河北阳原岩体辉石岩—正长岩组合与岩浆不混溶作用

THE PYROXENITE-SYENITE SUITE OF YANGYUAN COMPLEX IN HEBEI PROVINCE AND SILICATELIQUID IMMISCIBILITY

河北阳原杂岩体可分为两个岩石系列:辉石岩系和正长岩系,具辉石岩-正长岩“双峰”岩石组合特征。本文从两个岩系的矿物化学,主要是从微量元素地球化学诸方面论证了辉石岩系-正长岩系是岩浆不混溶作用和结晶分异作用的综合作用产物。研究提出阳原初始母岩浆不混溶形成辉石岩岩浆单元和正长岩岩浆单元。在1100～850℃揾度范围内,两岩浆单元处于互不混溶、平衡共存状态;当温度降至850℃时,两岩浆单元外始了各自的结晶分异作用,形成辉石岩系和正长岩系。本文最后指出,岩浆的成核作用是岩浆不混溶的重要方式。岩浆体系的对流循环可以有效地使不混溶的两液相分离。

<ABSTRACT> The Yangyuan complex in Hebei province is classfied into two rock series: pyroxenitic and syenitic series. The complex is characterized by the bimodal suite: pyroxenite-syenite. The paper has investigated the mineral chemistry, major and trace element geochemistry of Yangyuan complex and demonstrates that the pyroxenitic and syenitic series was formed from pyroxenitic and syenitic magma units respectively, which ever had equiliberated and had been immiscible with each other, by differentiation. It is suggested that the two magma units was produced by unmixing process of the Yangyuan parent magma within the range of 1100~ 8501, the two units was in a state of equilibrium and immiscibility. When temperature is lower than 8501 , they crystallized to form pyroxenitic and syenitic series respectively. The paper finally points out that the nucleation is the major way of silicate liquid immiscibility and convection may be the effective force, by which the two immiscible liquid was seperated each other.