Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the ...Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.展开更多
The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it i...The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.展开更多
Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geologica...Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geological interpretation.To elucidate the possible influence of heterogeneity on resource evaluation,a high-resolution sampling approach was applied to an 86.2 cm long core from the Lucaogou Formation of the Jimsar sag in the Junggar Basin.86 sets of samples were micro-drilled from the core and subjected to comparative Rock-Eval pyrolysis.Following the classical guidelines,the organic abundance,kerogen type,and maturity of source rocks were exhaustively analyzed.Experimental results revealed that organic richness and composition vary significantly under different sedimentary backgrounds,which in turn leads to differential hydrocarbon generation.The combination of hydrocarbon generation,transport,and expulsion results in peculiar patterns for hydrocarbon accumulation in the Lucaogou Formation.Laminated shales in the Lucaogou Formation serve as both hydrocarbon source rocks and reservoirs,with laminae being migration pathways.Organic-rich dolomites in the Lucaogou Formation have a considerable hydrocarbon-generating capacity and present the characteristics of self-generation and self-storage.However,massive mudstones act purely as hydrocarbon source rocks.展开更多
This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source...This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source rocks in the Wucaiwan sag,Junggar Basin,China as proxies(1)for evaluations of hydrocarbon potential,organic matter(OM)composition and thermal maturity of the OM in the source rocks,(2)for reconstruction of paleodepositional environment,and(3)for analysis of controlling factor of organic carbon accumulation.The P_(2)p Formation developed good-excellent source rocks with thermal maturity of OM ranging from low-mature to mature stages.The OM was mainly composed of C_(3)terrestrial higher plants and aquatic organisms including aerobic bacteria,green sulfur bacteria,saltwater and fresh algae,Sphagnum moss species,submerged macrophytes,Nymphaea,and aquatic pollen taxa.The proportion of terrestrial higher plants decreased and that of aquatic organisms increased from margin to center of the sag.The benthic water within reducing environment and brackishwater column were superposed by periodic/occasional fresh-water influx(e.g.,rainfall and river drain),which led to fresh-water conditions and well oxygenating in the water column during overturn process.The whole study area developed lacustrine source rocks without seawater intrusion.During periodic/occasional fresh-water influx periods with plenty of terrestrial plant inputs,the paleoredox conditions of the sag were relatively oxic in the shallow fresh-water which experienced strong oxidation and decomposition of OM,therefore were not conducive for the OM preservation.However,the overall middle primary productivity made up for this deficiency,and was the main controlling factor on the organic carbon accumulation.A suitable supply from terrestrial inputs can promote biotic paleoproductivity,and a relatively high sedimentation rate can reduce oxidation and decomposition times of OM.On the contrary,during the intervals of the fresh-water influxes,relatively reducing conditions are a more important controlling factor on the OM accumulation in the case that the decrease of the terrestrial biotic source.展开更多
Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located ...Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located in the southern Junggar Basin of northwestern China,has geological conditions with rich CBM resources.The 46 Xishanyao coal samples gathered from the drilling cores and coal mines cover 4 types of macrolithotypes(bright coal 1,semi-bright coal 2,semi-dull coal 3,and dull coal 4)and 2 types of coal structures(primary coal I and cataclastic coal II).Based on a range of pore testing experiments and analytical methods,the dual effects of different macrolithotypes and coal structures on pore structures were intensely studied.The results showed that the specific surface area(SSA)and total pore volume(TPV)of coal samples increased gradually from bright to dull coals.For the same macrolithotypes,the SSA and TPV of the primary coals were lower than those of the cataclastic coals.Generally,the pore structures of bright and semi-bright coals are simpler when compared to semi-dull and dull coals with the same coal structure,whereas cataclastic coals have more complicated pore structure systems than primary coals with the same macrolithotypes.The bright and semi-bright coals have higher vitrinite contents and more endogenous fractures,whereas well-developed structural fractures were identified in cataclastic coals.Therefore,bright and semi-bright coals have better pore connectivity than semi-dull and dull coals with the same coal structure,the pore connectivity of cataclastic coals being slightly better than that of primary coals under the same macrolithotypes.In terms of the CBM adsorption conditions,the eight type samples formed a descending order:Ⅱ-4>I-4>Ⅱ-3>Ⅰ-3>Ⅱ-2>Ⅰ-2>Ⅱ-1>Ⅰ-1,while they ranked as follows when consideration was given to the CBM seepage capacities:II-2>Ⅱ-1>Ⅰ-2>Ⅰ-1>Ⅰ-3>Ⅰ-4>Ⅱ-3>Ⅱ-4.As a result,it could be determined that the bright and semi-bright coals had stronger adsorption capacities,whereas the cataclastic coals had better pore connectivity and seepage capacities.Pore structure characteristics should be analysed under the dual control of different macrolithotypes and coal structures,so that they can provide greater value for guiding CBM exploration and exploitation,as along for preventing underground gas accidents.展开更多
This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of res...This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development.The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite,while those from intermediate rock denudation can be dissolved or transformed into illite.Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components.Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain,with a closed original geochemical systems,have been in the oxidizing environment for a long time.The tuffaceous matrices mainly transforms into hematite or illite.These minerals occupy the primary pores and are difficult to dissolve by felsic fluids,which inhibits the development of high-quality reservoirs.The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system.The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle's compaction resistance,but also can be fully dissolved,which promotes the formation of high-quality reservoirs.展开更多
The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations...The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.展开更多
1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Saresh...1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Sareshenke-from west to east,supplemented by two tin mineralized points,namely Hongtujingzi and Sujiquan(Figs.1b).according to the ore type and the composition of gangue minerals,the tin deposits in the region are classified into two groups:Quartz vein type and greisen type,with the Sareshenke deposit ascribed to the former and the remainder to the latter.展开更多
The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline mine...The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline minerals and serves as a high-quality source rock for hydrocarbon generation in alkaline lakes.However,its lithology is complex,and the origins of the salt minerals remain unclear.This study focuses on the salt minerals in the Fengcheng Formation of the Hashan area.Using core observation,thin section identification,scanning electron microscopy,electron probe micro-analysis,trace and rare earth element analysis,stable isotope analysis,fluid inclusion analysis,and zircon U-Pb dating,the sedimentary age of Fengcheng Formation and the mineralogical and geochemical characteristics of salt minerals were systematically studied.The salt minerals identified in the Fengcheng Formation include calcite,dolomite,eitelite,northupite,shortite,reedmergnerite,and Na-carbonate.According to the different types of salt minerals,the different contact relations between minerals,the different production positions and production styles of mineral combinations,the salt mineral assemblage in the study area is classified into three categories:The combination of calcite,dolomite,shortite,and reedmergnerite,The combination of Na-carbonates,eitelite,shortite,and reedmergnerite,The combination of dolomite,eitelite,shortite,and northupite.Two zircon U-Pb ages,307.8±2.7 Ma and 308.5±3.5 Ma,span the Carboniferous-Permian boundary,corresponding to an interglacial period within the Late Paleozoic Ice Age,aligning with the development of salt minerals.Salt minerals have the formation modes of sedimentation,replacement and hydrothermal transformation.Terrestrial weathering products,atmosphe ric,volcanic and hydrothermal processes,residual seawater,clay mineral transformation,thermal evolution of organic matter and tuffaceous alteration are material sources.The salt-forming fluid has the characteristics of weak acid-alkaline,medium-low temperature and high salinity,and is mainly driven by subduction zone high pressure,magmatic heat and gravity.The burial depth,temperature and CO_(2)concentration required for the formation of salt minerals were clarified,and the evolution sequence of salt-forming fluids from sedimentation to diagenesis and accompanied by hydrothermal(hot water)activities was summarized.The evolution model of salt minerals controlled by different genesis from the first member to the third member of Fengcheng Formation was established.The research findings are significant for understanding the paleoenvironment of the Fengcheng Formation,the formation mechanisms of high-salinity lakes,and the salt formation models.展开更多
Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,sys...Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,systems involving source-reservoir separated type are scarce.To explore the accumulation model of tight oil in conglomerate,this study focused on the Permian-Triassic tight conglomerate oil in Mahu sag,Junggar Basin,using well drilling,well logging,seismic profiling,oil testing,and laboratory data,and analyzed the formation conditions,formation types,and distribution patterns of conglomerate reservoirs.The results show that,the conglomerate reservoirs are predominantly lithologic reservoirs and partly fault-lithologic reservoirs;there is no water evident at the edge or bottom around the reservoirs.The tight conglomerate layer in the delta plain subfacies of each fan exhibits high clay content and intense diagenesis,and the argillaceous rocks in the pro-fan delta subfacies and shallow lacustrine facies form the sealing and floor conditions.The sandy conglomerate of fan delta front subfacies is the main reservoir body.Additionally,strikeslip faulting in the Indosinian-Himalayan period formed an efficient faulting system for trans-stratal migration with Hercynian-Indosinian inverse faulting.Oil migration is driven by the overpressure caused by hydrocarbon generation from alkali lacustrine source rocks.The distribution of reservoirs is primarily controlled by the large fan bodies,namely the Zhongguai,Baijiantan,Karamay,Huangyangquan,Xiazijie,Xiayan,and Dabasong fans.Each fan body forms a group of reservoirs or oilfields,resulting in a widely distributed pattern,according to which reservoir and sealing constitute one whole body—i.e.,patterns of“one sand and one reservoir,one fan and one field.”This results in a quasi-continuous accumulation model,which includes strong oil charging,efficient faulting transportation,trans-stratal migration,and lithologic trapped accumulation.The proposed model is an important supplement to the existing model of quasi-continuous oil and gas accumulation.Overall,this study enriches unconventional oil and gas accumulation theories.展开更多
Most oil reservoirs that were found in the Junggar Basin are located in the Mahu sag and neighboring areas.Oil sources and classifications remain unresolved in this region.Oil source assessment can be partially incons...Most oil reservoirs that were found in the Junggar Basin are located in the Mahu sag and neighboring areas.Oil sources and classifications remain unresolved in this region.Oil source assessment can be partially inconsistent on the basis of different molecular and isotopic parameters.In the present study,classifications for the 92 studied oils from the Mahu sag and neighboring areas were performed using chemometric analysis,e.g.,hierarchical cluster analysis(HCA)and principal component analysis(PCA)on the basis of integration of sixteen facies parameters.These parameters consist of isotope reversal index(RI),δ^(13)C of n-C_(25),Ph/n-C18,β-carotane/n-C21,six terpane ratios of Ts/C_(23) tricyclic terpanes,Ts/(C_(28)+C_(29) tricyclic terpanes),C_(29) Ts/C_(23) tricyclic terpanes,C_(29)Ts/(C_(28)+C_(29) tricyclic terpanes),C_(30) diahopane/C_(23) tricyclic terpane and C_(30) diahopane/(C_(28)+C_(29) tricyclic terpanes),and six ratios of polynuclear aromatic hydrocarbons(PAH)including trimethylnaphthalenes(TMNs)/(TMNs+phenanthrene(Phen)),tetramethylnaphthalenes(TeMNs)/(TeMNs+Phen),TMNs/(TMNs+methylphenanthrenes(MPs)),TeMNs/(TeMNs+MPs),TMNs/(TMNs+chrysene(Ch))and TeMNs/(TeMNs+Ch).These sixteen parameters are mainly influenced by source facies and less influenced by maturity as demonstrated in the crossplots of these sixteen parameters versus concentrations of C_(30) hopane.Oil classifications are more reliable and convenient using chemometric analysis(HCA and PCA)integrating the sixteen facies parameters,compared with using crossplots of two parameters or star charts of several parameters.The 92 oils are classified into three groups using HCA and PCA,i.e.,Group Ⅰ, Ⅱ and Ⅲ. Group Ⅰ and Ⅱ oils are derived from source rocks within the Lower Permian Fengcheng Formation(P_(1)f)and Middle Permian Lower Wuerhe Formation(P_(2)w),respectively.Group Ⅲ oils are mixtures of Group Ⅰ and Ⅱ oils. Group Ⅰ consists of fifty oils mainly located at the northeastern and central areas of the Mahu sag with only three oils at the southwestern area of the Mahu sag.Group Ⅱ consists of fourteen oils at the southwestern area of the Mahu sag.Group Ⅲ consists of twenty-eight oils located at the southwestern and central areas of the Mahu sag.Locations of Group Ⅰ, Ⅱ and Ⅲ oils reflect the distributions of effective source rocks containing oil-prone Type Ⅰ/Ⅱ kerogen within the Fengcheng(P_(1)f)and Lower Wuerhe formations(P_(2)w).展开更多
For deep prospects in the foreland thrust belt,southern Junggar Basin,NW China,there are uncertainties in factors controlling the structural deformation,distribution of paleo-structures and detachment layers,and distr...For deep prospects in the foreland thrust belt,southern Junggar Basin,NW China,there are uncertainties in factors controlling the structural deformation,distribution of paleo-structures and detachment layers,and distribution of major hydrocarbon source rocks.Based on the latest 3D seismic,gravity-magnetic,and drilling data,together with the results of previous structural physical simulation and discrete element numerical simulation experiments,the spatial distribution of pre-existing paleo-structures and detachment layers in deep strata of southern Junggar Basin were systematically characterized,the structural deformation characteristics and formation mechanisms were analyzed,the distribution patterns of multiple hydrocarbon source rock suites were clarified,and hydrocarbon accumulation features in key zones were reassessed.The exploration targets in deep lower assemblages with possibility of breakthrough were expected.Key results are obtained in three aspects.First,structural deformation is controlled by two-stage paleo-structures and three detachment layers with distinct lateral variations:the Jurassic layer(moderate thickness,wide distribution),the Cretaceous layer(thickest but weak detachment),and the Paleogene layer(thin but long-distance lateral thrusting).Accordingly,a four-layer composite deformation sequence was identified,and the structural genetic model with paleo-bulge controlling zonation by segments laterally and multiple detachment layers controlling sequence vertically.Second,the Permian source rocks show a distribution pattern with narrow trough(west),multiple sags(central),and broad basin(east),which is depicted by combining high-precision gravity-magnetic data and time-frequency electromagnetic data for the first time,and the Jurassic source rocks feature thicker mudstones in the west and rich coals in the east according to the reassessment.Third,two petroleum systems and a four-layer composite hydrocarbon accumulation model are established depending on the structural deformation strength,trap effectiveness and source-trap configuration.The southern Junggar Basin is divided into three segments with ten zones,and a hierarchical exploration strategy is proposed for deep lower assemblages in this region,that is,focusing on five priority zones,expanding to three potential areas,and challenging two high-risk targets.展开更多
The A-type granites with highly positiveε_(Nd)(t)values in the West Junggar,Central Asian Orogenic Belt(CAOB),have long been perceived as a group formed under the same tectonic and geodynamic setting,magmatic sourceq...The A-type granites with highly positiveε_(Nd)(t)values in the West Junggar,Central Asian Orogenic Belt(CAOB),have long been perceived as a group formed under the same tectonic and geodynamic setting,magmatic sourceq and petrogenetic model.Geological evidence shows that these granites occurred at two different tectonic units related to the southeastern subduction of Junggar oceanic plate:the Hongshan and Karamay granites emplaced in the southeast of West Junggar in the Baogutu continental arc;whereas the Akebasitao and Miaoergou granites formed in the accretionary prism.Here the authors present new bulk-rock geochemistry and Sr-Nd isotopes,zircon U-Pb ages and Hf-O isotopes data on these granites.The granites in the Baogutu continental arc and accretionary prism contain similar zirconε_(Hf)(t)values(+10.9 to+16.2)and bulk-rock geochemical characteristics(high SiO_(2)and K_(2)O contents,enriched LILEs(except Sr),depleted Sr,Ta and Ti,and negative anomalies in Ce and Eu).The Hongshan and Karamay granites in the Baogutu continental arc have older zircon U-Pb ages(315-305 Ma)and moderate^(18)O enrichments(δ^(18)_(O_(zircon))=+6.41‰-+7.96‰);whereas the Akebasitao and Miaoergou granites in the accretionary prism have younger zircon U-Pb ages(305-301 Ma)with higher^(18)O enrichments(δ^(18)_(O_(zircon))=+8.72‰-+9.89‰).The authors deduce that the elevated^(18)O enrichments of the Akebasitao and Miaoergou granites were probably inherited from low-temperature altered oceanic crusts.The Akebasitao and Miaoergou granites were originated from partial melting of low-temperature altered oceanic crusts with juvenile oceanic sediments below the accretionary prism.The Hongshan and Karamay granites were mainly derived from partial melting of basaltic juvenile lower crust with mixtures of potentially chemical weathered ancient crustal residues and mantle basaltic melt(induced by hot intruding mantle basaltic magma at the bottom of the Baogutu continental arc).On the other hand,the Miaoergou charnockite might be sourced from a deeper partial melting reservoir under the accretionary prism,consisting of the low-temperature altered oceanic crust,juvenile oceanic sediments,and mantle basaltic melt.These granites could be related to the asthenosphere's counterflow and upwelling,caused by the break-off and delamination of the subducted oceanic plate beneath the accretionary prism Baogutu continental arc in a post-collisional tectonic setting.展开更多
West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for unde...West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for understanding the tectonic framework and accretionary processes in West Junggar,Central Asian Orogenic Belt.A series of Early Carboniferous volcanic and intrusive rocks,namely,basaltic andesite,andesite,dacite,and diorite,occur in the Mayile area of southern West Junggar,northwestern China.Our new LA-ICPMS zircon U-Pb geochronological data reveal that diorite intruded at 334(±1)Ma,and that basaltic andesite was erupted at 334(±4)Ma.These intrusive and volcanic rocks are calc-alkaline,display moderate MgO(1.62%-4.18%)contents and Mg#values(40-59),and low Cr(14.5×10-6-47.2×10-6)and Ni(7.5×10-6-34.6×10-6)contents,and are characterized by enrichment in light rare-earth elements and large-ion lithophile elements and depletion in heavy rare-earth elements and high-field-strength elements,meaning that they belong to typical subduction-zone island-arc magma.The samples show low initial 87Sr/86Sr ratios(range of 0.703649-0.705008),positiveεNd(t)values(range of 4.8-6.2 and mean of 5.4),and young TDM Nd model ages ranging from 1016 to 616 Ma,indicating a magmatic origin from depleted mantle involving partial melting of 10%-25%garnet and spinel lherzolite.Combining our results with those of previous studies,we suggest that these rocks were formed as a result of northwestward subduction of the Junggar oceanic plate,which caused partial melting of sub-arc mantle.We conclude that intra-oceanic arc magmatism was extensive in West Junggar during the Early Carboniferous.展开更多
The Late Carboniferous and Early Permian igneous rocks are widely developed in the West Junggar, Xinjiang, which are considered to be related to the evolution of the Junggar-Balkhash Ocean. However, their tectonic set...The Late Carboniferous and Early Permian igneous rocks are widely developed in the West Junggar, Xinjiang, which are considered to be related to the evolution of the Junggar-Balkhash Ocean. However, their tectonic settings have been controversial for a long time. With the aim of providing new evidence for the Late Paleozoic tectonic evolution of the West Junggar, we present petrology, zircon U-Pb chronology, whole-rock major and trace elemental and Sr-Nd isotopic data, to discuss the petrogenesis and tectonic setting of Takergan pluton from the Barleik Mountains in the West Junggar. The Takergan pluton is mainly composed of quartz diorite porphyry and quartz monzonite. The quartz diorite porphyry has low Si O2(57.76 wt.%–57.81 wt.%), high total alkali contents(Na2 O+K2 O=6.29 wt.%–6.56 wt.%), and high Mg# values(45–46), with a zircon U-Pb age of 304±5 Ma. The quartz monzonite shows relatively high SiO2(58.71 wt.%–64.71 wt.%), total alkali contents(7.73 wt.%–9.70 wt.%), and Mg^(#) values(34–47), with the A/CNK values of 0.91–0.98, which belongs to shoshonitic and metaluminous I-type granite series. The quartz monzonite yields zircon U-Pb ages of 302±2 and 296±3 Ma, and is characterized by low initial Sr ratios of 0.703 97–0.704 09, high εNd(t) values of +6.8– +7.0, and young Nd model ages of 551–587 Ma. Both the quartz diorite porphyry and quartz monzonite are enriched in light rare earth elements and Rb, Th, U, K, and depleted in Nb, Ta, Ti, with different degrees of negative Eu anomalies. These features indicate that the Takergan pluton was most likely formed in a post-collisional setting by partial melting of a depleted mantle source that had been metasomatized by subduction-related fluids, with significant fractional crystallization and slightly contaminated by crustal materials. Combined with the widespread distribution of the coeval stitching plutons, the occurrences of terrestrial Late Carboniferous to Permian volcano-sedimentary formations, and the absence of subduction-related rocks later than Early Carboniferous, it is believed that the Junggar-Balkhash Ocean was closed at about 320 Ma, and the central West Junggar has transformed to a post-collisional environment during the Late Carboniferous and Early Permian.展开更多
According to the study on the peripheral orogenic belts of the Junggar basin and combined with the interpretation of geophysical data, this paper points out that there is an Early Paleozoic basement of immature contin...According to the study on the peripheral orogenic belts of the Junggar basin and combined with the interpretation of geophysical data, this paper points out that there is an Early Paleozoic basement of immature continental crust in the Junggar area, which is mainly composed of Neoproterozoic-Ordovician oceanic crust and weakly metamorphosed covering sedimentary rocks. The Late Paleozoic tectonism and mineralization were developed on the basement of the Early Paleozoic immature continental crust. The Junggar metallogenic province is dominated by Cr, Cu, Ni and Au mineralization. Those large and medium-scale deposits are mainly distributed along the deep faults and particularly near the ophiolitic melange zones, and formed in the Late Paleozoic with the peak of mineralization occurring in the Carboniferous-Permian post-collisional stage. The intrusions related to Cu, Ni and Au mineralization generally have low Is, and positive εNd(t) values. The δ34S values of the ore deposits are mostly near zero, and the lead isotopes are mostly of normal lead. All these indicate that the ore-forming material comes either directly from the mantle-derived magma (for chromite and Cu-Ni deposits) or from recirculation of the basement material of the Early Paleozoic immature crust (for most Cu and Au deposits).展开更多
A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure ...A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure of the western Junggar Basin(hereafter referred to simply as ‘the Basin'), and, in particular, the structure and property of the Basin's crystalline basement. A survey using seismically converted waves was conducted along this profile to determine the characteristics of the P-and Swave velocities typical of the crust and uppermost mantle. A joint inversion of gravitation and aeromagnetic data was also performed to acquire the density and magnetization intensity values found beneath the western Basin. This research revealed that the Basin is composed of the so-called Manasi terrain in the south, and the Wulungu terrain in the north. Their boundary is located along the WNW-trending Dishuiquan-Sangequan suture, linking the NE-striking Da'erbute suture(DS) in the west, and the WNWtrending Kalameili suture(KS) in the east. In its northern part, the Wulungu-type terrain has a doublelayered basement, of which the upper layer is a folded basement of Hercynian orogenic origin, and the lower layer is a crystalline basement of Middle–Upper Proterozoic age. The southern part of the Basin, i.e., the Manasi terrain, has a single-layered crystalline basement. The folded basement here is too thin to be clearly distinguished.展开更多
The base of the Saerba Member （Mbr） of the Hongguleleng Formation （Fm.） probably lies in the Famennian Palmatolepis crepida Zone; the Longkou Mbr is probably a sedimentary wedge that thins out northwards; the Dugu...The base of the Saerba Member （Mbr） of the Hongguleleng Formation （Fm.） probably lies in the Famennian Palmatolepis crepida Zone; the Longkou Mbr is probably a sedimentary wedge that thins out northwards; the Duguer Mbr has an approximate age from the upper part of the Pa. marginifera Zone or the Lower Pa. rugosa trachytera Zone through the top of the Pa. perlobata postera Zone; the Wulan Mbr has an age approximately corresponding to the whole Pa. gracilis expansa Zone. In the Bulongguoer section, the Lower Mbr of the Hongguleleng Fro. corresponds to Famennian Pa. crepida Zone through Pa. marginifera Zone; the Middle Mbr probably ranges from the Pa. r. trachytera Zone through the Pa. g. expansa Zone. The basal Namu Mbr of the Heishantou Fm. is probably the product during and after the Hangenberg Event in the upper part of the Siphonodellapraesulcata Zone, which is still within the Devonian. In this context, the underlying Chasi Mbr may approximately correspond to the lower part of the S. praesulcata Zone （before the Hangenberg Event）. Lateral distribution of strata indicates that the Upper Devonian in the Gennaren and Saerba areas each constitutes a structure of syncline, which differs from the previous recognition of a monocline structure.展开更多
The West Junggar of the western Central Asian Orogenic Belt is one of the typical regions in the term of ocean subduction, contraction and continental growth in the Late Paleozoic. However, it is still controversial o...The West Junggar of the western Central Asian Orogenic Belt is one of the typical regions in the term of ocean subduction, contraction and continental growth in the Late Paleozoic. However, it is still controversial on the exact time of ocean-continent transition so far. This study investigates rhyolites with columnar joint in the West Junggar for the first time.Based on zircon U-Pb dating, we determined that the ages of the newly-discovered rhyolites are between 303.6 and 294.5 Ma, belonging to Late Carboniferous–Early Permian, which is the oldest rhyolite with columnar joint preserved in the world at present. Geochemical results show that the characteristics of the major element compositions include a high content of SiO_2(75.78–79.20 wt%) and a moderate content of Al_2O_3(12.21–13.19 wt%). The total alkali content(K_2O +Na_2O) is 6.14–8.05 wt%, among which K_2O is 2.09–4.72 wt% and the rate of K_2O/Na_2O is 0.38–3.05. Over-based minerals such as Ne, Lc, and Ac do not appear. The contents of TiO_2(0.09–0.24 wt%), CaO(0.15–0.99 wt%) and MgO(0.06–0.18 wt%) are low. A/CNK=0.91–1.68, A/NK=1.06–1.76, and as such, these are associated with the quasi-aluminum-weak peraluminous high potassium calc-alkaline and some calc-alkaline magma series. These rhyolites show a significant negative Eu anomaly with relative enrichment of LREE and LILE(Rb, Ba, Th, U, K) and depletion of Sr, HREE and HFSE(Nb, Ta, Ti, P). These rhyolites also have the characteristics of an A2-type granite, similar to the Miaoergou batholith,which indicates they both were affected by post-orogenic extension. Combining petrological, zircon U-Pb dating and geochemical characteristics of the rhyolites, we conclude that the specific time of ocean-continent transition of the West Junggar is the Late Carboniferous–Early Permian.展开更多
The dolomitic rocks of the Fengcheng Formation are considered to be formed under special geologic conditions, and are significant hydrocarbon reservoir rocks in the Wu-Xia area in the Junggar Basin. Analyses of petrol...The dolomitic rocks of the Fengcheng Formation are considered to be formed under special geologic conditions, and are significant hydrocarbon reservoir rocks in the Wu-Xia area in the Junggar Basin. Analyses of petrologic characteristics and stable isotope composition indicate that the dolomitizing host rock is volcanic and the dolomitizing fluids probably consists of brine from shore- shallow lakes with great evaporation and salinity in the Fengcheng Formation, which have formed under arid climatic conditions, as well as residual Mg-rich seawater from the underlying Jiamuhe Formation and Carboniferous. Dust tuff in the area has significant plagioclase content. Anorthite and labradorite hydrolysis by CO2 can be coupled with calcite precipitation. Late Mg-rich brine percolated and replaced calcite formed in the early time, which lead to precipitate dolostones with different occurrences, such as graniphyric, random bedded or lumpy. The diagenetic dolostones with different occurrences resulting from particular formation conditions occurred in different tectonic settings. The dolomitizing fluid has been driven by the thermal convection flow generated by volcanic eruptions. At the same time, the overthrusts of the Wu-Xia growth fault have speeded up the flow of deep Mg-rich water upwards, and induced the water to quickly penetrate and horizontally migrate in the strata. Fracture is the major and the most important reservoir space in dolomitic reservoir of the Fengcheng Formation. Fracture and fault plays a decisive role in controlling the formation of dolostone and the distribution of favorable reservoirs. The deliverability of oil and gas is determined by the development and match relations of dissolved pores and fractures to a certain degree.展开更多
基金Supported by Leading Talent Program of Autonomous Region(2022TSYCLJ0070)PetroChina Prospective and Basic Technological Project(2021DJ0108)Natural Science Foundation for Outstanding Young People in Shandong Province(ZR2022YQ30).
文摘Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.
基金granted by the Xinjiang Geological Exploration Fund。
文摘The northwestern margin of Junggar Basin is the region with the richest oil sand resources in China.For better understanding the enrichment rules and deployment of exploration and development of regional oil sand,it is of great scientific significance to study the accumulation conditions of oil sand in different strata and mining areas of the Junggar Basin.Through a large number of field investigations,drilling verification and sampling tests,it is found that the oil sand in the region covers an area of 2000 km^(2),with shallow and thick reservoir,and predicted resource of 180 million tons.The oil sand resources are mainly distributed in four geological strata,namely the Middle Triassic Karamay Formation,Early Jurassic Badaowan Formation,Late Jurassic Qigu Formation,and Early Cretaceous Qingshuihe Formation.The reservoir is mainly composed of sandstone with high porosity and permeability,and the reservoir space is mainly intergranular pores with a medium average oil content.The oil sand deposit in the region is a typical destructive oil reservoir.The crude oil in the oil sand layer is degraded and thickened from the deep to the shallow,the content of saturated hydrocarbon decreased,and the content of aromatic hydrocarbon,non-hydrocarbon and asphaltene increased.The oil source comes from the deep Permian hydrocarbon-generating depression.Unconformities,faults and marginal fan delta-braided river depositional systems constitute effective migration and storage systems.Caprocks of the Upper Triassic Baijiantan Formation,Lower Jurassic Sangonghe Formation and Lower Cretaceous Hutubihe Formation were formed by three large scale lake transgressions.The Indosinian,Yanshan and Late Yanshan movements are the main driving forces for the migration of deep oil and gas to the shallow edge to form oil sand deposits.It is considered that the oil sand in the northwestern margin of Junggar Basin is of a slope complex migration type.
基金supported by the National Natural Science Foundation of China(No.U22B6004)the Basic Research and Strategic Reserve Technology Research Project of CNPC(No.2020D-5008-01)the Scientific Research and Technology Development Project of PetroChina Exploration&Development Research Institute(Nos.2021DJ0104 and 2021DJ1808)。
文摘Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geological interpretation.To elucidate the possible influence of heterogeneity on resource evaluation,a high-resolution sampling approach was applied to an 86.2 cm long core from the Lucaogou Formation of the Jimsar sag in the Junggar Basin.86 sets of samples were micro-drilled from the core and subjected to comparative Rock-Eval pyrolysis.Following the classical guidelines,the organic abundance,kerogen type,and maturity of source rocks were exhaustively analyzed.Experimental results revealed that organic richness and composition vary significantly under different sedimentary backgrounds,which in turn leads to differential hydrocarbon generation.The combination of hydrocarbon generation,transport,and expulsion results in peculiar patterns for hydrocarbon accumulation in the Lucaogou Formation.Laminated shales in the Lucaogou Formation serve as both hydrocarbon source rocks and reservoirs,with laminae being migration pathways.Organic-rich dolomites in the Lucaogou Formation have a considerable hydrocarbon-generating capacity and present the characteristics of self-generation and self-storage.However,massive mudstones act purely as hydrocarbon source rocks.
基金financially supported by the National Natural Science Foundation of China(NSFC)(No.42202154)the Science Foundation of China University of Petroleum,Beijing(No.ZX20220074)。
文摘This paper is a synthetic use of carbon isotope composition,Rock-Eval data,organic petrology,element composition of kerogen,major and trace elements,and biomarker characteristic of the Permian Pingdiquan(P_(2)p)source rocks in the Wucaiwan sag,Junggar Basin,China as proxies(1)for evaluations of hydrocarbon potential,organic matter(OM)composition and thermal maturity of the OM in the source rocks,(2)for reconstruction of paleodepositional environment,and(3)for analysis of controlling factor of organic carbon accumulation.The P_(2)p Formation developed good-excellent source rocks with thermal maturity of OM ranging from low-mature to mature stages.The OM was mainly composed of C_(3)terrestrial higher plants and aquatic organisms including aerobic bacteria,green sulfur bacteria,saltwater and fresh algae,Sphagnum moss species,submerged macrophytes,Nymphaea,and aquatic pollen taxa.The proportion of terrestrial higher plants decreased and that of aquatic organisms increased from margin to center of the sag.The benthic water within reducing environment and brackishwater column were superposed by periodic/occasional fresh-water influx(e.g.,rainfall and river drain),which led to fresh-water conditions and well oxygenating in the water column during overturn process.The whole study area developed lacustrine source rocks without seawater intrusion.During periodic/occasional fresh-water influx periods with plenty of terrestrial plant inputs,the paleoredox conditions of the sag were relatively oxic in the shallow fresh-water which experienced strong oxidation and decomposition of OM,therefore were not conducive for the OM preservation.However,the overall middle primary productivity made up for this deficiency,and was the main controlling factor on the organic carbon accumulation.A suitable supply from terrestrial inputs can promote biotic paleoproductivity,and a relatively high sedimentation rate can reduce oxidation and decomposition times of OM.On the contrary,during the intervals of the fresh-water influxes,relatively reducing conditions are a more important controlling factor on the OM accumulation in the case that the decrease of the terrestrial biotic source.
基金supported by the National Natural Science Foundation of China(Grant No.42102223)the Chinese Postdoctoral Science Foundation(Grant Nos.2021M693844,2022T150284)+1 种基金the Chinese Geological Survey Project(Grant No.DD20160204-3)the discipline innovation team of Liaoning Technical University(Grant Nos.LNTU20TD-14,LNTU20TD-30)。
文摘Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located in the southern Junggar Basin of northwestern China,has geological conditions with rich CBM resources.The 46 Xishanyao coal samples gathered from the drilling cores and coal mines cover 4 types of macrolithotypes(bright coal 1,semi-bright coal 2,semi-dull coal 3,and dull coal 4)and 2 types of coal structures(primary coal I and cataclastic coal II).Based on a range of pore testing experiments and analytical methods,the dual effects of different macrolithotypes and coal structures on pore structures were intensely studied.The results showed that the specific surface area(SSA)and total pore volume(TPV)of coal samples increased gradually from bright to dull coals.For the same macrolithotypes,the SSA and TPV of the primary coals were lower than those of the cataclastic coals.Generally,the pore structures of bright and semi-bright coals are simpler when compared to semi-dull and dull coals with the same coal structure,whereas cataclastic coals have more complicated pore structure systems than primary coals with the same macrolithotypes.The bright and semi-bright coals have higher vitrinite contents and more endogenous fractures,whereas well-developed structural fractures were identified in cataclastic coals.Therefore,bright and semi-bright coals have better pore connectivity than semi-dull and dull coals with the same coal structure,the pore connectivity of cataclastic coals being slightly better than that of primary coals under the same macrolithotypes.In terms of the CBM adsorption conditions,the eight type samples formed a descending order:Ⅱ-4>I-4>Ⅱ-3>Ⅰ-3>Ⅱ-2>Ⅰ-2>Ⅱ-1>Ⅰ-1,while they ranked as follows when consideration was given to the CBM seepage capacities:II-2>Ⅱ-1>Ⅰ-2>Ⅰ-1>Ⅰ-3>Ⅰ-4>Ⅱ-3>Ⅱ-4.As a result,it could be determined that the bright and semi-bright coals had stronger adsorption capacities,whereas the cataclastic coals had better pore connectivity and seepage capacities.Pore structure characteristics should be analysed under the dual control of different macrolithotypes and coal structures,so that they can provide greater value for guiding CBM exploration and exploitation,as along for preventing underground gas accidents.
基金supported by the National Natural Science Foundation of China(Grant Nos.42172109,41872113,42172108)China National Petroleum Corporation-China University of Petroleum(Beijing)Strategic Cooperation Science and Technology Project(Grant No.ZLZX2020-02)+1 种基金State's Key Project of Research and Development Plan(Grant No.2018YFA0702405)Science Foundation of China University of Petroleum(Beijing)(Grant Nos.2462020BJRC002,2462020YXZZ020)。
文摘This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development.The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite,while those from intermediate rock denudation can be dissolved or transformed into illite.Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components.Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain,with a closed original geochemical systems,have been in the oxidizing environment for a long time.The tuffaceous matrices mainly transforms into hematite or illite.These minerals occupy the primary pores and are difficult to dissolve by felsic fluids,which inhibits the development of high-quality reservoirs.The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system.The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle's compaction resistance,but also can be fully dissolved,which promotes the formation of high-quality reservoirs.
基金financially supported by the National Natural Science Foundation of China(Nos.41772132,41502157,41530314)the key project of the National Science&Technology(No.2016ZX05043-001)+1 种基金the Fundamental Research Funds for the Central Universities(No.2652019095)the China Postdoctoral Science Foundation(No.2021M692998)。
文摘The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.
基金supported by the National Key R&D Program of China(No.2021YFC2901802)project of the China Geological Survey(No.DD20240073)Key R&D Program of Shaanxi Province(No.2024GH-ZDXM-26).
文摘1.Objective The Eastern Junggar Kalamaili region in Xinjiang constitutes a significant tin metallogenic belt in northwest China(Fig.1a).It hosts four independent tin deposits-Kamusite,Ganliangzi,Beilekuduke,and Sareshenke-from west to east,supplemented by two tin mineralized points,namely Hongtujingzi and Sujiquan(Figs.1b).according to the ore type and the composition of gangue minerals,the tin deposits in the region are classified into two groups:Quartz vein type and greisen type,with the Sareshenke deposit ascribed to the former and the remainder to the latter.
基金funded by National Natural Science Foundation of China(Grant Nos.42172153)。
文摘The Fengcheng Formation in the Hashan area,located on the northwestern margin of the Junggar Basin,represents a saline-alkaline lake facies with fine-grained mixed sedimentation.This formation is rich in alkaline minerals and serves as a high-quality source rock for hydrocarbon generation in alkaline lakes.However,its lithology is complex,and the origins of the salt minerals remain unclear.This study focuses on the salt minerals in the Fengcheng Formation of the Hashan area.Using core observation,thin section identification,scanning electron microscopy,electron probe micro-analysis,trace and rare earth element analysis,stable isotope analysis,fluid inclusion analysis,and zircon U-Pb dating,the sedimentary age of Fengcheng Formation and the mineralogical and geochemical characteristics of salt minerals were systematically studied.The salt minerals identified in the Fengcheng Formation include calcite,dolomite,eitelite,northupite,shortite,reedmergnerite,and Na-carbonate.According to the different types of salt minerals,the different contact relations between minerals,the different production positions and production styles of mineral combinations,the salt mineral assemblage in the study area is classified into three categories:The combination of calcite,dolomite,shortite,and reedmergnerite,The combination of Na-carbonates,eitelite,shortite,and reedmergnerite,The combination of dolomite,eitelite,shortite,and northupite.Two zircon U-Pb ages,307.8±2.7 Ma and 308.5±3.5 Ma,span the Carboniferous-Permian boundary,corresponding to an interglacial period within the Late Paleozoic Ice Age,aligning with the development of salt minerals.Salt minerals have the formation modes of sedimentation,replacement and hydrothermal transformation.Terrestrial weathering products,atmosphe ric,volcanic and hydrothermal processes,residual seawater,clay mineral transformation,thermal evolution of organic matter and tuffaceous alteration are material sources.The salt-forming fluid has the characteristics of weak acid-alkaline,medium-low temperature and high salinity,and is mainly driven by subduction zone high pressure,magmatic heat and gravity.The burial depth,temperature and CO_(2)concentration required for the formation of salt minerals were clarified,and the evolution sequence of salt-forming fluids from sedimentation to diagenesis and accompanied by hydrothermal(hot water)activities was summarized.The evolution model of salt minerals controlled by different genesis from the first member to the third member of Fengcheng Formation was established.The research findings are significant for understanding the paleoenvironment of the Fengcheng Formation,the formation mechanisms of high-salinity lakes,and the salt formation models.
基金the National Science and Technology Major Project of China for their support。
文摘Research based on oil accumulation models is essential for exploring the hydrocarbon accumulation theory further.Studies on tight oil accumulation models focused on fan delta depositional systems,and in particular,systems involving source-reservoir separated type are scarce.To explore the accumulation model of tight oil in conglomerate,this study focused on the Permian-Triassic tight conglomerate oil in Mahu sag,Junggar Basin,using well drilling,well logging,seismic profiling,oil testing,and laboratory data,and analyzed the formation conditions,formation types,and distribution patterns of conglomerate reservoirs.The results show that,the conglomerate reservoirs are predominantly lithologic reservoirs and partly fault-lithologic reservoirs;there is no water evident at the edge or bottom around the reservoirs.The tight conglomerate layer in the delta plain subfacies of each fan exhibits high clay content and intense diagenesis,and the argillaceous rocks in the pro-fan delta subfacies and shallow lacustrine facies form the sealing and floor conditions.The sandy conglomerate of fan delta front subfacies is the main reservoir body.Additionally,strikeslip faulting in the Indosinian-Himalayan period formed an efficient faulting system for trans-stratal migration with Hercynian-Indosinian inverse faulting.Oil migration is driven by the overpressure caused by hydrocarbon generation from alkali lacustrine source rocks.The distribution of reservoirs is primarily controlled by the large fan bodies,namely the Zhongguai,Baijiantan,Karamay,Huangyangquan,Xiazijie,Xiayan,and Dabasong fans.Each fan body forms a group of reservoirs or oilfields,resulting in a widely distributed pattern,according to which reservoir and sealing constitute one whole body—i.e.,patterns of“one sand and one reservoir,one fan and one field.”This results in a quasi-continuous accumulation model,which includes strong oil charging,efficient faulting transportation,trans-stratal migration,and lithologic trapped accumulation.The proposed model is an important supplement to the existing model of quasi-continuous oil and gas accumulation.Overall,this study enriches unconventional oil and gas accumulation theories.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010104)the National S&T Major Project of China(Grant No.2017ZX05008-002-030)。
文摘Most oil reservoirs that were found in the Junggar Basin are located in the Mahu sag and neighboring areas.Oil sources and classifications remain unresolved in this region.Oil source assessment can be partially inconsistent on the basis of different molecular and isotopic parameters.In the present study,classifications for the 92 studied oils from the Mahu sag and neighboring areas were performed using chemometric analysis,e.g.,hierarchical cluster analysis(HCA)and principal component analysis(PCA)on the basis of integration of sixteen facies parameters.These parameters consist of isotope reversal index(RI),δ^(13)C of n-C_(25),Ph/n-C18,β-carotane/n-C21,six terpane ratios of Ts/C_(23) tricyclic terpanes,Ts/(C_(28)+C_(29) tricyclic terpanes),C_(29) Ts/C_(23) tricyclic terpanes,C_(29)Ts/(C_(28)+C_(29) tricyclic terpanes),C_(30) diahopane/C_(23) tricyclic terpane and C_(30) diahopane/(C_(28)+C_(29) tricyclic terpanes),and six ratios of polynuclear aromatic hydrocarbons(PAH)including trimethylnaphthalenes(TMNs)/(TMNs+phenanthrene(Phen)),tetramethylnaphthalenes(TeMNs)/(TeMNs+Phen),TMNs/(TMNs+methylphenanthrenes(MPs)),TeMNs/(TeMNs+MPs),TMNs/(TMNs+chrysene(Ch))and TeMNs/(TeMNs+Ch).These sixteen parameters are mainly influenced by source facies and less influenced by maturity as demonstrated in the crossplots of these sixteen parameters versus concentrations of C_(30) hopane.Oil classifications are more reliable and convenient using chemometric analysis(HCA and PCA)integrating the sixteen facies parameters,compared with using crossplots of two parameters or star charts of several parameters.The 92 oils are classified into three groups using HCA and PCA,i.e.,Group Ⅰ, Ⅱ and Ⅲ. Group Ⅰ and Ⅱ oils are derived from source rocks within the Lower Permian Fengcheng Formation(P_(1)f)and Middle Permian Lower Wuerhe Formation(P_(2)w),respectively.Group Ⅲ oils are mixtures of Group Ⅰ and Ⅱ oils. Group Ⅰ consists of fifty oils mainly located at the northeastern and central areas of the Mahu sag with only three oils at the southwestern area of the Mahu sag.Group Ⅱ consists of fourteen oils at the southwestern area of the Mahu sag.Group Ⅲ consists of twenty-eight oils located at the southwestern and central areas of the Mahu sag.Locations of Group Ⅰ, Ⅱ and Ⅲ oils reflect the distributions of effective source rocks containing oil-prone Type Ⅰ/Ⅱ kerogen within the Fengcheng(P_(1)f)and Lower Wuerhe formations(P_(2)w).
基金Supported by the Science and Technology Special Project of CNPC(2023YQX10111)Key Research and Development Special Project of Xinjiang Uygur Autonomous Region(2024B01015-3)。
文摘For deep prospects in the foreland thrust belt,southern Junggar Basin,NW China,there are uncertainties in factors controlling the structural deformation,distribution of paleo-structures and detachment layers,and distribution of major hydrocarbon source rocks.Based on the latest 3D seismic,gravity-magnetic,and drilling data,together with the results of previous structural physical simulation and discrete element numerical simulation experiments,the spatial distribution of pre-existing paleo-structures and detachment layers in deep strata of southern Junggar Basin were systematically characterized,the structural deformation characteristics and formation mechanisms were analyzed,the distribution patterns of multiple hydrocarbon source rock suites were clarified,and hydrocarbon accumulation features in key zones were reassessed.The exploration targets in deep lower assemblages with possibility of breakthrough were expected.Key results are obtained in three aspects.First,structural deformation is controlled by two-stage paleo-structures and three detachment layers with distinct lateral variations:the Jurassic layer(moderate thickness,wide distribution),the Cretaceous layer(thickest but weak detachment),and the Paleogene layer(thin but long-distance lateral thrusting).Accordingly,a four-layer composite deformation sequence was identified,and the structural genetic model with paleo-bulge controlling zonation by segments laterally and multiple detachment layers controlling sequence vertically.Second,the Permian source rocks show a distribution pattern with narrow trough(west),multiple sags(central),and broad basin(east),which is depicted by combining high-precision gravity-magnetic data and time-frequency electromagnetic data for the first time,and the Jurassic source rocks feature thicker mudstones in the west and rich coals in the east according to the reassessment.Third,two petroleum systems and a four-layer composite hydrocarbon accumulation model are established depending on the structural deformation strength,trap effectiveness and source-trap configuration.The southern Junggar Basin is divided into three segments with ten zones,and a hierarchical exploration strategy is proposed for deep lower assemblages in this region,that is,focusing on five priority zones,expanding to three potential areas,and challenging two high-risk targets.
基金jointly supported by the National Natural Science Foundation of China (41802093)the National Key Research and Development Program of China (2017YFC0601201 and 2018YFC0604002)+2 种基金the Project of Xinjiang Bureau of Geology and Mineral Resources (2011BAB06B03-3)the Project of China Geological Survey (DD20190405 and DD20190406)the Fundamental Research Funds for the Central Universities, Sun Yat-sen University (2021qntd23).
文摘The A-type granites with highly positiveε_(Nd)(t)values in the West Junggar,Central Asian Orogenic Belt(CAOB),have long been perceived as a group formed under the same tectonic and geodynamic setting,magmatic sourceq and petrogenetic model.Geological evidence shows that these granites occurred at two different tectonic units related to the southeastern subduction of Junggar oceanic plate:the Hongshan and Karamay granites emplaced in the southeast of West Junggar in the Baogutu continental arc;whereas the Akebasitao and Miaoergou granites formed in the accretionary prism.Here the authors present new bulk-rock geochemistry and Sr-Nd isotopes,zircon U-Pb ages and Hf-O isotopes data on these granites.The granites in the Baogutu continental arc and accretionary prism contain similar zirconε_(Hf)(t)values(+10.9 to+16.2)and bulk-rock geochemical characteristics(high SiO_(2)and K_(2)O contents,enriched LILEs(except Sr),depleted Sr,Ta and Ti,and negative anomalies in Ce and Eu).The Hongshan and Karamay granites in the Baogutu continental arc have older zircon U-Pb ages(315-305 Ma)and moderate^(18)O enrichments(δ^(18)_(O_(zircon))=+6.41‰-+7.96‰);whereas the Akebasitao and Miaoergou granites in the accretionary prism have younger zircon U-Pb ages(305-301 Ma)with higher^(18)O enrichments(δ^(18)_(O_(zircon))=+8.72‰-+9.89‰).The authors deduce that the elevated^(18)O enrichments of the Akebasitao and Miaoergou granites were probably inherited from low-temperature altered oceanic crusts.The Akebasitao and Miaoergou granites were originated from partial melting of low-temperature altered oceanic crusts with juvenile oceanic sediments below the accretionary prism.The Hongshan and Karamay granites were mainly derived from partial melting of basaltic juvenile lower crust with mixtures of potentially chemical weathered ancient crustal residues and mantle basaltic melt(induced by hot intruding mantle basaltic magma at the bottom of the Baogutu continental arc).On the other hand,the Miaoergou charnockite might be sourced from a deeper partial melting reservoir under the accretionary prism,consisting of the low-temperature altered oceanic crust,juvenile oceanic sediments,and mantle basaltic melt.These granites could be related to the asthenosphere's counterflow and upwelling,caused by the break-off and delamination of the subducted oceanic plate beneath the accretionary prism Baogutu continental arc in a post-collisional tectonic setting.
基金This study was jointly supported by the CAS"Light of West China"Program(2018-XBYJRC-003)the National Natural Science Foundation of China(41772059,92055208)+1 种基金the Guangxi Natural Science Foundation for Distinguished Young Scholars,China(2018GXNSFFA281009)the Fifth Bagui Scholar Innovation Project of Guangxi Zhuang Autonomous Region,China.We are grateful for editor's excellent editorial handling and constructive comments from two anonymous reviewers,which substantially improved the final presentation of the manuscript.This is a contribution to International Geoscience Programme(IGCP)662 and Guangxi Key Mineral Resources Deep Exploration Talent Highland.
文摘West Junggar is a key area for understanding intra-oceanic plate subduction and the final closure of the Junggar Ocean.Knowledge of the Carboniferous tectonic evolution of the Junggar Ocean region is required for understanding the tectonic framework and accretionary processes in West Junggar,Central Asian Orogenic Belt.A series of Early Carboniferous volcanic and intrusive rocks,namely,basaltic andesite,andesite,dacite,and diorite,occur in the Mayile area of southern West Junggar,northwestern China.Our new LA-ICPMS zircon U-Pb geochronological data reveal that diorite intruded at 334(±1)Ma,and that basaltic andesite was erupted at 334(±4)Ma.These intrusive and volcanic rocks are calc-alkaline,display moderate MgO(1.62%-4.18%)contents and Mg#values(40-59),and low Cr(14.5×10-6-47.2×10-6)and Ni(7.5×10-6-34.6×10-6)contents,and are characterized by enrichment in light rare-earth elements and large-ion lithophile elements and depletion in heavy rare-earth elements and high-field-strength elements,meaning that they belong to typical subduction-zone island-arc magma.The samples show low initial 87Sr/86Sr ratios(range of 0.703649-0.705008),positiveεNd(t)values(range of 4.8-6.2 and mean of 5.4),and young TDM Nd model ages ranging from 1016 to 616 Ma,indicating a magmatic origin from depleted mantle involving partial melting of 10%-25%garnet and spinel lherzolite.Combining our results with those of previous studies,we suggest that these rocks were formed as a result of northwestward subduction of the Junggar oceanic plate,which caused partial melting of sub-arc mantle.We conclude that intra-oceanic arc magmatism was extensive in West Junggar during the Early Carboniferous.
基金This work was supported by the National Natural Science Foundation of China(No.41802236)“the Fundamental Research Funds for the Central Universities”(No.N182410001)the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.2019101450049)。
文摘The Late Carboniferous and Early Permian igneous rocks are widely developed in the West Junggar, Xinjiang, which are considered to be related to the evolution of the Junggar-Balkhash Ocean. However, their tectonic settings have been controversial for a long time. With the aim of providing new evidence for the Late Paleozoic tectonic evolution of the West Junggar, we present petrology, zircon U-Pb chronology, whole-rock major and trace elemental and Sr-Nd isotopic data, to discuss the petrogenesis and tectonic setting of Takergan pluton from the Barleik Mountains in the West Junggar. The Takergan pluton is mainly composed of quartz diorite porphyry and quartz monzonite. The quartz diorite porphyry has low Si O2(57.76 wt.%–57.81 wt.%), high total alkali contents(Na2 O+K2 O=6.29 wt.%–6.56 wt.%), and high Mg# values(45–46), with a zircon U-Pb age of 304±5 Ma. The quartz monzonite shows relatively high SiO2(58.71 wt.%–64.71 wt.%), total alkali contents(7.73 wt.%–9.70 wt.%), and Mg^(#) values(34–47), with the A/CNK values of 0.91–0.98, which belongs to shoshonitic and metaluminous I-type granite series. The quartz monzonite yields zircon U-Pb ages of 302±2 and 296±3 Ma, and is characterized by low initial Sr ratios of 0.703 97–0.704 09, high εNd(t) values of +6.8– +7.0, and young Nd model ages of 551–587 Ma. Both the quartz diorite porphyry and quartz monzonite are enriched in light rare earth elements and Rb, Th, U, K, and depleted in Nb, Ta, Ti, with different degrees of negative Eu anomalies. These features indicate that the Takergan pluton was most likely formed in a post-collisional setting by partial melting of a depleted mantle source that had been metasomatized by subduction-related fluids, with significant fractional crystallization and slightly contaminated by crustal materials. Combined with the widespread distribution of the coeval stitching plutons, the occurrences of terrestrial Late Carboniferous to Permian volcano-sedimentary formations, and the absence of subduction-related rocks later than Early Carboniferous, it is believed that the Junggar-Balkhash Ocean was closed at about 320 Ma, and the central West Junggar has transformed to a post-collisional environment during the Late Carboniferous and Early Permian.
基金the Major State Basic Research Programs of the People’s Republic of China(No.2001CB409806).
文摘According to the study on the peripheral orogenic belts of the Junggar basin and combined with the interpretation of geophysical data, this paper points out that there is an Early Paleozoic basement of immature continental crust in the Junggar area, which is mainly composed of Neoproterozoic-Ordovician oceanic crust and weakly metamorphosed covering sedimentary rocks. The Late Paleozoic tectonism and mineralization were developed on the basement of the Early Paleozoic immature continental crust. The Junggar metallogenic province is dominated by Cr, Cu, Ni and Au mineralization. Those large and medium-scale deposits are mainly distributed along the deep faults and particularly near the ophiolitic melange zones, and formed in the Late Paleozoic with the peak of mineralization occurring in the Carboniferous-Permian post-collisional stage. The intrusions related to Cu, Ni and Au mineralization generally have low Is, and positive εNd(t) values. The δ34S values of the ore deposits are mostly near zero, and the lead isotopes are mostly of normal lead. All these indicate that the ore-forming material comes either directly from the mantle-derived magma (for chromite and Cu-Ni deposits) or from recirculation of the basement material of the Early Paleozoic immature crust (for most Cu and Au deposits).
基金supported by the Major Program of the National Natural Science Foundation of China (No. 41490611)the Joint Research Projects between the Pakistan Science Foundation and the National Natural Science Foundation of China (No. 41661144026)the Detailed Lithospheric Structure and Deep Processes of the Tibetan Main Collision Zone (No. 2016YFC0600301)
文摘A comprehensive geophysical profile stretching from Qingyijing at the southern edge of the Junggar Basin to Ubara on the northern margin of the Junggar Basin was conducted in an attempt to probe the crustal structure of the western Junggar Basin(hereafter referred to simply as ‘the Basin'), and, in particular, the structure and property of the Basin's crystalline basement. A survey using seismically converted waves was conducted along this profile to determine the characteristics of the P-and Swave velocities typical of the crust and uppermost mantle. A joint inversion of gravitation and aeromagnetic data was also performed to acquire the density and magnetization intensity values found beneath the western Basin. This research revealed that the Basin is composed of the so-called Manasi terrain in the south, and the Wulungu terrain in the north. Their boundary is located along the WNW-trending Dishuiquan-Sangequan suture, linking the NE-striking Da'erbute suture(DS) in the west, and the WNWtrending Kalameili suture(KS) in the east. In its northern part, the Wulungu-type terrain has a doublelayered basement, of which the upper layer is a folded basement of Hercynian orogenic origin, and the lower layer is a crystalline basement of Middle–Upper Proterozoic age. The southern part of the Basin, i.e., the Manasi terrain, has a single-layered crystalline basement. The folded basement here is too thin to be clearly distinguished.
基金financially supported by the National Natural Science Foundation of China(Grants 41502015 and 41290260)supported by China Petrochemical Corporation (Sinopec)
文摘The base of the Saerba Member （Mbr） of the Hongguleleng Formation （Fm.） probably lies in the Famennian Palmatolepis crepida Zone; the Longkou Mbr is probably a sedimentary wedge that thins out northwards; the Duguer Mbr has an approximate age from the upper part of the Pa. marginifera Zone or the Lower Pa. rugosa trachytera Zone through the top of the Pa. perlobata postera Zone; the Wulan Mbr has an age approximately corresponding to the whole Pa. gracilis expansa Zone. In the Bulongguoer section, the Lower Mbr of the Hongguleleng Fro. corresponds to Famennian Pa. crepida Zone through Pa. marginifera Zone; the Middle Mbr probably ranges from the Pa. r. trachytera Zone through the Pa. g. expansa Zone. The basal Namu Mbr of the Heishantou Fm. is probably the product during and after the Hangenberg Event in the upper part of the Siphonodellapraesulcata Zone, which is still within the Devonian. In this context, the underlying Chasi Mbr may approximately correspond to the lower part of the S. praesulcata Zone （before the Hangenberg Event）. Lateral distribution of strata indicates that the Upper Devonian in the Gennaren and Saerba areas each constitutes a structure of syncline, which differs from the previous recognition of a monocline structure.
基金supported by the China Geological Survey (grant numbers DD20160083 and DD20160344-05)the National Key Research and Development Program of China (grant numbers 2018YFC0603701)Fundamental Research Funds for Central Public Welfare Research Institutes (grant numbers CAGS-YWF201706)
文摘The West Junggar of the western Central Asian Orogenic Belt is one of the typical regions in the term of ocean subduction, contraction and continental growth in the Late Paleozoic. However, it is still controversial on the exact time of ocean-continent transition so far. This study investigates rhyolites with columnar joint in the West Junggar for the first time.Based on zircon U-Pb dating, we determined that the ages of the newly-discovered rhyolites are between 303.6 and 294.5 Ma, belonging to Late Carboniferous–Early Permian, which is the oldest rhyolite with columnar joint preserved in the world at present. Geochemical results show that the characteristics of the major element compositions include a high content of SiO_2(75.78–79.20 wt%) and a moderate content of Al_2O_3(12.21–13.19 wt%). The total alkali content(K_2O +Na_2O) is 6.14–8.05 wt%, among which K_2O is 2.09–4.72 wt% and the rate of K_2O/Na_2O is 0.38–3.05. Over-based minerals such as Ne, Lc, and Ac do not appear. The contents of TiO_2(0.09–0.24 wt%), CaO(0.15–0.99 wt%) and MgO(0.06–0.18 wt%) are low. A/CNK=0.91–1.68, A/NK=1.06–1.76, and as such, these are associated with the quasi-aluminum-weak peraluminous high potassium calc-alkaline and some calc-alkaline magma series. These rhyolites show a significant negative Eu anomaly with relative enrichment of LREE and LILE(Rb, Ba, Th, U, K) and depletion of Sr, HREE and HFSE(Nb, Ta, Ti, P). These rhyolites also have the characteristics of an A2-type granite, similar to the Miaoergou batholith,which indicates they both were affected by post-orogenic extension. Combining petrological, zircon U-Pb dating and geochemical characteristics of the rhyolites, we conclude that the specific time of ocean-continent transition of the West Junggar is the Late Carboniferous–Early Permian.
基金supported by the National Program for Fundamental Research and Development(973 Program 2011CB201104)
文摘The dolomitic rocks of the Fengcheng Formation are considered to be formed under special geologic conditions, and are significant hydrocarbon reservoir rocks in the Wu-Xia area in the Junggar Basin. Analyses of petrologic characteristics and stable isotope composition indicate that the dolomitizing host rock is volcanic and the dolomitizing fluids probably consists of brine from shore- shallow lakes with great evaporation and salinity in the Fengcheng Formation, which have formed under arid climatic conditions, as well as residual Mg-rich seawater from the underlying Jiamuhe Formation and Carboniferous. Dust tuff in the area has significant plagioclase content. Anorthite and labradorite hydrolysis by CO2 can be coupled with calcite precipitation. Late Mg-rich brine percolated and replaced calcite formed in the early time, which lead to precipitate dolostones with different occurrences, such as graniphyric, random bedded or lumpy. The diagenetic dolostones with different occurrences resulting from particular formation conditions occurred in different tectonic settings. The dolomitizing fluid has been driven by the thermal convection flow generated by volcanic eruptions. At the same time, the overthrusts of the Wu-Xia growth fault have speeded up the flow of deep Mg-rich water upwards, and induced the water to quickly penetrate and horizontally migrate in the strata. Fracture is the major and the most important reservoir space in dolomitic reservoir of the Fengcheng Formation. Fracture and fault plays a decisive role in controlling the formation of dolostone and the distribution of favorable reservoirs. The deliverability of oil and gas is determined by the development and match relations of dissolved pores and fractures to a certain degree.
