Geological Features And Analysis On Far-seeing Zone Of Geothermal Exploration In Jiamusi Basin

Based on the analysis of basic geological data,geothermal geological date in all sides and the field work,geophysical exploration,remote sensing survey,radio geochemical work in Jiamusi Basin,we did an overall research on the geological features,geothermal geological features,the geothermal system,and forcasted the far-seeing zone of geothermal exploration in this basin by the means of synthesis all the works'fruit above.The major contents of the thesis included subdivising and correlating the strata filling in the basin,the evolution of regional sedimental system,the structure of faults and folds,the features of geology and geothermal field,the types of geothermal system and forcasting the far-seeing zone at last.The emphasis were depositional environment and facies in cretaceous,structural features of main faults,establishing the geothemal source-reservoir-caps models and disclosing the abnormal enrichment law of radio-element,finally,we interpreted the AMT and CSAMT profiles.Jiamuai Basin is one of the Mesozoic-Cenozoic relic basins in eastern Heilongjian province.these basins were always the important exploration area around the Songliao Basin for many years. However,because of locking the basic data of deep well and seism, the strata system and structural features of the basins were still not given the concrete works.In this paper,we begined the research from emphasizing on the regional data and integral analysis ,for the purpose of holding the attribute of basin in the wider field and deeper degree .After sufficient understanding the regional structures and evolution setting with the field work and geophysicsl exploration,we got to kown the formation and the evolution history of Jiamusi Basin;hold the strtigraphic sequence and distribution; then analysed the depositional environment and facies on cretaceous;described the structure features of trunk faults and folds by making good use of profiles and samples from field work;at last,disclosed the law of geothermal field and geothermal geological features and discussed the termal source and the type of geothermal systerm.finally,circled the far-seeing zone of geothermal exploration at the basis of abnormal enrichment laws.Though the studies on geological features,geothermal geological features and geothermal field above,some conclusions were drawn below:1,Jiamusi Basin was a Mesozoic fault-depression relic basin.The fault structure were develop there, and the main tend strike were NW,NE.The mechanical property included pressure,extension and shear.The fold in the basin were mainly developed in the fragemtal depositional bed on later Cretaceous,we didn't find the inverted fold during the field work.The lithologic characters of basis is middle Preterozoic granite ,the maximum depth of burial is about 1700 meters.2,Though the profiles measure on the spot and the analysis on the result made by predecessor,we rearranged the paleogeographic conditions on Mesozoic of easern Heilongjiang province.The results shown that the sedimentary system which belonged to later Jurassic in the past belongs to the earily Cretaceous in fact now.At the basis of this result,we devided the sedimentary history of Jismusi Basin into four phases:the rise and erosion phase in the earily atage of earily Cretaceous;then the basin fallen off in the rest time of eariy cretaceous and deposited the Houshigou Formation;when the history of basin went into later Cretaceous , volcanals in this district became active and extensive volcanic rock was sedimnted at this stage;the last phase is at the end of late Cretaceous,the basin was uplift again as a whole but sedimented in some local district.We made the conclusion after analyzing on the depositional environment and facies in cretaceous of Jiamusi Basin:the main sedimental environment of early cretaceous was rever,swamp and alluvial fan;well,the late cretaceous was alluvial only.3,Associated with the data of rock radio intention and the features of regional geothermal field ,we disscused the geothermal resource of Jiamusi Basin,by the way of comparison the radio intention of element U,Th,K in the basis and the volcanic rock of early Cretaceous,we believed that the main geothermal source of Jiamusi Basin is from the conduction of mantal subject and the decomposion of radio elements of basis.4,The paper make a all-sides analyse on the geothermal geological situation and the type of geothermal system.the site of Jiamusi Basin is far away from the plate margin,and the geothermal field is also not formed by high temperature heat source.The regional geothermal gradient is 2～2.5℃/100m,the regional geothermal folw value is 37.37～46.675mw/m2.What's more, the basin did not exist the conventional hydro-thermal system related with shallow magmatic intrusion..So,the geothermal system belongs to the low-middle conventional geothermal model or innerplate orogenic geothermal system.5,The geothermal source-reservoir-cap of Jiamusi Basin was divided into three basic models :1)The geothermal district entirely lost the Sifengshan Formation and Aoqi Formation,the basis rock will be the geothermal source,the sandstone and conglomerate of Houshigou Formation acts as the reservoir and the cap is Quarternary;2)We only lost the Sifengshan Formation but not the Aoqi Formation,the thickness of quarternary,40~60m, is thicker than the first one;3)The basis rock and the volcanic rock of late Cretaceous act as the geothermal source;the fragmentary rock of Sifengshan Formation and Houshigou Formation is the reservoir,in this model,the thickness of cap is the thickest ,and it's undoubted the best models in this district.6,Synthetical used the methods of geology,geophysics and geochemisty, emphasis on the geochemical statistic analysis of radio elements,we forecasted the four far-seeing zones of geothermal exploration in Jiamusi Basin.