Sedimentary Response To Tectonism Of The Emoerhe Group In Kaikukang-Yixiken Area, Southeastern Mohe Foreland Basin

The research area is located in the northern edge of Erguna massif,and it's tectonic unit corresponding to Mohe foreland basin,and to the Mongolia-Okhotsk orogenic belt in north,is the product of the subduction and closing of Mongolia-Okhotsk Ocean.The study area has experienced history of its Paleoasian Ocean forming and the close of Mongolian-Okhotsk Ocean tectonic system as well as the Round Pacific Ocean tectonic system.It play an important role in the study on formation and evolution of Mohe Basin from Mongolia Okhotsk orogenic belt,and the tectonic genesis and evolution of the Northeast Asia.Emoerhe Group in the study area consists of Kaikukang Formation,Ershierzhan Formation and Mohe Formation,the contact relationship between them is conformable.Four groups of fault structures of the research area are in directions of mainly near EW,NW,NE and near SN.The stratum attitude of is symmetric from NW and SE side,combined with the data of gravity survey,aerial magnetical survey and remote sensing,It was considered that the study area is a large-scale synclinal structure,the core is located in the south of Xiushuishan intrusion,with the sedimentary features of the edge uplift and the center depression.By the field investigation and the comprehensive analysis of particle size analysis,fossil organism,we suggest that alluvial fan,fan delta,braid river,braid river delta and lake facies are the main precipitation facies in the study area.Kaikukang Formation mainly develops alluvial fan,fan delta deposit.ErshierzhanFormation mainly develops fan delta,lake,braid river and braid river delta deposit.Mohe Formation mainly develops braid river and braid river delta deposit.There is a symmetrical distribution of the sedimentary,that alluvial fan-fan delta-lake-braid river-braid river delta from the North to the SE side(Kaikukang Formation to Mohe Formation),and fan delta-lake-braid river-braid river delta from the South to the NW side(Ershierzhan Formation to Mohe Formation).Through the analysis of the paleocurrent direction,gravel components,detritus components,Artificial heavy concentrate tests,petrological geochemistry and the sedimentary facies,combined with the data of geological structure,the sediments is divided into two parts: mother rocks of intermediate-acid volcanics,intermediate-basic volcanic rocks,granite,metamorphic rocks and sedimentary rocks that are from the northern basin active continental margin of the southern margin of the Siberian plate;mother rocks of granite,metamorphic rocks and sedimentary rocks that are from the southern basin Erguna magma arc and underlying foundation bed.Through the source analysis and the study on the tectonic setting,we suggest that Late Jurassic Mohe basin foreland basin is a typical foreland basin,the formation and evolution of Mohe basins is related to the Mongolia Okhotsk orogenic belt,to be a far field effect caused by the orogenic belt.