粤西印支期那蓬岩体的岩石学、地球化学特征及其成因

那蓬岩体为混合岩化-花岗岩化作用的产物,主体岩性为中细粒(斑状)黑云母二长混合花岗岩、弱片麻状细粒黑云母二长混合花岗岩,富含堇青石、矽线石、红柱石等富铝矿物,靠近岩体边部为混合片麻岩、花岗片麻岩,逐渐过渡至围岩。对中细粒黑云母二长混合花岗岩进行LA-ICPMS锆石U-Pb同位素测年,锆石以变质锆石为主、岩浆锆石为辅,获得多期锆石UPb年龄,将最新的变质年龄252±1.9Ma作为成岩年龄,将那蓬岩体的成岩时代定为早三叠世。那蓬岩体形成于碰撞造山构造环境。

THE PETROLOGY, GEOCHEMICAL CHARACTERISTICS AND ORIGIN OF THE NAPENG GRANITE MASS FORMED IN INDO-CHINA PERIOD IN THE WEST OF GUANGDONG PROVINCE

The Napeng granite mass is the product of migmatization and granitization, in which major lithologies are medium-fine grained (porphyritic) biotite monzonitic migmatitic granite and weak gneissic fine grained biotite monzonitic migmatitic granite, rich in a number of Al-rich minerals such as cordierite, fibrolite, bucholzite, andalusite and so on. The lithologies closed to the edge of Napeng granite mass are migmatitic gneiss and granitic gneiss, migrating to the surrounding rocks. By means of LA-ICP-MS Zircon U-Pb isotope dating on the medium-fine grained biotite monzonitic migmatitic granite, it is found that metamorphic zircons are the main zircons and few are magmatic zircons, and it is determined that the diagenetic age of the Napeng granite mass is 252±1.9Ma, the early Triassic age, in the tectonic environment of collision orogeny.