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

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.