南冲绳海槽及其邻域的磁性基底与地壳结构

研究区域的基底断裂构造十分发育。EW、NEE和NE向基底大断裂宏观上构成和控制区域地质构造的基本格架;NS、NNW和NW向断裂多为张扭性平移断层,它们对基本格架起强烈的分割破坏和错断作用,形成和控制次一级区域差异性的构造运动和岩浆活动特征。东海陆架边缘隆起带磁性基底埋深一般为3～4km.基底由前中新世变质岩系及不同时期形成的火成岩类组成。地壳厚度为24-28km,为大陆地壳。南冲绳海槽盆地磁性基底埋深一般为5～7km,可划分出4个次一级盆地。基底极可能由前中新世以来海槽张裂运动所形成的玄武岩层或部分变质岩系组成,靠近陆坡坡脚处可能包括前第三纪的老地层。地壳厚度为15～20km,地壳为亚大洋型。

The magnetic basement and geological structure of the southernOkinawa Trough and its vicinity

-- Fault structures of basement in the study area develop well. The large basement faults in EW, NEE and NE directions construct and control the principle frame of the regional geological structure on a grand scale. The faults in NS, NNW and NWdirections are mostly tensile translational faults, which strongly cut apart, destroy and break the principle structure, form and control secondary differential regional tectonic movement and magmatism characteristics.The burial depth of magnetic basement in the edge rise zone of the East China Sea shelf is ordinarily 3 - 4 km. The basementcomprises Pre-Miocene metamorphic rock and series of igneous rocks formed in different epoches. The crust belongs to continentalcrust, whose thickness is 24 --28 km.The burial depth of magnetic basement in the southern Okinawa Trough basin is ordinarily 5 -7 km. The basin can be dividedinto 4 secondary basins. The basement may mostly comprise basalt or part-metamorphic rock formed by trough tensile movementsince Pre-Miocene, which may include old Pre-Tertiary stratigraphy close to continental slope foot. The crust belongs to suboceaniccrust, whose thickness is 15 -- 20 km.