福建政和—建瓯地区增生杂岩中玻安岩的认识及其地质意义

Recognition and Geological Significance of Boninite in the Accretion Complex Zone in Zhenghe and Jian'ou area,Fujian Province

政和—建瓯地区增生杂岩中,部分变质岩的岩石地球化学具有高含量SiO_(2)(50.5%~57.31%)和MgO(平均10.51%),低含量TiO_(2)(0.11%~0.46%),Cr、Ni、V相容元素含量高(Cr平均868×10^(-6)、Ni平均388×10^(-6)、V平均182×10^(-6)),Ti/Zr比值较高(28~124,平均74)等特征,其Mg^(#)平均大于0.65,REE总量低,HREE丰度低,δEu基本无异常(平均0.94)。这些特征与玻安岩基本一致,故原岩应为玻安岩或玻安岩系岩石,产于洋内弧或前弧环境,是洋壳初始俯冲削减作用的证据之一。

In the accretive complex in Zhenghe-Jian'ou area,the petrogeochemistry of some metamorphic rocks is characterized by high content of SiO_(2)(50.5%~57.31%)and MgO(average 10.51%),and low content of TiO_(2)(0.11%~0.46%),the high content of Cr,Ni and V compatible elements(Cr average 868×10^(-6),Ni average 388×10^(-6),V average 182×10^(-6)),and the ratio of Ti/Zr(28~124,average 74).The average Mg^(#)is greater than 0.65,the total amount of REE is low,the abundance of HREE is low,and the Eu is basically no anomaly(average 0.94).These characteristics are basically consistent with the bolivians,and the protolite should be bolivians or bolivians series rocks,which are produced in the inner arc or front arc environment,and is one of the evidences of the initial subduction and reduction of the oceanic crust.