一种罕见的岩石——富铁玄武岩/富铁苦橄岩研究进展  

THE SUMMARY ON A KIND OF RARE ROCK—FERROBASALTS/FERROPICRITES

作　　者：彭头平[1] 王岳军[1] 彭冰霞[1] 

机构地区：[1]中国科学院广州地球化学研究所

出　　处：《地球科学进展》2005年第5期525-532,共8页Advances in Earth Science

基　　金：国家自然科学基金项目"晋冀地区早元古代高铁镁质岩石成因及其构造指示"(编号:40303005);"澜沧江南段三叠纪共存高镁和高铝火山岩的岩石成因及其构造约束"(编号:40473019);中国科学院知识创新工程重要方向项目"华南中生代盆山系统及动力学研究"(编号:KZCXZ SW117)资助.

摘　　要：高铁镁质岩石(Ferrobasalts/Ferropicrites)较正常镁质岩石高FeO(通常在14%以上)、贫硅、低碱,具独特主量元素特征,属富铁拉斑玄武岩—富铁苦橄岩。在自然界中与普遍发育的具Bowen趋势的低铁富硅熔体不同,高铁贫硅岩浆(Fenner趋势)非常罕见,也没有直接的现代类比物可以对比以解释其岩石成因。为了解释其岩石成因,前人做过大量的研究,归纳起来主要有以下几种可能的成因类型:①普通洋脊型玄武岩在封闭系统中简单的分离结晶作用;②低压条件下俯冲板片的大比例部分熔融;③地幔柱头前锋富铁组分(Fe richstreaksinmantleplumestarting heads)的部分熔融。其成因机制的研究对于理解其岩浆深部构造背景、早期壳—幔演化、下地幔组成不均一性和核幔相互作用有着重要意义;同时,对于最近在我国南太行山地区及其它地区发现的具有高铁镁特征岩石的研究具有极其重要的意义。High-Fe, magnesian rocks (Ferrobasalts/Ferropicrites) are characterized by high FeO~* contents (tatal Fe as FeO~*)(generally >14%), silica-poor, and low alkaline. These rocks belong to the tholeiitic-Ferropicritic series. The iron-rich and silica-poor liquids (the Fenner trend), commonly different from the low iron and silica-rich liquids (the Bowen trend), are rare on the earth surface. There are not the same, which can be used to explain their petrogenesis at present. Summing up the previous studies, the type of petrogenesis mainly include: (1) high degrees of partial melting of the dehydrated subducting slab or the overlying mantle wedge which has been metasomatized by the slab melt, at low pressure; (2) Simply crystal fractionation from common mid-ridge type basaltic magmas in closed or nearly closed system; (3) Partial melting of high-Fe magnesian melts from mantle plume starting-heads. The study on the mechanism of petrogenesis of high-Fe magnesian magmas is important to understand the tectonic regime of magmas in depth, early evolution of crust, the heterogeneity of lower mantle and the interaction of core-mantle. Meanwhile, it is also most significative for us to understand the petrogenesis of high-Fe magnesian rocks discovered from southern Taihang Mountains and other regions, in China.

关 键 词：富铁拉斑玄武岩 富铁苦橄岩 Bowen趋势 Fenner趋势 部分熔融 分离结晶 

分 类 号：P59[天文地球—地球化学]