青藏高原东北缘祁连至阿拉善地块深部电性结构特征及其地质意义  

Deep electrical structure of Qilian to Alxa block in northeastern margin of Qinghai-Tibet Plateau and its geological significance

作　　者：刘会龙 陈楚桐 范俊杰 马德锡 彭伍胥 陈亮 LIU HuiLong;CHEN ChuTong;FAN JunJie;Ma DeXi;PENG WuXu;CHEN Liang(Center for Geophysical Survey,China Geological Survey,Langfang 065000,China;Technology Innovation Center for Earth Near Surface Detection,China Geological Survey,Langfang 065000,China)

机构地区：[1]中国地质调查局地球物理调查中心,廊坊065000 [2]中国地质调查局地球浅地表探测技术创新中心,廊坊065000

出　　处：《地球物理学进展》2024年第3期916-929,共14页Progress in Geophysics

基　　金：中国地质调查局地质调查专项(DD20230485,DD20208001,DD20243187);中国地质调查局地球物理调查中心科创基金(DKC20220001)联合资助。

摘　　要：为了获取青藏高原东北缘祁连至阿拉善地块的深部电性结构,研究祁连造山带、阿拉善地块的构造变形特征,本研究布设了一条甘肃天祝至阿拉善左旗的北东向大地电磁测深剖面,获取了48个观测点大地电磁测深数据.经过对剖面数据的处理、分析及二维反演,获得了剖面深部电性结构模型.结果表明:河西走廊过渡带中下地壳存在一变形的低阻带,低阻带的褶皱变形说明高原北东向扩展的远程作用到达了河西走廊过渡带的北部边缘;祁连北缘断裂系沿中下地壳的低阻滑脱带以“坡-坪”结构的断层发育模式向北逆冲推覆并发育次级断裂,部分挤压变形被断裂走滑分量吸收,致使阿拉善地块南缘缓慢向东运动;深部电性结构特征结合前人地质年代学数据表明,青藏高原东北缘祁连断裂带以“坡-坪”结构逐步逆冲扩展变形形成现今盆山构造格局,反映了中新世以来不同阶段的变形特征,揭示了青藏高原东北缘复杂的逆冲变形机制.In order to obtain the deep electrical structure of the Qilian orogenic belt to the Alxa block and to study the deformation characteristics of Qilian orogenic belt and Alax block,a large-scale northeast-tending Magnetotellurics(MT)profile was acquired from Tianzhu,Gansu to Alxa Zuoqi.The deep electrical structure model was obtained,and the 2-D MT data inversion modeling from 48 receiver sites.The result show that the lower crust of the middle of the Qilian-Alxa area is characterized by a low-resistivity deformation belt which suggests that the north-eastward extension of the Qinghai-Tibetan Plateau has reached the northeastern edge of the Qilian-Alxa area.The north Qilian fault zone along the lower crustal low-resistivity belt is a thrust fault with a “ramp-flat” structure and developed secondary faults with propagation propagation northward.The southern margin of the Alxa block moves slowly to the east due to the consumption of strike-slip separation along the fault.In addition,the deep electrical structural characteristics combined with the previous geochronology data show that the Qilian fault belt in the northeast margin of the Tibetan Plateau formed the present basin-mountain tectonic pattern by the sequential way thrust extension deformation of the “ramp-flat” structure,which reflects the deformation characteristics of different stages since the Miocene,and reveals the complex thrust deformation mechanism of the northeast margin of the Tibetan Plateau.

关 键 词：祁连地块 阿拉善地块 大地电磁测深 扩展边界 深部结构 

分 类 号：P313[天文地球—固体地球物理学]