摘要:
贵州五指山铅锌矿床为近年新勘探出的特大型铅锌矿床,其成矿时代不明,成因类型及控矿因素争议较大。本文测定的该矿床那雍枝矿段闪锌矿的Rb-Sr等时线年龄,为458.2±2.9Ma (MSWD=1.07,n=5),初始87Sr/86Sr=0.713823±0.000010,表明矿床的成矿时代为中奥陶世晚期至晚奥陶世早期,晚于赋矿地层沉积时代。结合矿床地球化学及矿床地质特征,认为五指山铅锌矿床为典型的后生矿床,成因类型属密西西比河谷型(MVT)铅锌矿床。五指山铅锌矿床的形成与加里东构造运动紧密相关,与黔中隆起构造事件对应。基底断层构造及破碎带是成矿作用的内在控制因素,而加里东期华夏地块与扬子陆块之间的碰撞造山运动,即都匀运动及广西运动是五指山特大型铅锌矿床成矿作用的外因。
Abstract:
The Wuzhishan Pb-Zn deposit explored in recent year is a giant carbonate-hosted strata bound Pb-Zn deposit in western Guizhou. However,it is much debatable about the mineralization age,genetic type and orecontrolling factor of the Pb-Zn deposit. The Rb-Sr dating of sphalerites in the disseminated and network sulfide ores from the Nayongzhi ore block in the Wuzhishan Pb-Zn deposit gives an isochron age of 458.2±2.9 Ma (MSWD=1.07,n=5),with an initial 87Sr/86Sr ratio of 0.713823±0.000010. The mineralization ages may be traced back to the late Middle Ordovician to early Late Ordovician,obviously later than the depositional periods of the host rocks,representing a typical epigenetic deposit. Geologically and geochemically,the Wuzhishan Pb-Zn deposit should be classified into a representative Mississippi Valley-type (MVT) Pb-Zn deposit. Tectonically,the Wuzhishan Pb-Zn deposit is genetically closely associated with the Caledonian orogeny in correspondence with the uplifting of central Guizhou. The basement fault structures and fracture zones are interpreted as the internally controlling facors of mineralization,whereas the collision and mountain building of the Cathysia and Yangtze continental masses during the Caledonian,corresponding to the Duyun and Guangxi movements,are believed to be the externally controlling factors of metallogenesis for the giant Wuzhishan Pb-Zn deposit.
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