四川北川县某地热区音频大地电磁测深和土壤氡气测量应用研究  

Application research of audio magnetotelluric sounding and soil radon gas measurement in a geothermal area in Beichuan County,Sichuan

作　　者：王一伟[1] 魏龙[1] 陈刚[1] WANG Yi-wei;WEI Long;CHEN Gang(Northwest Sichuan Geological Team,Sichuan Provincial Bureau of Geology and Mineral Exploration and Development,Mianyang 621000,Sichuan,China)

机构地区：[1]四川省地质矿产勘查开发局川西北地质队,四川绵阳621000

出　　处：《地下水》2022年第5期27-29,共3页Ground water

摘　　要：北川某地热区位于龙门山推覆构造带前缘,具备较完善的热储系统。为对该区域地热资源进行勘查评价,采用音频大地电磁测深和氡气测量相结合的办法,推测地热资源赋存空间和第四系隐伏断裂的空间位置。结果可知:音频大地电磁测深推测富水部位为三叠系飞仙关组、二叠系吴家坪组碳酸盐岩层和三叠系须家河组砾岩层及其破碎带等,并发现隐伏断层存在,深部断层倾角约40°~70°,向深部变缓;地热区整体土壤氡气浓度及背峰比值由西向东增高,在东侧A线和B线背峰比值达20~30倍,反映出断裂的导通性较强。结合剖面峰值点位及剖面走向,判断出第四系隐伏断层2条,其中F1断层经实地验证,与地热区香水断裂一致,F2断层为第四系隐伏断层,断层总体走向北东,断层破碎带在A线最宽可达60 m。研究结果可为地热资源评估及开发利用提供依据。A geothermal area in Beichuan is located at the front edge of the Longmenshan nappe structural belt and has a relatively complete thermal storage system.In order to investigate and evaluate the geothermal resources in this area,the combined method of audio magnetotelluric sounding and radon gas measurement is used to infer the occurrence space of geothermal resources and the spatial location of the Quaternary hidden faults.The results show that the audio-frequency magnetotelluric soundings infer that the water-rich parts are the Triassic Feixianguan Formation,the Permian Wujiaping Formation carbonate rock layer,and the Triassic Xujiahe Formation conglomerate layer and its fracture zone,etc,and found the existence of hidden faults,the dip angle of the deep faults is about 40°~70°,and it slows down to the deep.The overall soil radon concentration and the back-to-peak ratio in the geothermal area increased from west to east,and the back-to-peak ratio of the A-line and B-line on the east side was 20~30 times,reflecting the strong continuity of the fault.Combined with the profile peak point and profile trend,2 hidden faults of the Quaternary system are determined,of which the F1 fault has been verified in the field and is consistent with theFragrance Breakin the geothermal area.The F2 fault is a Quaternary concealed fault,and the fault generally strikes the northeast.The fault fracture zone can be up to 60 m wide on line-A.The research results can provide a basis for the evaluation and development and utilization of geothermal resources.

关 键 词：地热资源 音频大地电磁测深 土壤氡气测量 

分 类 号：P314.1[天文地球—固体地球物理学]