冲绳海槽火山岩岩石系列的厘定及构造环境意义  

Determination and Tectonic Significance of Volcanic Rock Series in the Okinawa Trough

作　　者：国坤[1,2] 翟世奎[1] 于增慧[1] 蔡宗伟 张侠[1] 

机构地区：[1]中国海洋大学海底科学与探测技术教育部重点实验室,山东青岛266100 [2]中国科学院海洋研究所,山东青岛266071

出　　处：《地球科学（中国地质大学学报）》2016年第10期1655-1664,共10页Earth Science-Journal of China University of Geosciences

基　　金：国家重大基础研究发展规划"973"项目(No.2013CB29702);中国大洋矿产资源研究开发协会"十二五"重大项目(Nos.DY125-11-R-01;DY125-12-R-03);青岛海洋科学与技术国家实验室鳌山人才计划项目(No.2015ASTP-0S17)

摘　　要：冲绳海槽是一个处于弧后扩张作用早期的年轻的弧后盆地,是研究弧后扩张作用早期盆地演化和壳幔过程的天然实验室.随着调查研究工作的逐步展开和深入,也发现了一些新的、重要的、亟待解决的科学问题,而火山岩岩石系列归属的厘定又是其他研究工作的基础.在系统收集和整理迄今已有冲绳海槽火山岩资料的基础上,结合近期分析测试数据,对冲绳海槽火山岩的岩石系列归属进行了重新厘定,探讨了火山岩的构造环境指示意义和浮岩与玄武岩之间的成因联系.研究结果表明:冲绳海槽火山岩分布具有以基性玄武岩和酸性(流纹)英安岩为主的双峰式特征,中性火山岩稀少,基性的玄武岩属于亚碱性系列的橄榄拉斑玄武岩,酸性浮岩可归属为亚碱性岩系的流纹英安岩或流纹岩;在构造环境判别上,冲绳海槽玄武岩表现出大洋中脊和岛弧构造环境的特点,既有别于大洋中脊扩张中心,也有别于成熟型弧后盆地,呈现出弧后早期扩张阶段盆地独特的构造环境特征;广泛分布于冲绳海槽的酸性浮岩表现出一定的岛弧环境的特点;酸性浮岩与玄武岩具有同源性,酸性岩是基性的玄武质岩浆经不同程度结晶分异和同化混染作用的产物.The Okinawa Trough is a young back-arc basin at its early back-arc spreading stage, and is a natural laboratory for understanding the formation and evolution of back-arc basins and crust-mantle interaction processes under this tectonic setting. However, with the gradually deepening of research work, the rock series of volcanic rocks from the Okinawa Trough are becoming an important and urgent need to solve problem. Based on the geochemical compositions of some pumices determined recently by authors and the petrologic and geochemical data of volcanic lavas from the Okinawa Trough in literatures, the rock series of volcanic rocks from the Okinawa Trough have been determined in detail. The tectonic significance of volcanic rocks and the genesis relationship between pumices and basalts have also been discussed. The magmatism in the Okinawa Trough is bimodal, being comprised dominantly of basic basalts and acidic rhyolites, accompanied by minor intermediate rocks. The basalts are mainly olivine tholeiitic basalts, which belong to subalkalic series, and the pumices are mostly rhyodacite or rhyolite, which belong to subalkalic series too. According to the geochemical compositions, basalts are not only similar to those from the midocean ridge but also from the island arc tectonic environment. They are different from those occurring at mid-ocean ridge spreading center or mature back-arc basins, but with distinct geochemical features associated with distinct tectonic environment their occurred, a back-arc basin at early spreading stage. The acid pumice, a widely distributed rock type in Okinawa Trough, is characterized by the geochemical compositions that are typical for volcanic rocks from island arcs. The magma of intermediate-acidic pumices, with same sources as associated basalts, may be formed by fractional crystallization of basalt magma.

关 键 词：岩石系列 岩浆作用 构造环境 冲绳海槽 海洋地质 

分 类 号：P588.14[天文地球—岩石学]