【摘要】 <正> 冲绳海槽是位于东海大陆架外缘、东海陆架边缘隆褶带与琉球岛弧之间的一个狭长带状弧间盆地。关于它的成因,已有古琉球弧直接张裂和断裂下陷两种观点,而笔者认为,它是由于菲律宾海板块从早中新世末以来,向欧亚大陆板块下俯冲所形成的沟—弧—盆系列的一个组成部分,在其生成和发展过程中,先后经历了拗陷、断陷和扩张三个阶段。然而,扩张刚刚开始。今后它将进一步裂开,琉球弧将更加向菲律宾海方向推进。 因受调查程度的限制,本文将以冲绳海槽北半部的资料为主要依据。更多还原

【Abstract】 The Okinawa Trough is a young, long and narrow marginal basin in the convergent zone on the northwest edge of the Pacific Ocean Plate. In this paper it is shown that the Okinawa Trough first experienced depression, then faulting and spreading, on the basis of the data obtained from the sea floor topograph, the sediment composition, the characteristics of gravity and magnetic anomalies, the profiles from reflection and refraction seismic survey, the distribution of the volcanoes and earthquake focuses in the Trough, and the geological and geophysical data obtained from both sides of the Trough——the Ryukyu Island Arc andthe continental shelf marginal upfold zone.The area from the East China Sea continental shelf to the Ryukyu Islands might have been a wide shallow sea from the Paleocene to the early Miocene. The Philippine Sea Plate, moving west-northwest, subducted underneath the Eurasia Plate in the later period of the early Miocene. Subduction pressure caused the Okinawa Trough to fold and subside, while at the same time it caused the Ryukyu Island Arc and continental shelf marginal upfold zone to fold and uplift. By the middle or later Miocene, most of the Ryukyu Island Arc and continental shelf marginal upfold zone had uplifted out of the sea surface. The further subsided Okinawa Trough became a narrow-long basin between the two island arcs. In the Pliocene period the strain in the bottom of the trough exceeded yield strength and then deep faults formed successively on the east and west slopes as well as on the axis of the trough, causing a fault-sink in the Okinawa Trough. Up to the Pleistocene period the Philippine Sea Plate subducted beneath the Okinawa Trough andthe stress——friction between the Plates caused magma formation in the mantle.As a result of high pressure, magma rose along the faults and erupted within the trough, forming a series of steep seamounts on the east slope and axis. Continuous invading of the mantle matter forced the Okinawa Trough to spread. It is deduced that in the future this spreading will continue and the Ryukyu Island Arc will further move toward the Philippine Sea.更多还原