西藏尕尔穷铜金矿床岩体地球化学特征

Geochemical characteristics of rock mass in the Gaerqiong Cu-Au deposit,Tibet

对班公湖-怒江缝合带西段尕尔穷中型铜金矿岩体进行了野外地质调查、岩相学研究及全岩地球化学分析。石英闪长岩和花岗斑岩均富集Rb、Ba、Th、U等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素;Rb/Sr远大于1;具负铌和弱负铕异常,轻重稀土分馏不明显;花岗斑岩明显亏损Sr和Ti元素。研究认为,石英闪长岩为岛弧环境的钙碱性重熔型中酸性岩体,花岗斑岩为陆-陆碰撞钙碱性重熔型酸性岩体。

A field geological survey,a petrographic study and a whole-rock geochemical analysis are performed on the rock of the Gaerqiong medium-sized Cu-Au deposit in the western segment of the Bangonghu-Nujiang suture zone.The results are as follows.Quartz diorite and granite porphyry are rich in large-ion lithophile elements（LILE）,such as Rb,Ba,Th and U,but devoid of high-field-strength elements（HFSE） like Nb,Ta,Zr and Hf.Furthermore,Rb/Sr is far above one.Negative Nb and weak negative Eu are abnormal and the fractionation of light and heavy REE is not obvious.The granite porphyry is apparently depleted of Sr and Ti.It is concluded that the quartz diorite belongs to the remelting calc-alkaline intermediate-acid rock in an island-arc setting and that the granite porphyry belongs to the remelting calc-alkaline rock derived from intra-continental collision.