| 西太平洋典型边缘海盆的岩浆活动 |
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| 引用本文： | 石学法,鄢全树.西太平洋典型边缘海盆的岩浆活动[J].地球科学进展,2013,28(7):737-750. |
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| 作者姓名： | 石学法 鄢全树 |
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| 作者单位： | 国家海洋局第一海洋研究所,海洋沉积与环境地质国家海洋局重点实验室,山东 青岛266061 |
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| 基金项目： | 国家自然科学基金重点项目"南海新生代扩张期后岩浆活动及其构造意义"，国家自然科学基金项目"西南太平洋劳海盆地幔源区性质及俯冲组分对地幔源区的影响" |
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| 摘 要： | 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 MaBP)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.
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| 关 键 词： | 边缘海盆 弧后盆地 岩浆活动 构造演化 西太平洋 |
Magmatism of Typical Marginal Basins (or Back-Arc Basins) in the West Pacific |
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| Shi Xuefa,Yan Quanshu.Magmatism of Typical Marginal Basins (or Back-Arc Basins) in the West Pacific[J].Advance in Earth Sciences,2013,28(7):737-750. |
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| Authors: | Shi Xuefa Yan Quanshu |
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| Institution: | Key Laboratory of Marine Sedimentary and Environmental Geology, The First Institute of Oceanography, State Oceanic Administration, Qingdao266061, China |
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| Abstract: | There developed about 75 percent of marginal basins (or back-arc basins) in the west Pacific in which there have built the biggest and most complex trench-arc back-arc system has been built. Based on ages inferred from magnetic anomaly stripes, these marginal basins can be divided into three spreading epochs. This paper, based on drilling results of the Deep sea Drilling Program (DSDP), the Ocean Drilling Program (ODP) and the Integrated Ocean Drilling Program (IODP), combined with other survey results, systematically describes the characteristics of the West Philippine Basin (WPB) (No. 1 spreading epoch), the South China Sea (SCS) and the Shikoku Basin (SKB) (No.2 spreading epoch), and the Okinawa Trough and Mariana Trough (No.3 spreading epoch). Rock types in WPB include NMORB (related to the back-arc spreading process similar to those in mid-ocean ridges), OIB (related to mantle plume) and arc volcanics (related to subduction process), reflecting that WPB has experienced complex tectonic evolution. In SKB, in addition to the occurrence of NMORB-EMORB which may be related to the back-arc spreading process, medium-K and super-K alkali basalts have been obtained from the Kinan seamount chain, and the latter may be produced by intraplate volcanism. In SCS, no oceanic basement rock, but alkali basalts from seamounts have been reported, and the dynamic origin for Cenozoic spreading of the SCS are still in debate. In Mariana trough, from south to north, rock types are transitional, ranging from MORB-like to IAB-like. The Okinawa Trough is a nascent basin, and rock types include MORB-like rock from southwestern segment, basaltic rocks and acidic rocks from the middle segment, and intermediate and acidic rocks from the northeastern segment. This paper also suggests that it should perform integrated studies of volcanism in the Mariana arc-trough system and the Ryukyu arc Okinawa trough, which will be very helpful to understand the relaitionship between subducting input and arc and back-arc volcanic output and provide some important clues to the tectonic evolution of the West Pacific. We should make full use of upcoming IODP legs 349 to 352 to improve our research skills in deep sea study area. |
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| Keywords: | Marginal basin Back-arc basin Magmatism Tectonic evolution West Pacific |
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