Setting up the hypostratotype of late Precambrian is the main aim of the research on the Meso- and Neoproterozoic in North China. The chronostratigraphic position is the key in this study. However, many key horizons h...Setting up the hypostratotype of late Precambrian is the main aim of the research on the Meso- and Neoproterozoic in North China. The chronostratigraphic position is the key in this study. However, many key horizons have not been calibrated with the high-quafity isotopic ages. Using the reported new U-Pb age with the Sensitive High-Resolution Ion Microprobe （SHRIMP Ⅱ）, a zircon U- Pb age was obtained of the ash bed in the Xiamaling Formation in North China Plate, yielding a weighted mean ^206pb/^238U age of 1368±12 Ma. It is the first SHRIMP U-Pb age from the Xiamaling Formation in the North China Plate, and represents the depositing time of the middle part of the Xiamaling Formation. The zircon age plays an important role to understanding geological evolution of the North China Plate during Meso- and Neoproterozoic.展开更多
Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters.In this study,scanning electron microscopy,hig...Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters.In this study,scanning electron microscopy,high-pressure mercury intrusion and low-temperature nitrogen adsorption experiments were used to qualitatively and quantitatively characterize the pore structure of black shale from the third member of the Xiamaling Formation in the Yanshan area.The pore heterogeneity was studied using fractal theory,and the controlling factors of pore development and heterogeneity were evaluated in combination with geochemical parameters,mineral composition,and geological evolution history.The results show that the pore structure of the reservoir was intricate and complicated.Moreover,various types of micro-nano scale pores such as dissolution pores,intergranular pores,interlayer pores,and micro-cracks are well developed in member 3 of the Xiamaling Formation.The average porosity was found to be 6.30%,and the mean value of the average pore size was 4.78 nm.Micropores and transition pores provided most of the storage space.Pore development was significantly affected by the region and was mainly related to the total organic carbon content,vitrinite reflectance and mineral composition.The fractal dimension,which characterizes the heterogeneity,is 2.66 on average,indicating that the pore structure is highly heterogeneous.Fractal dimension is positively correlated with maturity and clay mineral content,while it is negatively correlated with brittle mineral content and average pore size.These results indicate that pore heterogeneity is closely related to thermal history and material composition.Combined with the geological background of this area,it was found that the pore heterogeneity was mainly controlled by the Jurassic magmatism.The more intense the magma intrusion,the stronger the pore heterogeneity.The pore structure and its heterogeneity characteristics present today are a general reflection of the superimposed geological processes of sedimentary-diagenetic-late transformation.The influence of magmatic intrusion on the reservoir is the main geological factor that should be considered for detailed evaluation of the Xiamaling Formation shale gas reservoir in the Yanshan area.展开更多
Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reserv...Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs.This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section,Hebei Province,based on experimental data such as TOC,SEM,VRo,low-temperature N_(2)adsorption and high-pressure mercury injection.The results show that the dyke intrusion reduced the shale TOC content drastically―by up to 77%―and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion.Furthermore,the dyke intrusion might transform organic pores in surrounding shales into inorganic pores.There were two shale porosity peaks:one appeared when VRo=2.0%,caused by the increase of organic pores as thermal maturity increased,the other occurred when the VRo value was between 3%and 4%,caused by the increase of inorganic mineral pores.It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.展开更多
A suit of oil shales, predominated by black argillaceous silicalite and finely laminated black-brown shale, has been discovered in a set of carbonaceous-siliceous mudstone formations (350 m in thickness) in the third ...A suit of oil shales, predominated by black argillaceous silicalite and finely laminated black-brown shale, has been discovered in a set of carbonaceous-siliceous mudstone formations (350 m in thickness) in the third member of Xiamaling Formation of the Upper Proterozoic Qingbaikou Series (900―873 MaBP), Xiahuayuan, Hebei Province, China. The oil shale, combustible with strong bitumen odour, has su- per-high TOC contents ranging from 21.4% to 22.9%, bitumen “A” contents from 0.58% to 0.88% and oil length from 5.29% to 10.57%. The ultrathin section observation of the shale and the identification of its kerogen demonstrate that its hydrocarbon-generative parent material is mainly benthonic Rhodophyta whose specific tetrasporangia are legible and abundant. It is rarely reported in the literature that such a hydrocarbon-generative parent material, composed mainly of Rhodophyta and with extraordinarily high contents of TOC and bitumen “A”, developed into a set of high-quality source rocks. The extracts of the oil shale are characteristic of richness in 17α(H)-diahopanes and n-alkyl tricyclic terpenoids but low in steranes. Such a biomarker feature is obviously different from that of the extracts from other Proterozoic marine carbonate source rocks of the studied area. Since the biological constitution of this oil shale is rather simple, it is clear that these biomarkers most likely represent to certain extent the specific mo- lecular constitutions of the benthonic Rhodophyta identified in the ultrathin sections of the samples. Studies on its lithologic association and depositional sequences suggest that this suit of the carbona- ceous-siliceous mudstone formation, which contains oil shales, was probably developed in an under- compensation deep-bay environment when a maximum transgression occurred during the formation of the third member of Xiamaling Formation. The high concentration of SiO2 in this organic-rich rock and the positive correlation between TOC and some trace elements such as P, Cu, Ni, W and Mo indicate that this suit of rocks was affected by activities of bottom thermal currents as deposited.展开更多
The semi-closed pyrolysis simulation system under constant pressure was conducted to explore the characteristics and mechanisms of hydrocarbon generation from Xiamaling Formation shale in Xiahuayuan,North China.The ex...The semi-closed pyrolysis simulation system under constant pressure was conducted to explore the characteristics and mechanisms of hydrocarbon generation from Xiamaling Formation shale in Xiahuayuan,North China.The experiment results indicate the oil generated by the Xiamaling Formation shale in oil window should be classified as "aromatic-intermediate" type,whereas the decreasing of dry coefficient can be ascribed to the cracking of residual bitumen in source rock in the stage of high to post maturity.The amount of hydrocarbon gas generated from residual bitumen can be up to 1-2 m3 per ton rock in high to post mature stage by calculating hydrogen contents in the kerogen,the expelled hydrocarbon,and the residual hydrocarbon.This reveals the importance of residual bitumen as a gas source during high to post mature stage of the kerogen evolution,and also as the broad exploration prospect of these gases.This research highlights the attention should be paid to oil/gas reservoirs sourced from residual bitumen of organic-rich source rock in high mature stage,even the primary oil/gas reservoirs considered as the main exploration targets in middle-upper Proterozoic sediments of North China.展开更多
The rate of net primary production in the Proterozoic ocean was suggested to be no more than 10% of its modern value(Laakso and Schrag,2019),however,in the Mesoproterozoic Xiamaling Formation,the export production val...The rate of net primary production in the Proterozoic ocean was suggested to be no more than 10% of its modern value(Laakso and Schrag,2019),however,in the Mesoproterozoic Xiamaling Formation,the export production values could reach 20%-150% of the present-day Equatorial Atlantic average values(Zhang et al.,2016).Here,we report Zn and Cu isotope data for black shales from the Xiamaling Formation to illustrate the biogeochemical cycling of Zn and Cu in the Mesoproterozoic ocean.The ^(65)Cu-enriched signature in the authigenic fraction is similar to that in bioauthigenic Cu of the modern marine sediments.The Zn isotope ratios of sediments deposited in euxinic conditions are commonly higher than those of clastic sediments,indicating light Zn sinks in the coeval ocean.Combined with previously reported Mo isotope data,the proportion of organic carbon to total carbon burial in the Mesoproterozoic was about as half as that at present,which is larger than the previous estimation―a quarter of today’s value(e.g.,Ozaki et al.,2019) and is evidenced by a wide distribution of black shales.The organic burial may be ascribed to the increasing phosphorus inputs from large igneous provinces and consequently high primary productivity,which has spurred the hypothesized atmosphere-ocean oxygenation at ~1.4 Ga.展开更多
The accumulation of oxygen is one of the most important characteristics that distinguish Earth from other planets in the solar system,which is also considered to be the key factor influencing the birth and evolution o...The accumulation of oxygen is one of the most important characteristics that distinguish Earth from other planets in the solar system,which is also considered to be the key factor influencing the birth and evolution of complex life forms.The oxygenation process of the Earth surface has long been viewed to be episodic with two critical intervals occurring in the early Paleoproterozoic(2.45-2.10 Ga)and the late Neoproterozoic(0.80-0.54 Ga),with a 1.3-billion-year-long low oxygen period in between.Recently,increasing independent works carried out by different scientific teams in the Yanliao Basin,North China are demonstrating that the atmospheric oxygen concentrations had reached>4%PAL(present atmospheric levels)at least during 1.59-1.56,1.44-1.43,and 1.40-1.36 Ga.These estimated values are higher than the previously recommended values of<0.1-1%PAL.Such a scenario discovered in the Yanliao Basin is consistent with the synchronously deposited strata in Australia and Siberia,pointing to a Mesoproterozoic oxygenation event(1.59-1.36 Ga)between the two major oxygenation intervals during the Proterozoic.This Mesoproterozoic oxygenation event is coupled with the break-up of the Columbia(Nuna)supercontinent,the formation of organic-rich shales and Fe-Mn deposits,and the early innovation of eukaryotic algae,indicating that the geological and biological co-evolutionary processes control the Earth surface system.展开更多
Biomineralization was a key development in a wide variety of organisms,yet its history prior to the Ediacaran remains poorly understood.In this paper,we describe~1420-1330 million year old microscopic tubes preserved ...Biomineralization was a key development in a wide variety of organisms,yet its history prior to the Ediacaran remains poorly understood.In this paper,we describe~1420-1330 million year old microscopic tubes preserved as siderite(FeCO_(3)).In size and shape these tubes closely resemble cyanobacterial sheaths forming mineralized mats.We consider two competing explanations for their formation.First,the tubes and associated sediment were originally composed of Ca-carbonate that was subsequently replaced by siderite.In this case,siderite mineralization was early,but post-mortem,as in early silicification,and preferentially preserved the more resilient sheath.However,no relict calcite is observed.Second,the Fe-carbonate mineralogy of the tubes and sediment is synsedimentary.In this case,photosynthetic oxygen may have precipitated Fe-oxyhydroxide that was promptly converted to siderite by dissimilatory iron reduction(DIR).Primary siderite mineralization of cyanobacteria has not been described before.Both explanations link photosynthetic processes to preferential sheath mineralization during the life of the cyanobacteria,as observed in present-day calcified cyanobacteria.This process might include CO_(2)-concentrating mechanisms(CCMs)linked to relatively low levels of atmospheric CO_(2),consistent with empirical estimates of mid-Proterozoic CO_(2)levels based on paleosols and weathering rinds.In either case,these cyanobacterium-like fossils preserved in siderite provide an early example of biomineralization and suggest the interactive in-fluences of both metabolic processes and ambient seawater chemistry.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40621002 and Grant No.2006FY120300-1)the Program for Changjiang Scholars and Innovative Research Team in university(Grant No.IRT0546).
文摘Setting up the hypostratotype of late Precambrian is the main aim of the research on the Meso- and Neoproterozoic in North China. The chronostratigraphic position is the key in this study. However, many key horizons have not been calibrated with the high-quafity isotopic ages. Using the reported new U-Pb age with the Sensitive High-Resolution Ion Microprobe （SHRIMP Ⅱ）, a zircon U- Pb age was obtained of the ash bed in the Xiamaling Formation in North China Plate, yielding a weighted mean ^206pb/^238U age of 1368±12 Ma. It is the first SHRIMP U-Pb age from the Xiamaling Formation in the North China Plate, and represents the depositing time of the middle part of the Xiamaling Formation. The zircon age plays an important role to understanding geological evolution of the North China Plate during Meso- and Neoproterozoic.
基金supported by the Natural Science Foundation of Jiangsu Province (BK20181362)the National Natural Science Foundation of China (No. 41772141)+3 种基金the Scientific Research Foundation of Hebei Province (No. 2014995001)the National Science and Technology Major Project (2017ZX05035004)the Fundamental Research Funds for the Central Universities (2017CXNL03)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters.In this study,scanning electron microscopy,high-pressure mercury intrusion and low-temperature nitrogen adsorption experiments were used to qualitatively and quantitatively characterize the pore structure of black shale from the third member of the Xiamaling Formation in the Yanshan area.The pore heterogeneity was studied using fractal theory,and the controlling factors of pore development and heterogeneity were evaluated in combination with geochemical parameters,mineral composition,and geological evolution history.The results show that the pore structure of the reservoir was intricate and complicated.Moreover,various types of micro-nano scale pores such as dissolution pores,intergranular pores,interlayer pores,and micro-cracks are well developed in member 3 of the Xiamaling Formation.The average porosity was found to be 6.30%,and the mean value of the average pore size was 4.78 nm.Micropores and transition pores provided most of the storage space.Pore development was significantly affected by the region and was mainly related to the total organic carbon content,vitrinite reflectance and mineral composition.The fractal dimension,which characterizes the heterogeneity,is 2.66 on average,indicating that the pore structure is highly heterogeneous.Fractal dimension is positively correlated with maturity and clay mineral content,while it is negatively correlated with brittle mineral content and average pore size.These results indicate that pore heterogeneity is closely related to thermal history and material composition.Combined with the geological background of this area,it was found that the pore heterogeneity was mainly controlled by the Jurassic magmatism.The more intense the magma intrusion,the stronger the pore heterogeneity.The pore structure and its heterogeneity characteristics present today are a general reflection of the superimposed geological processes of sedimentary-diagenetic-late transformation.The influence of magmatic intrusion on the reservoir is the main geological factor that should be considered for detailed evaluation of the Xiamaling Formation shale gas reservoir in the Yanshan area.
基金funded by the National Key R&D Program(2017YFC060302)the National Natural Science Foundation of China(41872155,41872164 and 42172168)。
文摘Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale.Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs.This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section,Hebei Province,based on experimental data such as TOC,SEM,VRo,low-temperature N_(2)adsorption and high-pressure mercury injection.The results show that the dyke intrusion reduced the shale TOC content drastically―by up to 77%―and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion.Furthermore,the dyke intrusion might transform organic pores in surrounding shales into inorganic pores.There were two shale porosity peaks:one appeared when VRo=2.0%,caused by the increase of organic pores as thermal maturity increased,the other occurred when the VRo value was between 3%and 4%,caused by the increase of inorganic mineral pores.It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.
基金Supported by the China State 973 Scientific Program Contribution (Grant No. G19990433)
文摘A suit of oil shales, predominated by black argillaceous silicalite and finely laminated black-brown shale, has been discovered in a set of carbonaceous-siliceous mudstone formations (350 m in thickness) in the third member of Xiamaling Formation of the Upper Proterozoic Qingbaikou Series (900―873 MaBP), Xiahuayuan, Hebei Province, China. The oil shale, combustible with strong bitumen odour, has su- per-high TOC contents ranging from 21.4% to 22.9%, bitumen “A” contents from 0.58% to 0.88% and oil length from 5.29% to 10.57%. The ultrathin section observation of the shale and the identification of its kerogen demonstrate that its hydrocarbon-generative parent material is mainly benthonic Rhodophyta whose specific tetrasporangia are legible and abundant. It is rarely reported in the literature that such a hydrocarbon-generative parent material, composed mainly of Rhodophyta and with extraordinarily high contents of TOC and bitumen “A”, developed into a set of high-quality source rocks. The extracts of the oil shale are characteristic of richness in 17α(H)-diahopanes and n-alkyl tricyclic terpenoids but low in steranes. Such a biomarker feature is obviously different from that of the extracts from other Proterozoic marine carbonate source rocks of the studied area. Since the biological constitution of this oil shale is rather simple, it is clear that these biomarkers most likely represent to certain extent the specific mo- lecular constitutions of the benthonic Rhodophyta identified in the ultrathin sections of the samples. Studies on its lithologic association and depositional sequences suggest that this suit of the carbona- ceous-siliceous mudstone formation, which contains oil shales, was probably developed in an under- compensation deep-bay environment when a maximum transgression occurred during the formation of the third member of Xiamaling Formation. The high concentration of SiO2 in this organic-rich rock and the positive correlation between TOC and some trace elements such as P, Cu, Ni, W and Mo indicate that this suit of rocks was affected by activities of bottom thermal currents as deposited.
基金supported by National Natural Science Foundation of China(Grant Nos.40972093 and 41172112)Natural Science Foundation of Zhejiang Province(Grant No.R5080124)+1 种基金Foundation of State Key Laboratory of Enhanced Oil Recoverythe Foundation of State Key Laboratory of Petroleum Resource and Prospecting(Grant No.2009001)
文摘The semi-closed pyrolysis simulation system under constant pressure was conducted to explore the characteristics and mechanisms of hydrocarbon generation from Xiamaling Formation shale in Xiahuayuan,North China.The experiment results indicate the oil generated by the Xiamaling Formation shale in oil window should be classified as "aromatic-intermediate" type,whereas the decreasing of dry coefficient can be ascribed to the cracking of residual bitumen in source rock in the stage of high to post maturity.The amount of hydrocarbon gas generated from residual bitumen can be up to 1-2 m3 per ton rock in high to post mature stage by calculating hydrogen contents in the kerogen,the expelled hydrocarbon,and the residual hydrocarbon.This reveals the importance of residual bitumen as a gas source during high to post mature stage of the kerogen evolution,and also as the broad exploration prospect of these gases.This research highlights the attention should be paid to oil/gas reservoirs sourced from residual bitumen of organic-rich source rock in high mature stage,even the primary oil/gas reservoirs considered as the main exploration targets in middle-upper Proterozoic sediments of North China.
基金supported by the National Key R&D Program of China(No.2019YFA0708400)the National Natural Science Foundation of China(No.42003013)。
文摘The rate of net primary production in the Proterozoic ocean was suggested to be no more than 10% of its modern value(Laakso and Schrag,2019),however,in the Mesoproterozoic Xiamaling Formation,the export production values could reach 20%-150% of the present-day Equatorial Atlantic average values(Zhang et al.,2016).Here,we report Zn and Cu isotope data for black shales from the Xiamaling Formation to illustrate the biogeochemical cycling of Zn and Cu in the Mesoproterozoic ocean.The ^(65)Cu-enriched signature in the authigenic fraction is similar to that in bioauthigenic Cu of the modern marine sediments.The Zn isotope ratios of sediments deposited in euxinic conditions are commonly higher than those of clastic sediments,indicating light Zn sinks in the coeval ocean.Combined with previously reported Mo isotope data,the proportion of organic carbon to total carbon burial in the Mesoproterozoic was about as half as that at present,which is larger than the previous estimation―a quarter of today’s value(e.g.,Ozaki et al.,2019) and is evidenced by a wide distribution of black shales.The organic burial may be ascribed to the increasing phosphorus inputs from large igneous provinces and consequently high primary productivity,which has spurred the hypothesized atmosphere-ocean oxygenation at ~1.4 Ga.
基金This work was supported by the Strategic Priority Science and Technology Program of Chinese Academy of Sciences(Class A)(Grant No.XDA14010101)the National Key Research and Development Program(Grant No.2017YFC0603101)the National Natural Science Foundation of China(Grant Nos.41872125,41530317).
文摘The accumulation of oxygen is one of the most important characteristics that distinguish Earth from other planets in the solar system,which is also considered to be the key factor influencing the birth and evolution of complex life forms.The oxygenation process of the Earth surface has long been viewed to be episodic with two critical intervals occurring in the early Paleoproterozoic(2.45-2.10 Ga)and the late Neoproterozoic(0.80-0.54 Ga),with a 1.3-billion-year-long low oxygen period in between.Recently,increasing independent works carried out by different scientific teams in the Yanliao Basin,North China are demonstrating that the atmospheric oxygen concentrations had reached>4%PAL(present atmospheric levels)at least during 1.59-1.56,1.44-1.43,and 1.40-1.36 Ga.These estimated values are higher than the previously recommended values of<0.1-1%PAL.Such a scenario discovered in the Yanliao Basin is consistent with the synchronously deposited strata in Australia and Siberia,pointing to a Mesoproterozoic oxygenation event(1.59-1.36 Ga)between the two major oxygenation intervals during the Proterozoic.This Mesoproterozoic oxygenation event is coupled with the break-up of the Columbia(Nuna)supercontinent,the formation of organic-rich shales and Fe-Mn deposits,and the early innovation of eukaryotic algae,indicating that the geological and biological co-evolutionary processes control the Earth surface system.
基金supported by the National Natural Science Foundation of China(Grant Nos.41930320,41972028)the National Key Research and Development Project of China(Grant No.2020YFA0714803)the Chinese"111"Project(Grant No.B20011)。
文摘Biomineralization was a key development in a wide variety of organisms,yet its history prior to the Ediacaran remains poorly understood.In this paper,we describe~1420-1330 million year old microscopic tubes preserved as siderite(FeCO_(3)).In size and shape these tubes closely resemble cyanobacterial sheaths forming mineralized mats.We consider two competing explanations for their formation.First,the tubes and associated sediment were originally composed of Ca-carbonate that was subsequently replaced by siderite.In this case,siderite mineralization was early,but post-mortem,as in early silicification,and preferentially preserved the more resilient sheath.However,no relict calcite is observed.Second,the Fe-carbonate mineralogy of the tubes and sediment is synsedimentary.In this case,photosynthetic oxygen may have precipitated Fe-oxyhydroxide that was promptly converted to siderite by dissimilatory iron reduction(DIR).Primary siderite mineralization of cyanobacteria has not been described before.Both explanations link photosynthetic processes to preferential sheath mineralization during the life of the cyanobacteria,as observed in present-day calcified cyanobacteria.This process might include CO_(2)-concentrating mechanisms(CCMs)linked to relatively low levels of atmospheric CO_(2),consistent with empirical estimates of mid-Proterozoic CO_(2)levels based on paleosols and weathering rinds.In either case,these cyanobacterium-like fossils preserved in siderite provide an early example of biomineralization and suggest the interactive in-fluences of both metabolic processes and ambient seawater chemistry.
