辽宁青城子铅锌金银矿矿集区围岩原岩恢复及其构造背景

    PROTOLITH RESTORATION AND TECTONIC SETTING OF THE WALL ROCKS IN THE QINGCHENGZI LEAD-ZINC-GOLD-SILVER ORE CONCENTRATION AREA IN LIAONING PROVINCE

    • 摘要: 辽宁青城子矿集区产出在辽东裂谷凹陷带,是中国北方重要的铅锌金银多金属矿集区.矿体与含矿岩系呈整合产出,受一定层位和岩性控制,其中大石桥组是铅锌的矿源层,具有高金丰度和富As的盖县组是金银的矿源层,变质作用或者韧性剪切作用使得金得到富集而成矿.铅锌矿床围岩主要为大石桥亚群杨树沟岩组大理岩、变粒岩和浅粒岩;金银矿床围岩主要为上部盖县组片岩,少量大石桥组变粒岩.围岩的岩石地球化学特征及原岩恢复表明,青城子铅锌矿围岩中的大理岩原岩为灰岩、白云岩,变粒岩、浅粒岩原岩主要为泥质砂岩,个别为火山岩;金银矿围岩中的片岩类原岩为泥岩、砂质泥岩及粉砂岩,变粒岩原岩为泥质砂岩.青城子铅锌金银围岩中的大理岩和片岩构造环境应属稳定大陆边缘,变粒岩、浅粒岩构造环境应属活动大陆边缘或岛弧.结合区域构造演化历史认为,裂谷活动所造成的地壳拉张、变形及其相关的构造-岩浆活动,为铅锌矿床的形成提供有利环境;不同级别的裂谷盆地内的沉积作用以及海底火山喷气作用、沿同生断裂发生热水沉积作用,为矿源层的形成提供成矿物质和成矿流体;吕粱期变质作用对区内铅锌矿的叠加、富集起重要的控制作用.

       

      Abstract: TheQingchengzioreconcentrationarea,whichoccurs along the Liaodong rift depression zone of Liaoning Province, is an important Pb-Zn-Au-Ag polymetallic mineralization concentration area in northern China. The orebodies and orebearing rock series occur in conformity, controlled by certain horizon and lithology, among which the Dashiqiao formation is the source bed of lead and zinc, and the Gaixian formation with high abundance of Au and rich in As serves as the source bed of gold and silver. The metamorphism and ductile shearing contribute to the enrichment and mineralization of gold. The wallrock of Pb-Zn deposit is mainly composed of marble, granulite and leptite of the Yangshugou lithoformation, Dashiqiao subgroup; while that of Au-Ag deposit, mainly schist of upper Gaixian formation, with a little granulite of Dashiqiao formation. The lithogeochemical characteristics of the wall rocks and protolith restoration show that the protolith of the marble is composed of limestone and dolomite, and the protolith of the granulite and leptite is mainly argillaceous sandstone, with minus volcanic rocks. The protolith of schist are mudstone, sandy mudstone and siltstone; while the protolith of leptynite is argillaceous sandstone. The tectonic setting of the marble and schist should belong to stable continental margin, and that of granulite and leptite should be of active continental margin or island arc. Combined with the history of regional tectonic evolution, it is believed that the crustal extension, deformation and relevant tectonomagmatic activities caused by rift action offered a favorable environment for the formation of the Pb-Zn deposits. Sedimentation within different levels of rift basins, submarine volcanic exhalation and hydrothermal sedimentation along the contemporaneous faults offered oreforming substances and fluids for the formation of source bed. The metamorphism occurred in Luliang period played a key role in controlling the superimposition and enrichment of the Pb-Zn deposits in this area.

       

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