青海东昆仑造山型金矿硫、铅同位素地球化学

Sulfur and Lead Isotope Geochemistry of the Orogenic Gold Deposits in East Kunlun Area,Qinghai Province

对青海东昆仑地区典型金矿床基本地质特征及岩 (矿 )石S、Pb同位素地球化学进行了研究 ,认为矿床具有相似的地质 地球化学特征 ,并与这里的造山过程有密切的成因联系 ,为典型的造山型金矿床 ;硫化物S同位素组成变化较大且出现两个峰值 ,塔式分布效应明显 ;Pb同位素组成分布集中、比值较高且矿床围岩与矿石的Pb同位素组成十分接近 ,反映硫、铅等成矿物质主要来自围岩地层 ;晚古生代—早中生代强烈的俯冲与碰撞作用产生了深断裂、大型剪切带及次一级的褶皱和断裂 裂隙控矿构造 ,并诱发了流体成矿作用 。

Based on the basic geological characteristics and sulfur and lead isotopic geochemistry of four typical gold deposits, it is considered that these deposits have many similar geological-geochemical characteristics and are all related to the orogenic process in genesis. Therefore, they should belong to the type of orogenic gold deposits according to the newest classification of gold deposits by Kerrich et al.(2000). There exists remarkable variation (from -3.7‰ to 4.4‰) in the average δ 34S values of the sulfides selected from different deposits, and the tower-shaped distribution is apparent. The lead isotopes in four gold deposits are characterized by high ratios and minor changes,with 206Pb/ 204Pb, 207Pb/ 204Pb and 208Pb/ 204Pb respectively higher than 18.3380,15.5555 and 38.1796 in ores and wall rocks. It can thus be concluded that the ore-forming materials consisting of sulfur and lead are mainly derived from wall rocks. Besides forming deep faults,large-scale shear belts and low-order folds and faults, the intensive subduction and collision during late Paleozoic and early Mesozoic induced fluidization and mineralization and resulted in the formation and zonal distribution of several large-or medium-size gold deposits in this area.