Study On The Sedimentary Filling And Thermal Structures Of Mohe Basin

Mohe basin is located in the northernmost of China, It is connected with Russia’sWushu Meng as a unified basin, And in its north is “Mongolia Okhotsk Orogen”.The research of Mohe Basin sedimentary system and tectonic background, linking theGenetic mechanism of Mohe basin to“Mongolia Okhotsk Orogen”, It will provide thebasis of “Mongolia Okhotsk Orogen” orogenic process even reconstruction MesozoicEast Asia convergence,and it also has a good guidance for further exploration of theoil and gas in the basins.There are three main density interface,four density layer and two mainmagnetic boundary in this area by analyzing the geophysical property of sampledata.In this aera the anomalies of Gravity and magnetic are mainly in the near NorthWest.There are two Gravity high anomaly aeras in the near North West.And thegravity anomaly is more obvious, It is characterized by low-high-low-high from westto East, There are five magnetic anomaly area (two strong magnetic anomaly area,three weak magnetic anomaly zone)in this aera, and the high value of gravity anomalyis more obvious in the near northwest, the gravity anomaly is performance as higherin the West and lower in the East.Comprehensive analysis of gravity and magnetic, field geological phenomenaand seismic data, identified a total of75faults,20EW trending faults NE,25NEEtrending fault,23NW, NWW trending faults,7SN-trending faults. Among them, thenear EW trending to the faults has the reverse faults and the normal faults. Thereverse faults formed in late Jurassic. NE, NW, SN faults are faults, mainly formed inthe early cretaceous. And close to EW and NE to NW, to the individual in the basincontrolling fault activity is strongest.According to gravity and magnetic data interpretation, the Mohe basin is dividedinto six primary structural units (two long four trap),twelve secondary structuralelements (6convex6concave), the overall performance of the western region isrelatively deep, typically3000m Eastern region slightly shallow, usually2500m, thedeepest part of Changying area is located in the middle of the basin, reaching9000m. By EW fracture controlled depression in the main basin of the east-west. LateNE-NNE trending faults of the original EW structure caused damage andreconstruction, and on which is superimposed NE-NNE trending fault trap.Comprehensive logging, core observation and field geological profile, andidentified in the area mainly developed three kinds of sedimentary facies (alluvial fanfacies, fan delta facies and lacustrine facies), the overall performance of the basin outdeep water body to the north to the South gradually becomes shallow, from north tosouth sedimentary facies exhibit semi-deep lake-shallow lake-front fan delta-fan deltafront-fan delta plain-the law of the alluvial fan.Xiufeng group to22station group iscycle, development conglomerate in bottom;22station group to Emuer River group istrans cycle, the top development conglomerate, sedimentary characteristics exhibitedcompressive basin. Mohe basin showed lower positive cycle section of the upper partof the anti-cycle of a large segment of the overall late Jurassic. The early Cretaceousthe overall performance, lower (Tamulangou formation) is a positive cycle, the upper(Yiliekede group) for a large segment of the reverse cycle. Mohe Basin near the“Mongolia Okhotsk Orogen” deposited on one side of a mutually with the Okhotsksuture zone to the distribution, and due to the closure of the Okhotsk customs of thesqueezing effect, the center of the basin of deposition of center southward migrationof the phenomenon.Drawn by the district28apatite fission track ages, age samples are mainlydistributed in the137-110Ma,218-164Ma and326-299Ma. Basement of the MoheBasin in the Triassic early Jurassic rapid uplift, in the late Jurassic-Early Cretaceousuplifting slower.Finally,in the late Cretaceous-today again more rapid uplift. FromTriassic to early Jurassic sedimentary rocks in the source region of the uplift stage,after suffered erosion transport deposition and the formation of late Jurassic basinsedimentary caprock, and in120Ma-0Ma (Early Cretaceous-today) uplift againdenuded.Mongolia-Okhotsk closed Triassic begins and ends at the beginning of the LateJurassic-Early Cretaceous to the end.In this process,the formation of the Mohe-WushuMeng foreland basin. Since Triassic arc-continent collision after the formation of the arc small ocean basin-Wushu Meng basin, thus Wushu Meng Triassic marine stratabasin development, during the Triassic Wushu Meng basin are retroarc basin; asextrusion collision carried orogeny (continent-continent collision),basin cross sectionfurther expansion in the Late Jurassic Mohe basin in China began to develop thecontinental strata, in the late Jurassic Mohe-Wushu Meng basin are peripheralforeland basin.