滇西北羊拉铜矿床江边岩体岩石学、地球化学特征及锆石U-Pb年龄

羊拉铜矿是三江地区金沙江—哀牢山铜金成矿带的大型铜矿床,位于中咱微陆块与昌都—思茅地块相夹持的金沙江板块结合带,矿床与印支期侵入岩(花岗闪长岩体)有密切的时空成因联系。通过对江边花岗闪长斑岩体、花岗闪长岩体的地球化学研究,发现岩体富SiO₂、Al和大离子亲石元素,贫Fe、Mg、高场强元素,属准铝质-弱过铝质I型花岗岩;各岩石样品点均落入火山弧花岗岩和同碰撞花岗岩过渡区域,反映江边岩体属活动板块边缘产物,岩浆除幔源外,还混入了下地壳熔融物质。江边岩体锆石原位U-Pb定年分析得出2个花岗闪长斑岩(ZKJ1-1-14、ZKJ2-1-7)年龄为215 Ma、208 Ma,3个花岗闪长岩(ZKJ1-1-17、ZKJ2-1-6、ZKJ2-1-8)年龄为221 Ma、220 Ma和214 Ma,结合对路农、里农和贝吾花岗闪长岩体结晶年龄分析,得出羊拉矿区成矿岩体自南向北年龄逐渐变新的侵位序列;矿区内岩浆活动持续25 Ma,印证江边岩体同属俯冲-碰撞作用所致的造山期岛弧型花岗岩类,为碰撞后拉张背景的典型产物。

Characteristics of Petrology,Geochemistry and U-Pb Dating of Zircon from the Jiangbian Pluton in the Yangla Copper Deposit,Western Yunnan

Yangla copper deposit is a large deposit of Jinshajiang-Ailaoshan copper-gold metallogenic belt in Three-river area,which located in the bonding zone of Jinshajiang plate between Zhongza micro-continent fragment and Changdu-Simao block.The results show that the major elements of the Jiangbian granodiorite-rock mass is a typical I-type granite,with high SiO2,Al and lithophile elements,and deficit of Fe,Mg and high field strength elements.Besides,the samples mainly fall into the transitional regions of volcanic-arc granite and syn-collision granite,which reflects the Jiangbian granodiorite pluton is the products of active plate margin,and the main magmatic fluid compositions are mantle and accompanied with input of melting of the crust.Zircon U-Pb dating by LA-ICP-MS method indicated that the ages of ZKJ1-1-14 and ZKJ2-1-7 granodiorite porphyry were 215 Ma and 208 Ma,and ZKJ1-1-17,ZKJ2-1-6 and ZKJ2-1-8 granodiorite were 221 Ma,220 Ma and 214 Ma,respectively.Based on the crystallizing age of Lunong pluton,Linong pluton,Jiangbian pluton and Beiwu pluton,this paper hold that the magmatic intrusions tended to freshen from southern mining area to northern mining area.And the magmatism in the Jiangbian area was active for a long period(about 25 Ma).This research corroborated that the Jiangbian rock mass is a island-arc type granite associated subduction-collision and formed in post-collisional extensional environment.