日本飞弹变质带庄川岩体的岩石成因

主要从岩石学方面对飞弹变质带西北部的庄川岩体的成因进行探讨。该区侏罗纪岩体由闪长岩-石英闪长岩(以下简称D-Qd)和花岗闪长岩-石英二长岩(以下简称Gd-Ad)两类岩石构成。在野外,Gd-Ad侵入于D-Qd之中。D-Qd和Gd-Ad,其Sr含量随Rb/Sr的变化倾向,以及Eu/Eu~*),(La/Lu)cn随SiO_2含量的变化倾向明显不同,所以,两者可能是由不同的岩浆生成的。Gd-Ad的微量元素和稀土元素(REE)含量的分散现象可能是由飞弹变质岩类或(和)广泛分布飞弹变质带中的古期灰色花岗岩的混合作用引起的。

GENESIS OF ROCKS OF THE SHOGAWA MASSIF IN THE HIDA METAMORPHIC BELT,JAPAN

Petrographical study has given the Shogawa massif in the northwesternpart of the Hida metamorphic belt.The massif of the Jurassic age consistsof two types of granitic rocks: 1) the rock ranging from diorite to quartzdiorite (abbreviated to D-Qd) and 2) the rock ranging from granodioriteto adamellite (abbreviated to Gd-Ad). The latter intruded into the former.Although the D-Qd and the Gd-Ad show similar trend in variationdiagrams of major oxides versus SiO_2(Fig. 3), there is considerabledifference in the variation diagram of Sr versus Rb/Sr (Fig.5),and Eu/Eu], (La/Lu)_(Cn) versus SiO_2(Fig.7). These differences suggest that the D-Qdand the Gd-Ad might have been derived from different magmas. Further-more, the dispersion of the abundances of trace elements and rare earthelements (REE) in the Gd-Ad may be attributed to the assimilation of theHida metamorphic rocks and (or) of the older gray granite widely intrudedinto the Hida metamorphic belt.