The Application Of Gravimetry In Chengde Geothermal Exploration

In order to solve the geological problems related to geothermal distribution,such as basement uplift,depression,fracture and so on,and reduce the target area of geothermal exploration,In this paper,high-precision gravity survey is carried out in three research areas of Qijia,Kuancheng and Yudaokou pastures in Chengde.Through 1:50000high-precision gravity survey in the study area,combined with the previous geological,geophysical and drilling data,the survey data are comprehensively analyzed and checked The characteristics of the gravity field,the spatial distribution of regional geological structure and rock formation,the concealed geological body or structure and the favorable geothermal area are studied.Through the research,the following main understandings and conclusions are obtained:(1)In this paper,the horizontal derivative and tilt gradient derivative are compared to improve the reliability of the analysis results.(2)The distribution of geological structures in the three study areas has been basically ascertained.In Qijia study area,the two north-east-Jinshan faults are the main structure,and the north-west structure is developed.The ring structure of the crater can be clearly delineated in the north of the Kuancheng study area,and the NW and NE faults are the main faults in the south.In Yudaokouma research area,the ne structure is the main structure,and the NW structure is developed;there are two volcanic institutions in the area.(3)The distribution of rock formations in the three study areas has been basically ascertained.In the north of Qijia study area,the late Jurassic Zhangjiakou formation is reflected;in the Middle East,the volcanic sedimentary basin is generally reflected;in the middle and West,the Paleoproterozoic metamorphic basement is integrated with Triassic and Middle Jurassic intrusive rocks;in the south,the granite of different periods is reflected,and the uplift area is generally shown.The southwest of Kuancheng study area is the reflection of Jixian system,the southeast is the comprehensive reflection of Changcheng System,and the middle is the reflection of Mesozoic Jurassic system.The north part of Yudaokou pastures research area is the comprehensive reflection of Zhangjiakou formation of Cretaceous system;the middle part is the comprehensive reflection of quaternary system and Cretaceous system;the southeast part is the reflection of the intrusive rock body of undercurrent rhyolite,which is the uplift area.(4)On the basis of comprehensive analysis,the paper points out that the intersection of two Jinshan faults and NW faults in seven study areas is a favorable area for geothermal exploration;the northwest of F₇ fault,the south of Huaxicheng,the turning point of gravity anomaly is a favorable area for geothermal exploration in Kuancheng study area;the center or south of basin in Yudaokou pasture study area,It is a favorable area to look for the geothermal field of fault controlled basin complex type or basin type.(5)Through this application,the target area of geothermal exploration is effectively reduced and the application purpose is achieved.