念青唐古拉弧背断隆东段古近纪大规模火山作用及找矿意义

摘要

The east sag-uplift of the Nyanqentanglha arc-back is demarcated by the Naqu-Dangxiong fault on the west, the Shiquanhe-Namucuo-Jiali suture zone on the north and the east, and the Shamole-Maila-Milashan-Luobadui fault on the south. The geochemical data of the Pana group volcanic rocks indicate that they are high K calc-alkali-shoshonitic volcanic rock series. This group of volcanic rocks is formed in the transition zone of soft collision to hard collision. They are the mixed products of the basic differential magma derived from the mantle and the acid magma derived from the remelting continental crust. The abyssal sediments on the subducting slab participated in this process. Therefore, it is quite favorable to find metal sulfide deposits related to the acidic volcanic rocks because the rhyolites occur in the area.%探讨念青唐古拉弧背断隆东段古近纪火山岩的地质地球化学特征、成因机制、动力学背景以及找矿意义.通过对火山岩进行岩石学特征研究及全岩地球化学分析,结果表明该套火山岩相对富集不相容元素K、Rb、Th、Ce,而Sr、Ba、Ta、Nb、Ti呈现低谷,LREE富集且分馏明显,而HREE相对亏损且分馏不明显,稀土配分模式图呈以Eu为界左陡右缓的“右倾”武.这套火山岩形成于火山弧向同碰撞过渡的大地构造环境,由俯冲消减过程中幔源物质和壳源物质的同熔作用及增厚地壳的硅铝质部分熔融形成；此外,俯冲板片上部的深海沉积物也参与了岩浆的形成.研究区中酸性火山岩的地质地球化学特征及构造环境对于寻找与长英质火山岩有关的金属硫化物矿床十分有利,有较好的找矿前景.