共和盆地壳内部分熔融层存在的地球物理证据与干热岩资源区域性热源分析  

Analysis on Geophysical Evidence for Existence of Partial Melting Layer in Crust and Regional Heat Source Mechanism for Hot Dry Rock Resources of Gonghe Basin

作　　者：张森琦[1] 李旭峰[1] 宋健 文冬光[1] 李志伟 黎敦朋[3] 程正璞 付雷[1] 张林友 冯庆达 杨涛[1] 牛兆轩 Zhang Senqi;Li Xufeng;Song Jian;Wen Dongguang;Li Zhiwei;Li Dunpeng;Cheng Zhengpu;Fu Lei;Zhang Linyou;Feng Qingda;Yang Tao;Niu Zhaoxuan(Center for Hydrogeology and Environmental Geology Survey,China Geological Survey,Baoding 071051,China;State Key Laboratory of Geodesy and Earth's Dynamics,Innovation Academy for Precisiofi Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430077,China;School of Zijin Mine,Fuzhou University,Fuzhou 350116,China)

机构地区：[1]中国地质调查局水文地质环境地质调查中心,河北保定071051 [2]中国科学院精密测量科学与技术创新研究院,大地测量与地球动力学国家重点实验室,湖北武汉430077 [3]福州大学紫金矿业学院,福建福州350116

出　　处：《地球科学》2021年第4期1416-1436,共21页Earth Science

基　　金：国家重点研发计划项目(No.2018YFB1501801);中国地质调查局地质调查项目(No.DD20190131)。

摘　　要：新生代以来,共和盆地及其周缘造山带无火山、岩浆活动,印支期隐伏花岗岩体岩浆余热与放射性元素衰变生热等难以构成共和盆地干热岩资源的主要热源,而共和盆地又为一高温地热异常盆地.目前已基本探明了共和县恰卜恰与贵德县热水泉干热岩体2处,圈定出干热岩勘查目标靶区16处.区域重力和区域航磁调查、区域天然地震成像、盆地尺度天然地震背景噪声层析成像勘查,以及超高分辨率重力异常、电阻率与Rayleigh波群相速度线性反演结果均表明共和盆地下伏发育有壳内部分熔融层,进而构成地处板内环境、高热流区共和盆地干热岩资源的区域性热源.盆地尺度MT勘查结果表明,共和盆地西盆地壳内部分熔融层埋深15~35 km,东西向长约41 km,南北向宽约34 km,厚度2~12 km.综合分析认为,该部分熔融层熔融程度最高可达4%~7%,15 km深处温度约为574℃,主体位于贵南南山推覆体系与共和准推覆体系深部主拆离滑脱推覆界面之下,兴海大型复合推覆体系主拆离滑脱推覆界面之上.挽近地质时期深构相、多层次、近水平展布的韧性拆离滑脱推覆构造界面的连续动态剪切摩擦生热,可能是部分熔融层形成的主要因素.The volcanic magmatic activity has not been observed in the Gonghe basin and its surrounding orogenic belts since the Cenozoic. Heat generation from the magma of concealed granite body during the Indosinian period and the radioactive elements within the stratum are difficult to form the heat source of hot dry rock resources in the Gonghe basin. However, it has been widely recognized that this basin is a high-temperature geothermal abnormal basin. Nowadays, two hot dry rock masses were verified in the Qiabuqia of the Gonghe County and the Reshuiquan of the Guide County basically. Sixteen target areas of the hot dry rock exploration were also delineated in this region. Evidences from the regional gravity and aeromagnetic survey, regional natural seismic imaging profile, tomographic exploration of natural seismic background noise at basin scale, ultra-high resolution gravity anomalies, as well as linear inversion of resistivity and phase velocity of Rayleigh wave group all show that partial melting layer was developed in the crust of the Gonghe basin. This partial melting layer, located in the inner plate environment and characterized by high heat flow, constitutes the regional heat source of the hot dry rock resources in the Gonghe basin. The MT exploration reflects that the partial melting layer within the crust of the western basin of the Gonghe basin is characterized by a depth of15-35 km, length of about 41 km and 34 km in east-west and north-south directions respectively, thickness of 2-12 km.Comprehensive analysis shows that this partial melting layer, marked by a melting degree of 4%-7% and temperature of about574 ℃ at 15 km depth, is mainly located under the main detachment nappe interface between the nappe systems of the Guinan Nanshan and Gonghe, and above the main detachment nappe interface of Xinghai large composite nappe system. Heat generation from the continuous dynamic shear friction at the deep structural, multi-level, and near horizontal detachment nappe interface during the Neoid period is the

关 键 词：低速高导层 部分熔融层 干热岩 热源 共和盆地 构造 

分 类 号：P314[天文地球—固体地球物理学] P548[天文地球—地球物理学]