Sedimentary characteristics and lithofacies paleogeography of the Cambrian in Sichuan basin,Southwest China

Cambrian in Sichuan basin developed thick black shale,varies carbonate and clastic rock,which deposited in different sedimentary environment.Sichuan basin in the upper Yangtze platform contained a record of environment during the Cambrian.Detail facies analyses of Cambrian enable us to discuss the sedimentary environment and palaeogeographic setting.Sedimentation commenced in the Early Cambrian with the deposition of shelf facies(Qiongzhusi Formation and Canglangpu Formation).At this stage,thick shale and clastic rock deposited in Sichuan basin.At the end of the Early Cambrian,a carbonate platform developed in upper Yangtze platform,and Sichuan basin was located in restricted platform(Longwangmiao Formation).In the Middle Cambrian,tidal flat and restricted platform developed in Sichuan basin(Douposi Formation),because of continuous regression.During the Late Cambrian,Sichuan basin was located in carbonate platform again(Xixiangchi Formation).There are three types of sedimentary system in the Cambrian of Sichuan basin:clastic sedimentary system,clastics-carbonate mixed sedimentary system and carbonate sedimentary system.Vertically,the basin shows the evolutionary character of clastic-carbonate sedimentary systems.The three sedimentary systems correspond to three“transgression-regression”cycles of the Cambrian.The transgression in the initial period of the Early Cambrian led to the formation of clastic sedimentary system in the Qiongzhusi Formation of Lower Cambrian.The transgression in the later period of the Early Cambrian led to the formation of clasticcarbonate mixed sedimentary system in the Middle-Lower Cambrian.The transgression in the initial period of the Late Cambrian led to the formation of carbonate sedimentary system in the Xixiangchi Formation of Upper Cambrian.With the end of Late Sinian continental rifting ended,Sichuan basin entered a stable evolutionary stage of the craton basin,while the paleo-land developed in the north and southwest.In Qiongzhusi-Canglangpu period,the basin developed onshore-shelf sedimentary facies from west to east;In Longwangmiao-Xixiangchi period,the basin developed tidal flat-platform-slope sedimentary facies from west to east.

Dolomitization by Penesaline Sea Water in Early Cambrian Longwangmiao Formation, Central Sichuan Basin, China

The Lower Cambrian Longwangmiao Formation shoal dolostone reservoir in Sichuan Basin is currently an exploration and research highlight in China. Reservoir rocks mainly consist of crystalline dolomite with residual grain texture, and dolarenite of which the arene is mainly composed of muddy to micritic dolomite with some crystalline grain directionally aligned. The trace element indicates that the dolomites of Longwangmiao Formation may be related to the high salinity of sea water. The oxygen isotope values of crystalline dolomite and dolarenite are both similar to that of the Early Cambrian marine dolomites, and the carbon isotope values of every kind of dolomites are completely overlapped with that of the seawater in Early Cambrian, indicating the dolomitization fluid is originated from the Early Cambrian sea water. The restricted marine biological communities and a small amount of gypsum pseudonodule seen in muddy to micritic dolomite indicate that the sea water in Early Cambrian was restricted and evaporated. However, the general lack of massive evaporite mineral and gypsum karst breccia indicates that the salinity of sea water during dolomitization was lower than the value of gypsum＇s precipitation. The Longwangmiao Formation consists of several high-frequency sedimentary cycles, indicating frequent sea level changes. This study indicates that massive dolomitization may also occur in underwater palaeohigh in carbonate platform through the reflux of penesaline sea water driven by a combination of high-and low-frequency sea-level changes. This kind of dolomitization can explain the generation of massive dolomites in the absence of evaporite precipitation, and further indicates that replacement dolomites can be produced by sea water with a wide range of salinity（normal, penesaline to hypersaline）.

Evaluation of dolomite reservoirs in the Longwangmiao Formation,Lower Cambrian in Northern Sichuan basin,China

With the extended petroleum exploration of the carbonate reservoir in the Longwangmiao Formation,Lower Cambrian in Sichuan basin,looking for a new favorable exploration area is the primary task in current exploration.This paper focusing on the dolomite reservoir in the Longwangmiao Formation in the Northern Sichuan basin,will evaluate the reservoir conditions,including reservoir lithology,reservoir spaces,physical properties and other basic characteristics.Combined with sedimentary environment study and diagenesis analysis,the genetic mechanism of Longwangmiao reservoir in study area will be discussed.It indicates that the reservoir rocks of Longwangmiao Formation in the study area are composed of dolarenite and crystalline dolomite,and the main reservoir spaces are intergranular dissolved pores,intragranular dissolved pores and intercrystalline dissolved pores.However,most of dissolved pores have been filled with bitumen,which lead to the reservoir properties very poor,both the porosity and permeability are worse than that of central Sichuan basin,so the reservoir in the Longwangmiao Formation in the Northern Sichuan basin is low-porosity and low-permeability reservoir.During the Early Cambrian Longwangmiao period,the study was near the old-land,and the energy of sea water was not enough to deposit many grain shoals,which cause the sediments are small with lots of quartz and muds.Moreover,because lacking of large scale karstification in the late diagenesis,there isn't much dissolved pores and vugs develop in the Longwangmiao Formation.Some Intergranular dissolved pores and intercrystalline dissolved pores formed by the early atmosphere water dissolved exist as some reservoir spaces,but most of them have been filled with bitumen,which was residual when the ancient oil reservoir transformed.Above factors cause the Longwangmiao Formation in the Northern Sichuan basin become not a very favorable reservoir in Sichuan basin.

Spin-phonon coupling in two-dimensional magnetic materials

Recently,two-dimensional magnetic materials(2DMMs)have become a focused research direction in a broad range of two-dimensional materials,due to their underlying significance in fundamental research,as well as in technologically relevant applications for future spintronics,magnonics,quantum information and data storage.The rich toolbox of 2DMMs and their diverse tunability have enabled the unprecedented research concerning the two-dimensional magnetic order down to single atomic layer of materials,much beyond the classical thin film magnetism,showing an extremely promising avenue towards electronics,magneto-optics and photonics.Among various degrees of freedoms,the interaction between spin and phonon(i.e.,quanta of lattice vibration),hence the so-called spin-phonon coupling,serves as an important tuning knob to explore the two-dimensional magnetism,creates new types of quasiparticles and controls the magnetic order.This review overviews the latest developments in spin-phonon coupling investigations in 2DMMs.Various techniques utilizing spinphonon coupling to investigate two-dimensional magnetism are discussed.Recent progress in tuning two-dimensional magnetic order based on spin-phonon coupling is also summarized,with a focus to understand the new functionalities.Furthermore,device developments and concepts based on spin-phonon coupling are briefly discussed.This review will provide our perspectives on the existing challenges and future directions in spin-phonon coupling research in 2DMMs and their functional devices.

Sedimentary Facies of Marine Shale Gas Formations in Southern China： The Lower Silurian Longmaxi Formation in the Southern Sichuan Basin

Sedimentary facies is an important factor influencing shale gas accumulation. It not only controlls hydrocarbon generation, but also affects reservoir characteristics and distribution. This paper discusses the Lower Silurian Longmaxi Formation in the south of the Sichuan Basin. Outcrop, core, drilling and logging data identify the sedimentary facies of the formation as continental shelf facies, which is divided into two subfacies： an inner shelf and an outer shelf subfacies. These two subfacies can be further divided into seven microfacies： muddy silty shallow shelf, calcareous silty shallow shelf, muddy limy shallow shelf, storm flow, muddy deep shelf, silty muddy deep shelf and contour current microfacies. Vertical and horizontal distribution of microfacies establishes a sedimentation model of the continental shelf facies. Combined with analization or calculation of geochemical, mineralogical, physical and gas-bearing properties of samples, sedimentary microfacies is evaluated using nine parameters： total organic carbon content, effective shale continuous thickness, vitrinite reflectance, kerogen type, mineral components, porosity, permeability, water saturation and gas content. The evaluation revealed that the most favorable facies for shale gas exploration and development are the muddy deep shelf and part of the silty muddy deep shelf microfacies, with TOC more than 2%, siliceous component over 50%, clay less than 30%, porosity more than 3%, water saturation lower than 40%, gas content greater than 2 m3/t. These results provide a theoretical basis for deciston-making on the most promising areas for shale gas exploration in the Sichuan Basin and for marine shale gas exploration and development in South China.

Deciphering the upper ordovician Wufeng siliceous shale depositional environments(Wuxi,NE Chongqing)based on multi-proxy record

Based on stratigraphic variations of petrology,geochemistry(major,trace elements),and pyrite framboids,we study the sedimentary environment of siliceous rocks of the Wufeng Formation in Wuxi,Northeastern Chongqing,China.Coupled Al2O3/(Al2O3þFe2O3),SiO2/Al2O3,with AleFeeMn values indicate that Wufeng Formation are deposited in a continental margin and influenced by detrital input.UEF-MoEF and V/CreU/Th cross-plots suggest that the siliceous shale was formed in dysoxic to anoxic conditions.Redox proxies imply that the lower,the middle to upper,and the top part of the Wufeng sediments were deposited in an anoxic,dysoxic and oxic environment,respectively.Accordingly,the average size of pyrite framboids are gradually increased from bottom to top,showing that increased oxidisability.A complete vibratory third-order cycle of sea level fluctuations during the Wufeng deposition can be identified.During Wufeng to Longmaxi transition,the sedimentary environment exhibits a short-scale oscillatory pattern and was probably transformed from an outer shelf to inner shelf.Coupled multi-proxies are considered more reliable proxies for deciphering redox conditions in fine-grained sediment.

Tunable excitonic emission of monolayer WS2 for the optical detection of DNA nucleobases

Two-dimensional transition metal dichalcogenides （2D TMDs） possess a tunable excitonic light emission that is sensitive to external conditions such as electric field, strain, and chemical doping. In this work, we reveal the interactions between DNA nucleobases, i.e., adenine （A）, guanine （G）, cytosine （C）, and thymine （T） and monolayer WS2 by investigating the changes in the photoluminescence （PL） emissions of the monolayer WS2 after coating with nucleobase solutions. We found that adenine and guanine exert a clear effect on the PL profile of the monolayer WS2 and cause different PL evolution trends. In contrast, cytosine and thymine have little effect on the PL behavior. To obtain information on the interactions between the DNA bases and WS2, a series of measurements were conducted on adenine-coated WS2 monolayers, as a demonstration. The p-type doping of the WS2 monolayers on the introduction of adenine is clearly shown by both the evolution of the PL spectra and the electrical transport response. Our findings open the door for the development of label-free optical sensing approaches in which the detection signals arise from the tunable excitonic emission of the TMD itself rather than the fluorescence signals of label molecules. This dopant-selective optical response to the DNA nucleobases fills the gaps in previously reported optical biosensing methods and indicates a potential new strategy for DNA sequencing.

Constrains of eruption environment and hydrothermal fluid on the Permian pyroclastic reservoirs in the Sichuan Basin,SW China

A breakthrough has been recently made in the hydrocarbon exploration of the Permian pyroclastic rocks in the Jianyang Area,western Sichuan Basin,China.With an aim to decipher the impacts of the eruption environment,the temperature of hydrothermal fluids,and the paleo-salinity on the formation of authigenic mineral assemblage and pores,this study implements comprehensive petrographic and geochemical studies through the integrated core and thin section analyses.The data presented demonstrate that the Permian volcanic intervals are intensively affected by an event of Emei taphrogeny.During basaltic magma upward migration,fractional crystallization of anorthose results in slightlyalkaline magma.The specific pyroclastic rocks are formed by the eruption of slightly-alkaline magma in the sea or a salt lake and subsequent hydrothermal alteration.During deposition and diagenesis,the authigenic mineral association is constrained jointly by the sodium-rich and high salinity water environment,and mid-high temperature,high-salinity hydrothermal fluid.Specifically,the sodium-rich hydrothermal fluid,which may sustain till the late diagenesis stage,caused pervasive albitization of pyroclastic rocks,then leading to mineral transformation and formation of a series of mineral associations.Therefore,zeolitization of volcanic glass and vesicle-infillings of zeolite is an essential condition for later mineral transformation and dissolution.Albitization of analcite,recrystallization induced by deep hydrothermal fluids,and both meteoric and deep burial dissolution expanding the micro-pore space ultimately formed porous pyroclastic reservoirs.

Digital twin-driven complexity management in intelligent manufacturing[version 1;peer review:2 approved]

Complexity management is one of the most crucial and challenging issues in manufacturing.As an emerging technology,digital twin provides an innovative approach to manage complexity in a more autonomous,analytical and comprehensive manner.This paper proposes an innovative framework of digital twin-driven complexity management in intelligent manufacturing.The framework will cover three sources of manufacturing complexity,including product design,production lines and supply chains.Digital twin provides three services to manage complexity:(1)real-time monitors and data collections;(2)identifications,diagnoses and predictions of manufacturing complexity;(3)fortification of human-machine interaction.A case study of airplane manufacturing is presented to illustrate the proposed framework.

Pore-fillings of dolomite reservoirs in Sinian Dengying Formation in Sichuan basin

The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin.Its reservoirs were well developed.And many kinds of fillings which lead to the decrease of pores can be seen in reservoir pores and caves.In this paper,the pore fillings of the Dengying Formation reservoir in Sichuan basin are the object of study.The types and characteristics of the fillings are studied in detail by means of rock slices analysis,cathode luminescence,trace elements and inclusion temperature measurement.The study shows that the fillings include dolomite fillings and siliceous quartz fillings and bitumen fillings.Among them,dolomite fillings can be divided into botryoidal dolomite fillings,foliated dolomite fillings,finely-medium crystalline dolomite fillings and coarse crystalline dolomite fillings.50%–80%of the pores are filled by the dolomite fillings with botryoidal structure,and the pores can be partially full filled;0%–20%of pores are filled by foliated dolomite fillings;20–80%of the pores are filled by finely-medium dolomite fillings;20–80%of the pores are filled by coarse crystalline dolomite fillings.1%–5%of secondary pores are often filled by siliceous quartzs,and the pores can be partially full filled.Bitumen fillings often occur after the above-mentioned fillings,and the residual pores are often semi-filled by bitumens,which makes the original pores and throat smaller and reduces the effective porosity and permeability of the reservoir.So,it is a destructive diagenesis.The pore fillings make the secondary porosity in the reservoir significantly lower,which is not conducive to the formation and preservation of the Dengying Formation reservoir.