西菲律宾海盆本哈姆隆起玄武岩岩浆作用条件  

Magmatic Conditions of Basaltic Rocks From the Benham Rise in the West Philippine Basin and Its Geological Significances

作　　者：王睿睿 鄢全树[2,3,5] 田丽艳 张海桃 施美娟[2,3] Wang Rui-rui;Yan Quan-shu;Tian Li-yan;Zhang Hai-tao;SHI Mei-juan(Institute of Deep-sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China;The First Institute of Oceanography,SOA ,Qingdao 266061,China;Key Laboratory of Marine Sedimentology and Environmental Geology,Qingdao 266061,China;University of Chinese Academy of Sciences,Beijing 100049,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao266071,China)

机构地区：[1]中国科学院深海科学与工程研究所,海南三亚572000 [2]国家海洋局第一海洋研究所,山东青岛266061 [3]海洋沉积与环境地质国家海洋局重点实验室,山东青岛266061 [4]中国科学院大学,北京100049 [5]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,山东青岛266061

出　　处：《海洋科学进展》2018年第2期229-241,共13页Advances in Marine Science

基　　金：国家重点研发计划项目--海洋划界相关自然特征的影响因素分析及其特征提取技术研究(2017YFC1405502);中央级公益性科研院所基本科研业务费专项资金资助项目--"束星北"青年学者项目(2016S01);国家自然科学基金项目--科科斯脊俯冲组分及邻近大陆坡沉积物的地球化学研究及其对俯冲剥蚀机制的制约(41776070)和西南太平洋劳海盆西北部熔岩地球化学特征及其对洋内弧后扩张过程的制约(41506047);中国科学院战略性先导科技专项(B类)子课题--蛇纹岩在俯冲带元素循环中的作用(XDB06030103);青岛海洋科学与技术国家实验室"鳌山人才"计划项目(2015ASTP-ES16);山东省泰山学者工程项目

摘　　要：本哈姆隆起(Benham Rise)(形成时代为37～36 Ma)位于菲律宾海板块西侧的西菲律宾海盆内。此海底隆起靠近菲律宾海沟,水深2 000～3 000m,体积接近1×10~5 km^3,为一典型的海底高原。玄武岩样品中的橄榄石斑晶颗粒粒径为0.2～0.4mm,自形-半自形,部分橄榄石斑晶发生明显的伊丁石化,不具橄榄石捕虏晶所特有的环状裂隙和扭折结构;基质中的橄榄石微晶粒径为0.01～0.05mm。早期结晶出来的橄榄石斑晶被寄主岩浆携带向上运移到地表期间,与寄主岩浆相互作用有限,少数橄榄石颗粒出现弱的成分分带现象。利用橄榄石斑晶与寄主岩浆对本区域地幔潜在温度(Tp)进行了计算,结果显示本哈姆隆起之下的地幔潜在温度范围为1 660～1 683℃。与正常洋中脊之下的地幔潜在温度相比,本哈姆隆起高约185～230℃,表明本哈姆隆起之下的地幔可能存在热量异常。此外,本哈姆隆起玄武岩中斜长石斑晶的结晶温度平均为1 160℃,结合其具有较高的An值(100Ca/(Ca+Na),表明斜长石斑晶形成于快速上升的幔源岩浆中。本研究为本哈姆隆起为地幔柱成因的观点提供了证据。The Benham Rise（37～36 Ma）lies within the West Philippine Basin（WPB）,the Philippine Sea plate（PSP）,and is very close to the Philippine Trench and Luzon Arc.The Rise,below the water 2 000～3 000 m,with volume of up to 1×10^5 km3,belongs to a typical submarine plateau.The grain size of olivine microlites is just 0.2～0.4 mm,and the shapes of most of them are idiomorphic or hypidomorphic with slightly resorption,and some of them have altered into iddingsites.The phenocrysts don’t take on the peculiar ring fracture and deformation structure which olivine xenocrysts have.In groundmass,the grain size of olivine microlites is just 0.01～0.05 mm.The early crystalline olivine phenocrysts were entrained and transported upwards to the surface by host magmas,with limited interaction with host magmas,evidenced by only a small number of olivines showing weak compositional zonation.Using the Fo values（100 Mg/（Mg＋Fe2＋））of the core of olivine phenocrysts and the XFevalues XFeis cation fraction of Fe of the host magmas,we estimated the mantle potential temperatures（Tp）beneath the Benham Rise.These results show that the Tp values for the rise range from 1 660 to 1 683 ℃.And Tp beneath the Benham Rise is about 185～230℃ higher than those beneath the normal mid ocean ridge（1 453～1 475 ℃）,imply that there may exist thermal anomalies in the mantle beneath the Benham Rise.The average crystallization temperature of plagioclase phenocrysts of the basalts from the Benham Rise is 1160℃,and the high An values（100 Ca/（Ca＋Na））of plagioclase phenocrysts indicate that they were formed in rapid upwelling mantledevived magma.This study provide some key evidences for the existence of a thermal-driven mantle plume beneath the Benham Rise.

关 键 词：玄武岩 橄榄石 斜长石 地幔潜在温度 地幔柱 本哈姆隆起 

分 类 号：P736[天文地球—海洋地质]