As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale ...As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.展开更多
In the south of the Ordos Basin, the oil source of the Upper Triassic Yanchang Formation is confused all the time, which affects further exploration. In this study, oil sources from the oil layers of Ch6, Ch8 and Ch9 ...In the south of the Ordos Basin, the oil source of the Upper Triassic Yanchang Formation is confused all the time, which affects further exploration. In this study, oil sources from the oil layers of Ch6, Ch8 and Ch9 are all analyzed and confirmed. Through their carbon isotope value and biomarkers, characteristics of crude oils from the Yanchang Formation are analyzed. Then, the oil–source relation is discussed, with the source rocks' features.Finally, the oil–source relation is calculated through cluster analysis. It is believed that the oils from the Yanchang Formation deposit in a similar redox environment, with weak oxidation–weak reduction, and have all entered maturity stage. Ch9 crude oil is more mature than crude oils from Ch6 and Ch8, and has more advanced plants and fewer algae. Gas chromatography(GC) and gas chromatography–mass spectrometry(GC–MS) analysis show that crude oils from Ch6 and Ch8 may come from Ch7, and Ch9 crude oil may not. Cluster analysis displays that crude oils from Ch6 and Ch8 have closer squared Euclidean distance with Ch7 source rocks than Ch9 crude oil does,indicating crude oils from Ch6 and Ch8 stem from Ch7 source rocks. And Ch9 crude oil has rather close squared Euclidean distance with Ch9 source rocks, illustrating Ch9 crude oil may be from Ch9 source rocks. This research may provide the theoretical basis for the next exploration deploy in the south of Ordos Basin.展开更多
Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray d...Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield(average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals,quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As,Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K,Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V+ Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.展开更多
Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little at...Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little attention. Oil yield, major element, trace element, rare earth element, and total sulfur （TS） data from the oil shale within the Yanchang are here presented and discussed in the context of hydrothermal influence. Oil shale samples returned relatively high total organic carbon （TOC）, in the range of 4.69%-25.48%. A high correlation between TS and TOC suggests TS in the oil shale is dominated by organic sulfur and affected by organic matter. The low Al/ Si ratio of oil shale samples implies quartz is a major mineralogical component. Si/（Si ＋ Al ＋ Fe） values suggest close proximity of the oil shale to a terrigenous source. δEu; Fe versus Mn versus （Cu ＋ Co ＋ Ni）× 10; and SiO2/（K2O ＋ Na2O） versus MnO/TiO2, Fe/Ti, and （Fe ＋ Mn）/Ti are evidence of hydrothermal fluid activity during oil shale sedimentation, and δU and U/Th of the oil shale indicate reducing conditions. The Sr/Ba of oil shale samples suggests fresh-water deposition. The high correlations of Fe/Ti and （Fe ＋ Mn）/Ti with δU, U/Th, and TS demonstrate that hydrothermal fluid activity promotes reducing conditions. Sr/Ba ratios had low correlation with Fe/Ti and （Fe ＋ Mn）/Ti, implying that hydrothermal fluid activity had little impact （Fe ＋ Mn）/Ti, δU, U/Th, and on paleosalinity. Fe/Ti, Cu ＋ Pb ＋ Zn all exhibited high positive correlation coefficients with TOC in oil shale samples, suggesting that more intense hydrothermal fluid activity improves conditions in favor of formation and preservation of organic matter.展开更多
Analysis of tectonothermal history of the Yanchang Formation in the western Weibei Uplift and in the northwestern Weihe Basin can reconstruct the cooling history of the southwest most remained Upper Triassic source ro...Analysis of tectonothermal history of the Yanchang Formation in the western Weibei Uplift and in the northwestern Weihe Basin can reconstruct the cooling history of the southwest most remained Upper Triassic source rock of the North China Plate. Apatite fission-track(AFT) and(U-ThSm)/He(AHe) analysis were used to recover the cooling and uplift history of the Upper Triassic here. Ten sandstones from the Middle–Upper Triassic strata yield AFT ages between 179.8 ± 7.4 and 127.6 ± 8.1 Ma. AHe ages of two sandstones have the value of 37.7 ± 2.3–131.1 ± 8.1 and 45.7 ± 2.8–83.5 ± 5.2 Ma. Time-temperature modeling results showed that tectonothermal history of the Yanchang Formation was initially different in time-space relationships but then became almost identical through time followed by different cooling rate. Modeling results of the Triassic strata in the Qianyang area and the Yaojiagou area revealed three different uplift-cooling stages commencing in the Late Jurassic at ~165 Ma and in Early Cretaceous at ~110 Ma, respectively, both followed by first similar cooling histories to the Early Miocene at ~20 – 23 Ma and then different since the Late Miocene. Uplift-cooling rate since the Late Miocene at ~8 Ma were different between the Western Weibei Uplift and the Northwestern Weihe Basin. The timing, cooling-uplift rates of the Yaojiagou area, which was mainly controlled by movements related to the Liupanshan Mountains, the Qinling Orogens and the Weibei Uplift, had the earliest onset of uplift-cooling for the Upper Triassic series compared to other regions within the Weibei Uplift. Cooling paths for the Upper Triassic series became uniform regionally in the Early Cretaceous marking a key time for the tectonothermal evolutionary history of Upper Triassic series in the southwestern North China Plate.展开更多
The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion.In this prominent stage,rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been ...The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion.In this prominent stage,rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped.In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi,China in 2003.By studying on functional morphology and analogy with mouthpart of Punctatus,there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth.The appearance of coelenterates marks the real beginning of metazoan evolution.Therefore,it has the prominent position in the origin and evolutionary history of organisms.Perhaps the star-like organism represents the early types of coelenterate with original tentacles.These new materials provide new evidence for the origin,evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.展开更多
基金supported with funding from the National Natural Science Foundation of China (No. 41173055)the Fundamental Research Funds for the Central Universities (No. 310827172101)
文摘As an important unconventional resource, oil shale has received widespread attention. The oil shale of the Chang 7 oil layer from Triassic Yanchang Formation in Ordos Basin represents the typical lacustrine oil shale in China. Based on analyzing trace elements and oil yield from boreholes samples, characteristics and paleo-sedi- mentary environments of oil shale and relationship between paleo-sedimentary environment and oil yield were studied. With favorable quality, oil yield of oil shale varies from 1.4% to 9.1%. Geochemical data indicate that the paleo-redox condition of oil shale＇s reducing condition from analyses of V/Cr, V/（V ＋ Ni）, U/Th, δU, and authi genic uranium. Equivalent Boron, Sp, and Sr/Ba illustrate that paleosalinity of oil shale is dominated by fresh water. The paleoclimate of oil shale is warm and humid by calculating the chemical index of alteration and Sr/Cu. Fe/Ti and （Fe ＋ Mn）/Ti all explain that there were hot water activities during the sedimentary period of oil shale. In terms of Zr/Rb, paleohydrodynamics of oil shale is weak. By means of Co abundance and U/Th, paleo-water-depth of oil shale is from 17.30 to 157.26 m, reflecting sedimentary environment which is mainly in semi deep-deep lake facies. Correlation analyses between oil yield and six paleoenvironmental factors show that the oil yield of oil shale is mainly controlled by paleo-redox conditions, paleoclimate, hot water activities, and depth of water.Paleosalinity and paleohydrodynamics have an inconspicuous influence on oil yield.
基金supported with funding from the National Natural Science Foundation of China(No.41173055)
文摘In the south of the Ordos Basin, the oil source of the Upper Triassic Yanchang Formation is confused all the time, which affects further exploration. In this study, oil sources from the oil layers of Ch6, Ch8 and Ch9 are all analyzed and confirmed. Through their carbon isotope value and biomarkers, characteristics of crude oils from the Yanchang Formation are analyzed. Then, the oil–source relation is discussed, with the source rocks' features.Finally, the oil–source relation is calculated through cluster analysis. It is believed that the oils from the Yanchang Formation deposit in a similar redox environment, with weak oxidation–weak reduction, and have all entered maturity stage. Ch9 crude oil is more mature than crude oils from Ch6 and Ch8, and has more advanced plants and fewer algae. Gas chromatography(GC) and gas chromatography–mass spectrometry(GC–MS) analysis show that crude oils from Ch6 and Ch8 may come from Ch7, and Ch9 crude oil may not. Cluster analysis displays that crude oils from Ch6 and Ch8 have closer squared Euclidean distance with Ch7 source rocks than Ch9 crude oil does,indicating crude oils from Ch6 and Ch8 stem from Ch7 source rocks. And Ch9 crude oil has rather close squared Euclidean distance with Ch9 source rocks, illustrating Ch9 crude oil may be from Ch9 source rocks. This research may provide the theoretical basis for the next exploration deploy in the south of Ordos Basin.
基金supported by funding from the National Natural Science Foundation of China (No.41173055)the Fundamental Research Funds for the Central Universities (No.310827172101)
文摘Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield(average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals,quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As,Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K,Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V+ Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.
基金supported with funding from the National Natural Science Foundation of China (No. 41173055)the Fundamental Research Funds for the Central Universities (No. 310827172101)
文摘Hydrothermal fluid activity during sedimenta- tion of the Triassic Yanchang Formation in the Ordos Basin and the impact of said activity on formation and preservation conditions of source rocks have received little attention. Oil yield, major element, trace element, rare earth element, and total sulfur （TS） data from the oil shale within the Yanchang are here presented and discussed in the context of hydrothermal influence. Oil shale samples returned relatively high total organic carbon （TOC）, in the range of 4.69%-25.48%. A high correlation between TS and TOC suggests TS in the oil shale is dominated by organic sulfur and affected by organic matter. The low Al/ Si ratio of oil shale samples implies quartz is a major mineralogical component. Si/（Si ＋ Al ＋ Fe） values suggest close proximity of the oil shale to a terrigenous source. δEu; Fe versus Mn versus （Cu ＋ Co ＋ Ni）× 10; and SiO2/（K2O ＋ Na2O） versus MnO/TiO2, Fe/Ti, and （Fe ＋ Mn）/Ti are evidence of hydrothermal fluid activity during oil shale sedimentation, and δU and U/Th of the oil shale indicate reducing conditions. The Sr/Ba of oil shale samples suggests fresh-water deposition. The high correlations of Fe/Ti and （Fe ＋ Mn）/Ti with δU, U/Th, and TS demonstrate that hydrothermal fluid activity promotes reducing conditions. Sr/Ba ratios had low correlation with Fe/Ti and （Fe ＋ Mn）/Ti, implying that hydrothermal fluid activity had little impact （Fe ＋ Mn）/Ti, δU, U/Th, and on paleosalinity. Fe/Ti, Cu ＋ Pb ＋ Zn all exhibited high positive correlation coefficients with TOC in oil shale samples, suggesting that more intense hydrothermal fluid activity improves conditions in favor of formation and preservation of organic matter.
基金supported by the National Natural Science Foundation of China (Nos.41630312,41602128,41703055)the “Research Grants by China Geological Survey (No.DD20160060)”+2 种基金the “Fundamental Research Funds for the Central UniversitiesCHD (Nos.300102279206,300102278204)”the fund from China Scholarship Council。
文摘Analysis of tectonothermal history of the Yanchang Formation in the western Weibei Uplift and in the northwestern Weihe Basin can reconstruct the cooling history of the southwest most remained Upper Triassic source rock of the North China Plate. Apatite fission-track(AFT) and(U-ThSm)/He(AHe) analysis were used to recover the cooling and uplift history of the Upper Triassic here. Ten sandstones from the Middle–Upper Triassic strata yield AFT ages between 179.8 ± 7.4 and 127.6 ± 8.1 Ma. AHe ages of two sandstones have the value of 37.7 ± 2.3–131.1 ± 8.1 and 45.7 ± 2.8–83.5 ± 5.2 Ma. Time-temperature modeling results showed that tectonothermal history of the Yanchang Formation was initially different in time-space relationships but then became almost identical through time followed by different cooling rate. Modeling results of the Triassic strata in the Qianyang area and the Yaojiagou area revealed three different uplift-cooling stages commencing in the Late Jurassic at ~165 Ma and in Early Cretaceous at ~110 Ma, respectively, both followed by first similar cooling histories to the Early Miocene at ~20 – 23 Ma and then different since the Late Miocene. Uplift-cooling rate since the Late Miocene at ~8 Ma were different between the Western Weibei Uplift and the Northwestern Weihe Basin. The timing, cooling-uplift rates of the Yaojiagou area, which was mainly controlled by movements related to the Liupanshan Mountains, the Qinling Orogens and the Weibei Uplift, had the earliest onset of uplift-cooling for the Upper Triassic series compared to other regions within the Weibei Uplift. Cooling paths for the Upper Triassic series became uniform regionally in the Early Cretaceous marking a key time for the tectonothermal evolutionary history of Upper Triassic series in the southwestern North China Plate.
基金The author thank Qian Yi researcher proposed the constructive revision opinion and the suggestion to this article.
文摘The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion.In this prominent stage,rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped.In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi,China in 2003.By studying on functional morphology and analogy with mouthpart of Punctatus,there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth.The appearance of coelenterates marks the real beginning of metazoan evolution.Therefore,it has the prominent position in the origin and evolutionary history of organisms.Perhaps the star-like organism represents the early types of coelenterate with original tentacles.These new materials provide new evidence for the origin,evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.
