饶河杂岩地球物理资料处理及特征分析

Geophysical data processing and characteristics analysis of Raohe complex

东北亚陆缘增生造山过程深受古太平洋板块的俯冲作用影响,饶河杂岩作为古太平洋板块俯冲中央造山带东端的直接证据,分析研究其构造特征对于研究东北亚地区的构造演化具有重要意义.地球物理探测是研究地下岩性变化和深部结构的重要方法,本文布设了一条大地电磁剖面和同测线的人工反射地震,大地电磁测深方法采集点距500 m,频率范围为320 Hz~1000 s,对时间序列数据进行时频转换,预处理后进行二维非线性共轭梯度反演,得到最终的电性模型.人工地震采用爆破震源,满覆盖180次,记录6 s,采用CGG等软件对地震数据进行处理,叠加偏移后获得最终的地震剖面.电性模型显示饶河杂岩体具有不连续高阻体的特征,且西部的高阻体以西倾为主,中东部高阻体呈块状,东部的高阻体不规则,高阻体下存在低阻带,深部有高导体存在.在地震剖面上,饶河杂岩可以分为五个区域,其中西部为西倾的反射体,中部为斜交短反射体,东部上部为强弱不均的短反射体,东部下部为弱反射体,深部为长短不一的杂乱反射体.通过本次的地球物理观测和处理工作,饶河杂岩体可分为两部,浅部具有高阻体、西倾反射体的特征,深部为高导体、杂乱不均一反射体.上下层之间存在分界面,具有低阻带、较为连续的强反射轴的特征.

The accretionary orogenic process of Northeast Asian continental margin is deeply influenced by the subduction of the Paleo Pacific plate.Raohe complex is the direct evidence of the subduction of the Paleo Pacific plate to the eastern end of the Central Orogenic Belt.Geophysical exploration is an important method to study the underground lithology and deep structure.In this paper,a magnetotelluric section and an artificial reflection seismic are laid in the same line.The acquisition point distance of magnetotelluric sounding method is 500 m,and the frequency range is 320 Hz~1000 s.The time-frequency conversion of time series data is carried out.After preprocessing,the two-dimensional nonlinear conjugate gradient inversion is used to perform the TM inversion to the final electrical model.The seismic data are acquired using the explosive source with parameters for exploration seismology.The fold times are 180 and the recording time is 6 s.Standard oil-industry software CGG and Promax were used for data processing.And the migrated seismic profile is obtained.The electrical model shows that the Raohe complex has the characteristics of discontinuous high resistivity bodies and the high resistivity body in the west is mainly west dipping,the high resistivity body in the middle east is massive,the high resistivity body in the east is irregular,there is a low resistivity zone under the high resistivity body,and there is a high conductor in the deep.On the seismic section,Raohe complex can be divided into five areas,in which the west is marked by the west dipping reflector,the middle is marked by the oblique short reflector,the upper part of the east is marked by the uneven short reflector,the lower part of the East is marked by the weak reflector,and the deep part is marked by the chaotic reflector.Through the geophysical observation and processing,Raohe complex can be divided into two parts,the shallow part has the characteristics of high resistivity body and west dipping reflector,and the deep part is marked by high conductor and heterogeneous reflector.There is an interface between the upper and lower layers,which has the characteristics of low resistivity zone and continuous strong reflection axis.