【摘要】 琼东南盆地是南海西北陆缘上一个北东走向的伸展裂陷带,向西与北西走向的莺歌海盆地相接,因此其西南部的构造演化包含了较多红河断裂走滑活动的信息。综合地质分析,我们发现琼东南盆地的发育既受控于南海北部陆缘的南东-南南东向伸展作用,又受到红河断裂左行走滑作用的控制和影响。盆地西南部裂陷带内发育了复式裂陷结构,由复式半地堑和复式地堑构成;裂陷带边缘的斜坡带和隆起上,以半地堑样式为主。始新世-早渐新世岩浆活动较多,主要表现为顺层充填的火山活动;中中新世后的岩浆活动分布较广,主要沿北西走向大断裂分布,在地震剖面上主要表现为尖锥状火山式活动特点。海盆扩张期,凹陷内缺乏岩浆活动。推测复式裂陷特点和较多的岩浆活动与陆坡区地幔上涌较高,具有较高的地温梯度,导致岩石圈弹性厚度降低有关。更多还原

【Abstract】 Qiongdongnan basin is a NE-trending rift zone developing on the northwestern margin of the South China Sea.Bordering with Yinggehai basin to the west,its evolution must bears lots of information on Red River Fault zone.Compared with the Pearl River Mouth basin,the Qiongdongnan basin developed wide and flat Zhongsha-Xisha platform,which made the slope structure here much complicated.The research here will initiate our knowledge on the dynamics of different slope patterns.NE-to NEE-,EW-and NW-trending faults developed in the basin.The vertical offset rate of faults suggests that Tg-T60 is the main rifting stage,thereafter the fault activity is weak.Comprehensive researches suggest that the formation of the Qiongdongnan basin was controlled by SE to SSE extension and sinistral slip of the Red River Fault zone.In the southwestern segment of the Qiongdongnan basin,composite rifting structures developed in the rifting center but simple rifting structure on slope area of the uplift.Magmatic activities from Eocene to Early Oligocene were characterized by strata parallel volcanism.After Middle Miocene,peak volcanism was widely distributed in the area and erupted mainly along NW-trending faults.It suggests that the composite rifting structure and magmatic activities were controlled by the highly upwelling mantle,which lead to high temperature gradient and weaken lithosphere with decreased elastic thickness.更多还原