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[An intraplatform trough and associated platform margins formed in the Sichuan Basin, South China, during the Late Ediacaran to Early Cambrian. Seismic data show three stages of development of the trough. The first stage is characterized by considerable thinning of the lower two members of the Upper Ediacaran from the platform margins to the trough. In the second stage, in the late Late Ediacaran, the platform margins backstepped and the extent of the trough expanded significantly. The third stage, in the early Early Cambrian, was dominated by gradual filling of the trough and onlapping of the platform margins. Integrating with tectonic subsidence analysis, we infer that the trough was a palaeogeographic embayment in a large carbonate platform. , Abstract The Upper Ediacaran to Lower Cambrian of the Sichuan Basin in South China has long been considered to be dominated by shallow‐water deposition. Hydrocarbon exploration, however, has revealed that a NW‐SE trending intraplatform trough formed in the basin during the same period. Although different models have been proposed, the formation and evolution of the trough are still not fully understood. In this study, we investigate both the origin of the intraplatform trough and the formation of the Sichuan Basin by integrating seismic interpretation, well correlation and tectonic subsidence analysis. The seismic and well data clearly show three stages of development of the trough. The first stage, in the early Late Ediacaran, is characterized by considerable thinning of the lower two members of the Upper Ediacaran from the platform margins to the trough. In the second stage, in the late Late Ediacaran, the platform margins backstepped and the extent of the trough expanded significantly to a width of ca. ~400 km. The third stage, in the early Early Cambrian, was dominated by gradual filling of the trough and onlapping of the platform margins. Backstripped tectonic subsidence curves show one, or two closely spaced episodes of linear subsidence starting at ~550 Ma and then decreasing exponentially until ~450 Ma. The shape of the subsidence curves is consistent with formation of the Sichuan Basin by low, and slow amounts of lithospheric stretching of thickened cratonic lithosphere. The tectonic subsidence increases from the centre to the NW of the basin. Interestingly the margins of the trough do not correlate with contoured values of increased tectonic subsidence and we infer that the trough was a palaeogeographic embayment in a large carbonate platform that developed in a broad, ramp‐like area of slow and low subsidence tilting down to the proto‐Tethyan ocean located to the NW of the basin.]

The organic-rich shale of the Lower Cambrian Shuijingtuo Formation in the Yangtze area is considered a high-quality source rock in South China. Geochemical proxies are used to reveal the formation and preservation conditions of the Shuijingtuo shale in Yichang in the middle Yangtze area. Geochemical proxies for paleoredox (U/Th, V/Cr, Ni/Co, and UEF versus MoEF), paleoproductivity (Ba/Al, Cu/Al, and Ni/Al), and terrigenous influx (Al and Ti) have been employed to interpret the mechanism of organic matter (OM) accumulation. The total organic carbon (TOC) contents of the Shuijingtuo shale is between 0.19 wt% and 4.77 wt% (with an average of 1.38 wt%). The shale can be divided into two intervals based on TOC content, the lower interval with high TOC (TOC >2 wt%) and the upper interval with low TOC (TOC

A Dirac half-metal material, which has a gapped band structure in one spin channel but Dirac cones in the other, combines two intriguing properties of 100% spin polarization and massless Dirac fermions and has recently started to attract increasing attention. In this work, using first-principles calculations we predict that the disodium carbide (Na2C) monolayer is an intrinsic 2p Dirac half-metal material with 12 fully spin-polarized and symmetry-protected Dirac cones, and a slightly gapped (53 meV) spin-polarized nodal line coexisting in one spin channel, leaving the other spin channel insulated with a gap of 1.9 eV. There are two kinds of Dirac cones in Na2C, protected by different crystalline symmetries, both of which are robust against biaxial strains (±5%) and spin–orbit coupling effects, with Fermi velocities of up to 5.2 × 105 m s−1. Ferromagnetism is mainly contributed to by the unpaired 2p electrons in the carbon, with a Curie temperature estimated to be 382 K, and the origin of the 2p magnetism could be explained by the superexchange mechanism between C2− anions with the Na+ cation as a bridge. Our results not only indicate a promising candidate for high-speed spintronic devices, but also reveal the hidden mechanism of the origin of symmetric protection and ferromagnetic exchange interactions in a Dirac semi-metal, which would provide a feasible strategy for the design of Dirac materials.

The formation and preservation conditions of the organic matter (OM) in the Upper Devonian Shetianqiao Formation were investigated to assess the mechanism of the OM enrichment in the shale in the Shaoyang sag. The total organic carbon (TOC) contents of the shale range from 0.2% to 4.4%. The shale can be divided into three intervals. The terrestrial input during Interval 2, as indicated by the Al2O3 and Ti proxies, was relatively small. The chemical alteration index (CIA) shows that the Shetianqiao Formation mainly formed in a warm and humid climate, however, climate cooling occurred in Interval 2. Intervals 1 and 3 were mainly deposited in a restricted environment, whereas Interval 2 experienced upwelling. The climate cooling may have been the driver for the upwelling. The UEF, MoEF, and Mo-U covariation diagrams indicate that Interval 2 was mainly deposited under reducing conditions, whereas Intervals 1 and 3 were chiefly formed in an oxidizing environment. The Cu/Al ratios and excess Si (Sixs) suggest that Interval 2 was formed in significantly higher marine productivity than Intervals 1 and 3. The plot of Co (ppm) × Mn (%) versus Cd/Mo, the logarithmic relationship between Co (ppm) × Mn (%) and TOC, and the good correlations between TOC and the productivity proxies suggest that productivity was the primary factor for the OM enrichment. We constructed a depositional model that emphasizes the control of productivity driven by upwelling on the OM enrichment.

The Mesoproterozoic Hongshuizhuang Formation in Jixian, northern China, is a hydrocarbon source unit containing abundant organic matter. We investigated the mechanisms controlling this organic matter accumulation by analyzing the sedimentology and geochemistry of the Qinghe section, in the Kuancheng region of northern China. Trace element geochemistry suggests that organic matter accumulation was controlled primarily by marine productivity, which was the main determinant of redox conditions. Elevated marine productivity and consequent anoxic-sulfidic bottom water conditions were coincident with accumulation of the organic-rich (TOC > 1.0%) lower part of the Hongshuizhuang Formation. Deposition of the organic-lean upper Hongshuizhuang Formation appears to have been coeval with diminished productivity and a transition to oxic-suboxic redox conditions. Enhanced organic matter accumulation in the lower Hongshuizhuang Formation was promoted by a warm, humid paleoclimate and submarine hydrothermal activity. Average Rb/Sr ratios (3.42) and negative carbon isotope excursion reflect a warm climate, likely caused by the release of volcanogenic CO 2 . Warm conditions would have promoted continental weathering, and increased the flux of nutrients into the oceans, enhancing marine productivity. An increased supply of nutrients and enhanced marine productivity would have depleted oxygen in the bottom water environment and favored the proliferation of sulfate-reducing bacteria, leading to anoxic-sulfidic conditions. The relative stability of δ 13 C carb values suggests that organic matter enrichment in the Hongshuizhuang Formation reflects changes in surface water productivity and redox conditions, caused by climate-induced sea-level fluctuations. Shale-normalized rare earth element (REE) distributions show a depletion in light REEs and enrichment in heavy REEs, positive Eu anomalies, and mean Y/Ho and Ba/Sr ratios of 33.2 and 9.91, respectively, suggesting that deposition of the Hangshuizhuang Formation was accompanied by submarine hydrothermal activity.

The Sinian dolomite reservoir in Dengying Formation was developed extensively in the Sichuan Basin, and typically was the facies-controlled dolomite karstic reservoir. The development of this kind of the reservoir was related with the special deposits, diagenetic environment as well as the multi-phase and multi-type dissolution and fracturing actions. The arid-hot/dry paleo-climate was favourable to develop the large-scale microbial reef-shoal bodies and mound–shoal bodies, which was characterized by the organic framework and the sea floor hardening, thus forming primary matrix pore-type reservoir. In the background of the arid-hot/dry paleo-climate, the water-rock interaction was weak, the mineral stabilization process was slowly, and the vadose pisoliths, aragonite and high-magnesium calcite were well preserved, therefore, this diagenetic environment especially was beneficial for pore preservation. Moreover, the syngenetic and penecontemporaneous dissolution, especially three phases of weathered crust karstification due to three episodes of the Tongwan movement, led to further dissolution of spaces and form numerous non-fabric selective dissolution fractures and dissolution caves along faults and fractures. Multi-phase fractures, especially the late Yanshanian-Himalayan tectonic fractures, resulted in connection among pores, vugs and dissolution caves, and improved quality of the reservoir tremendously. Keywords: Dolomite karstic reservoir, Reservoir space, Diagenetic environment, Dissolution, Tongwan movement, Dengying Formation, Sichuan Basin

Based on the drilling, logging, seismic and outcrop data, the formation and evolution of the late Sinian to early Cambrian intraplatform basin in Sichuan Basin was studied. Through the analysis of the total residual thickness of Member 3 + Member 4 of Dengying Formation, the total thickness of Maidiping Formation + Qiongzhusi Formation, and lithofacies characteristics of Maidiping Formation, the distribution of the intraplatform basin was defined and its controlling effect on natural gas distribution of Dengying Formation was revealed. The intraplatform basin was characterized by small total residual thickness of Member 3 and Member 4 of Dengying Formation, the large total thickness of Maidiping Formation and Qiongzhusi Formation, and the deep-water phosphorous-carbonaceous-siliceous mudstone in Maidiping Formation. Horizontally, the intraplatform basin was mainly distributed in Qingchuan-Ziyang-Yibin area, and experienced four evolution periods. During the period of Member 1 and Member 2 of Dengying Formation, the Sichuan Basin was a rimmed carbonate platform with the well developed mounds and shoals on the platform margin and its interior. The intraplatform basin in western Sichuan Basin was initially formed due to the first episode of Tongwan movement. During the period of Member 3 and Member 4 of Dengying Formation, the depositional center was formed in Moxi, Changning and Zhengxiong area due to extension and rifting of the Upper Yangtze Craton, thereafter, the Sichuan Basin evolved into a rimmed carbonate platform with an intraplatform basin. The second episode of Tongwan movement between Sinian and Cambrian led to the overall uplift and exposure of Sichuan Basin characterized by weathering denudation at high position and downward fluid erosion at low position. During the period of Maidiping Formation, three lithofacies zones were developed horizontally, and the third episode of the Tongwan movement between Maidiping Formation and Qiongzhusi Formation modified the sedimentary geomorphology locally. During the period of Qiongzhusi Formation and Canglangpu Formation, continuous deposition made the Sichuan Basin evolve into a gentle siliciclastic ramp. The evolution of the intraplatform basin not only promoted formation of high-quality platform-margin dolomite reservoirs of Member 4 of Dengying Formation, but also controlled distribution of the high-quality source rocks of Maidiping Formation and Qiongzhusi Formation. The dolomite of Dengying Formation in the surrounding area of the intraplatform basin was the most favorable hydrocarbon exploration area because of its good source-reservoir configuration. Keywords: Dengying Formation, Source rock, Dolomite, Intraplatform basin, Paleogeography, Sichuan Basin

The exploration of Dirac materials is a great challenge in condensed matter physics and material chemistry. In this paper we present a novel 2D magnetic graphene-like Dirac material with a Honeycomb–Kagome (HK) lattice, named as C3Ca2. The ground state of C3Ca2 is a half-metal with a 100% spin polarized Dirac cone locating exactly at the Fermi level in the metallic spin channel, and has a large band gap in the insulating spin channel. In particular, C3Ca2 has 2p magnetism with the Dirac cones mainly contributed by pxy orbitals of C atoms, instead of 3d magnetism or pz dominated Dirac cones in other HK or Kagome materials, and it is robust against spin–orbit coupling and biaxial strains. The mechanism of magnetism could be understood by double exchange between carbon anions, using Ca2+ cations as bridges. These outstanding properties of C3Ca2 indicate it to be a promising 2D material for applications in spintronics.

The presence of elemental vacancies in materials are inevitable according to statistical thermodynamics, which will decide the chemical and physical properties of the investigated system. However, the controlled manipulation of vacancies for specific applications is a challenge. Here we report a facile method for creating large concentrations of S vacancies in the inert basal plane of MoS2 supported on semimetal CoMoP2. With a small applied potential, S atoms can be removed in the form of H2S due to the optimized free energy of formation. The existence of vacancies favors electron injection from the electrode to the active site by decreasing the contact resistance. As a consequence, the catalytic current is increased by 221% with the vacancy-rich MoS2 as electrocatalyst for hydrogen evolution reaction (HER). A small overpotential of 75 mV is needed to deliver a current density of 10 mA cm−2, which is considered among the best values achieved for MoS2. It is envisaged that this work may provide a new strategy for utilizing the semimetal phase for structuring MoS2 into a multi-functional material.

Based on the sedimentological and geochemical analysis of total organic carbon (TOC) and major and trace elements in the marine Upper Ordovician-Lower Silurian Wufeng-Longmaxi Formations in Yichang, Central Yangtze area, paleoredox conditions (indicated by U/Th, V/Cr, Ni/Co, TOC-TS-Fe diagram, and Mo–U covariations), paleoproductivity (indicated by Babio, Ba/Al, P/Ti, Ni/Al, Cu/Al, and Zn/Al), terrestrial detrital influx (indicated by Ti and Al), paleoclimate (indicated by chemical index of alteration and Rb/Sr), and upwelling (indicated by Co × Mn) are revealed within the framework of sea-level changes. The influences of these factors on organic matter enrichment are also discussed. The results identify four third-order sequence boundaries in the Wufeng-Longmaxi Formations; each sequence can be divided into one transgressive systems tract (TST) and one regressive systems tract (RST) according to sea-level changes. The high-TOC interval mainly developed in TST1 (average 3.44%) and TST2 (average 3.68%). The analysis of geochemical indicators shows that during the TST1 depositional stage, the climate was dry and cold, the bottom water was in a stable anoxic condition accompanied by rising sea level, and the seawater had moderate-high paleoproductivity. In the RST1 stage, extensive sea-level fall occurred, and the water was anoxic, with decreased productivity and weakened organic matter accumulation. In the TST2 stage, the sea level rise rapidly, extensive anoxicity and high productivity of the water produced the most ideal environment for organic matter enrichment and the highest TOC. In the RST2 stage, sea level slowly fell, the water column gradually became a stable oxidized environment, productivity was low, the terrestrial detrital influx increased and tended to stabilize, and the climate gradually changed to warm and humid conditions, forming relatively organic-poor shale. The upwelling mainly developed during the period of TST1 to TST2, and ceased in the RST2. The correlation analysis between TOC and the above indicators and the Co × Mn versus Cd/Mo diagram show that TOC is chiefly controlled by paleoredox, paleoproductivity, climatic conditions, and terrestrial detrital influx, indicating that preservation conditions are the crucial factor. Sea-level change played a key role in preservation conditions. In the transgression stages, sea-level rise led to the enhancement of reducing water, which controlled the organic matter enrichment in shale.

Contains fulltext : 166243.pdf (Publisher’s version ) (Closed access) Fe7Se8 exists as a hexagonal NiAs-like crystal structure with a large number of ordered intrinsic vacancies. It is an ideal candidate for studying the effect of defects on properties such as magnetism and electrical transport. In this work, highly crystalline Fe7Se8 with the 3c crystal structure was synthesized by a solid-state reaction. Sharp changes in the magnetization at 100 K confirm a rotation of the spins from the ab plane to the c axis with decreasing temperature. We observe an interesting metal–insulator transition at the same temperature as the spin-direction changes. We propose that locked spins in the grain boundaries induce electron localization and result in the metal–insulator transition. Electron localization is confirmed by X-ray photoelectron spectroscopy of the Fe 2p peaks, which exhibit two characteristic satellite peaks. This mechanism is also verified by comparing it with the properties of the 4c-Fe7Se8 crystal structure.

The gas reservoir of the Lower Cambrian Longwangmiao Fm in the Sichuan Basin is a supergiant integral marine carbonate gas reservoir whose single scale is currently the largest in China. In order to figure out its sedimentary model and reservoir genesis, its geological structures and sedimentary settings and facies were analyzed comprehensively and the lithofacies paleographic map was plotted. It is revealed that the following sedimentary facies are successively developed in the Longwangmiao Fm from West Sichuan to Southeast Chongqing: diamictic tidal flat at the back ramp, grain bank (the upper bank) at the inner/shallow ramp – interbank sea (depression), deeper open bay at the platform depression of inner ramp → evaporative lagoon → evaporative tidal flat, tempestite at the middle ramp – barrier beach – mud mound beach (the lower bank), and outer ramp – basin. Accordingly, the specific sedimentary model of dual grain banks in the Longwangmiao Fm carbonate ramp was established as follows. Firstly, in this model, dual grain banks are symmetrically developed with Wanzhou–Yibin platform depression as the axis, on whose dual sides the paleohighs have shallow water bodies with strong energy. Compared with the classical model, the new one has a new upper bank which is developed around the paleohighs covering an area of about 8 × 10 4 km 2 . Secondly, the upper bank is large for its paleogeomorphology being located at the highest position with the strongest water energy during deposition. Therefore, it is prone to dolomitization and meteoric dissolution respectively during contemporaneous–penecontemporaneous hot-dry and hot-humid periods, and especially the Caledonian–Early Hercynian denudation wedge out tends to undergo post-supergene multiphase karstification. Therefore, quality reservoirs are more developed on scale. Thirdly, the intergranular pores and vermes moldic pores were dissolved and enlarged due to the multiphase atmospheric fresh water leaching, and together with tectonism, grain bank facies controlled multicyclic laminated–quasi-laminated, fracture-pore and cellular vuggy karst reservoirs were formed.

Based on the field outcrops, drilling and seismic data of northwestern Sichuan Basin, this paper systematically discusses tectonic evolution characteristics from the Late Sinian to the Early Paleozoic, analyzes the petroleum geological significance, and points out the recent favorable exploration directions in this area. The area experienced mainly three times of tectonic evolution during the Late Sinian to the Early Paleozoic: (1) During the Late Sinian to the early period of Early Cambrian, this area was affected by tension action and formed two sets of nearly north-south trending continental rifts, and two sets of platform margins in the Sinian Dengying Formation. (2) During the middle period of the Early Cambrian to the Middle Ordovician, this area was eroded strongly (stronger in the northwest than in the southeast) because of multi-period uplifting of the northwestern Bikou paleo-land. (3) During the Late Ordovician to the Late Silurian, this area was eroded strongly again because of the compression of the Kwangsian Orogeny, and the erosion was stronger in the southwest than in the northeast. During the Late Sinian to the Early Cambrian, the formation of continental rifts controlled the development of bioherm beach facies reservoirs on the platform margins in the Dengying Formation and the high quality source rock in the Lower Cambrian series. During the middle of the Early Cambrian, the uplifting of the Bikou paleo-land controlled the distribution of the Kongmingdong Formation oolitic beach facies reservoirs around the paleo-land. It is suggested that, vertically, the fourth Member of the Dengying Formation and the Kongmingdong Formation be the main exploration targets, and, horizontally, the Jiulongshan structural trap be the most beneficial exploration belts recently due to its matching with petroleum migration and accumulation. Key words: Sichuan Basin, Late Sinian – Early Paleozoic, tectonic evolution, natural gas exploration, intracontinental rift, Bikou paleo-land, Dengying Formation, Kongmingdong Formation, Jiulongshan structure

The Mesoproterozoic Eon [1,600-1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were 4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.

Bacteria are the oldest life on the Earth. Some of them, such as cyanobacteria, can produce oxygen and organic matter through photosynthesis. However, the hydrocarbon generation ability of these bacterial biomass is still unclear. Here we reported the molecular evidence from the wrapped bitumen in well-preserved silicified concretions from the Xiamaling Formation, North China. The absence of steranes indicated negligible contribution of eukaryotic algae to the bitumen. Abundant hopanes, 13α(n-alkyl)-tricyclic terpanes and other biomarkers of bacteria prove that bacterial biogenic organic matter can generate hydrocarbons on a large scale. Combined with our previous microfossils and elements studies, these bitumen were considered to be from the Xiamaling shales, for the intrusion of Yanliao large igneous provinces into the organic-rich Xiamaling shales at ca. 1320 million years ago.

Botryoidal dolostones are abundant in the Second Member of the Upper Ediacaran Dengying Formation in the Western Yangtze Platform. Although they have been extensively discussed as important host rocks for giant gas reservoirs, there is no consensus on the microbial impact on mineralization processes in the botryoidal laminations. Typical botryoidal laminations were studied under optical microscopes and scanning electron microscopes (SEMs) to investigate their origin. There are three macroscopic morphological types of botryoidal lamination: stromatoid lamination, cavity-lining lamination, and spherical-encrusting lamination. These three types of lamination are composed of fibrous and bladed crystals growing perpendicular to the botryoidal laminae, which have hitherto been implicitly considered to be from abiogenic chemical precipitation. There are many lines of new evidence that demonstrate microbial activities in the interbedded dark and bright laminae constituting the laminations. In the dark laminae, euhedral dolomite rhombs are observed sticking to linear and tubular filaments, or wrapped in sheets of extracellular polymeric substances (EPS) with dolomite crystal sizes of generally

We use first-principles calculations to predict the occurrence of half-metallicity and anionogenic ferromagnetism at the heterointerface between two 2p insulators, taking the ${\mathrm{KO}}_{2}/{\mathrm{BaO}}_{2}$ (001) interface as an example. Whereas a sharp heterointerface is semiconducting, a heterointerface with a moderate concentration of swapped K and Ba atoms is half-metallic and ferromagnetic at ambient pressure due to the double exchange mechanism. The K-Ba swap renders the interfacial K-O and Ba-O atomic layers electron-doped and hole-doped, respectively. Our findings pave the way to realize metallicity and ferromagnetism at the interface between two $2p$ insulators, and such systems can constitute a new family of heterostructures with novel properties, expanding studies on heterointerfaces from $3d$ insulators to $2p$ insulators.

The aim of this study was to determine the concentration of Legionella pneumophila in the surface dust of the air ducts of central air conditioning systems and evaluate its effects on indoor air quality. Thirty dust samples were collected from thirty air ducts and analyzed using real-time TaqMan PCR targeting the mip gene. The concentration of surface dust, PM10 mass concentration of air, total plate count of surface dust, and total plate count of supply air were also investigated. Legionella pneumophila microorganisms were detected in 20 of the 30 samples (66.7%) with a mean copy number of 6212 copies/g surface dust. The Spearman’s rank correlation coefficient between Legionella pneumophila concentration and total plate count in surface dust of the air duct was 0.834 (P=0.000). The pollutants in the air ducts in central air conditioning systems were found to affect indoor air quality.

Karst reservoir paleofluid types of the Ordovician formation in the Tarim Basin are restored based on the analysis of element boron of filled mud, the test of fluid inclusions homogenization temperature and salinity, liquid anion and hydroxyl isotope of filled calcite in vug-fractures, and regional geologic background. The origin of the karst reservoirs are analyzed on this basis. The element boron contents of mud filled in vug-fractures are less than 80 μg/g generally; fluid inclusions have different homogenization temperatures in different regions, and the salinities are in a large range. The HCO3− contents are high, and the Cl− and SO42− contents are dispersive in the liquid component of the fluid inclusions. The hydroxyl isotope contents are relatively dispersive, with relatively negative δD value and positive δ18O value. This evidence shows that the paleofluid of the Ordovician was from supergene atmospheric freshwater, buried fresh-brackish mixed water, seawater or concentrated seawater, and buried brine from underlying dolomite or evaporate rock of the Cambrian formation. The main constructive diagenesis for the formation of vug-cave type reservoirs is erosion and dissolution caused by atmospheric freshwater, and the reservoirs have been subjected to thermal fluid reformation from underlying evaporate rock of the Cambrian during burial stage. Key words: Tarim Basin, karst reservoir, paleofluid restoration, reservoir forming mechanism, element boron, fluid inclusions homogenization temperature, fluid inclusions salinity, hydrogen and oxygen isotopic composition

Oil and gas discoveries within Proterozoic-Cambrian strata and the majority of shale gas production occurs in relatively stable tectonic regions and characterised by moderate thermal maturity (R o ° o °>°2.5%). The system comprises two components, namely a conventional Sinian–Cambrian dolomite-hosted gas resource and an unconventional Cambrian-Silurian shale gas deposit, both represent trillion cubic meter accumulations. The migration-accumulation type Sinian–Cambrian gas system, is a result of numerous processes, including (1) paleo-high trapping within a relatively stable tectonic setting, (2) appropriate source materials located in a paleo-rift trough, (3) large-scale dolomite grainstone reservoirs located near the paleo-high, (4) adequate gas produced from in-situ crude oil cracking, and, (5) gypsum-salt and shale cap rock preservation. The self-contained source-reservoir Cambrian–Silurian shale gas system, is localized by deepwater organic-rich shelf facies, characterized by high silicon and calcium contents. The recent discovery of these two massive gas fields in old and over-matured sedimentary strata, has effectively extended the upper maturity limit of R o over 3.0%, which may indicate the efficacy of broadening current natural gas exploration areas, thus potentially increasing global natural gas resources significantly. Furthermore, the discovery may spark interest in natural gas exploration in widely distributed old strata, thus encouraging co-development of conventional and unconventional petroleum accumulations.

Since 2008, Mainland China has undergone widespread outbreaks of hand, foot, and mouth disease (HFMD). In order to determine the characteristics of epidemics and enteroviruses (EV) associated with HFMD in Tianjin, in northern China, epidemiological and virological data from routine surveillance were collected and analyzed. In Tianjin, a persistent epidemic of HFMD was demonstrated during 2008-2013, involving 102,705 mild, 179 severe, and 16 fatal cases. Overall, 8234 specimens were collected from 7829 HFMD patients for EV detection during 2008-2013. Enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) were the dominant serotypes during 2008-2012, and they were replaced by CV-A6 as the major causative agent in 2013. Phylogenetic analysis based on complete VP1 nucleotide sequences revealed that multiple CV-A6 lineages co-circulated in Tianjin, which grouped together with strains from China and other countries and split into two distinct clusters (clusters 1 and 2). Most Tianjin strains grouped in cluster 1 and were closely related to strains from several eastern and southern provinces of China during 2012 and 2013. Estimates from Bayesian MCMC analysis suggested that multiple lineages had been transmitted silently before the outbreaks at an estimated evolutionary rate of 4.10 × 10(-3) substitutions per site per year without a specific distribution of rate variances among lineages. The sudden outbreak of CV-A6 in Tianjin during 2013 is attributed to indigenous CV-A6 lineages, which were linked to the wide spread of endemic strains around eastern and southern China.

The Anyue Sinian–Cambrian giant gas field was discovered in central paleo-uplift in the Sichuan Basin in 2013, which is a structural-lithological gas reservoir, with 779.9 km2 proven gas-bearing area and 4 403.8×108 m3 proven geological reserves in the Cambrian Longwangmiao Formation in Moxi Block, and the discovery implies it possesses trillion-cubic-meter reserves in the Sinian. Cambrian Formations in Sichuan Basin. The main understandings achieved are as follows: (1) Sinian–Cambrian sedimentary filling sequences and division evidence are redetermined; (2) During Late Sinian and Early Cambrian, “Deyang–Anyue” paleo-taphrogenic trough was successively developed and controlled the distribution of source rocks in the Lower-Cambrian, characterized by 20–160 m source rock thickness, TOC 1.7%–3.6% and Ro 2.0%–3.5%; (3) Carbonate edge platform occurred in the Sinian Dengying Formation, and carbonate gentle slope platform occurred in the Longwangmiao Formation, with large-scale grain beach near the synsedimentary paleo- uplift; (4) Two types of gas-bearing reservoir, i.e. carbonate fracture-vug type in the Sinian Dengying Formation and dolomite pore type in the Cambrian Longwangmiao Formation, and superposition transformation of penecontemporaneous dolomitization and supergene karst formed high porosity-permeability reservoirs, with 3%–4% porosity and (1–6)×10−3 μm2 permeability in the Sinian Dengying Formation, and 4%–5% porosity and (1–5)×10−3 μm2 permeability in the Cambrian Longwangmiao Formation; (5) Large paleo-oil pool occurred in the core of the paleo-uplift during late Hercynian—Indosinian, with over 5 000 km2 and (48–63)×108 t oil resources, and then in the Yanshanian period, in-situ crude oil cracked to generate gas and dispersive liquid hydrocarbons in deep slope cracked to generate gas, both of which provide sufficient gas for the giant gas field; (6) The formation and retention of the giant gas field is mainly controlled by paleo-taphrogenic trough, paleo-platform, paleo-oil pool cracking gas and paleo-uplift jointly; (7) Total gas resources of the Sinian–Cambrian giant gas field are preliminarily predicted to be about 5×1012 m3, and the paleo-uplift and its slope, southern Sichuan Basin depression and deep formations of the high and steep structure belt in east Sichuan, are key exploration plays. The discovery of deep Anyue Sinian–Cambrian giant primay oil-cracking gas field in the Sichuan Basin, is the first in global ancient strata exploration, which is of great inspiration for extension of oil & gas discoveries for global middle-deep formations from Lower Paleozoic to Middle–Upper Proterozoic strata. Key words: Sichuan Basin, Anyue gas field, Fuling shale gas field, paleo-taphrogenic trough, paleo-oil pool, paleo-uplift, carbonate platform, unconventional oil and gas, shale gas, Weiyuan shale gas field