峨眉火成岩省地幔热柱的主要元素及Cr、Ni地球化学特征

Chemical Characteristic of Major Elements,Cr and Ni of Mantle Plume in Emei Igneous Province

峨眉山玄武岩省晚古生代镁铁超镁铁岩可分为苦橄岩—橄榄玄武岩系和玄武岩系等两个岩石系列。它们的常量及微量元素特征均存在区别,这些区别可以通过对比两个岩系的Ni与Cr、MgO、Al_2O_3的相关关系加以明确。据此估算了峨眉火成岩省地幔、地幔热柱不同部位主元素、Mg#值和Cr、Ni含量,推算出成分接近原始岩浆的玄武岩、苦橄岩类和橄榄岩类分别为地幔7%～15%、25%～40%和>50%的部分熔融产物。

Mafic and ultramafic rocks of later paleozoic period in Emei igneous province consist of two rock series:picrite-peridotite and basalt suites,whose bulk and trace element characteristics are quite different,which can be further proved by comparing the abundance relationship between Ni and Cr、MgO、Al_2O_3 of the two rock series. According to the elemental abundance relationship, the paper estimates the Mg# (MgO/MgO+FeO)、bulk element、Cr and Ni contents of the mantle and the different parts of mantle plume in the Emei igneous province, makes the conclusion that the basalt (composition of which are close to that of primary magma), picrite and peridotite are products of different partial melting degrees of the mantle,the degrees of which are 7%～ 15%,25%～40% and >50% ,respectively.