马里亚纳南部弧内坡橄榄岩中的角闪石成分对于弧下地幔交代流体的指示  

The Amphibole in ultramafic rocks from southern Mariana trench inner slope:Implication for metasomatism in forearc setting

作　　者：董彦辉[1,2] 初凤友[1,2] 朱继浩[1,2] 张平萍[1,2] 

机构地区：[1]国家海洋局海底科学重点实验室,浙江杭州310012 [2]国家海洋局第二海洋研究所,浙江杭州310012

出　　处：《海洋学报》2011年第5期91-96,共6页

基　　金：国家自然科学基金青年基金(40906037);国家海洋局第二海洋研究所基本科研业务费项目(JG0901;JT1001;JT1104);国家基础研究发展规划项目(2007CB41170301)的资助

摘　　要：马里亚纳弧前的橄榄岩被认为是SSZ型蛇绿岩的现代等同物,记录了弧下地幔与俯冲流体的交代反应,其中的角闪石被认为是俯冲流体交代的产物。电子探针的数据表明角闪石主要包括透闪石和镁闪石两种,其中前者具有低的钠含量,后者则具有明显高的钠、铝含量,但Mg#较低。角闪石的组成反映了俯冲流体具有高硅、钙、铝、钠等元素的特征。形成成分不同的角闪石的原因可能是交代流体的来源深度不同,来源较浅的流体可能具有贫铝、钠而富硅、钙的特点,而与橄榄岩交代形成镁角闪石的流体的来源可能更深,具有富铝、钠的特征。The peridotites in landward-slope of Mariana trench regarded as the analogue of ophiolites,record the metasomatism between subducting slab fluid and subarc mantle wedge.Amphiboles is a product of the metasomatism.Our EPMA data suggest that the amphiboles in south Mariana trench inner-slope mainly tremolite and magnesiohornblende with little edenite.Magnesiohornblende have lower Mg# and significantly high Na2O and Al2O3 related to tremolite.The component of amphibole expectially magnesiohornblende suggests the matasomatic fluid contain high Si,Ca,Al,Na but extremely low Ti.The component difference between tremolite and magnesiohornblende might be attributed to fluid origin from difference depth.Fluid from relative shallow may be rich in Si and Ca but dilute Al and Na,and the fluid which formed magnesiohornblende may be origin from deeper slab which release more Al and Na.

关 键 词：马里亚纳 橄榄岩 地幔交代作用 角闪石 俯冲带 

分 类 号：P736.3[天文地球—海洋地质]