中文摘要：

从全球板块构造环境来看,与洋脊俯冲有关的板片窗占据绝大部分比例,俯冲洋脊板片正处于新生过程,热量大,具有正浮力（〈10 Ma）,在俯冲过程中容易撕裂形成板片窗。南海古扩张脊沿马尼拉海沟向菲律宾海板块俯冲,南海东部边缘火山活动在吕宋岛上表现为东西双火山链,上新世期间,西火山链停止活动,而东火山链内的岩浆活动几乎完全是在第四纪。东西双火山链在20°N向南开始分支,东火山链在17.8°N停止,西火山链往南一直延伸到民都洛岛,东西火山链之间的火山空隙即反映了南海古扩张脊沿马尼拉海沟向菲律宾海板块俯冲形成的板片窗构造。同时,根据吕宋岛晚中新世以来埃达克岩的空间分布空隙和时间空隙特征,反映在吕宋岛17°～17.5°N存在板片窗构造。

英文摘要：

Slab windows are generated from the subducting plate,but not necessarily on the subducting ridge.However,slab windows related to the ocean ridge are taken great proportions in the world.The young subduction ridge,which is usually less than 10 Ma,is much hotter and has positive buoyancy,so there is wide gap between two sides of subducting ridges.The fossil ridge of South China Sea has subducted under the Philippine Sea plate along the Manila Trench.There are double chains of volcanoes in the eastern edge of the South China Sea（Luzon）,where the west volcanic chain has stopped eruption since Pliocene,but the east one has a lot of volcanic activities up to now.The two volcanic chains are separated at20°N,and the east volcanic chain has extinguished at 17.8°N,while the west one has extended to the island of Mindoro.So the volcanic gap between volcanic chains suggest the slab window below Luzon,which was formed by the extinct ridge subduction.Moreover,the characteristics of time and space about adakites after late Holocene also implied that the slab window existed between 17°N and 17.5°N in the Luzon Island.