内蒙古柳坝沟金矿床^(40)Ar-^(39)Ar年代学及铅同位素  

^(40)Ar-^(39)Ar Dating and Lead Isotopes of Liubagou Gold Deposit,Inner Mongolia

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

机构地区：[1]中国地质大学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,成都610059 [3]中国人民武装警察部队黄金第二支队,呼和浩特010010

出　　处：《吉林大学学报（地球科学版）》2011年第5期1407-1422,共16页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40930423,40873036);国家“973”计划项目(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项目(2011PY0153)

摘　　要：内蒙古柳坝沟金矿床是华北地台北缘成矿带上,以广泛发育钾长石化为特色的大型金矿床。金矿体中钾长石的40 Ar-39 Ar同位素和矿石的铅同位素特征表明:40 Ar-39 Ar年龄密度图中260～360Ma峰值区反映了岩浆活动的主要时限,与区内岩体侵位年龄(220～350Ma)相符。40 Ar-39 Ar坪年龄为(217.9±3.1)Ma,结合邻区已有的同位素年代学研究成果,柳坝沟金矿床的成矿时代为印支早期。矿石中异常铅直线与第二阶段铅同位素演化曲线的上交点年龄为224Ma,印证了40 Ar-39 Ar法的定年结果,反映了柳坝沟金矿床的形成与印支早期岩浆热液活动最为密切。结合区域构造演化来看,海西—印支期多次岩浆侵位有利于断裂附近碱交代作用的发生和金的活化富集,印支期最新的岩浆活动(约220Ma)直接导致岩浆热液成矿。矿石铅同位素所计算的源区年龄约2.5Ga,暗示成矿物质主要来自于上太古界乌拉山群变质岩。Located in the northern margin of North China craton,the Liubagou gold deposit of Inner Mongolia is a large ore deposit characterized by widespread K-feldsparthization.The authors apply the 40Ar-39Ar isotopic dating of K-feldspar to define the mineralization age,and give a detailed study on the Pb isotopes of ore.In the density map of 40Ar-39Ar age,the peak region of 260-360 Ma is accordant with the main emplacement ages of the intrusions（220-350 Ma）.Combining with the published isotopic geochronology data of adjacent region,the 40Ar-39Ar plateau age of（217.9±3.1） Ma indicates that the Liubagou gold deposit formed in the Early Indosinian.The upper intersection point age of lead is 224 Ma,it may represent the main magmatic hydrothermal mineralization ages and serve a test for the reliability of the 40Ar-39Ar dating.Consequently,the Hercynian-Indosinian magmatism was favorable to the widely distributed alkali metasomatism and gold pre-enrichment.The latest magmatic activity of Indosinian（about 220 Ma） induced the magmatic hydrothermal mineralization directly.The age of source region is 2.5 Ga by calculation of Pb isotopic data,indicating that the ore-forming materials primarily came from the strata of the Archean Wulashan Group.

关 键 词：40Ar-39Ar年代学 铅同位素 柳坝沟金矿床 内蒙古 

分 类 号：P597[天文地球—地球化学] P618.51[天文地球—地质学]