基于高精度航磁数据的共和盆地干热岩勘查目标靶区圈定

发育于沉积盆地内的隐伏花岗岩体是干热岩资源勘查开发的主要对象。为分析青海共和盆地隐伏花岗岩体的分布规律，圈定该区干热岩勘查目标靶区，基于1∶50 000高精度航磁测量数据的反演计算结果，综合考虑该区地形地貌、水文地质条件、隐伏花岗岩体的分布面积与群聚性及沉积盖层厚度等因素，分析了该区隐伏花岗岩体的分布规律，并在航磁测区范围内圈定出15处隐伏干热岩资源勘查目标靶区（共和盆地13处，青海湖盆地和同德盆地各1处）。结论认为：①圈定出的恰卜恰隐伏印支期中酸性花岗岩体，经综合地球物理勘查和钻探验证为干热岩体，表明高精度航磁测量适用于区域性干热岩资源的初步勘查及目标靶区圈定；②隐伏印支期磁性花岗岩体主体呈NW向带状分布，与区域隐伏断裂构造展布方向基本一致，部分不规则状的隐伏印支期磁性花岗岩体主要出现在共和县城西，大致沿NE向赛日钦—达连海隐伏断裂分布；③赛日钦—达连海隐伏断裂与唐乃亥—罗汉堂隐伏断裂分别构成共和盆地东、西盆地深部热流上涌的主通道，与干热岩资源的成因关系较为密切；④在东西向上，由已知的东部恰卜恰干热岩体向西，各隐伏花岗岩体埋深逐渐增加；南北向上，由盆地南、北缘向盆地中心，各隐伏花岗岩体埋深有不断加深的趋势。

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.