Intense magmatism in the form of widespread volcanoes and lava flows is identified in high-resolution 3-D seismic data over a post-rift sequence of the northern South China Sea (SCS). Such a magmatism post-dates the end of seafloor spreading in the SCS by at least 6.8 m.y. A detachment (boundary) fault propagating into a deep-seated magma chamber provided the main vertical pathway for magma migration. In turn, normal faults and dykes constituted a shallow plumbing system through which the magma migrated from the boundary fault and was extruded onto the paleo-seafloor. Volcanism occurred in the study area from ca. 8.2 Ma to ca. 1.1 Ma in the form of two distinct events, dated ca. 5.2 Ma and ca. 2.8 Ma, which are correlated with the Dongsha Event. Extrusive magma formed volcano edifices and extensive lava flows; the latter of which were confined to the troughs of sediment waves or, instead, flowed along submarine canyons. As a corollary, this study shows that in the SCS: (1) young magmatism is widespread on the northern continental margin, (2) seafloor morphology greatly influences the architecture of deep-water volcanoes, and (3) syn-rift faults (especially detachment faults) reactivated by regional tectonics closely control the magma plumbing systems.

中文翻译：

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南海北部边缘的裂谷后岩浆活动

在南海北部（SCS）裂谷后序列的高分辨率3-D地震数据中，以广泛的火山和熔岩流形式出现了强烈的岩浆作用。这样的岩浆作用可以使海平面在SCS中的扩散结束的时间至少为6.8我。分离（边界）断层传播到深部的岩浆腔中，为岩浆运移提供了主要的垂直通道。反过来，正常的断层和堤坝构成了一个浅层的管道系统，岩浆通过岩浆系统从边界断层中迁移出来并被挤出到古海底。研究区从约公元前开始发生火山作用。8.2马至 1.1 Ma的两个不同事件的形式，日期大约为 5.2马和约 2.8 Ma，与东沙事件有关。喷出的岩浆形成了火山的建筑物和大量的熔岩流。后者被限制在沉积物波谷中，或者沿着海底峡谷流动。作为一项推论，这项研究表明，在南海，（1）年轻岩浆作用广泛分布在北部大陆边缘，（2）海底形态极大地影响了深水火山的构造，（3）同裂隙断层（特别是）区域构造重新激活的松动断层）紧密控制了岩浆管道系统。