Characteristics and origin of lacustrine dolostone of the PaleogeneShahejie Formation in Tanggu area,Bohai Bay Basin
Wang Bingjie1, Cai Mingjun2, Lin Chunming1, Zhang Xia1, Cheng Yuanzhong2, Qu Changwei1, Zhang Ni1,3
1 State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering, Nanjing University,Nanjing 210093,Jiangsu 2 PetroChina Dagang Oilfield Company,Tianjin 300280 3 Jinling Institute of Technology,Nanjing 211169,Jiangsu
Abstract：The Member 3 of Paleogene Shahejie Formation,in the Tanggu area of Huanghua Depression,Bohai Bay Basin,was formed in semi-enclosed lake bay environment,with one set of dolostone reservoir developed at its bottom.The dolostone,with a cumulative thickness up to 100 meters,was mainly distributed along the sides of a buried hill as controlled by a NE trending basement fault.Generally,it was interbedded with mudstone in this area.Petrological,mineralogical and geochemical characteristics were studied,which shows:(1)The dolomite minerals are mainly ankerite and ferruginous dolomite,which are micrites under an optical microscope while rhombohedral crystals under a scanning electron microscope(SEM).(2)X-ray diffraction analysis indicates that this kind of micritic dolostone was formed during the penecontemporaneous period,and is the product of rapid crystallization.(3)The analytical result of the carbon and oxygen isotopes and the rare earth elements shows that it was formed in a relatively closed and high salinity evaporitic environment,and owns an unified fluid source and the same genetic mechanism.Based on the above analyses,the author holds the view that the micritic dolostone experienced two stages,namely the seepage-reflux dolomitization during penecontemporaneous period and the isomorphous replacement during burial diagenesis period.
Wang Bingjie,Cai Mingjun,Lin Chunming et al. Characteristics and origin of lacustrine dolostone of the PaleogeneShahejie Formation in Tanggu area,Bohai Bay Basin[J]. JOPC, 2014, 16(1): 65-76.
