The role of microorganisms in the formation of giant ooids is one of the areas of long-term controversy in ooidal research,but it has not been confirmed conclusively.Abundant giant ooids developed in the Zhangxia Form...The role of microorganisms in the formation of giant ooids is one of the areas of long-term controversy in ooidal research,but it has not been confirmed conclusively.Abundant giant ooids developed in the Zhangxia Formation of the Cambrian Miaolingian Series in North China.Giant ooids in the study area were examined by using Polarized Light Microscopy and Field Emission Environmental Scanning Electron Microscopy.The nuclei of the ooids consist of micritic pellets or radial ooids with diameters less than 2 mm and are formed in a weak-agitating seawater environment.Their cortices are concentric,and are characterized by the alternations of the dark laminae of micritic calcite or Girvanella filaments and light laminae of microsparry calcite.In the environments of inter-bank sea with the alternating development of medium and low energy and chiefly weak-agitating conditions,giant ooids were formed under the joint action of Girvanella filamentous growth,biologically-induced calcification and/or biologically-influenced calcification and inorganic calcium carbonate precipitation.The microfossils of Girvanella are distributed in inner and outer cortices of giant ooids,especially dense in the latter.This distinctly indicates that microbes play a significant role in the formation of giant ooids,and also provides a vital example for discussing the microbial origin of giant ooids.展开更多
Coalbed gases (CBG) in Enhong syncline are characterized by high concentration of C2+ (C2-5 ), with the highest content of ethane over 30%. However, the concentrations of C2+ are not evenly distributed in the syncline...Coalbed gases (CBG) in Enhong syncline are characterized by high concentration of C2+ (C2-5 ), with the highest content of ethane over 30%. However, the concentrations of C2+ are not evenly distributed in the syncline. Based on the analysis of δ13C1 , δ13C2 , δ13C3 , δ13CO2 , δDCH4 of CBG and their origin diagrams in the normal and abnormal areas, this research shows that gases in both areas are thermogenic gases and the reason for the uneven distribution of C2+ is that the microbial degradation action on gases is stronger in the normal area than in the abnormal area. The secondary biologic gases in the normal area are mainly characterized by that the carbon isotopes become obviously lighter in methane and become heavier in ethane, whereas the molecular and isotopic compositions of CO2 change little. These features indicate that the secondary biologic gases are mainly generated by the microbial degradation of C2+ , not generated by the reduction of CO2 . The degradation process is selective to make the residual ethane being enriched in 13C and the generated methane rich in 12C.展开更多
基金financially supported by the National Natural Science Foundation of China(Giants No:41872111 and 41902115)。
文摘The role of microorganisms in the formation of giant ooids is one of the areas of long-term controversy in ooidal research,but it has not been confirmed conclusively.Abundant giant ooids developed in the Zhangxia Formation of the Cambrian Miaolingian Series in North China.Giant ooids in the study area were examined by using Polarized Light Microscopy and Field Emission Environmental Scanning Electron Microscopy.The nuclei of the ooids consist of micritic pellets or radial ooids with diameters less than 2 mm and are formed in a weak-agitating seawater environment.Their cortices are concentric,and are characterized by the alternations of the dark laminae of micritic calcite or Girvanella filaments and light laminae of microsparry calcite.In the environments of inter-bank sea with the alternating development of medium and low energy and chiefly weak-agitating conditions,giant ooids were formed under the joint action of Girvanella filamentous growth,biologically-induced calcification and/or biologically-influenced calcification and inorganic calcium carbonate precipitation.The microfossils of Girvanella are distributed in inner and outer cortices of giant ooids,especially dense in the latter.This distinctly indicates that microbes play a significant role in the formation of giant ooids,and also provides a vital example for discussing the microbial origin of giant ooids.
基金supported by the Key Program of the National Natural Science Foundation of China (No. 40730422)the Key Special Project of the National Science and Technology of China (No.2011ZX05034)the Fundamental Research Funds for the Central Universities of China (No. 2010QNA51)
文摘Coalbed gases (CBG) in Enhong syncline are characterized by high concentration of C2+ (C2-5 ), with the highest content of ethane over 30%. However, the concentrations of C2+ are not evenly distributed in the syncline. Based on the analysis of δ13C1 , δ13C2 , δ13C3 , δ13CO2 , δDCH4 of CBG and their origin diagrams in the normal and abnormal areas, this research shows that gases in both areas are thermogenic gases and the reason for the uneven distribution of C2+ is that the microbial degradation action on gases is stronger in the normal area than in the abnormal area. The secondary biologic gases in the normal area are mainly characterized by that the carbon isotopes become obviously lighter in methane and become heavier in ethane, whereas the molecular and isotopic compositions of CO2 change little. These features indicate that the secondary biologic gases are mainly generated by the microbial degradation of C2+ , not generated by the reduction of CO2 . The degradation process is selective to make the residual ethane being enriched in 13C and the generated methane rich in 12C.
