Origin of Lacustrine Dolomitic Rocks of the Lower Cretaceous Tengge'er Formation in Anan Sag, Erlian Basin
Wei Wei
Zhu Xiaomin
Zhu Shifa
Sun Shuyang
He Mingwei
Yang Dexiang
Wu Jianping
Wang Mingwei
Abstract：The Lower Cretaceous source rocks in Anan sag of Erlian basin develop a set of lacustrine fine-grained dolomitic rocks,composed of dolomitic mudstone,dolomitic tuffite,and dolomitic sandstone,which are rich in tight oil.But its petrological characteristics and origin of dolomite are still unclear.Analysis of core observation,thin section,Scanning Electron Microscope (SEM),and geochemical data show the dolomitic rocks mainly include:(1) The subhedral,micritic-powder crystalline dolomite distributing in laminated and star structure dolomitic mudstone and dolomitic tuffite;(2) The euhedral,powderfine crystalline dolomite distributed massive dolomitic tuffite and dolomitic sandstone.Their mechanisms of dolomitization are different:(1) The subhedral,micritic-powder crystalline dolomite with higher δ13 CPPDB values (av.5.4‰),higher δ18 CPDB (av.-13‰),and lower fluid inclusion homogenization temperature (50-75 ℃),is dominated by early diagenetic dolomitization associated with methanogenesis.The source of Mg2+ is mainly from alteration of tuffaceous materials.(2) The euhedral,powder-fine crystalline dolomite is characteristic of bigger and finer crystals,lower δ13 CPDB values (0.2‰-0.7‰),lower δ18 OPDB (av.-19.4‰),and higher fluid inclusion homogenization temperature (about 119 ℃).It is dominated by burial dolomitizationand affected by the controls of methanogenesis anddegradation of organic matter.The source of Mg2+ is mainly from transformation of clay minerals and deep fluid.
Keywords：lacustrine sedimentarydolomitic rocksdolomitizationmethanogenesisburial dolomitizationErlian basinpetroleum geology
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：15( 258-272 )