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
Based on the data of drilling,logging,experiment and gas testing in the Nanchuan area,southeastern Sichuan Basin,the hydrocarbon generation potential,gas genesis,occurrence state,migration,preservation conditions,pore...Based on the data of drilling,logging,experiment and gas testing in the Nanchuan area,southeastern Sichuan Basin,the hydrocarbon generation potential,gas genesis,occurrence state,migration,preservation conditions,pore and fracture features and accumulation evolution of the first member of Permian Maokou Formation(Mao 1 Member)are systematically studied,and the main controlling factors of unconventional gas enrichment and high production in marlstone assemblage of Mao 1 Member are discussed.(1)The enrichment and high yield of unconventional natural gas in the Mao 1 Member are controlled by three factors:carbon-rich fabric controlling hydrocarbon generation potential,good preservation controlling enrichment,and natural fracture controlling production.(2)The carbonate rocks of Mao 1 Member with carbon rich fabric have significant gas potential,exhibiting characteristics of self-generation and self-storage,which lays the material foundation for natural gas accumulation.(3)The occurrence state of natural gas is mainly free gas,which is prone to lateral migration,and good storage conditions are the key to natural gas enrichment.Positive structure is more conducive to natural gas accumulation,and a good compartment is created jointly by the self-sealing property of the Mao 1 Member and its top and bottom sealing property in monoclinal area,which is favorable for gas accumulation by retention.(4)Natural fractures are the main reservoir space and flow channel,and the more developed natural fractures are,the more conducive to the formation of high-quality porous-fractured reservoirs and the accumulation of natural gas,which is the core of controlling production.(5)The accumulation model of unconventional natural gas is proposed as“self-generation and self-storage,preservation controlling richness,and fractures controlling production”.(6)Identifying fracture development areas with good preservation conditions is the key to successful exploration,and implementing horizontal well staged acidizing and fracturing is an important means to increase production and efficiency.The study results are of referential significance for further understanding the natural gas enrichment in the Mao 1 Member and guiding the efficient exploration and development of new types of unconventional natural gas.展开更多
The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carbonif...The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carboniferous and subsequent intracontinental extension since the Triassic have been well documented in the Chinese Altai,the southwestern segment of the CAOB.Deciphering the petrogenetic evolution of this region during the Permian is thus crucial for advancing our understanding of its tectonic transitions.However,the Permian tectonic setting of the Chinese Altai remains contentious.To address this knowledge gap,this study presents new geochronological and geochemical data for the Jiangjunshan pluton in the southern Chinese Altai.Zircon U-Pb geochronology reveals that the gabbro and two-mica alkali feldspar granite—which collectively constitute the primary lithology of the Jiangjunshan pluton—were emplaced at∼272±3.5 and∼272±1.6 Ma,respectively.Geochemically,the gabbro exhibits pronounced light rare-earth element(LREE)depletion,low Nb/Yb(0.39–0.46)and Ti/V(23.7–25.3)ratios,and trace-element signatures akin to normal mid-ocean ridge basalts(N-MORB).However,its conspicuous Nb-Ta depletion parallels that of island arc basalts.Depleted Hf-Nd isotopic compositions(ε_(Hf)(t)=+0.60 to+4.63,ε_(Nd)(t)=+6.32 to+7.80)in the gabbro,coupled with negligible correlation betweenε_(Nd)(t)and SiO2 contents imply limited crustal assimilation during magma evolution.Petrological modeling,based on Sm/Yb and La concentrations,suggests the gabbroic melt derived from∼8%–20%spinel lherzolte mantle melting.Analogously depleted Hf-Nd isotopes(ε_(Hf)(t)=+6.81 to+9.10,ε_(Nd)(t)=+0.79 to+1.45)in the granite,together with petrographic evidence lacking mafic-ultramafic xenoliths,point to a juvenile lower-crustal source.Integrating the gabbro’s N-MORB-like affinity with arc-specific features,regional ultrahigh-temperature metamorphism in southern Chinese Altai,and Permian tectonics,we propose a ridge-subduction regime as the likely petrogenetic setting for the Jiangjunshan magmas.During ridge subduction,upwelling of asthenospheric mantle beneath the ridge induced partial melting of the lithospheric mantle,giving rise to the parental magma of the Jiangjunshan gabbro.This mafic magma underplating subsequently heated the juvenile lower crust,triggering its partial melting and generating the parental magma of the two-mica alkali feldspar granite.Our model indicates that ridge-subduction-related magmatism persisted in the Chinese Altai until the Middle Permian,followed by a tectonic shift from oceanic-continental subduction to intracontinental extension.展开更多
Based on the basic data of drilling,logging,testing and geological experiments,the geological characteristics of the Permian Dalong Formation marine shales in the northern Sichuan Basin and the factors controlling sha...Based on the basic data of drilling,logging,testing and geological experiments,the geological characteristics of the Permian Dalong Formation marine shales in the northern Sichuan Basin and the factors controlling shale gas enrichment and high yield are studied.The results are obtained in four aspects.First,the high-quality shale of the Dalong Formation was formed after the deposition of the Permian Wujiaping Formation,and it is developed in the Kaijiang-Liangping trough in the northern part of Sichuan Basin,where deep-water continental shelf facies and deep-water reduction environment with thriving siliceous organisms have formed the black siliceous shale rich in organic matter.Second,the Dalong Formation shale contains both organic and inorganic pores,with stratification of alternated brittle and plastic minerals.In addition to organic pores,a large number of inorganic pores are developed even in ultra-deep(deeper than 4500 m)layers,contributing a total porosity of more than 5%,which significantly expands the storage space for shale gas.Third,the limestone at the roof and floor of the Dalong Formation acted as seal rock in the early burial and hydrocarbon generation stage,providing favorable conditions for the continuous hydrocarbon generation and rich gas preservation in shale interval.In the later reservoir stimulation process,it was beneficial to the lateral extension of the fractures,so as to achieve the optimal stimulation performance and increase the well-controlled resources.Combining the geological,engineering and economic conditions,the favorable area with depth less than 5500 m is determined to be 1800 km2,with resources of 5400×10^(8) m^(3).Fourth,the shale reservoirs of the Dalong Formation are thin but rich in shale gas.The syncline zone far away from the main faults in the high and steep tectonic zone,eastern Sichuan Basin,with depth less than 5500 m,is the most favorable target for producing the Permian shale gas under the current engineering and technical conditions.It mainly includes the Nanya syncline,Tanmuchang syncline and Liangping syncline.展开更多
The Xing'an-Inner Mongolia Orogen is a critical tectonic unit for constraining the evolution of the Paleo-Asian Ocean.However,the location and time of the closure of the Paleo-Asian Ocean are still debated.Here,we...The Xing'an-Inner Mongolia Orogen is a critical tectonic unit for constraining the evolution of the Paleo-Asian Ocean.However,the location and time of the closure of the Paleo-Asian Ocean are still debated.Here,we select a representative basin in Dashizhai in northeastern China,using U-Pb zircon geochronology and geochemistry to analyze the sedimentary facies,depositional ages,and provenance.The results show that the ages of the Dashizhai Formation range from 400 to 347 Ma,the Shoushangou Formation range from 400 to 348 Ma,the Zhesi Formation range from 307 to 252 Ma,and the Linxi Formation range from 299 to 241 Ma.The Dashizhai Formation is composed of metamorphic andesite and clastic rocks.The Shoushangou Formation comprises siltstone,rhyolite,and argillaceous siltstone.The Zhesi and Linxi Formations are composed of mudstone and argillaceous siltstone.Geochemical data shows that these rocks are enriched in light rare earth elements and depleted in Eu with various La/Sc,Th/Sc,and La/Co ratios.The Permian Dashizhai Basin is from Permian volcanic and felsic igneous rocks from the Ergun,Xing'an,and Songliao blocks.The absence of the Late Carboniferous strata in the Dashizhai Basin indicates an extension setting during this period.Furthermore,we suggest the Xing'an-Inner Mongolia Orogen was an uplifting process associated with evolution the Paleo-Asian Ocean during the Late Permian.展开更多
We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and g...We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.展开更多
This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation(lower Mao 2 Member)in the Wusheng-Tongnan area o...This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation(lower Mao 2 Member)in the Wusheng-Tongnan area of the Sichuan Basin,SW China,through comprehensive analysis of geological,geophysical and geochemical data.The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone,which have typical karst characteristics of early diagenetic stage.The dolomites at the edge of the karst system and in the fillings have dissolved estuaries,and the dolomite breccia has micrite envelope and rim cement at the edge,indicating that dolomitization is earlier than the early diagenetic karstification.The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater.The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage,which are locally reformed by fractures and hydrothermal processes.The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence,and mainly occurs in the late highstand of the fourth-order cycle.Moreover,the size of dolomite is closely related to formation thickness,and it is concentrated in the formation thickness conversion area,followed by the thinner area.According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle,it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes,and the reservoir-forming model with shoal,dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established.On this basis,the paleogeomorphology in the lower Mao 2 Member is restored using well-seismic data,and the reservoir distribution is predicted.The prediction results have been verified by the latest results of exploration wells and tests,which provide an important reference for the prediction of thin dolomite reservoirs under similar geological setting.展开更多
Shale gas is abundant in the Paleozoic of the Yangtze Platform,and several high-yield shale gas fields have been built in the Upper Yangtze Platform,China.The Permian of the South Yellow Sea Basin(SYSB)in the Lower Ya...Shale gas is abundant in the Paleozoic of the Yangtze Platform,and several high-yield shale gas fields have been built in the Upper Yangtze Platform,China.The Permian of the South Yellow Sea Basin(SYSB)in the Lower Yangtze area is considered a potential target for shale gas exploration;however,the fundamental geological conditions of shale gas have not been studied.Based on the first whole-cored scientific drilling borehole(CSDP-2)in the SYSB,detailed tests involving petrology,organic geochemistry,and reservoir physical properties were conducted to evaluate the shale gas potential of the Lower Permian.The Lower Permian is dominated by organic-rich siliceous,clay,and clay-mixed shales.The average total organic carbon content is 5.99%,and the organic matter is mainly type Ⅱ_(1)−Ⅱ_(2),which has entered the high-over mature evolution stage.The pore types of organic-rich shales mainly include organic pores,dissolution pores,and intergranular pores,of which the meso-/macropores are well developed.The average porosity is 3.04%,and the total specific surface area and pore volume are 3.47 m^(2)/g and 7.21×10^(−3) cm^(3)/g,respectively.The average Langmuir volume obtained from the methane adsorption isotherms is 2.70 cm^(3)/g,and methane is mainly adsorbed in the meso-/macropores.The lower Permian shales are rich in methane as indicated by gas logging results,with an average content of 7.3%,which can reach up to 65.9%.A comparison of the study area with typical shale gas fields shows that the Lower Permian is brittle and shallowly buried and has a high potential for shale gas exploration and low-cost development.The depression areas of the SYSB are overlain by thick Mesozoic-Cenozoic sediments,show higher organic matter maturity,and may have greater shale gas potential.The shale gas exploration breakthrough of the study area is of great significance to ensure the energy supply of economically developed areas on the east China.展开更多
Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbon...Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.展开更多
To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The...To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The fractures and vugs of Middle Permian Qixia–Maokou formations are filled with multi-stage medium-coarse saddle dolomites and associated hydrothermal minerals,which indicates that the early limestone/dolomite episodic alteration was caused by the large-scale,high-temperature,deep magnesium-rich brine along flowing channels such as basement faults or associated fractures under the tectonic compression and napping during the Indosinian.The time of magnesium-rich hydrothermal activity was from the Middle Triassic to the Late Triassic.The siliceous and calcite fillings were triggered by hydrothermal alteration in the Middle and Late Yanshanian Movement and Himalayan Movement.Hydrothermal dolomitization is controlled by fault,hydrothermal property,flowing channel and surrounding rock lithology,which occur as equilibrium effect of porosity and permeability.The thick massive grainstone/dolomites were mainly altered by modification such as hydrothermal dolomitization/recrystallization,brecciation and fracture-vugs filling.Early thin-medium packstones were mainly altered by dissolution and infilling of fracturing,bedding dolomitization,dissolution and associated mineral fillings.The dissolved vugs and fractures are the main reservoir space under hydrothermal conditions,and the connection of dissolved vugs and network fractures is favorable for forming high-quality dolomite reservoir.Hydrothermal dolomite reservoirs are developed within a range of 1 km near faults,with a thickness of 30–60 m.Hydrothermal dolomite reservoirs with local connected pore/vugs and fractures have exploration potential.展开更多
Chansitheca (Sphenopteris) wudaensis sp. nov. is described based on the materials collected from the Lower Permian Shansi Formation of Wuda, Nei Mongol, China. The frond is small and at least two times pinnate. The pi...Chansitheca (Sphenopteris) wudaensis sp. nov. is described based on the materials collected from the Lower Permian Shansi Formation of Wuda, Nei Mongol, China. The frond is small and at least two times pinnate. The pinnule is sphenopteroid. The sori are borne on the abaxial surface of the pinnule, arranged in two rows parallel to the midvein, elliptic,and composed of 4-10 round sporangia. The indusium is absent. The annulus is transverse and complete, and consists of about 18 thickened cells. The features of the fertile parts, sori, sporangia and annulus and the absence of indusium indicate that the new species belongs to the Gleicheniaceae.展开更多
A kind of silicified fossil wood with mixed pits on the radial tracheid wall is described. The fossil wood was collected from the top of Taiyuan Formation (early Early Permian) in Wuda Mi...A kind of silicified fossil wood with mixed pits on the radial tracheid wall is described. The fossil wood was collected from the top of Taiyuan Formation (early Early Permian) in Wuda Mining District, Nei Mongol. Compared with the Paleozoic fossil woods in the world, it is put into Araucarioxylon Kraus and named as A. laoshidanense sp. nov. Based on the character of possessing mixed pittings (alternate and opposite pittings) on the radial tracheid wall, the fossil wood is believed to be one of the unknown primitive conifers.Diagnosis of the new species: Only secondary xylem preserved and consisting of axial tracheids and rays. Growth ring boundary, resin duct and axial parenchyma absent. One to Four (commonly 2 or 3) seriates of bordered pits (mostly alternate but sometimes opposite) on the radial tracheid wall. One to Four (commonly 1, rarely 2 to 4) Cupressoid pits in each cross_field. Rays usually uniseriate, sometimes partly_ biseriate and 2 to 39 (mainly 3-5) cells high.展开更多
Although the research on Cordaites of the Cathaysian Flora in China started early in 1883, the study of the cordaitean cuticles began late in 1991. Up to now, four types of cordaitean cuticles in situ and three types ...Although the research on Cordaites of the Cathaysian Flora in China started early in 1883, the study of the cordaitean cuticles began late in 1991. Up to now, four types of cordaitean cuticles in situ and three types of dispersed ones have been reported from the Cathaysian Flora in China. However compared with the Euramerican Flora, the research work on cordaitean cuticles from the Cathaysian Flora in China is much more insufficient. In this paper, three kinds of dispersed cordaitean cuticles are described in detail from the Permian coal-bearing strata in China. Among these cuticles two kinds are collected from the roof shale of Coal Seam No. A(1) in Shanxi Formation (Lower Permian) in Xinzhuangzhi Coal Mine of Huainan, Anhui Province, southern border of North China Subprovince of the Cathaysian Flora in China. The third one was collected from Coal Seam No. 11 in the top of Longtan Formation (lower Upper Permian) in Dahebian Coal Mine of Shuicheng Mining District, Guizhou Province, South China Subprovince of the Cathaysian Flora in China. Comparison of these three kinds of cordaitean cuticles with the known ones from the Cathaysian Flora in China and from the Euramerican Flora is made. The authors consider that they are all new types of cordaitean cuticles. The significance they bear on palaeobotany is discussed.展开更多
Three kinds of anatomically_preserved lepidodendralean leaves from Permian coal balls of China were studied. They all have double xylem strands, which is consistent with the genus Sigillariopsis Scott. Compared wi...Three kinds of anatomically_preserved lepidodendralean leaves from Permian coal balls of China were studied. They all have double xylem strands, which is consistent with the genus Sigillariopsis Scott. Compared with the species of Sigillariopsis , they are considered as three new species: S. shanxiensis sp. nov. and S. taiyuanensis sp. nov. from Coal Seam 7 in the upper part of the Taiyuan Formation (lower Lower Permian), Xishan Coal Field, Taiyuan, Shanxi Province and S. guizhouensis sp. nov. from Coal Seam 1 in the Wangjiazhai Formation (upper Upper Permian), Shuicheng Coal Mining District, Guizhou Province. Based on the associated organs of lepidodendraleans other than leaves and the information of the Euramerican lepidodendraleans, the affinities of the three new species of Sigillariopsis are discussed and they are probably leaves of Sigillaria Brongniart. In Euramerican Flora, Sigillaria (including its leaves Sigillariopsis ) mainly lived in the Carboniferous period and in the Cathaysian Flora they lived in the Upper Carboniferous to upper Upper Permian periods in rare localities. The leaves and fertile organs of Sigillaria have not been reported from the Cathaysian Flora to date. Three new species of the Permian anatomically_preserved leaves of Sigillaria not only increase the diversity of the Cathaysian sigillarian but also bear important significance on the evolution of sigillarian plants and the relationship of the Cathaysian and Euramerican lepidodendraleans.展开更多
The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its afterm...The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its aftermath. However, the age of the microbialite event remains controversial. New conodont collection across the Permian–Triassic（P–T） transition from Dajiang（Guizhou Province, South China） in this study enable us to discriminate four conodont zones, in ascending order, they are： Hindeodus parvus zone, Isarcicella lobata zone, Isarcicella isarcica zone and Hindeodus sosioensis zone. The age of microbialite in the P–T transition at the Dajiang Section is considered to be within the Hindeodus parvus zone and thus to clearly post-date the main extinction crisis. Reviewing the age of onset of microbialites throughout the Tethyan regions reveals two different ages： a Hindeodus changxingensis zone age is dominant in south-western and westernmost Tethys, whilst most other regions show microbialite deposition began in the Hindeodus parvus zone. Our investigation also indicates that two conodont changes occur at this time： an increase of hindeodid species immediately following a sequence boundary and the mass extinction, and a phase of extinction losses in the earliest Triassic Isarcicella isarcica zone during highstand development.展开更多
Laser ablation-inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating and geochemical data for the Permian gabbros and diorites in the Hunchun area are presented to constrain the regional tecton...Laser ablation-inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating and geochemical data for the Permian gabbros and diorites in the Hunchun area are presented to constrain the regional tectonic evolution in the study area. Zircons from gabbro and diorite are euhedral-subhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios （0.26-1.22）, implying their magmatic origin. The dating results indicate that the gabbro and diorite formed in the Early Permian （282-2 Ma） and in the Late Permian （255-3 Ma）, respectively. In addition, the captured zircons with the weighted mean age of 279-4 Ma are also found in the diorite, consistent with the formation age of the gabbro within uncertainty. The gabbros belong chemically to low-K tholeiitic series, and are characterized by low rare earth element （REE） abundances, fiat REE pattern, weak positive Eu anomalies （JEu）, and depletion in high field strength elements （HFSEs, Nb, Ta, and Ti）, similar to the high-aluminum basalts from island arc setting. Initial Hf isotopic ratios of zircons from the gabbro range from ＋7.63 to ＋14.6, suggesting that its primary magma could be mainly derived from partial melting of a depleted lithospheric mantle. The diorites belong to middle K calc-alkaline series. Compared with the gabbros, the diorites have higher REE abundance, weak negative Eu anomalies, and more depletion in HFSEs （Nb, Ta, and Ti）, similar chemically to the volcanic rocks from an active continental margin setting. Initial Hf isotopic ratios and Hf two-stage model ages of zircons from the diorite range from ＋11.22 to ＋14.17 and from 424 to 692 Ma, respectively, suggesting that its primary magma could be mainly derived from partial melting of the Early Paleozoic and/or Neoproterozoic accretted lower crust. Taken together, it is suggested that geochemical variations from the Early Permian gabbros to the Late Permian diorites reveal that the subduction of the Paleo-Asian oceanic plate beneath the Khanka Massif and collision between the arc and continent （Khanka Massif） happened in the late stage of the Late Paleozoic.展开更多
Since the principle of multiple stratigraphic classification has been widely accepted by Chinese stratigraphers, various new Permian chronostratigraphic units have been proposed in China, and they need to be redefined...Since the principle of multiple stratigraphic classification has been widely accepted by Chinese stratigraphers, various new Permian chronostratigraphic units have been proposed in China, and they need to be redefined. The establishment of a new global chronostratigraphic scheme of the Permian, compilation of Permian lithostratigraphic units and updating of Permian biostratigraphic sequences of China makes it possible to present a revised regional chronostratigraphic succession for the Permian System in China. This succession consists of three series and eight stages. The Chuanshanian Series includes two stages, the Zisongian and the Longlinian; the Yanghsinian (Yangxinian) Series is subdivided into the Chihsian (Qixiaan) and the Maokouan Subseries, of which the former comprises the Luodianian and the Xiangboan Stage, and the latter the Kufengian (Gufengian) and the Lengwuan Stage; the Lopingian (Lepingian) Series includes the Wuchiapingian (Wujiapingian) and the Changhsingian (Changxingian) Stage.展开更多
The amplitude of pre-Quaternary sea level drop, H, can be calculated by usingthe formula H = D + To, where To is the original thickness from the top of the tidal deposits onthe reef core to the bottom of the tidal dep...The amplitude of pre-Quaternary sea level drop, H, can be calculated by usingthe formula H = D + To, where To is the original thickness from the top of the tidal deposits onthe reef core to the bottom of the tidal deposits on the reef front, or to the bottom of the ancientmeteoric vadose zone, or to the edge of the mixed-water dolostone zone. The identity and similaritybetween the sea-level drop amplitudes calculated from different reefs far away from each otherindicates that such sea-level changes are eustatic rather than relative changes. Evidence of anend-Permian sea-level drop has been found on the Changxingian (i.e. the end of the Palaeofusulinazone) reefs at Ziyun in South China, including algal laminated deposits, sabkha-related dolostone,desiccation cracks, dissolution collapse breccia. According to calculation based on the meteoricdissolution zone of the reef-core sequence at Ziyun, Guizhou province, the amplitude of thesea-level drop at the end-Permian is about 89.3 m. Calculation via the dolomitized upper part of theChangxingian reef in Lichuan, Hubei Province, yields an 88.9 m amplitude of the sea-level drop atthe end-Permian. Comparison shows that the sea-level drop recorded in the two distantly locatedreefs may be of eustatic type. So the amplitude of the sea level drop of the Tethys Sea at theend-Permian might be at least 89.3 m.展开更多
The Carboniferous-Early Permian rift-related volcanic successions, covering large areas in the Chinese Tianshan and its adjacent areas, make up a newly recognized important Phanerozoic large igneous province in the wo...The Carboniferous-Early Permian rift-related volcanic successions, covering large areas in the Chinese Tianshan and its adjacent areas, make up a newly recognized important Phanerozoic large igneous province in the world, which can be further divided into two sub-provinces： Tianshan and Tarim. The regional unconformity of Lower Carboniferous upon basement or pre-Carboniferous rocks, the ages （360--351 Ma） of the youngest ophiolite and the peak of subduction metamorphism of high pressure-low temperature metamorphic belt and the occurrence of Ni-Cu-bearing mafic-ultramafic intrusion with age of ~352 Ma and A-type granite with age of ~358 Ma reveal that the final closure of the Paleo-Asian Ocean might take place in the Early Mississippian. Our summation shows that at least four criteria, being normally used to identify ancient asthenosphere upwelling （or mantle plumes）, are met for this large igneous province： （1） surface uplift prior to magmatism; （2） being associated with continental rifting and breakup events; （3） chemical characteristics of asthenosphere （or plume） derived basalts; （4） close links to large-scale mineralization and the uncontaminated basalts, being analogous to those of many ＂ore-bearing＂ large igneous provinces, display Sr-Nd isotopic variations between plume and EMI geochemical signatures, These suggest that a Carboniferous asthenosphere upwelling and an Early Permian plume played the central role in the generation of the Tianshan--Tarim （central Asia） large igneous province.展开更多
The Napo-Qinzhou Tectonic Belt （NQTB） lies at the junction of the Yangtze, Cathaysia and Indochina （North Vietnam） Blocks, which is composed of five major lithotectonic subunits： the Qinzhou-Fangcheng Suture Zone...The Napo-Qinzhou Tectonic Belt （NQTB） lies at the junction of the Yangtze, Cathaysia and Indochina （North Vietnam） Blocks, which is composed of five major lithotectonic subunits： the Qinzhou-Fangcheng Suture Zone （QFSZ）, the Shiwandashan Basin （SB）, the Pingxiang-Nanning Suture Zone （PNSZ）, the Damingshan Block （DB） and the Babu-Lingma Suture Zone （BLSZ）. On the basis of geochemical compositions, the Permian mafic igneous rocks can be divided into three distinct groups： （1） mafic igneous rocks （Group 1） from the Longjing region in the PNSZ and Hurun region in the BLSZ, which are characterized by intermediate Ti, P and Zr with low Ni and Cr contents; （2） mafic igneous rocks （Group 2） from the Naxiao and Chongzuo region in the DB, characterized by low-intermediate Ti, P and Zr with high Ni and Cr concentrations; and （3） mafic igneous rocks （Group 3） from the Siming region in the Jingxi carbonate platform of the northwestern margin of the NQTB, with intermediate-high Ti, P and Zr and low Ni and Cr contents. The Group 1 rocks yield a weighted mean 206 Pb/ 238 U age of 250.5±2.8 Ma and are geochemically similar to basalts occurring in back-arc basin settings. The Group 2 rocks exhibit geochemical features to those basalts in island arcs, whereas the Group 3 rocks show geochemical similarity to that of ocean island basalts. All three groups are characterized by relatively low ε Nd （t） values （-2.61 to ＋1.10） and high initial 87 Sr/ 86 Sr isotopic ratios （0.705309-0.707434）, indicating that they were derived from a subduction-modified lithospheric mantle and experienced assimilation, fractional crystallization, and crustal contamination or mixing during magmatic evolution. Accordingly, we propose the existence of an arc-back arc basin system that developed along the NQTB at the border of SW Guangxi Province （SW China） and northern Vietnam, and it was formed by continued northwestward subduction of the Cathaysian （or Yunkai） Block under the Yangtze Block, and northeastward subduction of the Indochina Block beneath the Yangtze Block during Permian time.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Supported by the National Science and Technology Major Project of China(2016ZX05061)Sinopec Science and Technology Department Project(P21042-4,P25030)。
文摘Based on the data of drilling,logging,experiment and gas testing in the Nanchuan area,southeastern Sichuan Basin,the hydrocarbon generation potential,gas genesis,occurrence state,migration,preservation conditions,pore and fracture features and accumulation evolution of the first member of Permian Maokou Formation(Mao 1 Member)are systematically studied,and the main controlling factors of unconventional gas enrichment and high production in marlstone assemblage of Mao 1 Member are discussed.(1)The enrichment and high yield of unconventional natural gas in the Mao 1 Member are controlled by three factors:carbon-rich fabric controlling hydrocarbon generation potential,good preservation controlling enrichment,and natural fracture controlling production.(2)The carbonate rocks of Mao 1 Member with carbon rich fabric have significant gas potential,exhibiting characteristics of self-generation and self-storage,which lays the material foundation for natural gas accumulation.(3)The occurrence state of natural gas is mainly free gas,which is prone to lateral migration,and good storage conditions are the key to natural gas enrichment.Positive structure is more conducive to natural gas accumulation,and a good compartment is created jointly by the self-sealing property of the Mao 1 Member and its top and bottom sealing property in monoclinal area,which is favorable for gas accumulation by retention.(4)Natural fractures are the main reservoir space and flow channel,and the more developed natural fractures are,the more conducive to the formation of high-quality porous-fractured reservoirs and the accumulation of natural gas,which is the core of controlling production.(5)The accumulation model of unconventional natural gas is proposed as“self-generation and self-storage,preservation controlling richness,and fractures controlling production”.(6)Identifying fracture development areas with good preservation conditions is the key to successful exploration,and implementing horizontal well staged acidizing and fracturing is an important means to increase production and efficiency.The study results are of referential significance for further understanding the natural gas enrichment in the Mao 1 Member and guiding the efficient exploration and development of new types of unconventional natural gas.
基金supported by the Xinjiang Key R&D Program(No.2022B03015-3)the National Natural Science Foundation of China(No.91962214)+1 种基金the Fundamental Research Funds for the Central Universities,Chang’an University(No.300102272201)the“Tianchi Talent”Plan to Chang-Zhi Wu.
文摘The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carboniferous and subsequent intracontinental extension since the Triassic have been well documented in the Chinese Altai,the southwestern segment of the CAOB.Deciphering the petrogenetic evolution of this region during the Permian is thus crucial for advancing our understanding of its tectonic transitions.However,the Permian tectonic setting of the Chinese Altai remains contentious.To address this knowledge gap,this study presents new geochronological and geochemical data for the Jiangjunshan pluton in the southern Chinese Altai.Zircon U-Pb geochronology reveals that the gabbro and two-mica alkali feldspar granite—which collectively constitute the primary lithology of the Jiangjunshan pluton—were emplaced at∼272±3.5 and∼272±1.6 Ma,respectively.Geochemically,the gabbro exhibits pronounced light rare-earth element(LREE)depletion,low Nb/Yb(0.39–0.46)and Ti/V(23.7–25.3)ratios,and trace-element signatures akin to normal mid-ocean ridge basalts(N-MORB).However,its conspicuous Nb-Ta depletion parallels that of island arc basalts.Depleted Hf-Nd isotopic compositions(ε_(Hf)(t)=+0.60 to+4.63,ε_(Nd)(t)=+6.32 to+7.80)in the gabbro,coupled with negligible correlation betweenε_(Nd)(t)and SiO2 contents imply limited crustal assimilation during magma evolution.Petrological modeling,based on Sm/Yb and La concentrations,suggests the gabbroic melt derived from∼8%–20%spinel lherzolte mantle melting.Analogously depleted Hf-Nd isotopes(ε_(Hf)(t)=+6.81 to+9.10,ε_(Nd)(t)=+0.79 to+1.45)in the granite,together with petrographic evidence lacking mafic-ultramafic xenoliths,point to a juvenile lower-crustal source.Integrating the gabbro’s N-MORB-like affinity with arc-specific features,regional ultrahigh-temperature metamorphism in southern Chinese Altai,and Permian tectonics,we propose a ridge-subduction regime as the likely petrogenetic setting for the Jiangjunshan magmas.During ridge subduction,upwelling of asthenospheric mantle beneath the ridge induced partial melting of the lithospheric mantle,giving rise to the parental magma of the Jiangjunshan gabbro.This mafic magma underplating subsequently heated the juvenile lower crust,triggering its partial melting and generating the parental magma of the two-mica alkali feldspar granite.Our model indicates that ridge-subduction-related magmatism persisted in the Chinese Altai until the Middle Permian,followed by a tectonic shift from oceanic-continental subduction to intracontinental extension.
基金Supported by the PetroChina Science&Technology Special Project(2023ZZ21YJ04)PetroChina Gas Reservoir Evaluation Project(20230304-08)。
文摘Based on the basic data of drilling,logging,testing and geological experiments,the geological characteristics of the Permian Dalong Formation marine shales in the northern Sichuan Basin and the factors controlling shale gas enrichment and high yield are studied.The results are obtained in four aspects.First,the high-quality shale of the Dalong Formation was formed after the deposition of the Permian Wujiaping Formation,and it is developed in the Kaijiang-Liangping trough in the northern part of Sichuan Basin,where deep-water continental shelf facies and deep-water reduction environment with thriving siliceous organisms have formed the black siliceous shale rich in organic matter.Second,the Dalong Formation shale contains both organic and inorganic pores,with stratification of alternated brittle and plastic minerals.In addition to organic pores,a large number of inorganic pores are developed even in ultra-deep(deeper than 4500 m)layers,contributing a total porosity of more than 5%,which significantly expands the storage space for shale gas.Third,the limestone at the roof and floor of the Dalong Formation acted as seal rock in the early burial and hydrocarbon generation stage,providing favorable conditions for the continuous hydrocarbon generation and rich gas preservation in shale interval.In the later reservoir stimulation process,it was beneficial to the lateral extension of the fractures,so as to achieve the optimal stimulation performance and increase the well-controlled resources.Combining the geological,engineering and economic conditions,the favorable area with depth less than 5500 m is determined to be 1800 km2,with resources of 5400×10^(8) m^(3).Fourth,the shale reservoirs of the Dalong Formation are thin but rich in shale gas.The syncline zone far away from the main faults in the high and steep tectonic zone,eastern Sichuan Basin,with depth less than 5500 m,is the most favorable target for producing the Permian shale gas under the current engineering and technical conditions.It mainly includes the Nanya syncline,Tanmuchang syncline and Liangping syncline.
基金the National Natural Science Foundation of China(No.41872232)。
文摘The Xing'an-Inner Mongolia Orogen is a critical tectonic unit for constraining the evolution of the Paleo-Asian Ocean.However,the location and time of the closure of the Paleo-Asian Ocean are still debated.Here,we select a representative basin in Dashizhai in northeastern China,using U-Pb zircon geochronology and geochemistry to analyze the sedimentary facies,depositional ages,and provenance.The results show that the ages of the Dashizhai Formation range from 400 to 347 Ma,the Shoushangou Formation range from 400 to 348 Ma,the Zhesi Formation range from 307 to 252 Ma,and the Linxi Formation range from 299 to 241 Ma.The Dashizhai Formation is composed of metamorphic andesite and clastic rocks.The Shoushangou Formation comprises siltstone,rhyolite,and argillaceous siltstone.The Zhesi and Linxi Formations are composed of mudstone and argillaceous siltstone.Geochemical data shows that these rocks are enriched in light rare earth elements and depleted in Eu with various La/Sc,Th/Sc,and La/Co ratios.The Permian Dashizhai Basin is from Permian volcanic and felsic igneous rocks from the Ergun,Xing'an,and Songliao blocks.The absence of the Late Carboniferous strata in the Dashizhai Basin indicates an extension setting during this period.Furthermore,we suggest the Xing'an-Inner Mongolia Orogen was an uplifting process associated with evolution the Paleo-Asian Ocean during the Late Permian.
基金financially supported by the Geological Survey of China(Grant Nos.DD20240075,and DD20243516)the National Natural Science Foundation of China(Grant No.41872209)Basic Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2314)。
文摘We report new SHRIMP zircon U-Pb ages,zircon Lu-Hf isotopic and whole rock geochemical data from Permian granitoids located in the Alxa area of Inner Mongolia,China.In combination with published geochronological and geochemical data,the granitoids in the region can be divided into two age groups:ca.285 Ma and ca.269 Ma.The granitoids of the first group are mainly composed of calc-alkaline to high-K calc-alkaline,weakly peraluminous Ⅰ-type granodiorites with ε_(Hf)(t)values of-19.6 to-4.3,which demonstrates evidence of crustal reworking;the granitoids of the second group,however,mainly consist of A-type granites that are high-K calc-alkaline to shoshonite,metaluminous to weakly peraluminous,and have high 10,000×Ga/Al ratios(2.59-3.12)and ε_(Hf)(t)values ranging from-11.3 to-2.7,all of which demonstrates a mixed crust-mantle source.We interpret the granitoids of the first group to have formed during the subduction of Central Asian oceanic crust and the second group to have formed by the asthenospheric upwelling caused by the formation of slab windows during late ocean ridge subduction.
基金Supported by the National Natural Science Foundation of China(42172166)National Natural Science Foundation and CNPC Joint Fund Project(U23B20154)CNPC-Southwest Petroleum University Science and Technology Cooperation Project(2020CX010000).
文摘This paper discusses the characteristics and formation mechanism of thin dolomite reservoirs in the lower submember of the second member of the Permian Maokou Formation(lower Mao 2 Member)in the Wusheng-Tongnan area of the Sichuan Basin,SW China,through comprehensive analysis of geological,geophysical and geochemical data.The reservoir rocks of the lower Mao 2 Member are dominated by porphyritic vuggy dolomite and calcareous dolomite or dolomitic limestone,which have typical karst characteristics of early diagenetic stage.The dolomites at the edge of the karst system and in the fillings have dissolved estuaries,and the dolomite breccia has micrite envelope and rim cement at the edge,indicating that dolomitization is earlier than the early diagenetic karstification.The shoal facies laminated dolomite is primarily formed by the seepage reflux dolomitization of moderate-salinity seawater.The key factors of reservoir formation are the bioclastic shoal deposition superimposed with seepgae reflux dolomitization and the karstification of early diagenetic stage,which are locally reformed by fractures and hydrothermal processes.The development of dolomite vuggy reservoir is closely related to the upward-shallowing sequence,and mainly occurs in the late highstand of the fourth-order cycle.Moreover,the size of dolomite is closely related to formation thickness,and it is concentrated in the formation thickness conversion area,followed by the thinner area.According to the understanding of insufficient accommodation space in the geomorphic highland and the migration of granular shoal to geomorphic lowland in the late highstand of the third-order cycle,it is proposed that the large-scale shoal-controlled dolomite reservoirs are distributed along structural highs and slopes,and the reservoir-forming model with shoal,dolomitization and karstification jointly controlled by the microgeomorphy and sea-level fluctuation in the sedimentary period is established.On this basis,the paleogeomorphology in the lower Mao 2 Member is restored using well-seismic data,and the reservoir distribution is predicted.The prediction results have been verified by the latest results of exploration wells and tests,which provide an important reference for the prediction of thin dolomite reservoirs under similar geological setting.
基金supported by the Natural Science Foundation of Shandong Province(ZR2023MD112)financially supported by Laoshan Laboratory(LSKJ202203401).
文摘Shale gas is abundant in the Paleozoic of the Yangtze Platform,and several high-yield shale gas fields have been built in the Upper Yangtze Platform,China.The Permian of the South Yellow Sea Basin(SYSB)in the Lower Yangtze area is considered a potential target for shale gas exploration;however,the fundamental geological conditions of shale gas have not been studied.Based on the first whole-cored scientific drilling borehole(CSDP-2)in the SYSB,detailed tests involving petrology,organic geochemistry,and reservoir physical properties were conducted to evaluate the shale gas potential of the Lower Permian.The Lower Permian is dominated by organic-rich siliceous,clay,and clay-mixed shales.The average total organic carbon content is 5.99%,and the organic matter is mainly type Ⅱ_(1)−Ⅱ_(2),which has entered the high-over mature evolution stage.The pore types of organic-rich shales mainly include organic pores,dissolution pores,and intergranular pores,of which the meso-/macropores are well developed.The average porosity is 3.04%,and the total specific surface area and pore volume are 3.47 m^(2)/g and 7.21×10^(−3) cm^(3)/g,respectively.The average Langmuir volume obtained from the methane adsorption isotherms is 2.70 cm^(3)/g,and methane is mainly adsorbed in the meso-/macropores.The lower Permian shales are rich in methane as indicated by gas logging results,with an average content of 7.3%,which can reach up to 65.9%.A comparison of the study area with typical shale gas fields shows that the Lower Permian is brittle and shallowly buried and has a high potential for shale gas exploration and low-cost development.The depression areas of the SYSB are overlain by thick Mesozoic-Cenozoic sediments,show higher organic matter maturity,and may have greater shale gas potential.The shale gas exploration breakthrough of the study area is of great significance to ensure the energy supply of economically developed areas on the east China.
基金This study was supported by the project ofthe Science and Technology Innovation Fund of Command Center of Natural Resources Intergrated Survey entitled“Temporal and spatial distribution of paleochannel and origin of organic carbon burial in the Western Bohai Sea since 2.28Ma”(KC20220011)the project entitled“Characterization of Carboniferous-Early Permian heterogeneous porous carbonate reservoirs and hydrocarbon potential analysis in the central uplift of the South Yellow Sea Basin”(KLSG2304)+3 种基金by the Key laboratory of Submarine Science,Ministry of Natural Resources,the project entitled“1∶50000 Marine regional Geological survey in Caofeidian Sea Area,Bohai Sea”(ZD20220602)“1∶250000 Marine regional Geological survey in Weihai Sea Area,North Yellow Sea”(DD20230412)“Geological survey on tectonic and sedimentary conditions of Laoshan uplift”(DD2016015)by the China Geological Survey,and the project entitled“Study on Hydrocarbon Accumulation Failure and Fluid Evolution Reduction of the Permian Reservoir in the Laoshan Uplift,South Yellow Sea”(42076220)organized by the National Natural Science Foundation of China.
文摘Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.
基金Supported by the National Science and Technology Major Project(2016ZX05007004-001)Innovation Fund Project of CNPC Carbonate Rock Key Laboratory(RIPED-HZDZY-2019-JS-695).
文摘To analyze the episodic alteration of Middle Permian carbonate reservoirs by complex hydrothermal fluid in southwestern Sichuan Basin,petrology,geochemistry,fluid inclusion and U-Pb dating researches are conducted.The fractures and vugs of Middle Permian Qixia–Maokou formations are filled with multi-stage medium-coarse saddle dolomites and associated hydrothermal minerals,which indicates that the early limestone/dolomite episodic alteration was caused by the large-scale,high-temperature,deep magnesium-rich brine along flowing channels such as basement faults or associated fractures under the tectonic compression and napping during the Indosinian.The time of magnesium-rich hydrothermal activity was from the Middle Triassic to the Late Triassic.The siliceous and calcite fillings were triggered by hydrothermal alteration in the Middle and Late Yanshanian Movement and Himalayan Movement.Hydrothermal dolomitization is controlled by fault,hydrothermal property,flowing channel and surrounding rock lithology,which occur as equilibrium effect of porosity and permeability.The thick massive grainstone/dolomites were mainly altered by modification such as hydrothermal dolomitization/recrystallization,brecciation and fracture-vugs filling.Early thin-medium packstones were mainly altered by dissolution and infilling of fracturing,bedding dolomitization,dissolution and associated mineral fillings.The dissolved vugs and fractures are the main reservoir space under hydrothermal conditions,and the connection of dissolved vugs and network fractures is favorable for forming high-quality dolomite reservoir.Hydrothermal dolomite reservoirs are developed within a range of 1 km near faults,with a thickness of 30–60 m.Hydrothermal dolomite reservoirs with local connected pore/vugs and fractures have exploration potential.
文摘Chansitheca (Sphenopteris) wudaensis sp. nov. is described based on the materials collected from the Lower Permian Shansi Formation of Wuda, Nei Mongol, China. The frond is small and at least two times pinnate. The pinnule is sphenopteroid. The sori are borne on the abaxial surface of the pinnule, arranged in two rows parallel to the midvein, elliptic,and composed of 4-10 round sporangia. The indusium is absent. The annulus is transverse and complete, and consists of about 18 thickened cells. The features of the fertile parts, sori, sporangia and annulus and the absence of indusium indicate that the new species belongs to the Gleicheniaceae.
文摘A kind of silicified fossil wood with mixed pits on the radial tracheid wall is described. The fossil wood was collected from the top of Taiyuan Formation (early Early Permian) in Wuda Mining District, Nei Mongol. Compared with the Paleozoic fossil woods in the world, it is put into Araucarioxylon Kraus and named as A. laoshidanense sp. nov. Based on the character of possessing mixed pittings (alternate and opposite pittings) on the radial tracheid wall, the fossil wood is believed to be one of the unknown primitive conifers.Diagnosis of the new species: Only secondary xylem preserved and consisting of axial tracheids and rays. Growth ring boundary, resin duct and axial parenchyma absent. One to Four (commonly 2 or 3) seriates of bordered pits (mostly alternate but sometimes opposite) on the radial tracheid wall. One to Four (commonly 1, rarely 2 to 4) Cupressoid pits in each cross_field. Rays usually uniseriate, sometimes partly_ biseriate and 2 to 39 (mainly 3-5) cells high.
文摘Although the research on Cordaites of the Cathaysian Flora in China started early in 1883, the study of the cordaitean cuticles began late in 1991. Up to now, four types of cordaitean cuticles in situ and three types of dispersed ones have been reported from the Cathaysian Flora in China. However compared with the Euramerican Flora, the research work on cordaitean cuticles from the Cathaysian Flora in China is much more insufficient. In this paper, three kinds of dispersed cordaitean cuticles are described in detail from the Permian coal-bearing strata in China. Among these cuticles two kinds are collected from the roof shale of Coal Seam No. A(1) in Shanxi Formation (Lower Permian) in Xinzhuangzhi Coal Mine of Huainan, Anhui Province, southern border of North China Subprovince of the Cathaysian Flora in China. The third one was collected from Coal Seam No. 11 in the top of Longtan Formation (lower Upper Permian) in Dahebian Coal Mine of Shuicheng Mining District, Guizhou Province, South China Subprovince of the Cathaysian Flora in China. Comparison of these three kinds of cordaitean cuticles with the known ones from the Cathaysian Flora in China and from the Euramerican Flora is made. The authors consider that they are all new types of cordaitean cuticles. The significance they bear on palaeobotany is discussed.
文摘Three kinds of anatomically_preserved lepidodendralean leaves from Permian coal balls of China were studied. They all have double xylem strands, which is consistent with the genus Sigillariopsis Scott. Compared with the species of Sigillariopsis , they are considered as three new species: S. shanxiensis sp. nov. and S. taiyuanensis sp. nov. from Coal Seam 7 in the upper part of the Taiyuan Formation (lower Lower Permian), Xishan Coal Field, Taiyuan, Shanxi Province and S. guizhouensis sp. nov. from Coal Seam 1 in the Wangjiazhai Formation (upper Upper Permian), Shuicheng Coal Mining District, Guizhou Province. Based on the associated organs of lepidodendraleans other than leaves and the information of the Euramerican lepidodendraleans, the affinities of the three new species of Sigillariopsis are discussed and they are probably leaves of Sigillaria Brongniart. In Euramerican Flora, Sigillaria (including its leaves Sigillariopsis ) mainly lived in the Carboniferous period and in the Cathaysian Flora they lived in the Upper Carboniferous to upper Upper Permian periods in rare localities. The leaves and fertile organs of Sigillaria have not been reported from the Cathaysian Flora to date. Three new species of the Permian anatomically_preserved leaves of Sigillaria not only increase the diversity of the Cathaysian sigillarian but also bear important significance on the evolution of sigillarian plants and the relationship of the Cathaysian and Euramerican lepidodendraleans.
基金supported by the Natural Science Foundation of China (Nos. 41172024, 41272044)the "973" Program (No. 2011CB808800)+2 种基金the "111" Project (No. B08030)the ‘Fundamental Research Funds for the Central Universities,China University of Geosciences (Wuhan)the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (No. GBL11202)
文摘The widespread microbialites deposition that followed the End-Permian mass extinction in the Tethyan realm have been intensively studied because of the evidence they provide on the nature of this crisis and its aftermath. However, the age of the microbialite event remains controversial. New conodont collection across the Permian–Triassic（P–T） transition from Dajiang（Guizhou Province, South China） in this study enable us to discriminate four conodont zones, in ascending order, they are： Hindeodus parvus zone, Isarcicella lobata zone, Isarcicella isarcica zone and Hindeodus sosioensis zone. The age of microbialite in the P–T transition at the Dajiang Section is considered to be within the Hindeodus parvus zone and thus to clearly post-date the main extinction crisis. Reviewing the age of onset of microbialites throughout the Tethyan regions reveals two different ages： a Hindeodus changxingensis zone age is dominant in south-western and westernmost Tethys, whilst most other regions show microbialite deposition began in the Hindeodus parvus zone. Our investigation also indicates that two conodont changes occur at this time： an increase of hindeodid species immediately following a sequence boundary and the mass extinction, and a phase of extinction losses in the earliest Triassic Isarcicella isarcica zone during highstand development.
基金supported by the Natural Science Foundation of China(Grant: 1212321013019,1212010070301,40672038 and 40872049)
文摘Laser ablation-inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating and geochemical data for the Permian gabbros and diorites in the Hunchun area are presented to constrain the regional tectonic evolution in the study area. Zircons from gabbro and diorite are euhedral-subhedral in shape and display fine-scale oscillatory zoning as well as high Th/U ratios （0.26-1.22）, implying their magmatic origin. The dating results indicate that the gabbro and diorite formed in the Early Permian （282-2 Ma） and in the Late Permian （255-3 Ma）, respectively. In addition, the captured zircons with the weighted mean age of 279-4 Ma are also found in the diorite, consistent with the formation age of the gabbro within uncertainty. The gabbros belong chemically to low-K tholeiitic series, and are characterized by low rare earth element （REE） abundances, fiat REE pattern, weak positive Eu anomalies （JEu）, and depletion in high field strength elements （HFSEs, Nb, Ta, and Ti）, similar to the high-aluminum basalts from island arc setting. Initial Hf isotopic ratios of zircons from the gabbro range from ＋7.63 to ＋14.6, suggesting that its primary magma could be mainly derived from partial melting of a depleted lithospheric mantle. The diorites belong to middle K calc-alkaline series. Compared with the gabbros, the diorites have higher REE abundance, weak negative Eu anomalies, and more depletion in HFSEs （Nb, Ta, and Ti）, similar chemically to the volcanic rocks from an active continental margin setting. Initial Hf isotopic ratios and Hf two-stage model ages of zircons from the diorite range from ＋11.22 to ＋14.17 and from 424 to 692 Ma, respectively, suggesting that its primary magma could be mainly derived from partial melting of the Early Paleozoic and/or Neoproterozoic accretted lower crust. Taken together, it is suggested that geochemical variations from the Early Permian gabbros to the Late Permian diorites reveal that the subduction of the Paleo-Asian oceanic plate beneath the Khanka Massif and collision between the arc and continent （Khanka Massif） happened in the late stage of the Late Paleozoic.
文摘Since the principle of multiple stratigraphic classification has been widely accepted by Chinese stratigraphers, various new Permian chronostratigraphic units have been proposed in China, and they need to be redefined. The establishment of a new global chronostratigraphic scheme of the Permian, compilation of Permian lithostratigraphic units and updating of Permian biostratigraphic sequences of China makes it possible to present a revised regional chronostratigraphic succession for the Permian System in China. This succession consists of three series and eight stages. The Chuanshanian Series includes two stages, the Zisongian and the Longlinian; the Yanghsinian (Yangxinian) Series is subdivided into the Chihsian (Qixiaan) and the Maokouan Subseries, of which the former comprises the Luodianian and the Xiangboan Stage, and the latter the Kufengian (Gufengian) and the Lengwuan Stage; the Lopingian (Lepingian) Series includes the Wuchiapingian (Wujiapingian) and the Changhsingian (Changxingian) Stage.
基金financially supported by the National Natural Science Foundation of China(No.40172007)the key project from the Chinese Academy of Sciences(No.K2951-B1-409)the Key Lab of Resources,CAS.
文摘The amplitude of pre-Quaternary sea level drop, H, can be calculated by usingthe formula H = D + To, where To is the original thickness from the top of the tidal deposits onthe reef core to the bottom of the tidal deposits on the reef front, or to the bottom of the ancientmeteoric vadose zone, or to the edge of the mixed-water dolostone zone. The identity and similaritybetween the sea-level drop amplitudes calculated from different reefs far away from each otherindicates that such sea-level changes are eustatic rather than relative changes. Evidence of anend-Permian sea-level drop has been found on the Changxingian (i.e. the end of the Palaeofusulinazone) reefs at Ziyun in South China, including algal laminated deposits, sabkha-related dolostone,desiccation cracks, dissolution collapse breccia. According to calculation based on the meteoricdissolution zone of the reef-core sequence at Ziyun, Guizhou province, the amplitude of thesea-level drop at the end-Permian is about 89.3 m. Calculation via the dolomitized upper part of theChangxingian reef in Lichuan, Hubei Province, yields an 88.9 m amplitude of the sea-level drop atthe end-Permian. Comparison shows that the sea-level drop recorded in the two distantly locatedreefs may be of eustatic type. So the amplitude of the sea level drop of the Tethys Sea at theend-Permian might be at least 89.3 m.
基金benefited from financial supports by Land and Resources Survey Project of China(Grant Nos.1212010611804, 121201120133)the National Natural Science Foundation of China(Grant No.40472044)
文摘The Carboniferous-Early Permian rift-related volcanic successions, covering large areas in the Chinese Tianshan and its adjacent areas, make up a newly recognized important Phanerozoic large igneous province in the world, which can be further divided into two sub-provinces： Tianshan and Tarim. The regional unconformity of Lower Carboniferous upon basement or pre-Carboniferous rocks, the ages （360--351 Ma） of the youngest ophiolite and the peak of subduction metamorphism of high pressure-low temperature metamorphic belt and the occurrence of Ni-Cu-bearing mafic-ultramafic intrusion with age of ~352 Ma and A-type granite with age of ~358 Ma reveal that the final closure of the Paleo-Asian Ocean might take place in the Early Mississippian. Our summation shows that at least four criteria, being normally used to identify ancient asthenosphere upwelling （or mantle plumes）, are met for this large igneous province： （1） surface uplift prior to magmatism; （2） being associated with continental rifting and breakup events; （3） chemical characteristics of asthenosphere （or plume） derived basalts; （4） close links to large-scale mineralization and the uncontaminated basalts, being analogous to those of many ＂ore-bearing＂ large igneous provinces, display Sr-Nd isotopic variations between plume and EMI geochemical signatures, These suggest that a Carboniferous asthenosphere upwelling and an Early Permian plume played the central role in the generation of the Tianshan--Tarim （central Asia） large igneous province.
基金Financial support for this study was jointly provided by the Hundred Talents Project of Ministry of Land and Resources of China, the Ten-Hundred-Thousand Talent Project of Guangxi (Grant No. 2006218)Guangxi Science Foundation (Grant No.0728089)+1 种基金Institute of Mineral Resources, Chinese Academy of Geological Sciences (Grant No. K0914)China Geological Survey (Grant No. 201111020 and1212010510805)
文摘The Napo-Qinzhou Tectonic Belt （NQTB） lies at the junction of the Yangtze, Cathaysia and Indochina （North Vietnam） Blocks, which is composed of five major lithotectonic subunits： the Qinzhou-Fangcheng Suture Zone （QFSZ）, the Shiwandashan Basin （SB）, the Pingxiang-Nanning Suture Zone （PNSZ）, the Damingshan Block （DB） and the Babu-Lingma Suture Zone （BLSZ）. On the basis of geochemical compositions, the Permian mafic igneous rocks can be divided into three distinct groups： （1） mafic igneous rocks （Group 1） from the Longjing region in the PNSZ and Hurun region in the BLSZ, which are characterized by intermediate Ti, P and Zr with low Ni and Cr contents; （2） mafic igneous rocks （Group 2） from the Naxiao and Chongzuo region in the DB, characterized by low-intermediate Ti, P and Zr with high Ni and Cr concentrations; and （3） mafic igneous rocks （Group 3） from the Siming region in the Jingxi carbonate platform of the northwestern margin of the NQTB, with intermediate-high Ti, P and Zr and low Ni and Cr contents. The Group 1 rocks yield a weighted mean 206 Pb/ 238 U age of 250.5±2.8 Ma and are geochemically similar to basalts occurring in back-arc basin settings. The Group 2 rocks exhibit geochemical features to those basalts in island arcs, whereas the Group 3 rocks show geochemical similarity to that of ocean island basalts. All three groups are characterized by relatively low ε Nd （t） values （-2.61 to ＋1.10） and high initial 87 Sr/ 86 Sr isotopic ratios （0.705309-0.707434）, indicating that they were derived from a subduction-modified lithospheric mantle and experienced assimilation, fractional crystallization, and crustal contamination or mixing during magmatic evolution. Accordingly, we propose the existence of an arc-back arc basin system that developed along the NQTB at the border of SW Guangxi Province （SW China） and northern Vietnam, and it was formed by continued northwestward subduction of the Cathaysian （or Yunkai） Block under the Yangtze Block, and northeastward subduction of the Indochina Block beneath the Yangtze Block during Permian time.
