Deep Tectonic Framework of Gonghe Basin and Its Influence on Heat Source of Dry Hot Rock
As a new type of geothermal resource,dry-hot geothermal resource is a type of clean energy with broad development prospects.The Gonghe basin in Qinghai Province is located in the northeastern margin of the Qinghai-Tibet Plateau.The regional geological activities are rich,which creates good conditions for the forma-tion of hot dry rock.Therefore,it is of great significance to study the tectonic framework of the Gonghe Basin and the heat generation model of dry-hot rock for geothermal resource exploration.Based on the normalized ver-tical derivative of total horizontal derivative of gravity anomaly(NVDR-THDR)and the fusion method of gravi-ty and magnetic anomalies,the fault tectonic framework of Gonghe basin has been divided.A total of 20 deep and large faults are identified,and 9 of them are not identified by predecessors.The inferred F1-15 fault is the east-west boundary fault of Gonghe basin,which is of great significance to the genesis of dry-hot rock in Gonghe basin.The results from the ultra-low frequency magnetotelluric sounding profile and the normalized to-tal gradient inversion of gravity anomalies show that the mantle material of the Gonghe basin migrated upward,heated and eroded the bottom of the lithosphere,resulting in melting and thinning of the bottom of the litho-sphere.The basin are subject to the thrust nappe of the Qinghai Nanshan and Guinan Nanshan,but there are ob-vious differences in the deep geological structure between the eastern part and western part.The degree of extru-sion deformation of the geological body in the western part is stronger than that in the eastern part.The density structure of the deep geological body in the western basin is characterized by an'eight'shape,which is charac-terized by a depressed basin,but the faults are less developed.A large number of deep faults are developed in the eastern basin,which provides a transmission channel for deep heat source materials and heat.Therefore,it is considered that the heat source of dry-hot rock in Gonghe basin is dominated by mantle heat flow conduction and partial melting layer in the crust,supplemented by heat generation of radioactive element decay,and the eastern part of the basin has more dry-hot rock accumulation conditions than the western part.
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