江苏盘石山幔源橄榄岩包体成因的地球化学

GENETIC GEOCHEMISTRY OF MANTLE-DERIVED PERIDOTITE XENOLITH FROM PANSHISHAN,JIANGSU

根据主要元素、微量元素、若干矿物相主要元素和单斜辉石微量元素测定认为：盘石山幔源橄榄岩包体是由接近原始地幔源区的地幔经不同比例部分熔融后的残余二辉橄榄岩和方辉橄榄岩组成，基本未受其它过程干扰。由主要元素和ＭｇＯ相关性的回归方程，根据二元混合规律估算了原始熔体的组成范围。计算了包体的平衡温度，认为较亏损的方辉橄榄岩可能位于弱亏损的二辉橄榄岩之上。全岩和单斜辉石中不相容元素含量有可能作为地幔部分熔融和地幔交代作用的指示剂。

The major and trace elements of mantle-derived spinel peridotite xenoliths and some contained significant minerals from Panshishan were determined using XRF、EMP and PIXE (proton microprobe). The systematic variation between MgO and CaO, Al2O3, TiO2, Na2O, Cu, V, Zr and Ni indicates that the studied xenoliths are probably the residue of partial melting from a relative uniform, primitive or very weakly depleted mantle source, and have not been disturbed by any other geochemical processes. The chemical compositions of primary melt are estimated based on the two end-member mixing model using the regression equation of MgO to other major oxides. The equilibrium temperatures of xenoliths are also calculated, and the results show that the depleted harzburgite probably occur above the weakly depleted lherzolite. Trace element concentrations in the whole rock and clinopyroxene may be used as an index of partial melting and metasomatism.