Geological Characteristics And Metallogenic Prediction Of Duocaima Pb-Zn Deposit,Qinghai Province

In recent years,large and medium-sized Lead-zinc-silver deposits have been discovered successively in the Tuotuohe area of the Yangtze River in Qinghai Province,which has become one of the potential prospecting areas for Lead-Zinc deposits.Based on Qinghai Geological and Mineral Bureau's"Duocaima Lead-Zinc Deposit Detailed Survey in Naqu'anduo City,Tibet",this paper systematically summarizes the geological characteristics,metallogenic geological conditions and prospecting indicators of Duocaima Lead-Zinc Deposit through indoor and outdoor research;and according to the metallogenic conditions and the development of prospecting indicators,the prospecting prospects in the deep and peripheral parts of Duocaima lead-zinc deposit are evaluated.The Duocaima lead-zinc deposit is a super-large deposit discovered in this area.It is located in the East Qiangtang massif and in the Kaixinling-Zaduo-Jinghong magmatic arc of the Tibet-Sanjiang orogenic system.The main outcropping strata in the mining area are the Permian Jiudaoban Formation,the Paleogene Tuotuohe,Yaxitsuo,and Wudaoliang Formation.The lithology is mainly limestone,quartz sandstone,glutenite and marl.The faults and fold structures developed in the area,of which the F2 fault is the main ore controlling structure in the mining area.The Lead-zinc ore bodies occur mostly in structural alteration fracture zones,from west to east,followed by Kongmolong ore section,Chaqupacha ore section and Duocaima ore section.Among them,6 main orebodies are circled in Kongmolong ore section,most of which are thin plate,dumbbell and spindle;5 ore bodies are circled in Chaqupacha ore section and 3 ore bodies are circled in Duocaima ore section.Ore types are massive,disseminated,and vein like ores.Metallogenesis can be divided into hydrothermal metallogenic stage?I quartz-pyrite stage,II chalcedony-barite-polymetallic sulfide stage,III carbonate-gypsum stage?and epigenetic stage?oxidation leaching stage?.Country rock alteration associated with mineralization includes carbonation,kaolinization and silicification.The deposit was formed in the collision orogenic overthrust environment.The ore-forming fluid mixed with the superficial fluid rich in H₂S,changed the physical and chemical conditions during its migration to the surface,and then precipitated into mineralization.It is a shallow medium-low temperature hydrothermal vein deposit.This paper summarizes the metallogenic geological conditions and geophysical and geochemical anomaly characteristics of the mining area,and summarizes the following prospecting indicators:1)the variegated strips formed by the oxidation reaction of surface polymetals by differentiation,denudation and leaching are the direct prospecting indicators;2)the main faults in the ore-bearing strata and the deriving more secondary fractures are the indicators of structural prospecting,and the carbonation,silicification and muddification in the structural fracture zone are the indicators of wall rock alteration;3)the many concentration centers of Pb-Zn-Ag-Cd-As in stream sediments,closely interlaced sections of elements and geochemical concentration centers of Pb and Zn in soils with large anomalous area and high content are geochemical indicators for finding lead and zinc;and 4)the analysis results of anomalous characteristics of apparent polarizability and apparent resistivity in induced polarization indicated that the Pb and Zn mineralized bodies showed high phase and high intensity characteristics,which was a important geophysical indicator.According to the geological characteristics,metallogenic geological conditions and geophysical and geochemical characteristics of prospecting indicators,it is considered that the prospecting potential in this area is huge and the total amount of resources is expected to exceed 10 million tons.To determine the key prospecting direction of the study area,four prospecting targets should be located in the deep and peripheral part of the mining area,including one grade I target area?distributed in the 11-36 exploration line?,one grade II target area?concentrated in the 40-64 exploration line?and two grade III target areas?located in the 68-128 exploration line in the Eastern part of the mining area and 15-29 in the western part of the mining area,respectively?.It provides basis for subsequent prospecting work arrangement.