【摘要】 本文根据反射地震、折射地震、磁力等资料,结合周边地质,探讨冲绳海槽南段基底组成。在海槽周边的东海陆架盆地、台湾褶皱带和琉球岛弧褶皱带,均出露不同程度变质的晚古生代、中生代和早第三纪地层。多道反射地震表明,海槽南段沉积盖层由上第三系和第四系组成,声学基底由下第三系及更老地层构成。邻近海槽的折射地震揭示,除第四系-中新统速度层之外,还存在纵波速度分别为4.7～5.3km/s和6.3km/s的下第三系和中生界速度层。磁异常分析和正反演拟合计算结果表明,海槽磁性基底主要由变质岩系构成,次为燕山期中酸性岩浆岩和喜山期中基性岩浆岩,磁性基底大部分相当声学基底。综合分析表明,海槽南段基底主要由不同程度变质的下第三系、中生界和上古生界构成;在海槽某些构造部位,已有喜山期基性岩浆岩形成。更多还原

【Abstract】 Based on the data of seismic reflection,seismic refraction and magnetism collected in the research area and geology obtained from adjacent areas,this paper deals with the issue of basement constitution of the southern part of the Okinawa Trough. In the shelf basin of the East China Sea,Taiwan folded belt and Ryukyu Islands folded belt which surround the trough,outcrop Later Paleozoic,Mesozoic and Eogene strata. In the southern trough,multichannel seismic reflection data indicate that the overlying strata are composed of Neogene and Quaternary deposits,and the acoustic basement consists of Eogent and even older strata. Seismic refraction profiles show that there are Eogene and Mesozoic velocity layers with longitudinal velocities of 4.7 -5.3 km/s and 6.3 km/s respectively beneath the Quaternary-Miocene Layers. Qualitative analysis and forward and reversed calculation of magnetic data show that the magnetic basement is mainly formed by metamorphic rocks,the Yanshanian neutral-acid magmatic rocks and the Himalayan neutral-basic magmatic rocks being the next components,and the magnetic basement is mostly corresponding to the acoustic basement. Comprehensive analyses demonstrate that the basement of the southern Okinawa Trough is mainly formed by Eogene system and Mesozoic and Upper Paleozoic groups metamorphosed in varying degrees,and the basic magmatic rocks of Himalayan epoch have been formed in some parts of the basin.更多还原