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在发育有全球最大、最复杂的弧—沟—盆体系的西太平洋地区,集中了全球75%左右的边缘海盆(弧后盆地)。根据磁异常条带年龄,这些边缘海盆可粗略分为3个扩张幕。主要根据DS-DP,ODP和IODP计划实施以来所获得的成果,结合其他海洋调查航次研究成果,系统阐述了分属3个扩张幕的西菲律宾海盆(第一扩张幕)、南海—四国海盆(第二扩张幕)和冲绳海槽(第三扩张幕)—马里亚纳海槽内的岩浆活动特点。西菲律宾海盆(扩张时代为65～35 Ma BP)从原先的赤道位置迁移至现今的位置,其内存在如似正常洋中脊玄武岩(NMORB)、洋岛玄武岩(OIB)及弧火山岩等多种岩石类型,其地球动力学背景分别与弧后扩张、地幔柱及火山弧等背景有关,其复杂的构造演化样式需要进一步研究;四国海盆(扩张时代为27～15 Ma BP)是由古伊豆—小笠原—马里亚纳弧(IBM)裂解形成的,其内除发育正常(N)—富集(E)的洋中脊玄武岩(NMORB-EMORB)外,还在扩张停止的同时出现了板内火山作用,形成了中K-超K碱性玄武岩。四国海盆的扩张模式并没有从岩石学和地质年代学角度进行明确制约,板内火山作用的地球动力学背景也不甚清楚。南海(扩张时代为32～15.5 Ma BP)是由来自华南地块的一些微陆块向东南裂离后的海底扩张所形成,并在海底扩张后2～8 Ma出现板内火山作用,截止目前,并没有获取到洋壳基底样品,主要获取到了南海海山似OIB的玄武岩,未来需要从岩石学和地质年代学角度对南海海底扩张动力学和时代以及扩张期后的板内火山作用动力学背景进行进一步制约。马里亚纳海槽(扩张时代为5 Ma BP至今)为一年青的洋内弧后盆地,其北段处于裂解增进阶段,其内出露有似MORB(中南段)及介于似MORB与似岛弧岩石之间过渡类型的玄武岩(增进端);虽然在扩张时代上与马里亚纳海槽相当,但冲绳海槽(扩张时代为4 Ma BP至今)为一陆缘、初生弧后盆地,从西南往东北方向,不同区段处于不同的伸展发育阶段,西南段出露有似MORB岩石,中段岩石主要为玄武质岩石和流纹质岩石组成双峰组合,而东北段为中酸性火山岩。正在活动的马里亚纳海槽与冲绳海槽的岩浆作用研究应和其伴随的火山岛弧及其相邻的海沟处正在俯冲的洋壳板块结合起来,完整理解板块俯冲输入(subduction input)与弧及弧后输出(volcanic output)之间的关系,这将为揭示西太平洋地区构造演化提供重要证据。即将在西太平洋地区实施的IODP 349～352航次,为我国科学家提供了研究西太平洋地区构造演化的契机。
In the western Pacific region where the world’s largest and most complex arc-gully-basin system is developed, about 75% of the world’s marginal basins (backarc basins) are concentrated. According to the age of magnetic anomaly bands, these marginal basins can be roughly divided into three expansion screens. Based on the achievements made since the implementation of the DS-DP, ODP and IODP programs, and combined with the achievements of other oceanographic survey voyages, the West Philippine basin (the first expansion curtain) and the South China Sea-Shikoku basin The second expansion) and the Okinawa Trough (third expansion) - magmatic activities within the Mariana Trough. The West Philippine Basin (65-35 Ma BP in the Era) migrated from its original equatorial position to its current location within a range of well-known features such as NMORB, OIB and archaeic volcanic rocks The types of rocks and their geodynamic background are related to the backgrounds of post-arc expansion, mantle plume and volcanic arc, respectively. The complicated tectonic evolution patterns need further study. The Siguang Basin (27 ~ 15 Ma BP in the expansion period) In addition to NMORB-EMORB, which was formed by the dissolution of the Ogasawara-Mariana arc (IBM), in addition to the normal (N) -enriched mid-ocean ridge basalts (NMORB-EMORB), an intraplate volcano Role, formed in the K-super K alkaline basalt. The expansion pattern of the Shikoku basin has not been explicitly restricted from the perspective of petrology and geochronology, and the geodynamic background of intraplate volcanism is not clear. The South China Sea (32 ~ 15.5 Ma BP in the expansion age) is formed by submarine expansion of some micro-continental blocks from south China block to the southeast after the seafloor expansion and intraplate volcanism occurs 2 ~ 8 Ma after the expansion of the sea floor, , No basal samples have been obtained from the oceanic crust, and basalts like seamounts like OIB in the South China Sea have been acquired. In the future, it is necessary to analyze the dynamics of the ocean floor in the South China Sea from the perspective of petrology and geochronology and the kinetic background of intraplate volcanism after the epoch and the expansion For further restrictions. The Mariana Trough (extending from 5 Ma BP to the present day) is a young intracontinental back-arc basin with its northern segment in the stage of enhanced cracking with intercalations like MORB (mid-south segment) and intercalation between MORB and The basalt (transitional) transitional type between arc-like rocks in the Shimadzu Islands. Although similar to the Mariana Trough during the expansion period, the Okinawa Trough (now 4 Ma BP in the dilapidation period) is a continental margin. The primary backarc basin , From southwest to northeast, the different sections are in different stages of extensional development, the MORB rocks are exposed in the southwest section, the middle section consists of bimodal assemblages of basaltic rocks and rhyolitic rocks, and the northeastern section is a medium-acidic volcanic rock . The study of the magmatic activity of the active Mariana Trough and the Okinawa Trough should be combined with the accompanying volcanic island arc and subducting oceanic crust at its adjacent trench to fully understand the subduction input and Arc and the output of volcanic output (volcanic output), which will provide important evidence to reveal the tectonic evolution in the western Pacific. The forthcoming IODP 349-352 voyages to be implemented in the western Pacific provide our scientists an opportunity to study the tectonic evolution in the western Pacific.