玉龙斑岩铜矿带莽总含矿斑岩体岩石学特征及锆石U-Pb年龄研究

Petrochemistry and Zircon LA-ICP-MS U-Pb Age of the Mangzong Porphyry Associated with Cu-Mo Mineralization in the Yulong Ore Belt

莽总斑岩铜钼矿床位于玉龙斑岩铜矿带中部,含矿岩体侵入下二叠统和上三叠统火山岩和硅质沉积岩中。含矿岩体出露面积约0.27km2,普遍发生蚀变,可分为早晚两个阶段。本文分析了含矿岩体化学组成及用锆石LA-ICP-MS U-Pb年龄分析斑岩体形成时代。早阶段岩体主要为花岗闪长斑岩,晚阶段岩体为石英二长斑岩及碱长花岗斑岩,晚阶段岩体相对富SiO2及K2O。莽总含矿斑岩体锆石LA-ICP-MS U-Pb年龄为(37.6±0.2)Ma,MSWD=1.41。据莽总含矿岩体形成时代及结合藏东地区在始新世至渐新世时的构造环境,提出莽总含矿岩体形成于扭压构造背景,和印度板块与欧亚板块产生的左行走滑断裂活动有关。

The Mangzong porphyry Cu-Mo deposit is located at the middle of the Yulong porphyry copper ore belt in the eastern Tibet with outcrop area of 0.27km2. The Mangzong porphyry which associated with Cu mineralization intruded the Lower Permain siltstone interlaid with limestone and underwent strong alteration. The porphyry consists mainly of early stage diorite granite porphyry and late stage quartz monzogranite porphyry and K-feldspar porphyry. The early stage porphyry and late stage porphyry are different in major compositions. The late stage porphyry is relatively rich in K20 and SiO2. The Mangzong porphyry yields zircon LA-ICP-MS U-Pb age of （37.6± 0.2） Ma （MSWD = 1.41）, which suggests that the Mangzong porphyry was emplaeed during Late Eocene. Based on the structural condition of Eocene to Oligoeene in eastern Tibet and the zircon LA-ICP-MS U-Pb age of the Mangzong porphyry, it is proposed that the Mangzong porphyry associated with Cu-Mo（Au） mineralization owe its origin to the local subduetion of sinistral fault movement caused by the collision of India with Asia.