大兴安岭地区内生铜矿床的成因类型、成矿时代与成矿动力学背景

Genetic type,mineralization epoch and geodynamical setting of endogenous copper deposits in the Great Xing’an Range

大兴安岭地区位于兴蒙造山带的东段,构造、岩浆活动强烈,蕴藏着丰富的内生有色金属、贵金属矿产资源。本文通过对该区内生铜矿床的地质特征、成因类型和年代学研究,初步将区内内生铜矿床划分为斑岩型、浅成热液高硫化型(铜银、铜锡)和接触交代型三种成因类型,除铜锡矿床外,它们的成矿作用均与高钾钙碱系列I型花岗质岩浆密切相关;其中斑岩型和浅成热液高硫化型(铜、银)的成矿分别发生在485Ma、180～170Ma和170～160Ma;而浅成热液高硫化型(铜锡)矿床与A型花岗质岩浆相关,成矿在150～135Ma之间;接触交代型与它们相伴生,主要发生在180～160Ma和150～135Ma。其成矿动力学背景分别与早古生代兴安地块与松嫩地块的拼合碰撞造山、中侏罗世的西伯利亚板块和华北板块的陆缘增生带碰撞缝合造山与早白垩世碰撞造山后的地壳伸展减薄作用过程相适应,矿床在不同阶段的造山挤压与伸展转换或造山期后的伸展阶段就位,这项研究为深入研究该区内生多金属成矿规律提供了科学依据。

The Great Xing’an Range,located in the eastern Mongolia-Hinggan orogenic belt,is characterized by intense tectonic and magma activity,abundant endogenous non-ferrous and precious metal mineral resources.Based on studies of geological characters,genetic type and chronology,the endogenous copper deposits can be divided into three genetic types：porphyry copper deposits,epithermal high-sulphidation deposits（Cu-Ag,Cn-Sn） and contact-metasomatic deposits.The mineralization is collectively closely related to high-K calc-alkaline I-type granitic magmas,except for Cu-Sn deposits.In the eastern part of the area,porphyry copper deposits were mostly emplaced during 180～170Ma,with a small amount in around 485Ma,whereas epithermal high-sulphidation copper-silver deposits,in the middle of the Great Xing’an Range,have an emplacement age of 170～160Ma.In the west,epithermal high-sulphidation Cu-Sn deposits which emplaced between 150Ma and 135Ma are related to A-type granitic magma.The contact-metasomatic deposits are associated with above two types,concentrated in 180～160Ma and 150～135Ma.Conclusions can be drawn that the metallogenic geodynamic setting is consistent with Early Paleozoic collision between the Xing＇an block and Songnen block,Middle Jurassic collision between the Siberia and North China plates epicontinental accretional belt,and the crustal extension and thinning effects of Early Cretaceous collisional orogeny.Accordingly,these deposits emplaced in intra-continental transformation orogenic regime or post-orogenic extension stages.This result will provide a scientific basis for in-depth study of the endogenous polymetallic mineralization regularity.