Sanukite(赞岐岩)的地球化学特征、成因及其地球动力学意义  

Geochemistry, petrogenesis and geodynamic implications of sanukite

作　　者：张旗[1] 钱青[1] 翟明国[1] 金惟浚[1] 王焰[2] 简平[3] 王元龙[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]香港大学地球科学系 [3]中国地质科学院地质研究所,北京100037

出　　处：《岩石矿物学杂志》2005年第2期117-125,共9页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目 (4 0 472 0 47) ;国家自然科学重点基金资助项目 (4 0 2 3 40 45 ) ;中国科学院知识创新工程基金资助项目 (KZCX 1_0 7;KZCX2_SW_119)

摘　　要：赞岐岩 (サヌカイト ,sanukite)是指发现于日本四国北部的一种富Mg的火山岩 ,主要产于日本中新世 (11～14Ma)Setouchi火山岩带 ,是一种黑色玻璃质的火山岩。其化学成分以富Si质 (安山英安质 )、具很高的Mg# 值 (>0 .6 )、高的Cr、Ni丰度和K/Na值 (0 .33～ 0 .5 2 )为特征。赞岐岩的形成与菲律宾海板块年轻的热的岩石圈俯冲和四国盆地的张开有关 ,产于岛弧的弧前或弧后盆地环境。赞岐岩不只代表火山岩 ,也包括侵入岩。Shirey和Hanson(1984 )将该术语引入太古宙 ,将太古宙具上述赞岐岩特征 (Si过饱和、Mg# 高和Ni、Cr、LILE含量高 )的深成岩和火山岩称为sanukite岩套。赞岐岩与埃达克岩具有大体类似的地球化学特征 ,但前者更富Mg、Cr和Ni,表明赞岐岩可以直接由地幔岩部分熔融形成 ,而埃达克岩只能由玄武岩部分熔融形成。现代的赞岐岩很少见 ,而太古宙的赞岐岩比较常见 ,暗示太古宙导致板片熔融的消减的岩石圈本身或上地幔可能具有更高的温度。赞岐岩集中出现在晚太古代 (<3.0Ga) ,表明板块消减作用可能在 3.0Ga之后才成为一个重要的过程 。Sanukite is a type of black vitreous Mg-rich volcanic rocks first recognized in the northern part of Shikoku in Japan. It occurs mainly in the Miocene (11～14 Ma) Setouchi volcanic belt, and is typically high in Mg number (Mg/Mg+Fe^(2+)>0.6), SiO_2 (andesitic to dacitic), Cr and Ni contents and K/Na ratios (0.33～0.52). The Setouchi sanukite is located in fore- or back-arc basins, and originated in subduction of the young and hot Philippine Sea plate and pull-apart of the Shikoku basin. Shirey and Hanson (1984) first used 'sanukitoid' to name some Archaean intrusive and extrusive rocks with the above geochemical characteristics. Geochemically, sanukite resembles adakite except for somewhat higher Mg, Cr and Ni contents, indicating that it can be produced directly from a mantle source through partial melting, whereas adakite is merelyproducedbypartial melting of a basaltic source. Sanukite is widespread in Archaean, indicating a higher geotherm of the mantle wedge or the subducting plate. The early sanukite has only been found in Late Archaean (<3.0 Ga), probably indicating that the modern style plate tectonics was initiated at that time and that plate subduction came to be an important geological process only after 3.0 Ga.

关 键 词：Sanukite(赞岐岩) 埃达克岩 地球化学 岩石成因 

分 类 号：P588.1[天文地球—岩石学]