Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore charact...Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.展开更多
In light of the principle of sequence stratigraphy, detailed analysis of depositionalsequences and systematical carbon isotope measurements were done for the Triticites zone ofthe typical Late Carboniferous section in...In light of the principle of sequence stratigraphy, detailed analysis of depositionalsequences and systematical carbon isotope measurements were done for the Triticites zone ofthe typical Late Carboniferous section in the Dushan area of southern Guizhou. Two sequencesand seventeen parasequences, which can be correlated with the two sequences and seventeensubsequences in the North American Midcontinent, are distinguished in the Gzhelian, whichprovides convincing evidence of the global synchroneity of the depositional records. The inter-nal relations between carbon isotope evolution and eustasy were studied and the evolutionarycharacteristics of carbon isotopes in depositional sequences have been summarized.展开更多
A new Mazon-Creek-type fossil specimen is described as Sumixam maximus gen.and sp.nov., assigned to the taxon Archaeorthoptera Bethoux and Nel,2002(composed of Orthoptera and some fossil relatives):it exhibits one of ...A new Mazon-Creek-type fossil specimen is described as Sumixam maximus gen.and sp.nov., assigned to the taxon Archaeorthoptera Bethoux and Nel,2002(composed of Orthoptera and some fossil relatives):it exhibits one of the diagnostic character states of this taxon,which is the fusion of CuA(emerging from M+CuA)with CuP,or a branch of it.A more precise taxonomic assignment is out of reach.The new taxon exhibits a fusion of the anterior branch of MA with RP,and a point of divergence of MA and MP located near the point of divergence of CuA(from M + CuA),but lack a branching of CuPa.This unique combination of character states is probably derived with respect to a number of contemporaneous species.Sumixam maximus gen.and sp.nov.is most likely the closest known relative of the panorthopterans,which include all the recent Archaeorthoptera.展开更多
基金Supported by the PetroChina Science and Technology Innovation Fund Project(2021DQ02-1003)Basic Research Project for Central Universities(2022JCCXDC02).
文摘Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.
基金This study was jointly supported by the national research project "sequence stratigraphy of ancient continent and peripheral areas and change of sea level in East China" and the doctoral station of sedimentology at University of Petroleum,Beijing.
文摘In light of the principle of sequence stratigraphy, detailed analysis of depositionalsequences and systematical carbon isotope measurements were done for the Triticites zone ofthe typical Late Carboniferous section in the Dushan area of southern Guizhou. Two sequencesand seventeen parasequences, which can be correlated with the two sequences and seventeensubsequences in the North American Midcontinent, are distinguished in the Gzhelian, whichprovides convincing evidence of the global synchroneity of the depositional records. The inter-nal relations between carbon isotope evolution and eustasy were studied and the evolutionarycharacteristics of carbon isotopes in depositional sequences have been summarized.
文摘A new Mazon-Creek-type fossil specimen is described as Sumixam maximus gen.and sp.nov., assigned to the taxon Archaeorthoptera Bethoux and Nel,2002(composed of Orthoptera and some fossil relatives):it exhibits one of the diagnostic character states of this taxon,which is the fusion of CuA(emerging from M+CuA)with CuP,or a branch of it.A more precise taxonomic assignment is out of reach.The new taxon exhibits a fusion of the anterior branch of MA with RP,and a point of divergence of MA and MP located near the point of divergence of CuA(from M + CuA),but lack a branching of CuPa.This unique combination of character states is probably derived with respect to a number of contemporaneous species.Sumixam maximus gen.and sp.nov.is most likely the closest known relative of the panorthopterans,which include all the recent Archaeorthoptera.
