论东秦岭印支-燕山期岩浆活动与成矿作用

Mineralization and Magmatic activities of Indosinian-Yanshan Period in East Qinling Mountains

东秦岭中生代构造体制发生了重大调整,由南北向主构造应力场向近东西向主构造应力场的构造体制转换,在此过程中岩石圈发生大规模拆沉减薄并诱发强烈的印支期-燕山期岩浆活动。印支期花岗岩类主体成岩时代为三叠纪,成岩年龄介于230~200Ma,花岗质岩浆活动高峰期为220Ma±;显示具I型花岗岩地球化学特征,岩浆源区以壳源为主,形成构造环境与秦岭主碰撞造山后期由挤压向伸展构造体制转换的构造应力松弛阶段有关。燕山期花岗岩主体成岩时代为早侏罗-早白垩世,成岩年龄介于200~100Ma,花岗质岩浆活动高峰期为140Ma±;显示具I型向I-A过渡型再向A型演变的特征,岩浆源区以上地幔或壳幔混源为特点,形成构造环境与太平洋板块向欧亚板块俯冲作用的远程效应有关。东秦岭早中生代(印支期)花岗岩类成矿作用时限介于230~200Ma,成矿高峰期为210Ma±;晚中生代(燕山期)花岗岩成矿作用时限介于200~125Ma,成矿高峰期为130Ma±。印支期成矿作用与燕山期成矿作用整体构成了秦岭成矿带中生代成矿大爆发,暗示东秦岭内生金属矿床成矿作用具有多期与多阶段和中生代集中成矿的特点。

In the Mesozoic era,the tectonic system of the East Qinling Mountains undergone a major readjustment,from the south-north to the main tectonic stress field to the near-east-west to the main tectonic stress field.During this process,a large-scale delamination and thinning of the lithosphere resulted in intense indosinian-yanshanian magmatism.The main diagenetic age of Indosinian granitoids is Triassic,the diagenetic age is between 230 and 200 Ma,and the peak of granitic magmatism is 220 Ma±;It shows the geochemical characteristics of I-type granite,and the magma source area is mainly crust source.The tectonic environment is related to the tectonic stress relaxation stage of the transformation from compression to extension tectonic system in the late period of the main collision orogeny in the Qinling Mountains.The main diagenetic age of Yanshanian granite is Early Jurassic and Early Cretaceous,the diagenetic age ranges between 200 and 100 Ma,and the peak of granitic magmatism is 140 Ma±;It shows the characteristics of transition from I-type to I-A type and then to A-type.The magma source area is characterized by mantle or crust mantle mixed source.The tectonic environment is related to the remote effect of the subduction of the Pacific plate to the Eurasian plate.The mineralization time limit of Early Mesozoic(Indosinian)granitoids in the East Qinling Mountains is between 230 and 200 Ma,and the mineralization peak is 210 Ma±;The mineralization time limit of late Mesozoic(Yanshanian)granite is between 200~125 Ma,and the mineralization peak is 130 Ma±.Indosinian mineralization and Yanshanian mineralization as a whole constituted the Mesozoic metallogenic explosion in the Qinling metallogenic belt,suggesting that the mineralization of endogenetic metal deposits in the East Qinling Mountains has the characteristics of multi period,multi stage and Mesozoic concentrated metallogenesis.