A new model is suggested for the history of the Baikal Rift, in deviation from the classic twostage evolution scenario, based on a synthesis of the available data from the Baikal Basin and revised correlation between ...A new model is suggested for the history of the Baikal Rift, in deviation from the classic twostage evolution scenario, based on a synthesis of the available data from the Baikal Basin and revised correlation between tectonic-lithological-stratigraphic complexes （TLSC） in sedimentary sections around Lake Baikal and seismic stratigraphic sequences （SSS） in the lake sediments. Unlike the previous models, the revised model places the onset of rifting during Late Cretaceous and comprises three major stages which are subdivided into several substages. The stages and the substages are separated by events of tectonic activity and stress reversal when additional compression produced folds and shear structures. The events that mark the stage boundaries show up as gaps, unconformities, and deformation features in the deposition patterns. The earliest Late Cretaceous-Oligocene stage began long before the India-Eurasia collision in a setting of diffuse extension that acted over a large territory of Asia. The NW-SE far-field pure extension produced an NE-striking half-graben oriented along an old zone of weakness at the edge of the Siberian craton. That was already the onset of rift evolution recorded in weathered lacustrine deposits on the Baikal shore and in a wedge-shaped acoustically transparent seismic unit in the lake sediments. The second stage spanning Late Oligocene-Early Pliocene time began with a stress change when the effect from the Eocene India-Eurasia collision had reached the region and became a major control of its geodynamics. The EW and NE transpression and shear from the collisional front transformed the Late Cretaceous half-graben into a U-shaped one which accumulated a deformed layered sequence of sediments. Rifting at the latest stage was driven by extension from a local source associated with hot mantle material rising to the base of the rifted crust. The asthenospheric upwarp first induced the growth of the Baikal dome and the related change from finer to coarser molasse deposition. With time展开更多
Located at the northwest continental slope of the South China Sea, the Qiongdongnan Basin bears valley-shaped bathymetry deepening toward east. It is separated from the Yinggehai Basin through NW-trending Indo-China-R...Located at the northwest continental slope of the South China Sea, the Qiongdongnan Basin bears valley-shaped bathymetry deepening toward east. It is separated from the Yinggehai Basin through NW-trending Indo-China-Red River shear zone, and connected with NW subsea basin through the Xisha Trough. Along with the rapid progress of the deepwater exploration, large amounts of high resolution geophysical and geological data were accumulated. Scientific researches about deepwater basins kept revealing brand new tectonic and sedimentary discoveries. In order to summarize the structural features and main controlling factors of the deepwater Qiongdongnan Basin, a series of researches on basin architecture, fault activities, tectonic deformation and evolution were carried out. In reference to analogue modeling experiments, a tectonic situation and a basin formation mechanism were discussed. The researches indicate that：the northern boundary of the Qiongdongnan Basin is strongly controlled by No. 2 fault. The overlapping control of two stress fields from the east and the west made the central depression zone extremely thinned. Combined with the changed stress field, the segmentation of a preexisting weakness zone made the sags in the east experiencing different rifting histories from the west ones. The NE-trending west segment of the Qiongdongnan Basin experienced strong rifting during Eocene, while the roughly EW-trending sags in the east segment show strong rifting during late Eocene and early Oligocene. Local structures such as NW-trending basal fault and inherited uplifts controlled the lateral segmentation. So first order factors such as regional stress field and preexisting weakness zone controlled the basin zonation, while the second order factors determined the segmentation from east to west.展开更多
Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those...Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation （Es4s） on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope （SEM） observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as ＂alkaline-acidic-alkaline-acidic-weak alkaline＂. As a result, dissolution and cementation are also very complex, and the sequence is ＂early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation＂. The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inne展开更多
By examining structures,sediments,reservoirs and accumulation assemblages in the Deyang-Anyue rift and its surrounding area,four new understandings are obtained.First,during the initiation period of Deyang-Anyue rift,...By examining structures,sediments,reservoirs and accumulation assemblages in the Deyang-Anyue rift and its surrounding area,four new understandings are obtained.First,during the initiation period of Deyang-Anyue rift,multiple groups of faults developed in the rift due to the effect of tensile force,bringing about multiple mound and shoal belts controlled by horsts in the second member of the Sinian Dengying Formation;in the development stage of the rift,the boundary faults of the rift controlled the development of mound and shoal belts at the platform margin in the fourth member of Dengying Formation;during the shrinkage period of the rift,platform margin grain shoals of the Cambrian Canglangpu Formation developed in the rift margin.Second,four sets of large-scale mound and shoal reservoirs in the second member of Dengying Formation,the fourth member of Dengying Formation,Canglangpu Formation and Longwangmiao Formation overlap with several sets of source rocks such as Qiongzhusi Formation source rocks and Dengying Formation argillaceous limestone or dolomite developed inside and outside the rift,forming good source-reservoir-cap rock combinations;the sealing of tight rock layers in the lateral and updip direction results in the formation model of large lithologic gas reservoirs of oil pool before gas,continuous charging and independent preservation of each gas reservoir.Third,six favorable exploration zones of large-scale lithologic gas reservoirs have been sorted out through comprehensive evaluation,namely,mound and shoal complex controlled by horsts in the northern part of the rift in the second member of Dengying Formation,isolated karst mound and shoal complex of the fourth member of Dengying Formation in the south of the rift,the superimposed area of multi-stage platform margin mounds and shoals of the second and fourth members of Dengying Formation and Canglangpu Formation in the north slope area,the platform margin mounds and shoals of the second and fourth members of Dengying Formation in the west side of展开更多
The Mesoproterozoic rifts are developed in the Ordos Basin located in the western margin of the North China Plate.Based on the latest 3D seismic data and previous research results,this study intends to discuss the zon...The Mesoproterozoic rifts are developed in the Ordos Basin located in the western margin of the North China Plate.Based on the latest 3D seismic data and previous research results,this study intends to discuss the zonal differential deformation characteristics and genetic mechanism of the Mesoproterozoic rifts in the Ordos Basin.NE-trending rifts are developed in the Mesoproterozoic in the south-central Ordos Basin,the main part of which are located near the western margin of the North China Plate.NNW-trending rifts are developed in the north of the basin,while NW-NNW rifts in the Mesoproterozoic in Hangjinqi area.The genetic mechanism of the Mesoproterozoic rifts is related to regional extensional stress field,plate boundary conditions and internal preexisting structures.The main extensional stress direction strikes NWW-SSE(120°)in the western margin of the North China Plate,based on the forward rift trend of the northern Mesoproterozoic.In Hangjinqi area,the reactivation of the existing NWtrending Wulansu fault and NW-NW-trending Daolao fault,results in dextral shear stress field.The boundary between the western margin of the North China Plate and its adjacent plates forms a nearly NS-trending preexisting basement tectonic belt,which intersects with the NWW-SSE(120°)extensional stress at an acute angle of 60°.Therefore,the western margin of the North China Plate is formed by oblique normal faults under oblique extension.Due to the long time span of Columbia Supercontinent breakup(1.8e1.6 Ga),the oblique rift in the south-central Ordos Basin is formed under the continuous oblique extension at the western margin of the North China Plate.展开更多
文摘A new model is suggested for the history of the Baikal Rift, in deviation from the classic twostage evolution scenario, based on a synthesis of the available data from the Baikal Basin and revised correlation between tectonic-lithological-stratigraphic complexes （TLSC） in sedimentary sections around Lake Baikal and seismic stratigraphic sequences （SSS） in the lake sediments. Unlike the previous models, the revised model places the onset of rifting during Late Cretaceous and comprises three major stages which are subdivided into several substages. The stages and the substages are separated by events of tectonic activity and stress reversal when additional compression produced folds and shear structures. The events that mark the stage boundaries show up as gaps, unconformities, and deformation features in the deposition patterns. The earliest Late Cretaceous-Oligocene stage began long before the India-Eurasia collision in a setting of diffuse extension that acted over a large territory of Asia. The NW-SE far-field pure extension produced an NE-striking half-graben oriented along an old zone of weakness at the edge of the Siberian craton. That was already the onset of rift evolution recorded in weathered lacustrine deposits on the Baikal shore and in a wedge-shaped acoustically transparent seismic unit in the lake sediments. The second stage spanning Late Oligocene-Early Pliocene time began with a stress change when the effect from the Eocene India-Eurasia collision had reached the region and became a major control of its geodynamics. The EW and NE transpression and shear from the collisional front transformed the Late Cretaceous half-graben into a U-shaped one which accumulated a deformed layered sequence of sediments. Rifting at the latest stage was driven by extension from a local source associated with hot mantle material rising to the base of the rifted crust. The asthenospheric upwarp first induced the growth of the Baikal dome and the related change from finer to coarser molasse deposition. With time
基金The Major National Science and Technology Programs of China under contract No.2011ZX05025-003-005the Joint Program of the National Science Foundation and Guangdong Province under contract No.U1301233
文摘Located at the northwest continental slope of the South China Sea, the Qiongdongnan Basin bears valley-shaped bathymetry deepening toward east. It is separated from the Yinggehai Basin through NW-trending Indo-China-Red River shear zone, and connected with NW subsea basin through the Xisha Trough. Along with the rapid progress of the deepwater exploration, large amounts of high resolution geophysical and geological data were accumulated. Scientific researches about deepwater basins kept revealing brand new tectonic and sedimentary discoveries. In order to summarize the structural features and main controlling factors of the deepwater Qiongdongnan Basin, a series of researches on basin architecture, fault activities, tectonic deformation and evolution were carried out. In reference to analogue modeling experiments, a tectonic situation and a basin formation mechanism were discussed. The researches indicate that：the northern boundary of the Qiongdongnan Basin is strongly controlled by No. 2 fault. The overlapping control of two stress fields from the east and the west made the central depression zone extremely thinned. Combined with the changed stress field, the segmentation of a preexisting weakness zone made the sags in the east experiencing different rifting histories from the west ones. The NE-trending west segment of the Qiongdongnan Basin experienced strong rifting during Eocene, while the roughly EW-trending sags in the east segment show strong rifting during late Eocene and early Oligocene. Local structures such as NW-trending basal fault and inherited uplifts controlled the lateral segmentation. So first order factors such as regional stress field and preexisting weakness zone controlled the basin zonation, while the second order factors determined the segmentation from east to west.
基金co-funded by the National Natural Science Foundation of China (41102058)the National Science and Technology Special Grant (2011ZX05006-003)the Fundamental Research Funds for the Central Universities (12CX04001A)
文摘Diagenetic traps in conglomerate in nearshore subaqueous fans in the steep slope zones of rift basins have been important exploration targets for subtle reservoirs in eastern China. However, the mechanism of how those traps were formed is not clear, which inhibits further exploration for this type of reservoir. In order to solve the problem, we take as an example nearshore subaqueous fans in the upper part of the fourth member of the Shahejie Formation （Es4s） on the north slope of the Minfeng Subsag in the Dongying Sag. Combining different research methods, such as core observation, thin section examination, scanning electron microscope （SEM） observation, fluid-inclusion analysis, carbon and oxygen isotope analysis of carbonate cements, and analysis of core properties, we studied the genetic mechanisms of diagenetic traps on the basis of diagenetic environment evolution and diagenetic evolution sequence in different sub/micro-facies. Conglomerate in Es4s in the north Minfeng Subsag experienced several periods of transition between alkaline and acidic environments as ＂alkaline-acidic-alkaline-acidic-weak alkaline＂. As a result, dissolution and cementation are also very complex, and the sequence is ＂early pyrite cementation / siderite cementation / gypsum cementation / calcite and dolomite cementation- feldspar dissolution / quartz overgrowth quartz dissolution / ferroan calcite cementation / ankerite cementation / lime-mud matrix recrystallization / feldspar overgrowth carbonate dissolution / feldspar dissolution / quartz overgrowth / pyrite cementation＂. The difference in sedimentary characteristics between different sub/micro-facies of nearshore subaqueous fans controls diagenetic characteristics. Inner fan conglomerates mainly experienced compaction and lime-mud matrix recrystallization, with weak dissolution, which led to a reduction in the porosity and permeability crucial to reservoir formation. Lime-mud matrix recrystallization results in a rapid decrease in porosity and permeability in inne
基金Supported by the National Science and Technology Major Project(2016ZX05007-002)。
文摘By examining structures,sediments,reservoirs and accumulation assemblages in the Deyang-Anyue rift and its surrounding area,four new understandings are obtained.First,during the initiation period of Deyang-Anyue rift,multiple groups of faults developed in the rift due to the effect of tensile force,bringing about multiple mound and shoal belts controlled by horsts in the second member of the Sinian Dengying Formation;in the development stage of the rift,the boundary faults of the rift controlled the development of mound and shoal belts at the platform margin in the fourth member of Dengying Formation;during the shrinkage period of the rift,platform margin grain shoals of the Cambrian Canglangpu Formation developed in the rift margin.Second,four sets of large-scale mound and shoal reservoirs in the second member of Dengying Formation,the fourth member of Dengying Formation,Canglangpu Formation and Longwangmiao Formation overlap with several sets of source rocks such as Qiongzhusi Formation source rocks and Dengying Formation argillaceous limestone or dolomite developed inside and outside the rift,forming good source-reservoir-cap rock combinations;the sealing of tight rock layers in the lateral and updip direction results in the formation model of large lithologic gas reservoirs of oil pool before gas,continuous charging and independent preservation of each gas reservoir.Third,six favorable exploration zones of large-scale lithologic gas reservoirs have been sorted out through comprehensive evaluation,namely,mound and shoal complex controlled by horsts in the northern part of the rift in the second member of Dengying Formation,isolated karst mound and shoal complex of the fourth member of Dengying Formation in the south of the rift,the superimposed area of multi-stage platform margin mounds and shoals of the second and fourth members of Dengying Formation and Canglangpu Formation in the north slope area,the platform margin mounds and shoals of the second and fourth members of Dengying Formation in the west side of
文摘The Mesoproterozoic rifts are developed in the Ordos Basin located in the western margin of the North China Plate.Based on the latest 3D seismic data and previous research results,this study intends to discuss the zonal differential deformation characteristics and genetic mechanism of the Mesoproterozoic rifts in the Ordos Basin.NE-trending rifts are developed in the Mesoproterozoic in the south-central Ordos Basin,the main part of which are located near the western margin of the North China Plate.NNW-trending rifts are developed in the north of the basin,while NW-NNW rifts in the Mesoproterozoic in Hangjinqi area.The genetic mechanism of the Mesoproterozoic rifts is related to regional extensional stress field,plate boundary conditions and internal preexisting structures.The main extensional stress direction strikes NWW-SSE(120°)in the western margin of the North China Plate,based on the forward rift trend of the northern Mesoproterozoic.In Hangjinqi area,the reactivation of the existing NWtrending Wulansu fault and NW-NW-trending Daolao fault,results in dextral shear stress field.The boundary between the western margin of the North China Plate and its adjacent plates forms a nearly NS-trending preexisting basement tectonic belt,which intersects with the NWW-SSE(120°)extensional stress at an acute angle of 60°.Therefore,the western margin of the North China Plate is formed by oblique normal faults under oblique extension.Due to the long time span of Columbia Supercontinent breakup(1.8e1.6 Ga),the oblique rift in the south-central Ordos Basin is formed under the continuous oblique extension at the western margin of the North China Plate.
