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The southeastern Central Asian Orogenic Belt (CAOB) records the assembly process between several micro-continental blocks and the North China Craton (NCC), with the consumption of the Paleo-Asian Ocean (PAO), but whether the S-wards subduction of the PAO beneath the northern NCC was ongoing during Carboniferous–Permian time is still being debated. A key issue to resolve this controversy is whether the Carboniferous magmatism in the northern NCC was continental arc magmatism. The Alxa Block is the western segment of the northern NCC and contiguous to the southeastern CAOB, and their Carboniferous–Permian magmatism could have occurred in similar tectonic settings. In this contribution, new zircon U–Pb ages, elemental geochemistry and Sr–Nd isotopic analyses are presented for three early Carboniferous granitic plutons in the southwestern Alxa Block. Two newly identified aluminous A-type granites, an alkali-feldspar granite (331.6 ± 1.6 Ma) and a monzogranite (331.8 ± 1.7 Ma), exhibit juvenile and radiogenic Sr–Nd isotopic features, respectively. Although a granodiorite (326.2 ± 6.6 Ma) is characterized by high Sr/Y ratios (97.4–139.9), which is generally treated as an adikitic feature, this sample has highly radiogenic Sr–Nd isotopes and displays significantly higher K2O/Na2O ratios than typical adakites. These three granites were probably derived from the partial melting of Precambrian continental crustal sources heated by upwelling asthenosphere in lithospheric extensional setting. Regionally, both the Alxa Block and the southeastern CAOB are characterized by the formation of early Carboniferous extension-related magmatic rocks but lack coeval sedimentary deposits, suggesting a uniform lithospheric extensional setting rather than a simple continental arc.

Microseismic monitoring technology has become an important technique to assess stability of rock mass in metal mines. Due to the special characteristics of underground metal mines in China, including the high tectonic stress, irregular shape and existence of ore body, and complex mining methods, the application of microseismic technology is more diverse in China compared to other countries, and is more challenging than in other underground structures such as tunnels, hydropower stations and coal mines. Apart from assessing rock mass stability and ground pressure hazards induced by mining process, blasting, water inrush and large scale goaf, microseismic technology is also used to monitor illegal mining, and track personnel location during rescue work. Moreover, microseismic data have been used to optimize mining parameters in some metal mines. The technology is increasingly used to investigate cracking mechanism in the design of rock mass supports. In this paper, the application, research development and related achievements of microseismic technology in underground metal mines in China are summarized. By considering underground mines from the perspective of informatization, automation and intelligentization, future studies should focus on intelligent microseismic data processing method, e.g., signal identification of microseismic and precise location algorithm, and on the research and development of microseismic equipment. In addition, integrated monitoring and collaborative analysis for rock mass response caused by mining disturbance will have good prospects for future development.

This article outlines the research progress on radiocarbon (14C) dating of the Erlitou site. The Erlitou site, belonging to the Bronze Age, located in Yanshi, Henan province, China, was discovered by archaeologists in 1959 when they investigated the Xia people’s remains in the area where the Xia people lived according to the records of ancient documents. Since then, there has been a standing debate about whether the site belongs to the Xia or Shang dynasty. By the mid-1990s, several hundred discussion articles on the issue had been published, but the question was still unresolved. Therefore, evidence from the chronology has attracted a great amount of attention. The dating of the Erlitou site began in the 1970s, and since the Xia-Shang-Zhou Chronology Project began in the mid-1990s, by application of wiggle-matching on the basis of improving the dating accuracy, the date of the Erlitou site has gradually become clear, which provides a basis for the archaeological research on the Xia and Shang dynasties.

Coal seam mining is one of the most widely participated engineering activities in China. This study examined the failure process induced by underground thin coal seam mining of Wangxia perilous rock in Chongqing, China. Numerical simulation was conducted on the stress, displacement and plastic deformation with Fast Lagrangian Analysis of Continua 3D (FLAC3D). Results show that tensile stress is dominant and it keeps increasing during coal mining. The stability failure process experiences four stages from the perspective of crack propagation. A new simplified subsidence prediction method was proposed for quick engineering applications. The relationship between mining geometric parameters and rock mass stability was established and the ultimate mining dimensions were suggested. The simplified method was demonstrated to be reliable.

This article describes the Zhongbao landslide that occurred in Liujing Village, Tudi Township, Wulong District, Chongqing, China, on July 25, 2020. Due to the catastrophic soil and rock landslide, the houses and village roads of three villagers in the landslide area are damaged and formed weirs. The landslide eventually formed a barrier lake. In order to reveal the failure mechanism of the landslide, aerial data was collected on the landslide site using UAV and high-resolution remote sensing images. The characteristics of the landslide are analyzed based on the geological conditions and the properties of the rock formations in the landslide area. The continuous intense rainfall increased the water content of the landslide in this area, increasing its weight. Increasing the water content softens the sliding surface and lowers strength. Therefore, the rock and soil mass on the upper slope slides along the sliding surface under the action of gravity, causing a shale rock mass of about 1.3 million cubic meters to slide quickly from the upper part of the slope into the V-shaped valley and form a barrier dam and barrier lake. By evaluating the rising height of the initial dammed lake, the affected area can be predicted. Through the analysis of the study area, it can provide references for the failure mechanism of landslides, the characteristics of landslide bounce, and the risk assessment of cofferdams in Southwest China.

Based on finite element method, we develop a model of the induced geoelectric field (IGF) occurring in land-sea boundary regions during large geomagnetic field disturbances. The model is used first to study the effects of the changes in the lithospheric conductivity, ionospheric current, and ocean depth on the distribution of IGF in a typical land-sea boundary region. The results show that the changes in the lithospheric conductivity and ionospheric current (frequency, magnitude and direction) have major effects and ocean depth has minor effect on IGF in coastal areas. Then by incorporating a realistic 3-D conductivity variation of Jiaodong Peninsula (JDP) in China obtained from measured data, the model is used to simulate the IGF variation in JDP covering its land-sea boundaries for east-west and north-south ionospheric currents. The results show a new aspect that extremely large IGF development on the land side of the coastal bay areas perpendicular to the currnet compared to plane coastal areas. The results can stimulate detailed investigations of IGF (and GIC, geomagnetically induced current) in coastal areas.

The effective participation of rural residents in tourism social entrepreneurship can improve their quality of life and promote community transformation. Hence, it is important to understand the strategies and process of community mobilization by social entrepreneurs. This study focuses on the strategy of village cadre, who play the dual roles of an entrepreneur and a policy implementer to mobilize community residents to participate in collective tourism entrepreneurship and the mechanism for changing residents’ attitudes in a rural China context, by using the longitudinal research method of nonparticipatory observation and 50 interviews conducted in Yuanjia Village, Shaanxi Province. The results show that the community mobilization of social entrepreneurs has not been accomplished overnight but has undergone a 3-stage dynamic process of change. These results indicate that social enterprises should incorporate indigenous people into their value network in the early stage of tourism development and continue to explore the mechanism of affiliating residents with benefits, so as to further increase residents’ in-depth participation. Residents play the dual roles of producer and collaborator in tourism social entrepreneurship and work with social entrepreneurs to promote the sustainable development of rural tourism and achieve common prosperity.

To study the difference in the failures of laboratories #7 and #8 of the China Jinping Underground Laboratory Phase II (CJPL-II), different loading and unloading stress path tests were carried out under a true triaxial compression condition based on the measured in situ stress of CJPL-II. The strength, deformation and failure mechanisms of Jinping marble under different stress paths were thoroughly investigated. The results showed that under the same stress state as that at sample failure, the bearing capacity and deformation of the unloading stress path were greater than those of the loading stress path. The bearing capacity and deformation in the σ2 and σ3 directions of stress path II and stress path III were similar, and the others decreased from stress path IV to stress path V under unloading conditions. The failure mode results reflect the violence of the unloading failure. The failure features and mechanisms of different stress paths were analysed though the acoustic emission (AE) ring, cumulative energy and strain energy trend. This research may provide a reference for the excavation and support of deep underground works.

The middle Jurassic Zhiluo Formation in the Dongsheng is comprised of a big set of green sandstone/mudstone with most of uranium orebodies occurring in close proximity to its footwall. By synthesizing field observations, region analysis, data collected from previous coal and uranium borehole, a regional north-south geological profile across the entire orefield is conducted. Experiments on sandstone/mudstone including rock mineral identification, clastic micromorphology and element geochemistry were carried out. Information from the geological profile indicates that green sandstone/mudstone is widely present in a stable horizon with clear boundaries to the country rock. Microscopic observations and geochemical data on sandstone/mudstone exhibit similar mineral composition with almost identical slightly flat, minor Eu enriched, Ce depleted chondrite-normalized REE patterns. Furthermore, the green clay membrane of the clasts has a complex composition containing chlorite/smectite, green smectite, chlorite, and green kaolinite, with elements including Fe, Mg, Si, and Al. These above results indicate that the green sandstone/mudstone underwent resemble sedimentary diagenetic processes as the country rock without transformation by large-scale regional fluid, while the existence of Fe2+-rich membrane is the main factor to the green sandstone/mudstone. Further concentration of the pre-enrichment uranium during diagenetic process led to the final formation for uranium deposits. The above studies are conducive to enrich the metallogenic mechanism of sandstone type uranium deposits and could provide certain reference for uranium exploration and deployment.

The stability evaluation of the damaged landslide is important for rescue work and emergency operation. This paper investigated a predisposing geological emergence, inducing the factors and deformation processes of the Zhongbao landslide, which happened on 25 July 2020. The stability of the damaged landslide was evaluated by an integrated monitoring system consisting of ground-based radar, unmanned aerial vehicles, airborne Lidar, thermal infrared temperature monitoring, GNSS displacement monitoring, deep displacement monitoring and rainfall monitoring. The strata and weak layer controlled the landslide failure, and topography defined the boundary of the failed rock mass. A continually intensive rainfall caused the deformation and accelerated failure of the landslide. The shallow and steep deposit (Part I) firstly slid at a high velocity, and then pushed the rear part of the landslide (Part II) to deform, forming numerous cracks, and the rainfall infiltrated into the rock mass. Finally, the rock and soil mass sliding along the weak layer, a barrier dam and a barrier lake were formed. The monitoring results showed that after the landslide failure, there were still local collapse and deformation occurrence which threatened rescue work and barrier lake excavation. Therefore, the barrier dam wasn’t excavated until the accumulation rate gradually stabilized on July 28. Moreover, most of the reactivated deposits still accumulated in the transportation and source areas. Thus, in August, the displacement of the damaged landslide gradually accelerated in a stepwise manner, and responded strongly to rainfall, especially in the accumulation area, so that it was inferred that the damaged landslide could slide again and caused a more threatening and severe failure. The analysis results of the study area can provide references for the failure mechanism of a rainfall-induced landslide and the stability evaluation of a damaged landslide.

Garnet-bearing mafic granulites occur as lenses within TTG gneiss or metapelite in the Fuping Complex, middle Palaeoproterozoic Trans-North China Orogen. They are composed mainly of garnet, clinopyroxene, orthopyroxene, hornblende, plagioclase, quartz and accessary zircon and titanite. Four stages of metamorphic mineral assemblages have been found in these mafic granulites: (a) the prograde assemblages (M1) are inclusions preserved in the garnet porphyroblasts, including clinopyroxene, hornblende, plagioclase and quartz; (b) the metamorphic peak assemblages (M2) consist of garnet porphyroblasts plus matrix minerals clinopyroxene + orthopyroxene + hornblende + plagioclase + quartz + zircon + titanite; (c) the first retrograde assemblages (M3) are represented by clinopyroxene + orthopyroxene + plagioclase + quartz symplectites rimming the garnets; and (4) the final retrograde assemblages (M4) are hornblende + plagioclase + quartz symplectites rimming or adjacent to the garnets. The retrieved metamorphic P-T paths pass from 530–600 °C/6.5–7.0 kbar (M1) through 680–820 °C/7.2–11.7 kbar (M2) to 730–760 °C/3.2–3.9 kbar (M3) and finally to 600–640 °C/3.2–3.7 kbar (M4). All the P-T paths of the mafic granulites are clockwise, two of these even contain near isothermal decompression (ITD) and subsequent near isobaric cooling (IBC) segments. SHRIMP U-Pb dating of metamorphic zircons of the mafic granulites yields a mean weighted age of ∼1849 ± 9Ma, which is consistent with the metamorphic time of surrounding TTG gneisses. Therefore, the Fuping Complex records the collision event between the Eastern and Western Blocks of the North China Craton that led to the final assembly of this craton during the late Paleoproterozoic.

Geothermobarometry and phase equilibria modeling were conducted for garnet-bearing amphibolite of the Inyoni Shear Zone (ISZ), southwestern Barberton Greenstone Belt, South Africa. The prograde (M1), metamorphic peak (M2) and retrograde (M3) metamorphic P-T conditions were estimated to be ∼560 °C/∼8 kbar, 660–730 °C/7–9.5 kbar and 570–630 °C/5–6 kbar, respectively. The amphibolite records clockwise P-T paths, and the metamorphic peak P-T conditions belong to the medium P/T facies series. The retrograde segment of the P-T path documents near isothermal decompression which may reflect relative fast exhumation. The estimated apparent geotherm is 20–30 °C/km. SIMS U-Pb dating of metamorphic zircon suggests that the metamorphism of the ISZ amphibolite have occurred during ∼3.26–3.22 Ga, and the metamorphic peak might occur at ∼3.24 Ga. Furthermore, 40Ar/39Ar dating of hornblende indicates that the cooling stage might occur at ∼3.20 Ga. It is anticipated that the protolith of the amphibolite of the ISZ may have been involved in a subduction-like tectonic process along with the TTG plutons and was metamorphosed during 3.26–3.22 Ga, then uplifted from within the surrounding TTG plutons at ∼3.20 Ga.

A recent study suggests that the deep dolomites in well Xike-1 located more than 1000 m deep have a very low porosity, and no permeability for most of the samples. Given that the largest oil and gas fields in the South China Sea are all composed of biohermal dolomites while the deep dolomites of Xike-1 serve as the caprock formations rather than the reservoirs, this represents the first discovery and is of great theoretical importance. In this paper, core photos of the tight dolomites are presented. Hand specimens description and systematic porosity-permeability reveal a very low porosity, and no permeability for most of the samples. PLM, SEM and XRPD analysis discovered that the dolostones in the deep tight dolomites are quite large in size and euhedral or subhedral in shape. Alizarin red-stained sections are mostly pink in color and have a full coverage, which are considered as evidence for multiple calcite intrusions after the formation of ankerite dolomites. Biological relict textures are developed. The order degree is medium to low. The dolomites could be the product of penecontemporaneous dolomitization.

Hydrocarbon source rocks of MTZ survey deep Yingcheng formation in Shuangcheng depression in the eastern part of Songliao Basin are widely developed, and the combination of vertical upper reservoir cover has a good exploration prospect, which is an important replacement field for deep oil and gas resources in Daqing Oilfield. High-density 3D seismic acquisition was deployed in this survey in 2018, with serious variations in seismic acquisition observation system, high-energy multi-stage refraction wave development on single shot record with particularly low SNR, and the conventional linear noise attenuation technique is difficult to suppress the coherent noise of irregular sampling based on the assumption of regular observation system. Basing on the time-frequency analysis of noise classification and partition, we design a fan filter in F-X domain. The least square method is used to estimate the weighted coefficients of all the frequency components in each trace, to simulate the noise model of the weight value in reverse performance of the real position, and finally to suppress the coherent noise by adaptive matching subtraction, we refer to the above denoising method as non-uniform coherent noise suppression technique. For the actual seismic data processing in the MTZ survey, the coherent noise in the variable-observation system area can be suppressed accurately without the need of pre-stack data regularization, the processing results have good amplitude-preserving, high profile imaging accuracy, clear structural interface and wave formation characteristics. This technique provides high-quality seismic data for the optimal selection of oil and gas exploration targets for small faults on Songliao Basin.

Detrital ilmenite and its altered minerals are common in sandstone-hosted U deposits in the northern Ordos Basin, north China. Petrographic observation, SEM-EDS, EMPA, and LA-MC-ICP-MS were utilized to characterize the spatial relationship between altered ilmenite and the U minerals, and to investigate the U enrichment mechanism and alteration processes of ilmenite. Ilmenite was completely or partially altered to leucoxene and anatase along its rim and crack in ore-bearing sandstone. Framboidal and cement pyrite of BSR and TSR origin were identified around altered ilmenite. Two U phases closely related to altered ilmenite contain Ti-coffinite (I) and coffinite (II). These data indicate that ilmenite alteration and the associated processes of U enrichment can be divided into two stages. Stage one involves U pre-enrichment and adsorption, with stage two involving U enrichment via TiO2 (leucoxene and anatase) catalytic reduction. Ilmenite was altered into porous leucoxene that can adsorb U as uraniferous leucoxene and Ti-coffinite (I) and framboidal pyrite directly by reactions with H2S, produced by sulfate-reducing bacteria during synsedimentary and early diagenesis stages. Altered ilmenite can enrich U in the form of coffinite (II) through a catalytic reduction reaction which is triggered by β and γ radiation produced by previously adsorbed U during the uplift of ore-bearing bed in the Late Cretaceous period. In addition, cement pyrite can also reduce U6+ into U4+ which deposits on its surface in the form of coffinite (II). These results demonstrate a new mechanism, mediated by adsorption and catalytic reduction, to enrich U in sandstone-hosted U deposits.

As a common phenomenon in landslides, entrainment of loose bed material along the sliding path can enhance both the volume and mobility of the sliding mass, posing a great threat to the life and property safety of people in the affected area. For the purpose of revealing the mechanism of entrainment phenomenon of sliding material in the runout process, a dynamic slice-based model was firstly proposed in the present study. In this model, the motion of landslide body is assumed to follow the rheological law proposed by Voellmy. Additionally, through Voellmy model, the increase in kinetic energy, mass and volume of landslide body and entrainment depth caused by the entrainment phenomenon were taken into consideration. Subsequently, on the basis of the dynamic slice-based model, back-analyses were performed on the Wenjia gully landslide. The effect of entrainment phenomenon on the post-failure motion was analyzed. The calculated results shows that the travel distance obtained from proposed model is closer to field data than that resulted from Scheidegger’s empirical method. Moreover, the peak value of the maximum velocity calculated by this model is in good agreement with that get from the dynamic analysis model (DAN3D). When considering the entrainment phenomenon, the volume of sliding mass increases greatly in post-failure motion. This paper provides a new method for analyzing the entrainment phenomenon in landslide motion.

The newly discovered Shangmachang epithermal gold (> 11 t Au; Heilongjiang province, NE China) and Beidagou epithermal tellurium-gold (> 5 t Au) deposits are located at the northeastern margin of the Central Asian Orogenic Belt and are hosted in Early Cretaceous volcanic rocks. At the Shangmachang deposit, gold occurs largely as electrum microparticles (5–120 μm) with a fineness of approximately 401–697 in quartz, calcite, and pyrite. Silver-bearing minerals include electrum, polybasite, and minor argentite. The main mineral paragenetic assemblages consist of pyrite-electrum and galena-polybasite, while the hydrothermal alteration minerals include quartz, calcite, sericite, chlorite, and pyrite. Trace elements in the gangue minerals show that the Al contents of gold-bearing quartz veins are lower than those of pure quartz veins (early stage). Fluid inclusions in quartz and calcite mainly comprise liquid-vapor, and the components contain a liquid phase consisting of Na+, Cl−, and SO42− and a gas phase consisting of N2, CO2, and CH4. The Shangmachang fluid inclusions homogenize at 142.8°–303.0 °C and are of low salinity (0.2–8.8 wt% NaCl equiv.), while the Au mineralization formed at 150°–225 °C. The calcite δ18Ofluid values range from − 17.8‰ to − 13.1‰, and the carbon isotope compositions range from − 8.2‰ to − 4.5‰. Zircon U-Pb dating of the Longjiang Formation andesite yields 119.4 ± 1.9 Ma, and the granite yields 118.6 ± 1.2 Ma, suggesting that local magmatism occurred during the Early Cretaceous. Calcite Sm-Nd dating suggests that the Au mineralization has an age of approximately 113.6 ± 4.0 Ma. At the Beidagou deposit, the main mineral paragenetic assemblages consist of sphalerite-galena-hessite and chalcopyrite-altaite-petzite-hessite, while the hydrothermal alteration minerals include quartz, calcite, anhydrite, chlorite, and pyrite. The components of the fluid inclusions in quartz contain a fluid phase consisting of Na+, K+, Cl−, and SO42− and a gas phase consisting of N2, CO2, CH4, and C2H6. The Beidagou fluid inclusions homogenize at 133.8°–370.1 °C and are of low salinity (0.2–8.7 wt% NaCl equiv.), while the Au mineralization formed at 175°–250 °C. The δ18Ofluid and δDSMOW values of the quartz samples from Beidagou range from − 8.2‰ to − 5.0‰ and − 101.6‰ to − 92.8‰, respectively. The Al contents of gold-bearing quartz veins are higher than those of pure quartz veins. Rb-Sr dating of ore-bearing quartz veins suggests that the Te-Au-Ag mineralization has an age of about 115.5 ± 4.4 Ma. In summary, the interpretation of new data from the geological setting, fluid inclusions, O-H-C isotopes, and geochronology, suggests that the ore-forming fluids predominantly comprised meteoric fluids, while the metal content was derived from a mantle source at both the Shangmachang and Beidagou deposits. A geochemical model suggests that the fluids responsible for quartz deposition had a neutral pH and that adiabatic boiling and mixing triggered the gold, silver and tellurium precipitation. Both Shangmachang and Beidagou are interpreted as low-sulfidation epithermal gold deposits.

In north-central China, subsistence practices transitioned from hunting and gathering to millet-based agriculture between the early and middle Holocene. To better understand how ancient environmental changes influenced this shift in subsistence strategies and human activities at regional to local levels, we conducted palynological and lithologic analyses on radiocarbon-dated sediment cores from the Luoyang Basin, western Henan Province. Our palynological results suggest that vegetation shifted from broad-leaved deciduous forest (9230–8850 cal yr BP) to steppe-meadow vegetation (8850–7550 cal yr BP), and then to steppe with sparse trees (7550–6920 cal yr BP). Lithologic analyses also indicate that the stabilization of the Luoyang Basin’s floodplain after ~8370 cal yr BP might have attracted people to move into the basin, promoting the emergence of millet-based agriculture during the Peiligang culture period (8500–7000 cal yr BP). Once agricultural practices emerged, the climatic optimum after ~7550 cal yr BP likely facilitated the expansion of the Yangshao culture (7000–5000 cal yr BP) in north-central China. As agriculture intensified, pollen taxa related to human disturbance, such as Urtica, increased in abundance.

The Dongsheng uranium district, located in the northern part of the Ordos Basin, contains the largest known sandstone-hosted uranium deposit in China. This district contains (from west to east) the Daying, Nalinggou, and Dongsheng uranium deposits that host tens of thousands of metric tonnes of estimated recoverable uranium resources at an average grade of 0.05% U. These uranium orebodies are generally hosted by the lower member of the Zhiluo Formation and are dominantly roll or tabular in shape. The uranium deposits in this district formed during two stages of mineralization (as evidenced by U–Pb dating) that occurred at 65–60 and 25 Ma. Both stages generated coffinite, pitchblende, anatase, pyrite, and quartz, with or without sericite, chlorite, calcite, fluorite, and hematite. The post-Late Cretaceous uplift of the Northern Ordos Basin exposed the northern margins of the Zhiluo Formation within the Hetao depression at 65–60 Ma, introducing groundwater into the formation and generating the first stage of uranium mineralization. The Oligocene (∼25 Ma) uplift of this northern margin exposed either the entirety of the southern flank of the Hetao depression or only the clastic sedimentary part of this region, causing a second gravitational influx of groundwater into the Zhiluo Formation and forming the second stage of uranium mineralization.

Amphibolites in the Shuixiakou area of the southern Dunhuang Orogenic Belt, southernmost Central Asian Orogenic Belt (CAOB), occur as lenses within hornblende-biotite-plagioclase gneiss or pelitic schist, exhibiting block-in-matrix feature of tectonic mélange. Three generations of metamorphic mineral assemblages (M1, M2, and M3) have been recognized in the garnet-bearing amphibolite lenses. The metamorphic prograde assemblage (M1) is documented with inclusion trails (hornblende + plagioclase + quartz) within garnet porphyroblasts, and are estimated to be formed under 610–690 °C and 6.5–10.2 kbar. The metamorphic peak assemblage (M2) consists of garnet + hornblende + clinopyroxene + plagioclase + quartz in the matrix and records metamorphic peak P-T conditions of 720–750 °C and 13.4–14.7 kbar. The retrograde assemblage (M3) is represented by the symplectic assemblage (hornblende + plagioclase + quartz ± biotite ± magnetite) rimming the garnet porphyroblast, formed in the decompression stage under P-T conditions of 630–730 °C and 3.8–7.2 kbar. The derived metamorphic P-T paths show similar tight clockwise loops including nearly isothermal decompression processes, typical of orogenic metamorphism. SIMS dating of metamorphic zircons from the amphibolites confirm that the high-pressure metamorphism (M2) occurred at ca. 438–398 Ma.

Newly acquired high-resolution seismic profiles reveal a nearshore and an offshore mud depocenter offthe southern Shandong Peninsula in the Yellow Sea. The nearshore depocenter is distributed in bands along the south coast of Shandong Peninsula. The offshore depocenter is part of the distal subaqueous deltaic lobe, which deposited around the southeastern tip of the Shandong Peninsula. Between the two depocenters is a linear depression. The mud deposits directly overlie the postglacial transgressive surface and can be divided into lower and upper units by the Holocene maximum flooding surface. The nearshore and offshore units display different seismic structures. The lower unit of the nearshore deposit exhibits basal onlap, whereas the upper unit is characterized by progradation. The lower and upper units of the offshore deposit display distinct acoustic features. The lower unit has low-angle aggradation with internal reflectors generally dipping seaward and truncated by the Holocene maximum flooding surface, whereas the upper unit is characterized by aggradation and progradation landward rather than seaward. Results of geochemistry analysis of QDZ03 sediments and mineral analysis of WHZK01 sediments suggest that the nearshore deposit and the lower unit of the offshore deposit are derived from the proximal coastal sediments of the Shandong Peninsula and the Huanghe (Yellow) River sediments. The upper unit of the offshore deposit is mainly Huanghe River-derived. The lower unit of the mud deposit represents a post-glacial transgressive system tract according to dates of core QDZ03, and the upper unit represents a highstand system tract from middle Holocene to the present. These results will be of great significance to further understanding of the transportation of the Huanghe River sediments into the Yellow Sea and the spatial distribution of the subaqueous delta.

The Xisha Block is a minor one in the South China Sea and an important tectonic unit in the northwestern part of the region. Zircon SHRIMP U-Pb ages for three volcanic intrusive core samples from Xike-1, an exploratory well penetrating the bioherms of the Xisha Islands. The core samples are from the Miocene reef carbonate bedrock and are recognized as dark-gray biotite-hornblende gabbro, gray fine-grained biotite diorite, and gray fine-grained granite, respectively. Zircon cathodoluminescence (CL) images and trace Th, U and Pb compositions of the zircons show that these rocks are of volcanic intrusive origin. Zircon SHRIMP U-Pb dating yielded six groups of ages, ranging from 2451-1857 Ma to early Cretaceous, which indicate that the formation and evolution of the Xisha Block was affected by the evolution and closure of Neotethys Ocean, probably within its eastern extension into South China Sea. Both old, deep-sourced material, including fragments from Rodina supercontinent, and recent mantle-derived magma products contributed to the emergence and formation of the Xisha block. The SHRIMP U-Pb results also proved that this process differed from that of the Kontum massif, the Hainan Block, and the South China Block, but is similar to that of the Nansha and Zhongsha blocks. The process was associated with the effects of Yanshanian magmatism induced by subduction mechanisms of the Paleo-Pacific Plate or the reworking of the multiple magmatisms since the Early to mid-Yanshanian, possibly jointly experienced by the Xisha-Zhongsha-Nansha Block.

The newly discovered Daxintun Sb-Au deposit (Heilongjiang province, NE China) is located at the north-eastern margin of the Central Asian Orogenic Belt, and it is hosted by Neoproterozoic to Early-Cambrian two-mica schist and marble. The antimony-bearing minerals include stibnite, famatinite, tetrahedrite, boulangerite, freibergite, and minor andorite. Gold occurs largely as native gold microparticles (0.1–20 μm) with high fineness (974–983) accompanied by quartz, stibnite, calcite and pyrite. Fluid inclusions in ore-bearing quartz and calcite phases mainly comprise liquid–vapor and minor CO2-bearing three-phase types, and the gas phases contain CO2, CH4 and H2S. The Daxintun fluid inclusions homogenize at 111.8–353.4 °C and are of low salinity (0.53–12.51 wt% NaCl equiv.). The δ18OSMOW of the Daxintun quartz falls into a wide range (4.2‰–16.9‰), yet the δDSMOW falls into a narrow range (−108.0‰ to −87.3‰), suggesting that the ore-forming fluids formed from metamorphic fluids that mixed with meteoric water. The stibnite δ34S ranges between −0.9‰ and 5.1‰ (mean = 2.8‰). The stibnite has 206Pb/204Pb of 18.234–18.306, 207Pb/204Pb of 15.537–15.561 and 208Pb/204Pb of 38.103–38.227, implying a metamorphic fluid source. The conditions of gold and antimony precipitation are comprised of neutral pH and fluid mixing, with decreasing fS2 and fO2. Zircon U-Pb dating of the fine-grained Daxintun granite yields a Late-Jurassic age (154.0 ± 2.0 Ma), and the Daxintun diorite dike yields a weighted mean age of 122.1 ± 1.3 Ma. Stibnite Rb-Sr dating suggests that the Sb-Au mineralization has an age of approximately 152.8 ± 2.4 Ma. The observed ore deposit geology, as well as new data on the ore-forming fluids, H-O-S-Pb isotopes, and Rb-Sr geochronology, suggest that the Daxintun Sb-Au deposit is best described as an orogenic type gold deposit that formed during subduction of the Palaeo-Pacific and the Mongolia–Okhotsk Oceans during the Late-Jurassic.

Carbonate rocks are important reservoirs for global petroleum exploration. The largest oilfield in the South China Sea, Liuhua 11-1, is distributed in the massive carbonate reef area of the Zhujiang (Pearl) River Mouth Basin. Previous studies showed that one 802.17-m-long core from well Xichen-1 in the South China Sea mainly consisted of white and light gray-white organic reefs. Recently, a Miocene whole core (161.9 m long) of well Xiyong-2, near well Xichen-1, was found to contain six layers of yellowish brown, light yellowish gray, iron black, or light yellowish gray-white organic reefs. Scanning electron microscope images of these layers reveal a typical ferroan dolomite rich in Fe (up to 29%), with the high concentrations of Mn, Cu, W, Zn, Cr, Ni, and Co. Systematic X-ray powder diffraction analysis yields a 1.9–6.1 match in phase ratio with ankerite, 5.4–26.9 with dolomite, and zero with calcite, which indicate that the samples can be classified as ferroan dolomite. The iron and heavy metals are inferred to be originated from multiple volcanic eruptions of Gaojianshi Island in the Dongdao Atoll during the middle-late Miocene. These elements were dissolved in seawater, likely as a sol, and carried to Yongxing Island in the Xuande Atoll by sea currents and tides enhanced by prevailing winds, and deposited as a part of the sedimentation process in the study area. The ferroan dolomite has Sr content of (125–285)×10-6, which is lower than the accepted Sr boundary value of dolomite. This finding suggests that dolomitization occurred during large-scale global glacial regression in the late Miocene. The isolated Xisha carbonate platform, exposed to air, underwent freshwater leaching and dolomitization induced by mixed water, and caused the extensive Fe-Mg exchange along the organic reef profile to form ankerite and ferroan dolomite. These results may help to understand paleoceanographic environmental changes in the South China Sea during the Miocene.

The discrete mafic granulite and amphibolite enclaves within the Pingyang trondhjemitic pluton, Fuping metamorphic terrane, middle Trans-North China Orogen, ubiquitously record three stages of metamorphic assemblages. For the mafic granulite enclaves, the prograde metamorphic assemblage (M1) is represented by mineral inclusions (clinopyroxene + hornblende + plagioclase + quartz ± apatite) preserved in the garnet porphyroblast, the metamorphic peak (M2) assemblage consists of garnet and matrix minerals of clinopyroxene + orthopyroxene + hornblende + plagioclase + quartz ± magnetite ± ilmenite ± zircon, and the retrograde (M3) stage is represented by symplectite assemblage of orthopyroxene + plagioclase ± clinopyroxene ± hornblende ± quartz rimming the garnet porphyroblast. The metamorphic P-T paths of the mafic granulite enclaves are defined to pass from 560–750 °C/6–9 kbar (M1) through 740–880 °C/11–14 kbar (M2) to 720–800 °C/6–8 (M3), indicative of a collisional orogenic process. The metamorphic P-T path of the amphibolite enclave experienced from 670–730 °C/9.3–11.8 kbar to 710–730 °C/3.9–5.5 kbar, further certify such metamorphic feature of an orogenic belt. SIMS U-Pb dating of zircons of the trondhjemitic gneiss yields the magmatic crystallization age of ∼2.52 Ga, and both the trondhjemitic gneiss and the mafic granulite enclaves yield the metamorphic age of ∼1.89–1.86 Ga. Therefore, it can be concluded that the Fuping terrane was involved in the late Palaeoproterozoic subduction-collision-uplifting tectonic process caused by amalgamation of the Eastern and Western Blocks of the North China Craton along the Trans-North China Orogen.

The slip vector on a fault is an important parameter in the study of the movement history of a fault and its faulting mechanism. Although there exist many graphical programs to represent the shear stress (or slickenline) orientations on faults, programs to quantitatively calculate the orientation of fault slip based on a given stress field are scarce. In consequence, we develop Slicken 1.0, a software to rapidly calculate the orientation of maximum shear stress on any fault plane. For this direct method of calculating the resolved shear stress on a planar surface, the input data are the unit vector normal to the involved plane, the unit vectors of the three principal stress axes, and the stress ratio. The advantage of this program is that the vertical or horizontal principal stresses are not necessarily required. Due to its nimble design using Java SE 8.0, it runs on most operating systems with the corresponding Java VM. The software program will be practical for geoscience students, geologists and engineers and will help resolve a deficiency in field geology, and structural and engineering geology. Software designed using Java SE 8.0.Non-Andersonian stress state.Direction of resolved shear on fault planes.

The Hongliuxia tectonic melange of the southern Dunhuang terrane, northwestern China, southernmost Central Asian Orogenic Belt (CAOB), consists of eclogite, mafic granulite, and amphibolite as puddingstones within a matrix of metapelitic gneiss and marble; these rocks are interpreted to be part of an ancient subduction zone setting. Secondary ion mass spectrometry U-Pb dating of metamorphic zircons obtained from the puddingstones and matrix metapelite suggests that the metamorphism occurred at ca. 428–391 Ma. The metamorphic rocks all record similar clockwise metamorphic pressure-temperature-time ( P - T - t ) paths of the western Alpine type. However, remarkable differences between metamorphic peak P - T conditions ranging from 830 °C and 24.2 kbar for the eclogite puddingstone to 700 °C and 10.2 kbar for the metapelite matrix were found in the melange rocks. This indicates the mixing of rocks from significantly different depths to create a tectonic melange in a subduction channel, possibly juxtaposed during the uplift stage. These data suggest that the southernmost CAOB underwent subduction and subsequent exhumation caused by subduction of the Paleozoic Hongliuxia ocean during the middle Silurian to middle Devonian.

Garnet-bearing mafic granulites and amphibolites from the Hongliuxia area of the southern Dunhuang orogenic belt, northwestern China, commonly occur as lenses or boudinages enclosed within metapelite or marble, which represent the block-in-matrix feature typical of orogenic melange. Three to four generations of metamorphic mineral assemblages are preserved in these rocks. In the high-pressure amphibolites, prograde mineral assemblages (M1) occur as inclusions (hornblende + plagioclase + quartz ± chlorite ± epidote ± ilmenite) preserved within garnet porphyroblasts, and formed at 550–590 °C and 7.7–9.2 kbar based on geothermobarometry. The metamorphic peak mineral assemblages (M2) are composed of garnet + hornblende + plagioclase + quartz + clinopyroxene, as well as titanite + zircon + rutile + apatite as accessory minerals in the matrix, and are estimated to have formed at 640–720 °C and 14.1–16.0 kbar. The first retrograde assemblages (M3) are characterized by “white-eye socket” symplectites (hornblende + plagioclase + quartz ± biotite ± epidote ± magnetite) rimming garnet porphyroblasts, which formed at the expense of the garnet rims and adjacent matrix minerals during the decompression stage under P – T conditions of 610–630 °C and 5.6–11.8 kbar. The second retrograde assemblages (M4) are intergrowths of actinolite and worm-like quartz produced by the breakdown of the matrix hornblendes, and formed under P – T conditions of ∼490 °C and ∼2.8 kbar. For the high-pressure mafic granulites, the prograde assemblages (M1) are represented by plagioclase + quartz preserved within the garnet porphyroblasts. The metamorphic peak assemblages (M2) are garnet + matrix minerals (clinopyroxene + plagioclase + quartz + hornblende + rutile + zircon) and were estimated to have formed at ∼680 °C and ∼15.4 kbar. The retrograde assemblages (M3) are characterized by fine-grained patches of hornblende + plagioclase + quartz rimming the garnet porphyroblasts, as well as hornblende rimming clinopyroxene in the matrix, and were inferred to have formed at ∼620 °C and ∼4.2 kbar. For the metapelitic gneiss, the metamorphic peak assemblages are the garnet porphyroblasts plus the matrix minerals (biotite + plagioclase + quartz + ilmenite + zircon), which were estimated to have formed at ∼630 °C and ∼8.9 kbar. The mafic granulites and amphibolites record fairly similar clockwise P–T paths that include nearly isothermal decompression processes, which suggest that they experienced subduction and subsequent rapid tectonic exhumation. SIMS and LA-ICP-MS U–Pb dating of zircons and 40Ar/39Ar dating of hornblende suggest that the metamorphism occurred at ∼430–390 Ma. Field occurrences, different protolith ages of the mafic granulites and amphibolites, and the considerable gap in peak P – T conditions between the amphibolite and mafic granulite boudinages and their country rock may suggest a melange accumulation process during the Paleozoic caused by the Silurian–Devonian orogeny, which is possibly associated with the closure of the Liuyuan ocean, a branch of the Paleo-Asian ocean near the southern Central Asian Orogenic Belt.

Metamorphic evolution and geochronology of pelitic granulites were reported for the first time in the Taihua metamorphic complex, Mts. Huashan area, southern segment of the trans-North China Orogen (TNCO). Three generations of metamorphic mineral assemblages are recognized: (1) the prograde metamorphic mineral assemblages (M1) are represented by mineral inclusions within the garnet porphyroblasts; (2) the metamorphic peak assemblage (M2) are the garnet porphyroblasts and minerals in the matrix (biotite + orthopyroxene + plagioclase + quartz + K-feldspar + ilmenite + zircon + magnetite); and (3) the retrograde metamorphic mineral assemblages (M3) are represented by the symplectic assemblages around the garnet porphyroblasts, resulted from decomposition reactions between garnet rims and neighboring minerals in the matrix. Calculated by both conventional thermobarometry and pseudosection modeling in the NCKFMASHT system using the Perple_X technique, the P–T conditions of these three metamorphic stages are constrained to be of 4–5 kbar/520–530 °C for the M1 stage, 6.8–8.6 kbar/730–810 °C for the M2 stage and 4.1–6.4 kbar/570–740 °C for the M3 stage, respectively. The derived clockwise P–T paths imply that the Mts. Huashan terrane involved in the subduction and subsequent collision between the Eastern and Western Blocks of the North China Craton (NCC) along the Palaeoproterozoic Trans-North China Orogen (TNCO). High resolution SIMS U–Pb dating of metamorphic zircons reveals the metamorphic ages of 1.85–1.82 Ga. Combined with geochronological data from the literature, it is concluded that the tectonothermal evolution between the Eastern and Western Blocks started as early as ∼1.97 Ga and lasted as late as 1.80 Ga. Furthermore, the eastern Taihua complex records older metamorphic ages and higher peak metamorphic pressures than those of the western Taihua complex, possibly suggesting an eastward subduction model for the TNCO.

The Taihua metamorphic complex in the southern part of the North China Craton is composed of tonalite-trondhjemite-granodiorite (TTG) gneisses, amphibolites, metapelitic gneisses, marbles, quartzites, and banded iron formations (BIFs). The protoliths of the complex have ages ranging from ∼2.1 to ∼2.9 Ga and was metamorphosed under the upper amphibolite to granulite facies conditions with NWW-SEE-striking gneissosity. Metapelitites from the Wugang area have three stages of metamorphic mineral assemblages. The prograde metamorphic mineral assemblage (M1) includes biotite + plagioclase + quartz + ilmenite preserved as inclusions in garnet porphyroblasts. The peak mineral assemblage (M2) consists of garnet porphyroblasts and matrix minerals of sillimanite + biotite + plagioclase + quartz + K-feldspar + ilmenite + rutile + pyrite. The retrograde mineral assemblage (M3), biotite + plagioclase + quartz, occurs as symplectic assemblages surrounding embayed garnet porphyroblasts. Garnet porphyroblasts are chemically zoned. Pseudosection calculated in the NCKFMASHTO model system suggests that mantles of garnet porphyroblasts define high-pressure granulites facies P–T conditions of 12.2 kbar and 830 °C, whereas garnet rims record P–T conditions of 10.2 kbar and 840 °C. Integrating the prograde mineral assemblages, zoning of garnet porphyroblasts with symplectic assemblages, a clockwise metamorphic P–T path can be retrieved. High resolution SIMS U−Pb dating and LA−ICP−MS trace element measurements of the metamorphic zircons demonstrate that metapelites in Wugang possibly record the peak or near peak metamorphic ages of ∼1.92 Ga. Furthermore, 40Ar/39Ar dating of biotite in metapelites suggests that the cooling of the Taihua complex may have lasted until ∼1.83 Ga. Therefore, a long-lived Palaeoproterozoic metamorphic event may define a slow exhumation process. Field relationship and new metamorphic data for the Taihua metamorphic complex does not support the previous model in which the Tran-North China Craton (TNCO) was formed through the collision between the East and West blocks.

Tonalite-trondhjemite-granodiorite (TTG) suite and potassic granite volumetrically expose in the Neoarchean to Paleoproterozoic Taihua complex, Mts. Huashan region, southernmost segment of the Trans-North China Orogen (TNCO). Zircon U–Pb dating on the trondhjemite, granitic gneiss, K-feldspar granite and coarse-grained granite samples show three episodes of magmatism (2.55–2.49 Ga, 2.33–2.25 Ga and 1.87–1.80 Ga) with distinct geochemical features in this area during the Paleoproterozoic. The trondhjemite samples have high SiO2 (67.46–71.73 wt%), Na2O (4.83–5.95 wt%), low Mg# (31–40) and HREE contents, with moderate (La/Yb)N values (16.8 to 35.3) and Sr/Y ratios (15.8 to 34). The potassic granite samples show high SiO2 (65.2–75.43 wt%), K2O (3.9–8.6), low Na2O (1.74–4.17 wt%), Mg# (2–46) and HREE contents, with moderate to high (La/Yb)N values (10.3 to 226) and Sr/Y ratios (12.8 to 208). All these granitoid samples are characterized by high SiO2 and low Mg#, Cr, Ni with moderate to high (La/Yb)N values and Sr/Y ratios. The absence of evidence of any pre-existing high Sr/Y and La/Yb sources in this region led to that the granitoids probably generated from partial melting of hydrous mafic rocks with garnet and amphibole in the residue. Therefore, partial melting of thickened lower curst is the most likely origin. Combined with previous studies, the first episodic magmatism (2.55–2.49 Ga) represented by TTG and granitic gneisses with positive whole rock ƐNd(t) and zircon ƐHf(t) values is interpreted as melts from partial melting of juvenile thickened lower crust. The second episodic magmatism (2.33–2.25 Ga) represented by TTG, granitic gneisses and K-feldspar granite with positive to negative whole rock ƐNd(t) and zircon ƐHf(t) values is suggested as the product of partial melting of both juvenile and pre-existing crustal material. The third episodic magmatism (1.87–1.80 Ga) is represented by these potassic granites, which is synchronism with the metamorphism recorded in this region and probably resulted from partial melting of pre-existing crustal materials in a syn-orogenic or post-orogenic setting during the collision between the Eastern and Western Blocks of the North China Craton. Multistage continental accretion (at 2.84–2.72 Ga, 2.57–2.43 Ga and 2.36–2.25 Ga) and reworking (at 2.36–2.25 Ga, 2.19–2.07 Ga and 1.87–1.80 Ga) occurred in the southern segment of the TNCO from Neoarchean to Paleoproterozoic. Transformation from an Andean-type continental margin arc setting on the western margin of the Eastern Block to continent-arc-continent collision in the southern TNCO during Late Neoarchean to Late Paleoproterozoic is suggested in this paper.

The Dongping gold deposit hosted in syenites is one of the largest hydrothermal gold deposits in China and composed of ore veins in the upper parts and altered zones in the lower parts of the ore bodies. Pervasive potassic alteration and silicification overprint the wall rocks of the ore deposit. The alteration minerals include orthoclase, microcline, perthite, quartz, sericite, epidote, calcite, hematite and pyrite, with the quartz, pyrite and hematite assemblages closely associated with gold mineralization. The phases of hydrothermal alteration include: (i) potassic alteration, (ii) potassic alteration - silicification, (iii) silicification - epidotization - hematitization, (iv) silicification - sericitization - pyritization and (v) carbonation. Mass-balance calculations in potassic altered and silicified rocks reveal the gain of K2O, Na2O, SiO2, HFSEs and transition elements (TEs) and the loss of REEs. Most major elements were affected by intense mineral reactions, and the REE patterns of the ore are consistent with those of the syenites. Gold, silver and tellurium show positive correlation and close association with silicification. Fluid inclusion homogenization temperatures in quartz veins range from 154 °C to 382 °C (peak at 275 °C–325 °C), with salinities of 4–9 wt.% NaCl equiv. At temperatures of 325 °C the fluid is estimated to have pH = 3.70–5.86, log fO2 = − 32.4 to − 28.1, with Au and Te transported as Au (HS)2− and Te22 − complexes. The ore forming fluids evolved from high pH and fO2 at moderate temperatures into moderate-low pH, low fO2 and low temperature conditions. The fineness of the precipitated native gold and the contents of the oxide minerals (e.g., magnetite and hematite) decreased, followed by precipitation of Au- and Ag-bearing tellurides. The hydrothermal system was derived from an alkaline magma and the deposit is defined as an alkaline rock-hosted hydrothermal gold deposit.

The Taihua metamorphic complex exposes in the southern Trans-North China Orogen (TNCO) and records at least three episodes of magmatism. The Shanxian TTG gneisses obtained at 2.54–2.48 Ga have high SiO 2 , variable Mg# with high (La/Yb) N and Sr/Y ratios (15.08–93.26 with average of 37.31 and 7.33–115.05 with average of 49.59, respectively). They show negative Nb and Ta but positive Zr and Hf anomalies with low Nb/Ta and Gd/Yb, and high Zr/Hf and Zr/Sm ratios (4.97–18.8, 1.92–6.37, 23.71–50.26, and 29.18–75.23, respectively), and have positive e Hf (t) values (+1.7 to +7.9) and e Nd (t) values (+0.72 to +2.55), indicating that they were possibly produced by partial melting of lower crust derived from metasomatized lithospheric mantle with the residue of minor garnet. The Sihe granitic gneisses recorded at 2.35–2.30 Ga are enriched in silica, Al 2 O 3 contents (13.59–15.33), K 2 O/Na 2 O ratios (1.13–1.7), defined as high-Al TTG. They exhibit high Sr/Y, Zr/Sm and Zr/Hf ratios and low Nb/Ta and Gd/Yb ratios (44.71–83.09, 47.79–62.58, 36.05–37.43, 12.04–16.36, and 2.95–3.68, respectively) with negative Eu anomaly. Combined with Hf and Nd isotopes (−2.5 to +4.7 and −0.74 to +0.36), the Sihe granitic gneiss was possibly generated from partial melting of lower crust with minor ancient material contributions, leaving residual amphibole and minor garnet in the source. The Muce monzonitic gneisses emplaced at 2.17–2.16 Ga have high Mg#, Ni and Cr contents, constant Sr/Y and (La/Yb) N (42.39–50.33, 19.8–41.4, 33.6–74.2, 31.32–34.14, and 15.32–16.7, respectively), with relatively low and constant Dy/Yb ratio (1.82–1.85). Together with Hf and Nd isotopes (−6.5 to −0.9 and −2.07 to −2.86), the Muce monzonitic gneisses might be derived from partial melting of Neoarchean pre-existing crustal materials, possibly in an arc setting. It is therefore found that four episodes of crustal growth and/or reworking in the southern segment of the TNCO have occurred at 2.85–2.72 Ga, 2.57–2.48 Ga, 2.35–2.30 Ga and 2.2–2.0 Ga, respectively, likely to connect with the subduction–collision between the Eastern and Western Blocks along the TNCO in the North China Craton.

Sixty-six passive continental margin basins around the world were compared comprehensively from the aspect of seismogeology on the basis of plate tectonics. According to their textural and structural differences, passive continental margin basins were classified into seven subdivisions, i.e., rifted basin, non-saline faulted depression basin, saline faulted depression basin, non-saline depression basin, saline depression basin, delta reformed basin and positive reverse deformed basin. The passive continental margin basins around the world have been generated with the formation of Mesozoic and Cenozoic Atlantic and Indian Oceans and they have experienced superimposition of three prototypes, including intra-continental rift in rifting period, intercontinental rift in transitional period and passive continental margin in drifting period. In rifted basins, the petroleum systems are mainly located in the lower lacustrine/marine rift series of strata and the thinner depression series of strata at the upper part are only regional cap-rocks. Large oil and gas fields are mainly concentrated in structural traps of rift series of strata. In non-saline faulted depression basins, hydrocarbon generation and expulsion peaks occur in both upper thicker marine depression series of strata and lower rift series of strata. Reservoirs are formed in the structures of rift series of strata, and oil and gas are highly concentrated at slope fans in depression series of strata. In saline faulted depression basins, large oil and gas fields are mainly distributed in the lagoon carbonate rocks of subsalt series of strata and the deepwater slope fans of suprasalt depression series of strata. In saline depression basins, only petroleum systems in depression series of strata are active, and various traps are developed, such as slope fan, salt structure and bioherm. In non-saline depression basins, large oil and gas fields are mainly located in submarine fan groups of depression series of strata because this type of basins are of narrow continental shelf and steep continental slope. In delta reformed basins, four major ring-like structure belts (i.e., growth faulting-mud diapir-thrust nappe-foredeep gentle slope) are formed from the shore to the deepwater and large oil and gas fields can be formed in each belt. Positive reverse reformed basins are the passive continental margin basins which are influenced by global orogenesis since the Miocene. In this type of basins, oil and gas are concentrated in compressional anticlines of reverse series of strata. Key words: passive continental margin, prototype basin, basin structure, basin classification, large oil and gas field, distribution rules

Garnet-bearing mafic granulite and amphibolite exposed as lenses, boudins, or interlayers within metasediments in the Qingshigou area, Dunhuang block, southernmost Central Asian orogenic belt, record important information for understanding the tectono-metamorphic evolution of subduction and collision zones in the southern Central Asian orogenic belt during the mid-Paleozoic. Three stages of metamorphic assemblages (M1, M2, M3) are recognized in the high- and medium-pressure mafic granulite and amphibolite. In the high-pressure mafic granulite, the prograde assemblage (M1) is represented by inclusion minerals (hornblende + plagioclase + quartz) preserved in garnet porphyroblasts; the metamorphic peak assemblage (M2) is characterized by garnet porphyroblasts and matrix minerals (garnet + clinopyroxene + plagioclase + quartz ± zircon ± titanite); and the retrograde assemblage (M3) is marked by coronitic symplectite (hornblende + plagioclase + quartz ± magnetite) rimming the garnet porphyroblasts. In the medium-pressure mafic granulite, the prograde assemblage (M1) of hornblende + plagioclase + quartz is included in the garnet porphyroblasts; the peak assemblage (M2) consists of garnet + orthopyroxene + clinopyroxene + plagioclase + quartz ± zircon ± titanite (M2) in the matrix; and the retrograde assemblage (M3) of hornblende + orthopyroxene + plagioclase + quartz (M3) surrounds the garnet porphyroblasts. In the amphibolite, the prograde assemblage (hornblende + plagioclase + quartz + ilmenite) is preserved as inclusions in garnet (M1); the peak assemblage (M2) is composed of garnet + hornblende + plagioclase + quartz ± zircon ± titanite; and the retrograde assemblage (M3), consisting of hornblende + biotite + plagioclase + quartz + epidote + magnetite, rings the garnet porphyroblasts. Geothermobarometric calculations suggest that the metamorphic pressure-temperature paths pass from 568 °C and 8.8 kbar through 607 °C and 10.6 kbar and 861 °C and 16.9 kbar and finally to 598 °C and 4.4 kbar for the high-pressure mafic granulite; from 756 °C and 9.0 kbar through 750–874 °C and 9.3–11.6 kbar to 675 °C and 4.7 kbar for the medium-pressure mafic granulite; and from 686 °C and 7.6 kbar through 715–766 °C and 10.6–11.2 kbar to 671 °C and 5.6 kbar for the amphibolite, and the paths show clockwise pressure-temperature loops typical of an orogenic process. The metamorphic peak of the high-pressure mafic granulite lies in the eclogite facies, which is indicative of a subduction zone environment. High-resolution secondary ion mass spectrometry (SIMS) U-Pb dating of metamorphic zircon indicates that the metamorphism occurred in the Early Silurian (ca. 430 Ma) and lasted for at least 65 m.y. This study reveals a possible southward subduction history of a branch of the Paleo–Asian Ocean, the Liuyuan Ocean, from the Silurian to Late Devonian, which may be an important event in the accretionary history of the Central Asian orogenic belt.