内蒙古西沙德盖钼矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义  

ZIRCON U-Pb AND MOLYBDENITE Re-Os DATING FOR THE XISHADEGAI MOLYBDENUM DEPOSIT IN INNER MONGOLIA AND ITS GEOLOGICAL SIGNIFICANCE

作　　者：章永梅[1] 顾雪祥[1] 董树义[1,2] 程文斌[1] 黄志全[3] 李福亮[3] 杨伟龙[3] 

机构地区：[1]中国地质大学(北京)地质过程与矿产资源国家重点实验室,北京100083 [2]成都理工大学地球科学学院,四川成都610059 [3]中国人民武装警察部队黄金第二支队,内蒙古呼和浩特010010

出　　处：《矿物岩石》2011年第2期33-41,共9页Mineralogy and Petrology

基　　金：国家自然科学基金(40930423,40873036);国家重点基础研究发展计划“973”项目(2009CB421003-01);长江学者和创新团队计划项目(IRT0755);高等学校学科创新引智计划项目(B07011);中国人民武装警察部队科研项目(07-3KC35-2);中央高校基本科研业务费专项资金资助(2011PY0153)

摘　　要：内蒙古西沙德盖钼矿是华北地台北缘成矿带上的一处中型斑岩钼矿床。采用锆石LA-ICP-MS铀-铅同位素测年技术,针对其含矿钾长花岗岩和矿石进行的成岩成矿年代学测定。获得西沙德盖似斑状钾长花岗岩体的成岩年龄为245 Ma±10 Ma;通过对7件辉钼矿样品进行Re-Os同位素分析,获得同位素模式年龄介于223.2 Ma^232.6 Ma,等时线年龄为225.4 Ma±2.6 Ma(MSWD=0.30);两种方法获得的年龄相近(成矿年龄略小于成岩年龄),成岩与成矿作用均发生于中三叠世末,属印支期碰撞后伸展环境下构造?岩浆活动的产物。结合对已有年龄资料的归纳和分析,认为区内在印支期曾发生过重要的岩浆-(金钼)成矿事件,该事件虽可能遭受了燕山期构造-岩浆活动的改造或破坏,但在一定区域和一定程度上仍有记录或保留。Located in the metallogenic belt on the northern margin of North China Plate,the Xishadegai deposit is a medium-sized porphyry-type Mo deposit recently discovered in Urad Front Banner,Inner Mongolia.The ore deposit is temporally and spatially associated with the potassium feldspar granite.This study provides highly precise dating of molybdenites and host granite.The dating of zircon from Xishadegai granite determined by LA-ICP-MS yielded an age of 245 Ma±10 Ma.Re-Os isotopic dating on seven molybdenites defined model ages from 223.2 Ma to 232.6 Ma and outlined a good isochron age of 225.4 Ma±2.6 Ma（MSWD=0.30）.The consistency of the above dating data indicates an accurate time limit for the formation of the Xishadegai Mo deposit and its host granite.Both of them were formed at the end of Triassic and related to the Indo-China acid magmatic activities under the post-collisional extensional setting.Considering other reported data,it can be inferred that a significant magmatism-mineralization（Au and Mo） event occurred during Indo-China Period.This event,however,was modified or destroyed later,and could still be recorded in some area of the north margin of North China Plate It should be highly valued in the future ore prospecting.

关 键 词：U-PB年龄 RE-OS年龄 西沙德盖钼矿 西沙德盖岩体 内蒙古 

分 类 号：P597.3[天文地球—地球化学]