哈达门沟金矿床成岩成矿时代的定点定年研究  

SHRIMP CHRONOLOGICAL STUDY OF THE GRANITOIDS AND MINERALIZATION IN THE HADAMENGOU GOLD DEPOSIT,INNER MONGOLIA

作　　者：苗来成[1] Yumin Qiu 关康[3] Neal M cNaughton 裘有守[3] 罗镇宽[3] David Groves 

机构地区：[1]中国地质大学 [2]Centre for Strategic Mineral Deposits,Department of Geology and Geophysics,the University of Western Australia [3]冶金部天津地质研究院

出　　处：《矿床地质》2000年第2期182-190,共9页Mineral Deposits

基　　金：中国-西澳经济技术基金

摘　　要：哈达门沟大型钾长石 -石英脉型金矿床位于华北地台北缘西段的乌拉山地区。矿区西部的大桦背花岗岩和矿区内的伟晶岩脉与金矿化均具有较为密切的空间关系 ,这导致不少研究者认为哈达门沟金矿床与大桦背岩体或伟晶岩之间也具有时间和成因联系。通过采用先进的高灵敏的高分辨率的离子探针 (SHRIMP)对大桦背岩体、伟晶岩脉和钾长石化蚀变岩进行的锆石 U- Pb定点定年研究表明 :伟晶岩脉形成于 (1836± 5)× 10 6a,属吕梁旋回 ;大桦背岩体形成于 (353± 7)× 10 6a,应为海西旋回早期产物 ;金矿化年龄小于或等于 (132± 2 )× 10 6a,应为燕山晚期。这些年龄结果说明 ,本区金矿化比大桦背岩体晚至少 2 2 0× 10 6a,这排除了金矿化与大桦背岩体和伟晶岩脉之间有任何成因联系的可能性。蚀变岩的年龄还证明 ,虽然乌拉山和胶东地区金矿床的围岩和年龄不同 ,但两地区的金矿化却几乎同时发生。此外 ,大桦背岩体的形成年龄与华北地块和蒙古古陆块碰撞作用发生的时间基本一致 ,因此大桦背岩体的 SHRIMP年龄为这一碰撞作用提供了可靠的年代学证据。The Hadamengou gold deposit,located in Wulashan area of Inner Mongolia,namely the western part of the northern marginal zone of the North China Craton,is hosted in Archean metamorphic rocks of Wulashan Group.Dahuabei and Shadegai granites which intruded respectively into western and northern parts of the deposit are two major intrusions in the area.In addition,there is a swarm of pegmatite and diabase dikes.In this study,three zircon samples from the Dahuabei granite,a pegmatite dike,and an altered rock,respectively,were analyzed by using the advanced Sensitive High Resolution Ion MicroProbe(SHRIMP)technique.The analytical results suggest that the pegmatite dike was formed at (1836±6)× 10\+6 a, the Dahuabei granite at (353±7)±10\+6 a and the altered rock at (132±2)×10\+6 a.As the altered rock was mineralized,the gold mineralization in the area must have taken place at or after (132±2)×10\+6 a(Late Yanshanian).These dating results indicate that gold mineralization in the area is at least 220×10\+6 a younger than the Dahuabei granite and the pegmatite dikes.This rules out the possibility of direct genetic links between gold mineralization and the granite or pegmatite dikes.The age of the Dahuabei granite is consistent with the time of the collision between the North China and paleo\|Mongolia blocks,which provides reliable chronological evidence for the collision.The above results suggest that,although Wulashan area and East Shandong are geographically far spaced,and the host rocks and ages of the gold deposits in the two regions are different,the gold mineralization in the two areas took place almost simultaneously.This further demonstrates that gold mineralization is controlled by plate tectonics,not by petrology.

关 键 词：金矿庆 锆石 定点定年 成岩 成矿时代 

分 类 号：P618.510.5[天文地球—矿床学] P618.510.2[天文地球—地质学]