Sedimentology And Geochemical Characteristics Of Classic Rocks In The Member I Of Xiamaling Formation And The Member I Of Chuanlinggou Formation,Proterozoic

In this paper,the outcrop samples of the member I of Xiamaling formation in Huayuan district and the member I of Chuanlinggou formation in Xuanhua city are taken as the research objects,guided by the theories and methods of organic geochemistry and element geochemistry,combined with sedimentology,sedimentary facies and previous research results,this paper analyzes in detail the geochemical characteristics of the first member of Chuanlinggou formation and the first member of Xiamaling formation in North China,and advances the possible iron bearing structures of the two horizons based on experimental data The paleosedimentary environment formed by source rocks in this area is systematically restored and reconstructed.The experimental results show that the distribution of organic carbon and total sulfur is in the range of 0.04%-1.46%and 0.028%-0.171%in the first member of Chuanlinggou formation.The distribution pattern of n-alkanes in the samples is mainly bimodal,with obvious odd even advantage.The mean value of Morane/Hopane is 0.14,which indicates that the organic matter in the first member of Chuanlinggou formation is mainly from prokaryotic bacteria and algae.The correlation diagram of Ph/nC₁₈-Pr/nC₁₇and gamma wax number indicate that the sedimentary period of this section should be in barrier island lagoon environment.The mean value of MPI-1 and Rc is 0.31 and 2.12 in the methylphenanthrene parameter,which reflect that the evolution of organic matter has reached over mature stage.The results of ordinary trace element analysis show that the layer is affected by the input of material source to a certain extent and not by the activity of hydrothermal solution.The parameters of V/(V+Ni),Ni/Co and U/Th indicate that the layer is mainly located in the anoxic reduction environment,and the enrichment factors of Mn,Co and Mo are significantly different.In the first member of Xiamaling formation,TOC organic carbon is between0.079%-0.525%,total sulfur is between 0.0048%-0.038%,organic matter type is Type?,thermal evolution has reached mature stage.The distribution pattern of n-alkanes in the samples is mainly single peak type,and the odd even advantage is not obvious.The mean value of Morane/Hopane is 0.29,which reflects that the organic matter of the first member of Xiamaling formation mainly comes from prokaryotic bacteria and algae,but eukaryotes also have an important contribution to its organic matter.The correlation diagram of Ph/nc18-Pr/nc17 and the gamma wax number indicate that the sedimentary period of this section should be in a normal shallow water partial reduction environment.The mean value of MPI-1 and Rc is 0.39 and 2.07 respectively,which indicates that the evolution degree of organic matter has reached the mature over mature stage.The results of ordinary trace element analysis show that this layer is affected by a large extent of source input,not by hydrothermal activity.The parameters of trace elements such as Ni/Co,V/(V+Ni)and U/Th indicate that this section is mainly located in anoxic reduction environment,and the enrichment factors of Cu elements in the upper and lower sections show obvious differences.The TOC of the member I of Xiamaling formation and the member I of Chuanlinggou formation is relatively low,both of them are in the over mature stage,belong to the non hydrocarbon source rock horizon,and the oil and gas exploration prospect is relatively low.