西藏嘎拉勒夕卡岩型金(铜)矿床地球化学特征与锆石的LA-ICP-MS定年及意义  

Geochemical characteristics and zircon LA-ICP-MS U-Pb dating of Galale skarn gold(copper) deposit,Tibet and its significance

作　　者：吕立娜[1,2] 崔玉斌[3] 宋亮[3] 赵元艺[1,2] 曲晓明[1,2] 王江朋[3] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]国土资源部成矿作用与矿产资源评价重点实验室,北京100037 [3]中国地质大学(北京),北京100083

出　　处：《地学前缘》2011年第5期224-242,共19页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目"青藏高原南部增生造山成矿系统发育机制"(2011CB403103);国家科技支撑课题"西藏班公湖岛弧带铜;金;富铁矿评价与综合找矿技术方法示范研究"(2006BAB01A05);中国地质调查局青藏专项"西藏班公湖-怒江成矿带找矿远景区评价"(1212010818097)

摘　　要：嘎拉勒金(铜)矿床位于西藏班公湖—怒江缝合带的西段,为夕卡岩型金(大型)铜(小型)矿床。矿区主要岩石为巨斑状石英闪长岩、中细粒花岗闪长岩与闪长玢岩。该矿床岩石样品的REE分异程度较高,Eu呈弱负异常,w(Al2O3)为14.45%～15.84%,铝过饱和指数A/CNK为1.33～1.46,均大于1,表明为S型花岗岩。经微量元素的相关分析,该矿岩体为板内花岗岩,形成期接近于同碰撞期。锆石的LA-ICP-MS定年结果表明巨斑状石英闪长岩的年龄为(131±17)Ma,中细粒花岗闪长岩为(86.52±0.41)Ma,两个闪长玢岩的年龄分别为(88.59±0.45)和(88.09±0.41)Ma,其中巨斑状石英闪长岩为非成矿岩体,其测年数据代表了成岩时代下限;矿体只产在中细粒花岗闪长岩和闪长玢岩岩体与灰岩和粉砂岩夹硅质岩的接触带,为燕山期成矿。由测年结果可将该矿床的岩浆演化过程大致分为两个阶段,早白垩世非成矿岩体巨斑状石英闪长岩岩体的侵入和晚白垩世成矿岩体的形成,发生在白垩纪班公湖—怒江中特提斯洋构造演化的第4个阶段弧-陆碰撞造山阶段。The Galale gold（copper） deposit is located in the west section of Bangong lake-Nujiang suture zone in Tibet.It is a gold（of large scale） and copper（of small scale） skarn deposit.There are mainly huge porphyritic quartz diorite,middle-fine grain granodiorite and diorite porphyrite in the mine area.The REE differential degree of rock sample in this ore deposit has a relatively higher value,and Eu negative anomaly is weak.The content of Al2O3 is 14.45%-15.84%.The aluminum supersaturation index（A/CNK） ranges between 1.33 and 1.46,which is greater than 1,indicating its being S-type granite.According to the analysis of trace elements,the magmatic body belongs to MPG.The forming stage is close to the collision stage.The result of zircon LA-ICP-MS dating indicates that the age of huge porphyritic quartz diorite is 131±17 Ma,that of the middle-fine grain granodiorite is 86.52±0.41 Ma,and those of the two diorite porphyrites are 88.59±0.45 Ma and 88.09±0.41 Ma.Among them,the huge porphyritic quartz diorite is a non-mineralization magmatic body,and the dating data represents the lower limit of the mineralization age.The copper-gold orebody was only produced in the contact zone of the middle-fine grain granodiorite and the diorite porphyrite magmatic body with the limestone and the siltstone with silicalite.So it was mineralized in the stage of Yanshan.According to the result of dating,the evolutionary process of this ore deposit can be approximately divided into two stages： the invasion of non-mineralization magmatic body-huge porphyritic quartz diorite in the early cretaceous and the formation of mineralization magmatic body in the late Cretaceous.They occurred in the Cretaceous,the fourth stage of Prototethys tectonic evolution,i.e.,the orogenesis stage of arc-continent collision.

关 键 词：班公湖—怒江缝合带 嘎拉勒 LA-ICP-MS 夕卡岩型金(铜)矿床 燕山期成矿 

分 类 号：P594[天文地球—地球化学]