【作者】 颜彬；

【导师】 韩宗珠；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2008， 硕士

【摘要】 四国海盆-帕里西维拉海盆和冲绳海槽是西北太平洋沿岸典型的扩张型弧后盆地,也是我们深入研究板块运动和壳幔物质循环的理想地区。本文对采自四国海盆-帕里西维拉海盆和冲绳海槽的共8个浮岩样品进行了岩石地球化学初步研究,结果表明:样品的SiO₂含量处于55.26%～69.58%之间,为中、酸性火山岩;Na₂O+K₂O含量为5.45%～10.39%,属于钙碱性系列。样品具有斑状结构,斑晶矿物主要为斜长石、单斜辉石,基质为隐晶质或玻璃质。从微量元素组成来看,样品的微量元素配分图式表现出明显的岛弧特征。稀土配分型式呈现右倾图式,La_N=44.84～206.61,（La/Yb）_N=1.59～10.67,轻稀土元素富集,轻重稀土比值高;而HFSE保留了原始的玄武质岩浆的特征;稀土元素配分图上明显的Eu负异常,表明岩浆经历了一定程度的结晶分异;Ce负异常表明岩浆受到了海水或俯冲组分的影响;Ta、Sr亏损表明样品具有岛弧特征。综合四国-帕里西维拉海盆和冲绳海槽的浮岩样品的岩石地球化学研究成果发现,样品的岩浆形成于俯冲带下伏板块的俯冲熔融、并在熔融过程中受到俯冲组分的影响从而表现出明显的岛弧特征。更多还原

【Abstract】 The Shikoku - Parece Vela Basin and Okinawa Trough lying on the west Pacific are typical extension back-arc basins which are ideal for the researching of plate tectonics and Asthenosphere convecting.In this thesis,8 pumice samples from the study areas are examined by Petrology Geochemistry methods and the results show that:the pumice are calc-Alkalie series with the SiO₂ of about 55.26%～69.58%and Na₂O+K₂O of about 5.45%～10.39%;The minerals in the crystal of pumice are Plagioclase and Clinopyroxene with aphanitic-vitric matrix.The Spider Diagram of Trace Elements data shows the typical island arc pattern.The REE diagram shows a right-leaned pattern with La_N=44.84～206.61,（La/Yb）_N = 1.59～10.67,Pumices from both the two researching areas are enriched in LILE and LREE,while HFSE keeps its initial pattern of basaltic lava.The negative Eu anomaly indicates that the lava has the process of crystallization;The Ce anomaly indicates the lava has been effected by subduction composition or ocean water.The negative Ta、Sr anomaly also indicate the island arc pattern.The Petrological Geochemistry study of pumice samples from both the Shikoku - Parece Vela Basin and the Okinawa Trough proves that the lava of pumices coming from the extension back-arc basins is formed by the melting of subducting plate and effected by the subduction composition before its breaking out.So the lava expresses the property of both island arc pattern on both the Spider Diagram and REE diagram.更多还原