云南墨江金矿热水喷流沉积成岩成矿的地质地球化学证据

Evidence for Geology and Geochemistry of Hydrothermal Exhalative Genesis from Mojiang Gold Deposit,Yunnan

在墨江金矿区发现了两个热水喷流沉积旋回 ,赋矿地层烂山段出露的硅质岩和 (黄铁矿 )硫化物岩具有低TiO2 、Al2 O3 和富含As、Sb、Au、Ag、Hg含量特征 ,稀土元素具有总量低 ,轻稀土总量高于重稀土特征 ,其球粒陨石标准化模式为向右倾曲线 ,大多数样品具有负Eu异常 ;而其北美页岩标准化曲线向左倾。在SiO2 Al2 O3 、Al Fe Mn和Al2 O3 TFeO CaO等地球化学图解上 ,大多数样品位于热水沉积区 ,当样品中含有火山角砾成分时偏离热水沉积区 ,研究表明硅质岩和 (黄铁矿 )硫化物岩主要由热水喷流沉积形成的。再结合矿床地质特征 ,认为墨江金矿存在早期热水喷流沉积成岩成矿作用 ,形成了矿化或低品位矿石 ,并可能与下伏火山喷发有关。

The two hydrothermal exhalative sedimentary cycles have been found in Mojiang gold deposit. The siliceous rock and pyrite-bearing sulfide rock of ore-bearing stratum have characteristics of low TiO 2 and Al 2O 3, and abundant hydrothermal sediment element (Au, Ag, As, Sb, Au, Ag, Hg). Rare-earth elements are characterized by a low content, and most of samples have Eu anomaly. Chondrite normalized REE patterns of samples studied have an inclination to right, and North American Shale normalized REE distribution patterns of samples incline to left. In Al 2O 3 -SiO 2, Al-Fe-Mn and Al 2O 3-TFeO-CaO triangle diagram, most of the samples fall into the hydrothermal field except for those samples with volcano-brecciated composition. The values of Ni/Co of samples are bigger than 1, and the Zn/(Zn+Pb) values of these samples approach to 1. Combining with deposit setting, it suggests that there is later Devonian hydrothermal exhalative mineralization in Mojiang gold deposit, which is early metallization episode. The author thinks that affirmance of hydrothermal exhalative metallogenic in Mojiang gold deposit open a new thinking Way of the genesis way of deposits and exploration.