龙门山中段映秀地区花岗岩单元特征

CHARACTERISTICS OF GRANITE UNITS IN YINGXIU REGION, LONGMEN MOUNTAINS

映秀地区花岗岩属龙门山推覆构造带“彭灌杂岩”南段之组成部分，岩石类型以二长花岗岩、英云闪长岩为主，少量花岗闪长岩。按照同源岩浆演化序列的观点，根据岩石学、岩石化学及地球化学、接触关系等特征，将该区花岗岩划分为８个花岗岩单元。其岩石为稀土总量偏低、具负铕右倾型式的钙碱性次铝及过铝型酸性侵入岩，分属造山前陆弧Ｉ型花岗岩的成分演化序列及造山晚期Ｓ型花岗岩的结构演化序列，其形成时代为中─晚元古代。

The granite in Yingxiu region is one part of the “Peng-Guan complex” in Longmen Mountains. The granites are mainly monzogranite,tonalite,and a bit of granooiorite.According to the series of comagmatic evolution,the granites are divided into eight granite units on the basis of the characteristics of petrology,petrochemistry,geochemistry and contact relations.The granites are calc-alkalic,hypoaluminous or Peraluminous,and acidic intrusive rocks of lower total content and chondrite normallized pattsrn of REE in right oblique type and negative Eu anomaly. The granites belong to I-type granite of evolutionary series of composition in epicontinental arc before orogenesis of late orogenic S-type granite of evolutionary series of texture. They formed in Middle-Late Proterozoic era.