We investigated the continent-ocean transition (COT) structure of three main marginal seas in the western Pacific Ocean (South China Sea, Coral Sea, and Woodlark Basin) to determine the tectono-magmatic processes acting during continental breakup. The COT formed from the activity of a low-angle normal fault system localizing deformation during final rifting. Extension was contemporaneous with magmatic activity, including volcanic edifices, dikes, and sills in the distalmost parts of these basins. The COT shows a sharp juxtaposition in space and time of continental crust against igneous oceanic crust, and its overall structure differs from that of magma-poor or magma-rich passive-margin archetypes. We propose that this mode of breakup is characteristic of marginal seas due to the high extension rates imposed by kinematic forces of nearby subduction zones. Revealed in the context of marginal seas, this mode of breakup and the resulting COT structures highlight the underestimated diversity of continental breakup mechanisms.

中文翻译：

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边缘海大陆分裂模式

我们研究了西太平洋三个主要边缘海（南海、珊瑚海和伍德拉克盆地）的大陆-海洋过渡（COT）结构，以确定大陆分裂过程中的构造-岩浆过程。COT 是由小角度正断层系统在最终裂谷过程中局部变形活动形成的。延伸与岩浆活动同时发生，包括这些盆地最远端的火山大厦、岩脉和岩床。COT显示了大陆地壳与火成洋地壳在空间和时间上的鲜明对比，其整体结构不同于贫岩浆或富岩浆被动边缘原型。我们认为，由于附近俯冲带的运动力施加的高延伸率，这种分裂模式是边缘海的特征。在边缘海的背景下揭示，这种分裂模式和由此产生的 COT 结构突出了被低估的大陆分裂机制的多样性。