Delineation of hot dry rock exploration target area in the Gonghe Basin based on high-precision aeromagnetic data

Concealed granite masses developed in sedimentary basins are the main objects for the exploration and development of hot dry rocks. In order to analyze the distribution laws of the concealed granite masses in the Gonghe Basin, Qinghai, this paper delineated the exploration target areas of hot dry rocks in this area. Then, based on the inverse calculation result of high-precision aeromagnetic survey data (1: 50 000), the distribution laws of the concealed granite masses in the Gonghe Basin were analyzed by comprehensively considering the topographic, geomorphologic and hydrologic geological conditions, the distribution area and cybotaxis of concealed granite masses and the sedimentary thickness of cap rocks in this area. Finally, fifteen exploration target areas of concealed hot dry rocks were delineated in the aeromagnetic survey area, including thirteen in the Gonghe Basin, one in the Qinghai Lake Basin and one in the Tongde Basin. And the following conclusions were reached. First, comprehensive geophysical exploration and drilling results show that the concealed Indosinian intermediate-acid granite mass which is delineated in Qiabuqia area is a hot dry rock mass. It is indicated that high-precision aeromagnetic survey is applicable to the preliminary exploration and target area delineation of regional hot dry rocks. Second, the main part of the concealed Indosinian magnetic granite mass is distributed along NW in the form of band, which is basically accordant with the distribution direction of the regional concealed faulted structure. And some irregular concealed Indosinian magnetic granite masses are mainly located in the west of Gonghe County, and they are distributed approximately along NE striking Sairiqin-Dalianhai concealed fault. Third, Sairiqin-Dalianhai concealed fault and Tangnaihai-Luohantang concealed fault act as the main upwelling pathway of deep-seated heat flow in the east and the west of the Gonghe Basin, respectively, and they are in a close relationship with the genesis of hot dry rocks. Fourth, in the direction of east-west, the burial depth of the concealed granite masses increases gradually from the delineated Qiabuqia hot dry rock in the east to the west. And in the direction of north-south, the burial depth of the concealed granite masses presents an increasing trend from the northern and southern margins to the center of the basin. © 2020, Natural Gas Industry Journal Agency. All right reserved.