【摘要】 西沙群岛中新世以来广泛发育生物礁,记录了大量的构造活动信息。利用在西沙群岛海域取得的单道地震剖面结合前人研究成果,对该区构造运动和活动性进行了研究。研究结果表明:西沙群岛周缘发育多NE-NEE、NW向深大断裂,地块上发育NE、EW向断裂;这些断裂与先存断裂位置基本相同,受多期构造运动的影响多次活动,常伴有火山活动,一些火山出露海底数百米;西南次海盆扩张对中—西沙地块NW向挤压,使西沙群岛处于挤压环境;沿EW向断裂南北两侧地层变形表现出鲜明差异,两侧地层向相反方向逆冲,北侧地层变形较大,说明两侧地层处于不同的构造环境;西沙群岛更新世火山活动停止后,构造趋于稳定,仅部分断裂现今仍活动。更多还原

【Abstract】 Organic reef, widely developed since the Miocene around the Xisha Islands, provides rich information of tectonic movement and activity. Using single-channel seismic profiles acquired and combining with other research in this area, this paper discusses the tectonic movement and activity around the Xisha Islands. The results show that there are NE-NEE and NW trending faults along the Xisha block boundary and NE and EW trending faults in the Xisha block. These faults are inherited from old ones, and the reactivation of the faults accompanied by volcanicity is affected by multiphase tectonic movements. Result from the NW direction stress caused by the opening of the Southwest Sub-basin, the Zhong-Xisha block is in a compression environment. The seismic profile shows that there is a distinct difference between the two sides of the EW fault in terms of formation, which indicates that the two sides of the formation are in different tectonic environments. After the Pleistocene, volcanic and most of faulting activity stopped, and the Xisha Islands behave as a stable tectonic entity.更多还原