河南鲁山鸡冢岩体岩浆混合特征及意义

Magma Mixing Feature of Jizhong Granite in Lushan Mts,Henan Province

鸡冢岩体为经历两次岩浆脉动上侵而成的复式深成岩体,化学成分表现为贫SiO2,低MgO,富CaO、Na2O,岩石类型为偏铝质高钾钙碱性岩系,属岩浆混合花岗岩。研究表明,花岗岩及其中暗色微粒包体在地球化学特征上具有相似的稀土、微量元素含量和配分模式。成分变异图解显示,SiO2与Al2O3、K2O、CaO、MgO、FeO 、TiO2及稀土、微量元素La-Ce、Nd-Sm、La-Ba、Th/Yb-Ta/Yb之间具有较好的线性关系。氧同位素地球化学特征表明花岗岩形成过程中有大量幔源组分加入,说明鸡冢岩体为岩浆混合作用产物,其形成与华北陆块南缘陆内俯冲造山作用有关。

Jizhong granite rock is a compound body forming by two-times magma puls inventions. The chemical compositin is poor in SiO_2, MgO and rich in CaO, Na_2O. It belongs to magmatic granite of high-potassium calc-alkalic rock series. The granite and the dark-coloured micro-grain enclaves in it have the same features of the REE partitioning model, micro-elments. There are good linearity relationship between SiO_2 and Al_2O_3,K_2O,CaO,MgO,FeO~*,TiO_2, and between La-Ce, Nd-Sm, La-Ba, Th/Yb-Ta/Yb. Based on the study of the δ^(18)O, it is suggested that there is a lot of mantle materials dopping into the granite, which means the granite is from mingling of magma. Its formation is related to the intracontinental subduction orogenic movement in the north margin of the North China block.