Characteristics and control factors of feldspar dissolution in gravity flow sandstone of Chang 7 Member,Triassic Yanchang Formation,Ordos Basin,NW China

To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.

Microfacies and diagenetic alteration in a semi-deep to deep lacustrine shale: The Yanchang Formation in the Ordos Basin, China

The mineralogical development and diagenetic sequence of lacustrine shales in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are detailed studied.A model of their depositional system and a diagenetic diagram are proposed in this study.Through detailed petrographic,mineralogical,and elemental analyses,four distinct shale types are identified:argillaceous shale,siliceous shale,calcareous shale,and carbonate,clay,and silt-bearing shale.The main diagenetic process in argillaceous shale is the transformation of illite to smectite,negatively impacting shale porosity.Siliceous shale undergoes carbonate cementation and quartz dissolution,contributing to increased porosity,particularly in mesopores.Calcareous shale experiences diagenesis characterised by carbonate formation and dissolution,with a prevalence of siderite.In carbonate,clay,and silt-bearing shale,the dissolution of K-feldspar contributes to illitization of kaolinite.Argillaceous shale,characterised by more clay minerals and lower mesopore volume,is identified as a potential hydrocarbon seal.Siliceous shale,with the highest pore volume and abundant inter-mineral pores,emerges as a promising shale oil reservoir.These findings contribute to a comprehensive understanding of shale properties,aiding in the prediction of shale oil exploration potential in the studied area.

Enrichment and exploration of deep lacustrine shale oil in the first member of Cretaceous Qingshankou Formation, southern Songliao Basin, NE China

Pure shales in the first member of Qingshankou Formation(simplified as Qing 1 Member)in the southern Songliao Basin,i.e.,the semi-deep and deep lacustrine shales,are characterized by a high content of clay minerals and poor hydrocarbon mobility,making the development of shale oil difficult.According to the drilling and testing results,the shale of Qing 1 Member can be classified into 3 lithofacies,i.e.,bedded argillaceous shale,laminated diamictite shale,and interbedded felsic shale.The TOC and brittle minerals control the enrichment of shale oil,of them,TOC controls the total oil content,in other words,the total oil content increases with the increase of TOC;while the laminae made up of brittle minerals contain a large number of bigger intergranular pores which are favorable enrichment space for movable shale oil.In consideration of the origins of the 3 lithofacies,two shale oil enrichment models are classified,i.e.,the deep lacustrine high-TOC bedded argillaceous shale(Model-I)and the semi-deep lacustrine moderate-high-TOC laminated diamictite shale(Model-II).In the Model-I,the shale is characterized by high hydrocarbon generation ability,high total oil content,abundant horizontal bedding fractures,and vertical and high angle fractures locally;the complex fracture network formed by horizontal bedding fractures and vertical fractures improve the storage capacity and permeability of the shale reservoir,increase the enrichment space for movable oil.In the Model-II,the shale is characterized by good hydrocarbon generation ability and fairly high total oil content,and as the brittle laminae contain large intergranular pores,the shale has a higher movable oil content.Based on the two models,shale oil sweet-spot areas of 2880 km2 in the southern Songliao Basin are favorable for further exploration.Aimed at the difficulties in reservoir fracturing of the lacustrine shale with a high content of clay minerals,the composite fracturing technology with supercritical carbon dioxide was used in the shale oil reservoir for the first time,realizing large-scale volume fracturing in shale with a high content of clay minerals and strong heterogeneity,marking a breakthrough of oil exploration in continental shale with a high content of clay minerals in China.

Reconstruction of paleo river systems and distribution of sedimentary facies of Shanxi and lower Shihezi formations in southern Ordos basin

The study area is located in the south of Huanxian county,in Yan'an and Puxian counties and to the north of Xi'an.The Shanxi and lower Shihezi formations are important gas-bearing formations.Given our analysis of the direction of rivers,the contents of stable heavy minerals and of feldspar of palaeo river systems,the study area is divided into six palaeodrainage patterns corresponding to six feldspar regions and six sedimentary facies regions.On this basis,the distribution of sedimentary facies was also analyzed.During the Shanxi stage,a delta front was deposited in the Huanxian region and delta plains and fronts were deposited in the Pingliang,Chunhua-Yaoxian and Hancheng-Chengcheng regions.In the Yan'an-Daning region,only a delta front was developed.The distribution of sedimentary facies in the earlier Shihezi stage originated from the Shanxi stage.A delta front was developed in the Huanxian region while a delta plain and front developed in the Pingliang-Zhenyuan region during the same time.Lakes originated only in the Zhenyuan-Huanxian-Huachi-Zhengning and Daning-Jixian zones.This analytical method shows that different palaeodrainage patterns can be effectively distinguished in order to forecast sedimentary facies.

Favorable lithofacies types and genesis of marine- continental transitional black shale: A case study of Permian Shanxi Formation in the eastern margin of Ordos Basin, NW China

Based on core description,thin section identification,X-ray diffraction analysis,scanning electron microscopy,low-temperature gas adsorption and high-pressure mercury intrusion porosimetry,the shale lithofacies of Shan23 sub-member of Permian Shanxi Formation in the east margin of Ordos Basin was systematically analyzed in this study.The Shan23 sub-member has six lithofacies,namely,low TOC clay shale(C-L),low TOC siliceous shale(S-L),medium TOC siliceous shale(S-M),medium TOC hybrid shale(M-M),high TOC siliceous shale(S-H),and high TOC clay shale(C-H).Among them,S-H is the best lithofacies,S-M and M-M are the second best.The C-L and C-H lithofacies,mainly found in the upper part of Shan23 sub-member,generally developed in tide-dominated delta facies;the S-L,S-M,S-H and M-M shales occurring in the lower part of Shan23 sub-member developed in tide-dominated estuarine bay facies.The S-H,S-M and M-M shales have good pore struc-ture and largely organic matter pores and mineral interparticle pores,including interlayer pore in clay minerals,pyrite inter-crystalline pore,and mineral dissolution pore.C-L and S-L shales have mainly mineral interparticle pores and clay mineral in-terlayer pores,and a small amount of organic matter pores,showing poorer pore structure.The C-H shale has organic mi-cro-pores and a small number of interlayer fissures of clay minerals,showing good micro-pore structure,and poor meso-pore and macro-pore structure.The formation of favorable lithofacies is jointly controlled by depositional environment and diagen-esis.Shallow bay-lagoon depositional environment is conducive to the formation of type II2 kerogen which can produce a large number of organic cellular pores.Besides,the rich biogenic silica is conducive to the preservation of primary pores and en-hances the fracability of the shale reservoir.

Reconsideration of the sediment characteristics of the second member of the Triassic Xujiahe Formation in Sanhuiba,Huaying Mountain

The second member of the Triassic Xujiahe Formation in the Sanhuiba area in Huaying Mountain is an important section of sedimentary delta facies in the Chongqing Tianfu Geological Survey and Training Base. In spite of some initial efforts on its lithology and lithofacies, the existing research is yet to be completed and suffers from contradictory conclusions and inadequate evidence. Starting from the sedimentary microfaeies types and cyclic features, we analyzed the vertical sequence of a sedimentary delta model and discovered that this section is a constructional delta deposit. Eight incomplete and asymmetric regressive cycles are marked off, given that frequent erosion surfaces appeared in the section. Based on the analysis of structural characteristics of every monocycle, we summarized the system of cycles, tracts and sequence characteristics of the overall section. In view of this systematic series of cycles, we discussed the features of the syndepositional tectonic movements in the area and conclude that, due to frequent erosion, migration and diversion of a sub-channel branch was brought about by oscillating movements of the crust. In a comparison with neighboring sections, we explored the cause of erosion and the relations between erosion and cycles. This study greatly strengthens existing research and theories, makes an important and comprehensive contribution to geological surveys and training in the area and provides essential suggestions for coal exploration, oil and gas evaluation and in general to exploration and development in the target stratum.

Oderly accumulation theory of shale system petroleum resource and its prospecting significance-A case study of Chang 7 Member of Yanchang Formation in Ordos Basin

1 Introduction Shale formations bear abundant mineral resource and*unconventional petroleum resource,and the unconventional petroleum resource that contain in the shale formation should be integrated and researched.

Hydrocarbon accumulation and exploration prospect of mound-shoal complexes on the platform margin of the fourth member of Sinian Dengying Formation in the east of Mianzhu-Changning intracratonic rift, Sichuan Basin, SW China

Drilling,seismic and logging data were used to evaluate the hydrocarbon accumulation conditions of the mound-shoal complexes in the platform margin of the fourth member of Sinian Dengying Formation in the east side of the Mianzhu-Changning intracratonic rift in the Sichuan Basin.The four understandings are:(1)The platform margin belt of the Deng 4 Member can be divided into three sections,northern,middle and southern;the middle section is at the core of the Gaoshiti-Moxi paleouplift and the structural high now,while the southern and northern sections are at the slope of the paleouplift and the structural lows now;the three sections have similar development characteristics and reservoir features of platform margin mound-shoal complex.(2)In the margin of the east side of the rift,there are several faults nearly perpendicular to the platform margin belt,the faults divide the platform margin belt into rugged paleo-landform,and the high part developed platform margin mound-shoal complexes and the reservoirs are good in physical properties,while the low part developed inter-beach depression and no mound-shoal complexes,where the reservoirs are poor in physical properties.(3)The six groups of faults nearly perpendicular to the platform margin belt divide the platform margin belt into seven large mound-shoal complexes which have similar hydrocarbon accumulation conditions and accumulation evolution process and are rich in petroleum.(4)The inter shoal depressions between the mound-shoal complexes are characterized by tighter lithology,which can block the updip direction of the mounds and shoals at the lower part of the slope of the paleouplift and are favorable for the later preservation of mound-shoal gas reservoirs.This has been proved by Well Jiaotan 1 and Heshen 2 drilled successfully.The mound-shoal complexes on the platform margin of the structural slope area have a good exploration prospect.

Sequence stratigraphic framework and sedimentary model of Shanxi Formation in northeast Zhoukou Depression of the North China Plate

The sequence stratigraphic framework of Shanxi Formation in the northeast Zhoukou Depression was established based on detailed sequence stratigraphical and sedimentological analysis by utilizing the logging and core data of six wells drilled in the eastern tectonic unit of Zhoukou Depression.It was divided into three third-order sequences,namely SQs1,SQs2,and SQs3 from bottom to top.Each sequence can be divided into a transgressive system tract(TST)and a highstand system tract(HST).Furthermore,four sequence boundaries and three maximum flooding surfaces were identified,and they are the bottom interface SBs and maximum flooding surface mfss1 of SQs1,the bottom interface SBs1 and maximum flooding surface mfss2 of SQs2,the bottom interface SBs3 and maximum flooding surface mfss3 of SQs3,and the top interface SBx from bottom to top.Carbonate tidal flat–clastic tidal flat sedimentary system developed in Shanxi Formation in the northeast Zhoukou Depression(also referred to as the study area)under the control of regression.Meanwhile,four sedimentary microfacies were identified in the sedimentary system,which are lime-mud flats,sand flats,mixed flats,and mud flats.The transgression in the study area occurred from the southeast to the northwest.Therefore,the northwestern part is the seaward side,and the southeastern part is the landward side.As revealed by relevant drilling data,SQs1 of the Shanxi Formation is characterized by the development of limestone and carbonaceous mudstone,with limestone,dark mudstone,and carbonaceous mudstone mainly developing.Meanwhile,lime-mud flats were mainly deposited in it.During the periods of SQs2 and SQs3,the sedimentary environment of the study area changed from the carbonate tidal flats to clastic tidal flats as the coastline migrated towards the sea.In these periods,sand flats mainly developed near the maximum flooding surfaces and were relatively continuous in the eastern and southern parts of the transgressive system tract;mixed flats were relatively continuous in the western and northern parts of the transgressive system tract as well as the eastern and southern parts of the highstand system tract;mud flats widely developed in the highstand system tract.Peat flats mainly developed in the period of HSTs2,with coal seams relatively developing in the southeastern part of the study area as revealed by drilling data.The peat flats in SQs2 are favorable hydrocarbon source layers,the lime-mud flats in SQs1 and sand flats formed in the transgression periods of SQs2 and SQs3 constitute favorable hydrocarbon reservoirs,and the mud flats form in the transgressions periods serve as favorable cap rocks.Therefore,the study area features a reservoir-cap assemblage for self-generating and self-storing of hydrocarbon,and the southeastern part of the study area can be taken as a favorable exploration area.

Characteristics and evolution of lacustrine turbidite of Chang-7 Member of Yanchang Formation in northern Shaanxi

Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.

Hydrocarbon Reservoir Model of Glutenite in the Fourth Member of Shahejie Formation in Northern Dongying Depression

The glutenite in the fourth member of Shahejie Formation(Es^4) in northern Dongying depression straightforwardly penetrated into the muddy bathyal -abyss facies.The conditions of reservoir is very superior:(1) the high quality thick bedded oil source rock is developed very well in the Lijin sag and Minfeng sag of the study area,and it has the higher capability of generating hydrocarbon;(2) the

Effect of Shale Reservoir Characteristics on Shale Oil Movability in the Lower Third Member of the Shahejie Formation, Zhanhua Sag

To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil.

Distribution characteristics of delta reservoirs reshaped by bottom currents:A case study from the second member of the Yinggehai Formation in the DF1-1 gas field,Yinggehai Basin,South China Sea

The Dongfang1-1 gas field(DF1-1)in the Yinggehai Basin is currently the largest offshore self-developed gas field in China and is rich in oil and gas resources.The second member of the Pliocene Yinggehai Formation(YGHF)is the main gas-producing formation and is composed of various sedimentary types;however,a clear understanding of the sedimentary types and development patterns is lacking.Here,typical lithofacies,logging facies and seismic facies types and characteristics of the YGHF are identified based on high-precision 3D seismic data combined with drilling,logging,analysis and testing data.Based on 3D seismic interpretation and attribute analysis,the origin of high-amplitude reflections is clarified,and the main types and evolution characteristics of sedimentary facies are identified.Taking gas formation upper II(IIU)as an example,the plane distribution of the delta front and bottom current channel is determined;finally,a comprehensive sedimentary model of the YGHF second member is established.This second member is a shallowly buried“bright spot”gas reservoir with weak compaction.The velocity of sandstone is slightly lower than that of mudstone,and the reflection has medium amplitude when there is no gas.The velocity of sandstone decreases considerably after gas accumulation,resulting in an increase in the wave impedance difference and high-amplitude(bright spot)reflection between sandstone and mudstone;the range of high amplitudes is consistent with that of gas-bearing traps.The distribution of gas reservoirs is obviously controlled by dome-shaped diapir structural traps,and diapir faults are channels through which natural gas from underlying Miocene source rocks can enter traps.The study area is a delta front deposit developed on a shallow sea shelf.The lithologies of the reservoir are mainly composed of very fine sand and coarse silt,and a variety of sedimentary structural types reflect a shallow sea delta environment;upward thickening funnel type,strong toothed bell type and toothed funnel type logging facies are developed.In total,4 stages of delta front sand bodies(corresponding to progradational reflection seismic facies)derived from the Red River and Blue River in Vietnam have developed in the second member of the YGHF;these sand bodies are dated to 1.5 Ma and correspond to four gas formations.During sedimentation,many bottom current channels(corresponding to channel fill seismic facies)formed,which interacted with the superposed progradational reflections.When the provenance supply was strong in the northwest,the area was dominated by a large set of delta front deposits.In the period of relative sea level rise,surface bottom currents parallel to the coastline were dominant,and undercutting erosion was obvious,forming multistage superimposed erosion troughs.Three large bottom current channels that developed in the late sedimentary period of gas formation IIU are the most typical.

Energy Dispersive X-Ray Spectroscopy of the Sohnari Member of Laki Formation from Southern Indus Basin of Pakistan

This study determines the geochemical and depositional environment analysis of the sediments of the Sohnari Member of the Laki Formation, Northern Kirthar Fold Belt of Pakistan. The Energy-Dispersive-X-Ray Spectroscopy (EDS) technique is used for the detection of major elements and the effects of shifting depositional climatic conditions of six representative samples which were acquired from the Sohnari Member of the Laki Formation at Lakhra area, Sindh, Pakistan. The sedimentological studies clarify that the sediments the Sonahri Member are relatively immature and most migrated in clastic mode. The availability of Silica shows that the Member was formed due to biochemical precipitation and detrital mode and was deposited at a fast rate of sediment deposition under the fluvio-deltaic depositional system. This is also deduced that the rapid rate of sediment deposition might be created a reducing atmosphere and allowing for the mineralization of sulphur.

Characteristics and main controlling factors of reservoirs in the fourth member of Sinian Dengying Formation in Yuanba and its peripheral area, northeastern Sichuan Basin, SW China

Based on the abundant outcrops and 3 D seismic data in Yuanba and its surrounding areas in northeastern Sichuan Basin,the characteristics,main controlling factors and development regularities of reservoirs in the fourth member of Sinian Dengying Formation(shortened as Deng 4 Member)were analyzed comprehensively.The results show that the reservoirs were mainly developed in microbial dolomite associated with the microbial mound and dolarenite associated with grain beach,and had intergranular dissolution pores,inter-frame dissolution pores and karst caves as main storage space.The reservoirs were large in scale and strong in heterogeneity.The analysis of the reservoir genetic mechanisms shows that the reservoirs in the fourth member of Dengying Formation were the products of karstification on mound-beach facies deposited in the second episode of Tongwan movement.The karstification had the marks of eogenetic karstification such as granophyric karst system and half-dissociation zone.The reservoirs were controlled by the sedimentary facies belt,the mound beach facies was the decisive factor in reservoir development.Further analysis indicates that the Yuanba area had a geological background of well-developed platform margin mound beach facies,so mound beach bodies can be taken as a favorable exploration target.

Closed-system pyrolysis-based hydrocarbon generation simulation and gas potential evaluation of the Shanxi Formation shales from the Ordos Basin, China

The Shanxi Formation(Shan 1 and Shan 2 Members)shales show good prospects in shale gas development in the Yan'an area of Ordos Basin.Based on the simulation experiment of hydrocarbon generation of low maturity shale samples,the hydrocarbon generation characteristics of shale samples was studied systematically.Then,combined with the geochemical analysis of shale and gas generation simulation,shale gas potential was evaluated.The results reveal that Shan 1 and Shan 2 shale samples are favorable for shale gas enrichment by and large,with C_(1)-C_(5) maximum yields of 146.96-160.83 mg/g TOC and 148.48-148.67 mg/g TOC respectively at a heat rate of 20℃/h and 2℃/h.The Shan 1 and Shan 2 shales are basically the same in terms of organic carbon production potential of each unit.The carbon isotopic composition of alkane gas reveals that heteroatomic compounds(NSOs)cracking is an important mechanism for shale gas generation of Shanxi Formation shales,and conducive to gas generation at highto over-mature stages.Given thermal history and kinetic parameters of hydrocarbon generation,the shales of Shanxi Formation reached the maximum gas production potential in the Late Cretaceous,with a maximum yield of 160.3 mg/g TOC under present geological conditions.During geological history,the Shanxi Formation shales went through high-to over-maturity evolution,mainly producing dry gas,and their gas generation capacity was controlled by the organic matter abundance and cracking capacity.The gas generation potential of Shan 2 shale is higher than that of Shan 1,due to its higher TOC.

Geochemical evidence of paleogeography and paleoclimate during deposition of the 2nd Member of Kongdian Formation in Kongnan area

The 2nd Member of Kongdian Formation has been made up of a large number of oil shale and mudstone in the Kongnan aera of Huanghua depression around the Bohai Bay.In the Kongnan area,the lake basins were very large and deep during the deposition of the 2nd Member of Kongdian Formation.During that period,the lakes were sealed,uncommunicated with the sea water and the paleoclimate was very warm and wet in Kongnan area.Analyzing the content of the trace element and the rare earth element,carbon and oxygen isotope in the disquisition,The authors prove the two views correct.

Provenance, Tectonic Setting and Geochemistry of Ahwaz Sandstone Member(Asmari Formation, Oligo-Miocene), Marun Oilfield, Zagros Basin, SW Iran

The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene.Lithologically,the Asmari Formation consists of limestone,dolomitic limestone,dolomite,argillaceous limestone,some anhydrite （Kalhur Member） and sandstones （Ahwaz Member）.This study is based on the analysis of core samples from four subsurface sections （wells Mn-68,Mn-281,Mn-292 and Mn-312） in the Marun Oilfieid in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member.Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz,1.6% feldspar,and 0.9% rock fragments and all samples are classified as quartz arenites.The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies.Petrographic analysis reveals that mono-and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources.Chemically,major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting.As indicated by the CIW index （chemical index of weathering） of the Ahwaz Sandstone （average value of 82） their source area underwent ＂intense＂ recycling but ＂moderate to high＂ degree of chemical weathering.The petrography and geochemistry results are consistent with a tropical,humid climate and low-relief highlands.

A New Specimen of Shansisuchus shansisuchus Young, 1964 (Diapsida: Archosauriformes) from the Triassic of Shanxi, China

Shansisuchus shansisuchus Young, 1964 was restudied on the basis of a new specimen. Some anatomical features that were either briefly or not described at all in the original study were detailed. The new specimen not only provides further information on the skull anatomy and the vertebral column but also expands the range of the geographical distribution of the taxon. With new information, the diagnosis ofS. shansisuchus was emended and its phylogenetic relationships were further analyzed. S. shansisuchus differs from other archosauriforms primarily in the presence of a large subnarial fenestra anterior to the antorbital fenestra, tongue-in-groove articulations between the ascending process of the premaxilla and nasal and between the premaxilla and maxilla, a tall and posterodorsally directed ascending process of the maxilla, a knee-shaped process of the postorbital projecting into the orbit, a broad descending process of squamosal distally well forked and a large, deeply bow-shaped intercentrum tightly anchoring/capping the sharp ventral edges of two neighboring centra together in cervical and at least first eight dorsal vertebrae. With additional information derived from the new specimen, the phylogenetic relationships of S. shansisuchus were reanalyzed; it is closely related to Erythrosuchus- Vjushkovia clade.

Geochemical characteristics of REY, Li, Ga trace elements in the No. 9 coal seam of the Daheng mine, Ningwu coalfield, Shanxi Province, China

To understand the geochemical characteristics of the No.9 coal in the Daheng Mine of the Ningwu coalfield,the trace element analysis was conducted through X-ray fluorescence spectroscopy(XRF)and inductively coupled plasma mass spectrometry(ICP-MS).The sedimentary environment was discussed according to the element geochemical parameters.The results show that Li,Ga,Hf,Zr,Nb,Th,and Ta are slightly enriched in the No.9 coal of Daheng Mine.The average value of the rare earth elements and yttrium(ΣREY)in coal here is 144.20μg/g(excluding parting),which is higher than the average value ofΣREY in the world’s coal and China’s coal.The light rare earth elements(LREY)are enriched.The content of Eu was 0.12‒2.10μg/g with an average of 0.57μg/g,and the Eu is obviously negatively abnormal.Most of the trace elements in the coal are positively correlated with the ash content,which shows that the occurrence of these trace elements is related to inorganic minerals.The results of sequential chemical extraction experiments show that rare earth elements mainly exist in coal in the form of aluminosilicate.The value of the Sr/Ba and the content of S reflect that the coal-forming environment was influenced by seawater.The values of V/Cr and Ni/Co reflect that the peat swamp is in an anaerobic environment and a strongly reducing environment during the coal-forming period.