云南大平掌铜多金属矿区花岗闪长斑岩地球化学特征及年代学研究

滇西普洱大平掌铜多金属矿床为典型的与中酸性火山岩有关的VHMS型矿床。侵入于含矿火山岩系中的花岗闪长斑岩岩体规模较大,在野外调研的基础上,对该岩体的产出特征、岩石学、岩石化学和年代学开展了较系统的分析研究。研究表明,花岗闪长斑岩体与火山岩呈典型的侵入接触关系;岩石化学特征显示属钙碱性岩系过钙性岩,微量元素及稀土元素配分模式显示火山弧花岗岩特征;岩体中锆石的LA-ICP-MS U-Pb年龄为401.0±1.7 Ma,相当于志留纪末—泥盆纪初,说明矿区花岗闪长斑岩体并非印支期产物。本文的研究结果同时证实,矿区含矿火山岩及其中的火山喷流沉积矿床的形成时代应属中晚志留世,而非晚泥盆世—早石炭世。

Geochemistry and chronology of granodiorite porphyry in the Dapingzhang Cu polymetallic deposit

The Dapingzhang Cu-polymetallic deposit is a typical VHMS(volcanics-hosted massive sulfides) deposit related to intermediate-acid rocks.The granodiorite porphyry that intruded into the ore-bearing volcanic series is large in size,but its research has been very insufficient.Based on field investigation,the authors studied systematically the formation characteristics,petrology,petrochemistry and chronology of the intrusive body.The results show that the granodiorite porphyry and the volcanic rocks have typical intrusive contact relationship.The granodiorite porphyry,belonging to calc-alkaline high calcium volcanic series,shows volcanic arc granite characteristics as evidenced by distribution patterns of trace elements and rare earth elements.LA-ICP-MS zircon U-Pb age of the granodiorite porphyry is 401.0±1.7 Ma,suggesting early stage of Early Devonian period.This means that the granodiorite porphyry was not formed in the Indosinian period.It is also shown that the age of the volcanics and the VHMS deposit should be early Devonian,rather than late Devonian-early Carboniferous.