metamorphic age of the eclogite facies. So the eclogites are likely the result of high pressure metamorphism due to subduction of the newly formed Eastern European continental margin under the Syum-Keu intra-oceanic arc, and not metamorphosed ophiolite (Paleo-Urals oceanic crust).

Eclogites from the Baijingsi area in the North Qilian orogen at NW China were analyzed for major and trace element abundances as well as Sr, Nd, and Hf isotope ratios to evaluate the impacts from subduction processes on these compositional parameters and to reveal the complexity in protolith characteristics. The major element compositions of the Baijingsi eclogites are within the ranges for basalts. However, the absence of systematic variations among major oxides indicates varying extents of metamorphic modifications. Seven samples are characterized by profound Nb and Ta depletions. Six of them form coherent trends in the La versus Th, HFSE, and LREE plots. They are classified as the Group 1 samples. Other eight samples, referred to as the Group 2 samples, define distinct La–Zr and La–Sm trends and have flat variation patterns with slight Th–Nb–Ta–LREE depletions in the primitive mantle-normalized multiple-element diagram. Group 1 dominates the 87Sr/86Sr–87Rb/86Sr, 143Nd/144Nd–147Sm/144Nd and 176Hf/177Hf–176Lu/177Hf trends for relatively larger variations in the isotope and abundance ratios. Based on the errorchron ages from the samples, closure temperatures of the isotope systems, and isotope ratio versus 1/X plots (e.g., 87Sr/86Sr–1/Sr), it is inferred that the Rb–Sr isotope system was subjected to metamorphic modification, whereas the Sm–Nd and Lu–Hf isotope systems mainly reflect protolith characteristics. In addition to the Nb and Ta depletions, the Group 1 samples generally have eHf(510) values (protolith initial at 510 Ma) higher than those of MORB at a given eNd(510), reflecting derivation from relatively high Lu/Hf ratio sources. They also plot within the fields for arc lavas in the Ta/Yb–Th/Yb and Th–Ta–Hf/3 diagrams. All these features are consistent with derivation from protoliths of an arc origin. In contrast, the Group 2 samples have eNd(510) values slightly higher than those of the Group 1 samples at a given eHf(510), plotting on the low eNd(510) margin of the MORB field. They also deviate from the Ta/Yb–Th/Yb trend defined by MORB and OIB toward higher Th/Yb values within the fields of back-arc basin basalts. Therefore, it is inferred that the protoliths of the Group 2 samples were generated as back-arc basin basalts possibly associated with the protoliths of the Group 1 samples in a common supra-subduction zone. The eNd(510)–eHf(510) relationship of the Baijingsi eclogites shows an affinity to the Indian ocean type mantle, implying protolith generation at the southern hemisphere on the margin or a fragment of the Gondwana continent, most likely in the Qilian Block. Based on the current tectonic configuration, a southward subduction is required for protolith generation and might eclogitize the arc protoliths by subduction erosion. Alternatively, the northward subduction in a bidirectional subduction system might become dominant during the amalgamation of the Qilian Block and the North China Craton to eclogitize the arc protoliths in the Qilian Block. Resolving these two possibilities requires more petrological, geochemical, and structural evidence from the North Qilian orogen.

The Heishan mafic–ultramafic complex in the Qimantag Mountains of the Eastern Kunlun Orogen, consists of olivine pyroxenites, pyroxenites, gabbros, and massive basalts. Zircons from the gabbros have magmatic sector zoning, with Th/U ratios of 0.5–2.3, and yield a SHRIMP age of 486 ± 6 Ma (MSWD = 0.31), which is taken as the time of magma crystallization. Spinel, pyroxene, and plagioclase mineral compositions indicate that the rocks formed in an island arc environment. The cumulates have low (La/Yb)N ratios (0.6–0.8) and depleted LREE patterns, high abundances of Cr (3031–1185 ppm), Co (119–50 ppm), and Ni (953–291 ppm), and eNd(t) values of about + 8.0. The massive basalts have somewhat higher contents of TiO2 (1.0%–1.3%), Na2O (2.6%–2.8%), total REE and Mg#s (55–63) than those of the cumulates. The (La/Yb)N ratios of the basalts range from 0.8 to 1.2 and the chondrite-normalized REE patterns are flat. eNd(t) values of the basalts range from + 7.7 to + 9.4. The compositions of the cumulates and volcanic rocks, especially their similar Nd isotopes, suggest that the rocks were derived from similar depleted mantle sources. The primary magmas were probably generated in an initial arc environment. We conclude that the Heishan mafic–ultramafic complex in the Qimantag area preserves a record of Proto-Tethyan oceanic lithosphere formed in the early Paleozoic. It possibly marks a suture between the Qaidam and North Kunlun terranes in the western segment of the Eastern Kunlun Orogen.

Eclogites discovered in the eastern part of the East Kunlun Mountains, Western China, are primarily composed of garnet + omphacite + quartz + rutile. The garnets show end-member components of 48–55% almandine, 1–2% spessartine, 19–29% grossularite and 16–29% pyrope, and the omphacite has a jadeite content of 21–63%. The peak-metamorphic assemblage of eclogites records a P–T condition of > 1.6 GPa and 590 °C–650 °C. Zircon U–Pb dating of the inherited magmatic zircons from fine-grained eclogite reveals a Neoproterozoic age of 934 Ma, representing the protolith age of the eclogite. Zircons from the coarse-grained eclogite contain inclusions of garnet, omphacite and rutile, and yield a weighted mean age of 428 Ma, indicating the metamorphic age of eclogite. The eclogites, together with the Late Cambrian (508 Ma) high-pressure granulite to the west, constitute an Early Paleozoic high-pressure metamorphic belt in the East Kunlun.

In this contribution, we present new petrological, geochemical, zircon U–Pb and Hf isotopic data for eclogitic metasediments from the north Qilian orogenic belt, in which early Paleozoic ophiolitic sequences and HP/LT metamorphic rocks have been previously recognized. The studied metasediments contain eclogite facies assemblages reflecting P–T conditions of 450–560 °C and 1.9–2.4 GPa, consistent with those of adjacent eclogites. REE compositions of the eclogitic metasediments overlap those of average upper continental crust. The SHRIMP and LA-MC-ICPMS U–Pb data of zircons from metasediments demonstrate input from sources with major age components about 500 Ma and 1600–1900 Ma (peak at ~ 1800 Ma), with a smaller population at 660–800 Ma (peak at 750 Ma), and minor > 1.9 Ga zircon ages. The youngest detrital zircons suggest a maximum depositional age of ca. 475 Ma, and combined with P–T conditions and previously determined metamorphic age suggest a burial rate of > 0.6–0.7 cm/yr. Zircon Hf isotopic analyses show that 500 Ma zircons have positive eHf(t) (mainly between + 8 and + 16). By contrast, Meso- to Paleoproterozoic detrital zircons show a broad spectrum of eHf(t) (mainly between − 5 and + 10) with T DM Hf of 1800–2500 Ma. These data suggest that eclogitic metasediments are derived from a mixture of Proterozoic continent crust and juvenile early Paleozoic oceanic and/or island arc crust, and their protoliths likely were deposited in a terrigenous-dominated continental margin basin rather than a pelagic oceanic crust environment. The new results are consistent with subduction erosion of the active continental margin during south-dipping subduction, as these sediments, formed in a fore-arc environment close to the Qilian block to the south, were transported in the subduction zone to 60–70 km depth prior to their exhumation.

High-pressure, low-temperature metamorphic rocks record subduction of oceanic crust and sediments into the mantle, but the timing of subduction initiation is commonly difficult to determine. However, the appearance of fluid activity in the mantle wedge above a subduction zone can be correlated with incipient subduction. Here we describe jadeitite veins up to 5 m wide, which are hosted in serpentinites of the Syum-Keu ultramafic complex, Polar Urals, Russia. The jadeitites consist of both jadeite (86–88 mol% jd) and omphacite (54–75 mol% jd). Multi-stage growth of the jadeite is indicated by variations in color and structure, such as growth zoning and the distribution of fluid inclusions. We consider that the jadeitite veins formed from Na–Al–Si-rich fluids under HP/LT conditions during active subduction, and that the source material was subducted ocean crust. SHRIMP U–Pb dating of zircons from the jadeitite yielded a concordant weighted mean 206Pb/238U age of 404 ± 7 Ma, which we interpret as the age of peridotite serpentinization and jadeitite formation in the suprasubduction zone mantle. This age indicates that subduction was initiated about 40 Ma earlier than peak metamorphism (360–355 Ma) of eclogite in the Polar Urals.

Coesite-bearing eclogites from >100 km 2 in the southern Dulan area, North Qaidam Mountains (NQM) of western China, contain zircon that records protolith crystallization and ultra high pressure (UHP) metamorphism. Sensitive High-Resolution Ion Microprobe (Mass Spectrometer) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry U-Pb analyses from cathodoluminescence (CL)-dark zircon cores in a coesite-bearing eclogite yield an upper intercept age of 838 ± 50 Ma, and oscillatory zoned cores in a kyanite-bearing eclogite gave a weighted mean 206 Pb ⁄ 238 U age of 832 ± 20 Ma. These zircon cores yield steep heavy rare earth element (HREE) slopes and negative Eu anomalies that suggest a magmatic origin. Thus, c. 835 Ma is interpreted as the eclogite protolith age. Unzoned CL-grey or -bright zircon and zircon rims from four samples yield weighted mean ages of 430 ± 4, 438 ± 2, 446 ± 10 and 446 ± 3 Ma, flat HREE patterns without Eu anomalies, and contain inclusions of garnet, omphacite, rutile, phengite and rare coesite. These ages are interpreted to record 16 ± 5 Myr of UHP metamorphism. These new UHP ages overlap the age range of both eclogite and paragneiss from the northern Dulan area, suggesting that all UHP rock types in the Dulan area belong to the same tectonic unit. Our results are consistent with slow continental subduction, but do not match oceanic subduction and diapiric exhumation UHP model predictions. These new data suggest that, similar to eclogites in other HP ⁄ UHP units of the NQM and South Altyn Tagh, protoliths of the eclogites in the Dulan area formed in a continental setting during the Neoproterozoic, and then subducted to mantle depth together with continental materials during the Early Palaeozoic.

A megacrystal zircon occurs in serpentinized dunite veins from North Qaidam, northwestern China. It is red-brown and 3–4 mm long and 2 mm wide in size. BSE imaging shows the presence of micro-grains (30–50 μm) of zircon between olivine and serpentine, part of them gathering into clusters (100–300 μm). Thus we infer that these zircon crystals were precipitated from hydrothermal fluid. Inclusions of baddeleyite (white) in the shape of isolated island locally occur in the large zircon (grey), implying that the former formed earlier than the latter. The mirco-baddeleyite (50–100 μm) aggregate consists of baddeleyite (3–5 μm) and olivine (

Coesite provides direct evidence for ultrahigh pressure metamorphism. Although coesite has been found as inclusions in zircon in paragneiss of the north Qaidam Mountains, it has never been identified in eclogite. In this contribution, based on petrographic observations and in situ Raman microprobe spectroscopy, coesite was identified as inclusions in garnet of eclogite from the Aercituoshan, Dulan UHP metamorphic unit, north Qaidam Mountains. Coesite is partly replaced by quartz, showing a palisade texture. This is the first report on coesite in eclogite from the north Qaidam Mountains, and is also supported by garnet-omphacite-phengite geothermobarometry (2.7–3.25 GPa, 670–730°C). Coesite and its pseudomorphs have not been found in eclogites and associated rocks of other units of the north Qaidam Mountains. Further studies are required to confirm if all metamorphic units in the north Qaidam Mountains underwent the ultrahigh-pressure metamorphism.

Eclogite protoliths provide clues for understanding paleomagmatism and tectonic architecture. A subgroup of eclogites from Maobei in the Sulu metamorphic terrane in eastern China are characterized by (1) low SiO2 contents of 38.2–42.8%, (2) high FeOtotal abundances of 16.7–20.9%, (3) high TiO2 concentrations of 3–4%, and (4) decoupling between high field strength elements (HFSE), specifically, Ti enrichment accompanied by relative depletions in Nb–Ta–Zr–Hf. These features are also characteristic of eclogites cored by the Chinese Continental Scientific Drilling (CCSD) project at the depth range of 530–600 m (subunit 8). Except for the relatively low SiO2 concentrations, major element concentrations of these high Fe–Ti eclogites are comparable to those of basalts and gabbros. The low SiO2 reflects the combined effect of fluid infiltration and garnet enrichment by metamorphic segregation. In contrast, there is no evidence for rutile segregation, and the high TiO2 contents are protolith characteristics. The major and trace element abundances as well as the decoupling between Ti and other HFSEs in these high Fe–Ti eclogites are interpreted as characteristics of gabbroic cumulates crystallized from melts with compositions similar to that of the CCSD eclogites cored at depth ranges of 318–380 and 420–470 m (subunits 4 and 6, respectively). The mineral proportions of such cumulates are ∼41% plagioclase, ∼39% clinopyroxene, ∼8% olivine and ∼12% Fe–Ti oxides, consistent with crystallization at 2–8 kbar. The basaltic melts in equilibrium with the gabbroic protoliths of the high Fe–Ti eclogites must be depleted in Nb, Ta, Zr and Hf. These are the characteristics of arc lavas and crustally contaminated continental basalts. An arc origin for these protoliths is consistent with the existence of arc belts on the margins of the Yangtze Block during protolith formation. However, this does not preclude contemporary plume magmatism within the interior of the Yangtze block.

The north Qilian high-pressure (HP)/low-temperature (LT) metamorphic belt is composed mainly of blueschists, eclogites and greenschist facies rocks. It formed within an Early Palaeozoic accretionary wedge associated with the subduction of the oceanic crust and is considered to be one of the best preserved HP/LT metamorphic belts in China. Here we report new lawsonite-bearing eclogites and eclogitic rocks enclosed within epidote blueschists in the North Qilian Mountains. Five samples contain unaltered lawsonite coexisting with omphacite and phengite as inclusions in garnet, indicating eclogite facies garnet growth and lawsonite pseudomorphs were observed in garnet from an additional 11 eclogites and eclogitic rocks. Peak pressure conditions estimated from lawsonite omphacite-phengite-garnet assemblages were 2.1–2.4 GPa at temperatures of 420–510 °C, in or near the stability field of lawsonite eclogite, and implying formation under an apparent geothermal gradient of 6–8 °C km−1, consistent with metamorphism in a cold subduction zone. SHRIMP U-Pb dating of zircon from two lawsonite-bearing eclogitic metabasites yields ages of 489 ± 7 Ma and 477 ± 16 Ma, respectively. CL images and mineral inclusions in zircon grains indicate that these ages reflect an eclogite facies metamorphism. An age of 502 ± 16 Ma is recorded in igneous cores of zircon grains from one lawsonite pseudomorph-bearing eclogite, which is in agreement with the formation age of Early Ordovician for some ophiolite sequences in the North Qilian Mountains, and may be associated with a period of oceanic crust formation. The petrological and chronological data demonstrate the existence of a cold Early Palaeozoic subduction zone in the North Qilian Mountains.

Diamonds and a wide range of unusual minerals were originally discovered from the chromitite and peridotite of the Luobusa ophiolite along the Yarlong–Zangbu suture zone in southern Tibet. To test whether this was a unique occurrence or whether such minerals were present in other ophiolites, we investigated the Ray-Iz massif of the early Paleozoic Voikar–Syninsk ophiolite belt in the Polar Urals (Russia) for a comparative study. Over 60 mineral species, including diamond, moissanite, native elements and metal alloys have been separated from ~ 1500 kg of chromitite collected from two orebodies in the Ray-Iz ophiolite. More than 1000 grains of microdiamond were recovered from the chromitite and, of particular importance, 2 grains were found as in-situ inclusions in chromite grains, proving that these minerals are intrinsic to the rock, and not the result of natural or anthropogenic contamination. The native elements include Cr, W, Ni, Co, Si, Al and Ta, commonly associated with carbides such as SiC and WC, and metallic alloys, such as CrFe, SiAlFe, NiCu, AgAu, AgSn, FeSi, FeP, and AgZnSn also occur. These minerals are accompanied by oxides (wustite, periclase, eskolaite, rutile, baddeleyite, ilmenite, corundum, chromite, NiO and SnO2) and silicates (kyanite, zircon, garnet, feldspar, and quartz). Sulfides of Fe, Ni, Cu, Mo, Pb, Ab, AsFe, FeNi, CuZn, and CoFeNi are common, as are various iron minerals, such as native Fe, FeO, and Fe2O3. Here, we focus on the composition and character of the diamonds, native elements and metal alloys. All of the minerals discussed here are similar to those reported from chromitites of the Luobusa ophiolite, Tibet, indicating that they are not restricted to one ophiolite or one geographic region; rather, they may be widespread in the oceanic mantle. The diamonds recovered from these ophiolites are completely different from most of those in kimberlites and ultra-high pressure (UHP) metamorphic rocks, and represent a new occurrence of diamonds on Earth. A three-stage model is proposed to explain the source of the diamonds and highly-reduced minerals, their formation, and their preservation in ophiolites.

An early Paleozoic ultrahigh pressure metamorphic belt occurs in the north Qaidam–Altun mountains and was offset about 400 km southwestward by the Altyn Tagh strike-slip fault. Eclogites in the belt consist of major basaltic and minor picritic rock types and can be subdivided into three groups: high TiO2 (2–5 wt%), medium TiO2 (1–2 wt%) and low TiO2 (

Felsic gneisses near Yuka, western North Qaidam Mountains (NQD), and (60 km SE) near Xitieshan, central NQD, enclose eclogite-bearing mafic boudins. Inclusions in prograde-zoned garnets from a Yuka eclogite record pre-eclogite facies conditions of 12.1 ± 2.1 kbar, 603 ± 36 °C. The phengite-bearing matrix assemblage records peak conditions near or in the coesite stability field (23–28 kbar, 600–730 °C), but no coesite or coesite pseudomorphs have been found. Amphibolitized eclogite in the boudin margin records retrograde conditions of 10.9 ± 1.2 kbar, 630 ± 44 °C. Garnets from the Xitieshan eclogite lack prograde inclusions and compositional zoning. The bimineralic matrix assemblage records minimum eclogite-facies conditions of > 14 kbar, 730–830 °C. Symplectites of plagioclase and clinopyroxene record early retrograde conditions of 10–14 kbar, 750–865 °C. Positive eNd values from two Yuka and five Xitieshan eclogites indicate a depleted mantle source, consistent with formation of the eclogite protoliths in a continental rift or incipient oceanic basin setting. A Sm–Nd WR–Grt–Cpx isochron age of 435 ± 49 Ma obtained from one Xitieshan eclogite represents a cooling age. Zircon U–Pb TIMS and SHRIMP geochronology, combined with CL and inclusion analysis indicates a magmatic protolith age of ca. 750–800 Ma, and eclogite–facies zircon growth at 486–488 Ma. For the Yuka eclogite, exhumation to lower-crustal depths occurred before 477 ± 8 Ma (amphibole 40Ar–39Ar), and a 466 ± 5 Ma phengite 40Ar–39Ar age indicates an average cooling rate of 13–19 °C/Ma. In contrast, the 407 ± 4 Ma amphibole 40Ar–39Ar age from the Xitieshan eclogite indicates a much slower cooling rate of 3–4 °C/Ma. HP/UHP rocks of similar age 200 km SE near Dulan, eastern NQD, and in the Altun Mountains on the NW side of the Altyn Tagh fault suggest that the Altun, Yuka, Xitieshan, and Dulan localities are part of the same early Paleozoic HP/UHP metamorphic belt.

High-pressure kyanite-bearing felsic granulites in the Bashiwake area of the south Altyn Tagh (SAT) subduction–collision complex enclose mafic granulites and garnet peridotite-hosted sapphirine-bearing metabasites. The predominant felsic granulites are garnet + quartz + ternary feldspar (now perthite) rocks containing kyanite, plagioclase, biotite, rutile, spinel, corundum, and minor zircon and apatite. The quartz-bearing mafic granulites contain a peak pressure assemblage of garnet + clinopyroxene + ternary feldspar (now mesoperthite) + quartz + rutile. The sapphirine-bearing metabasites occur as mafic layers in garnet peridotite. Petrographical data suggest a peak assemblage of garnet + clinopyroxene + kyanite + rutile. Early kyanite is inferred from a symplectite of sapphirine + corundum + plagioclase ± spinel, interpreted to have formed during decompression. Garnet peridotite contains an assemblage of garnet + olivine + orthopyroxene + clinopyroxene. Thermobarometry indicates that all rock types experienced peak P–T conditions of 18.5–27.3 kbar and 870–1050 °C. A medium–high pressure granulite facies overprint (780–820 °C, 9.5–12 kbar) is defined by the formation of secondary clinopyroxene ± orthopyroxene + plagioclase at the expense of garnet and early clinopyroxene in the mafic granulites, as well as by growth of spinel and plagioclase at the expense of garnet and kyanite in the felsic granulite. SHRIMP II zircon U-Pb geochronology yields ages of 493 ± 7 Ma (mean of 11) from the felsic granulite, 497 ± 11 Ma (mean of 11) from sapphirine-bearing metabasite and 501 ± 16 Ma (mean of 10) from garnet peridotite. Rounded zircon morphology, cathodoluminescence (CL) sector zoning, and inclusions of peak metamorphic minerals indicate these ages reflect HP/HT metamorphism. Similar ages determined for eclogites from the western segment of the SAT suggest that the same continental subduction/collision event may be responsible for HP metamorphism in both areas.

Field observations and petrological data suggest a new high-pressure/low temperature (HP/LT) metamorphic terrane in the northern Altyn Tagh. Newly recognized eclogites, blueschists, and metapelites constitute part of a coherent HP/LT metamorphic terrane that occurs as a tectonic slab in an ophiolitic melange. Geobarometry and geothemometry show that peak metamorphic conditions of the eclogites were T = 430-540°C and P = 20-23 kbar. Petrographic data, P-T estimates, and amphibole compositions indicate distinctly different metamorphic histories for two outcrops about 1.2 km apart. For blueschists from outcrop I, the retrograde P-T path is a relatively straight line directed towards the greenschist facies, suggesting simultaneous cooling and decompression. In contrast, interlayered blueschist and eclogite in outcrop II underwent isothermal decompression from eclogite/blueschist facies to epidote-amphibole facies conditions during exhumation. This implies that rocks from these two outcrops experienced differe...

The Qiashikansayi granodiorite is foliated resulting in a granodioritic gneiss. Its geochemical features, such as alumina saturation index(A/CNK) of 0.81–0.99, Na2O/K2O values> 1, TiO2 contents < 1.0%, LREE enrichment with high fractionation factors, weakly negative or no Eu anomalies, and significant Ba and Ti negative anomalies, suggest that it is similar to a typical island arc pluton. The trace elements of the Qiashikansayi granodiorite are plotted in the island arc field in the tectonic setting discrimination diagrams as well. Cathodoluminescence images demonstrated that the zircons have clear rhythmic crystallized zoning, without any remnant core and new crystallized rim, suggesting the zircons be magmatic ones. Their U and Th contents vary in the range of 574–870 μg/g, and 279–556 μg/g respectively, with the Th/U ratio in the range of 0.52–0.68. SHRIMP zircon U-Pb dating yielded the 481.5±5.3 Ma age for the intrusion of the granodiorite, which is coeval with the island arc volcanic rocks in the northern Qilian Mountain, and confirms that there is an early Paleozoic island arc in the Hongliugou-Lapeiquan area.

Sapphirine-bearing high pressure mafic granulites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic granulites. Sapphirine occurs as intergrowths with corundum, spinel and Ca-rich plagioclase in symplectite in between garnet and clinopyroxene. Reaction textures and mineral compositions indicate that sapphirine-bearing symplectites formed by reactions consuming kyanite, garnet and clinopyroxene. Therefore, both petrographic observations and the mineral compositions suggest that these quartz-free mafic granulites had an eclogite origin with an assemblage of garnet + clinopyroxene + kyanite, which is estimated to be stable atT = 1000 °C andP ⩾ 2.1 GPa. The sapphirine-bearing symplectites are resulted from isothermal decompression or decompression with slight cooling during exhumation of the host rock.

Zircon SHRIMP dating from Qaidamshan granite shows that the granite age is 446 Ma, similar to that of eclogite in the UHP belt. We think that both granite and eclogite may be formed at different stages during tectonic evolution of this area. Together with other studies we suggested that the collision of ocean and continent plates may occur at the early Caledonian in this area, forming the eclogite, and the collision of continent and continent plates at the late Caledonian, forming the Qaidamshan granite with the zircon SHRIMP age of 446 Ma.