秘鲁南部Don Javier斑岩铜钼矿床岩石地球化学与岛弧成因

Lithogeochemistry and island arc origins of Don Javier porphyry copper-molybdenum deposit in southern Peru

秘鲁南部古新世—始新世斑岩铜钼成矿带是安第斯成矿带的重要组成部分,产出有大量世界级斑岩铜钼矿床,最近勘探的Don Javier斑岩铜钼矿床是该成矿带中的又一重大发现。本文对Don Javier矿床的含矿斑岩、围岩的岩石学和地球化学进行了研究,以探讨岩石成因和矿床形成的构造环境。主量元素和微量元素地球化学特征表明:(1)含矿斑岩体属过铝质钙碱性系列英安斑岩,围岩为过铝质钙碱性系列的花岗闪长岩,且二者具有相同的物质来源;(2)两类岩石均具有轻稀土富集,富大离子亲石元素特征,在球粒陨石标准化稀土配分曲线图上呈明显的右倾型,左陡而右缓,且二者均显示Eu负异常,表明岩浆岩的成岩过程中有结晶分异作用或其他地质作用参与;(3)含矿斑岩体和围岩形成于岛弧环境,为经典岛弧岩石;(4)Don Javier铜钼矿床可能是在纳斯卡板块向南美板块俯冲,熔融形成的钙碱性岩浆、岩浆弧走滑挤压环境的有利条件下形成。

The belt of Palaeocene-Eocene copper-molybdenum porphyry deposits in southern Peru is an important part of the Andes metallogenic belt with a large number of world-class porphyry copper-molybdenum deposits.The recently explored Don Javier porphyry copper-molybdenum deposit is another major discovery in this belt.In this paper,studies of the petrology and geochemistry of ore-bearing porphyry and surrounding rocks were conducted to validate their petrogenesis and tectonic setting.According to major and trace element characteristics,the authors have reached some conclusions:①The ore-bearing porphyry belongs to peraluminous calc alkaline series dacite porphyry,the surrounding rocks belong to peraluminous calc alkaline series of granodiorite,and both have the same material source.②The two types of rocks are enriched in light rare earth element and large ion lithophile elements;in chondrite normalized rare-earth element pattern,they show obvious right deviation type characterized by left steep and right slow,and both show Eu negative anomaly,which indicates that the petrogenesis of magmatic rocks involved crystallization differentiation or other geological processes.③The ore-bearing porphyry and surrounding rocks were formed in an an island arc environment,belonging to a classic rock island.④The Don Javier copper molybdenum deposit may have been formed in favourable conditions of the subduction of Nazca Plate to the South American plate,the melting of calc alkaline magma and the strike slip extrusion.