Research On The Geological And Geochemical Characteristics And Genesis Of Nayongzhi Lead-zinc Deposit In Puding County,Guizhou Province

Nayongzhi lead-zinc deposit within the Wuzhishan ore concentration area is located in the west of Guiyang complex tectonic deformation zone,Yangtze paraplatform,to the southwest of Weining northwestern tectonic deformation zone.Mineral exploration and development works have been carried out since 1960's in Wuzhishan ore concentration area,but scientific research level of lead-zinc deposits is still low,ore deposits genesis exist controversy,and "deep-ore prospecting" problem have not been effective soluted.Nayongzhi lead-zinc deposit is one large-scale and typical Pb-Zn deposit occurred in the early Cambrian system in the northwestern Guizhou.The paper aims to explore the geological and geochemical characteristics and ore deposit genesis of Nayongzhi lead-zinc deposit.Based on collection,summary and analysis of the related data,and field work as well as indoor geochemical analysis,the surrounding rocks and ore were observed and analyzed,constant elements,trace elements and rare earth elements geochemistry,inclusions and isotopic geochemistry,petrology were deeply studied.The source of ore-forming materials,ore-forming fluid,metallogenic age,and deposit genesis were further discussed.The results can be summarized as follows:The lead-zinc orebodies,with layered,stratiform-like,and lenticular shapes are hosted in the Lower Cambrian Qingxudong Formation.I,?,and ? mineralization layers can be divided upwards.The surrounding rocks are mainly grain dolostone and nodular fine crystalline dolostone.The occurrence of ore-bodies and surrounding rocks are basically identical.The ore minerals are mainly sphalerite,pyrite,galena,the gangue minerals are mainly dolomite,and less dolomite,calcite,quartz and so on.Ore structures include banded structure,fine vein structure,brecciated structure,layer structure,block structure,and irregular reticular structure,and so on.The ore structures includes idiomorphic crystal,hypidiomorphic crystal,and xenomorphic granular structures,metasomatic dissolution,metasomatism residual structure,and so on.The spider diagram of trace element of ore samples are similar to those of the dolomite of surrounding rock sample,which shows part of the material of lead and zinc ore might come from dolomite of Qingxudong group.The geochemical characteristics of rare earth elements and their distribution pattern of lead and zinc ores and the surrounding dolomite show obvious similarities,with the same sedimentary environment.The research of inclusions shows that the ore-forming fluid is particular of low temperature,low salinity,and low density.The analysis of characteristics of carbon and oxygen isotopes of the ore and surrounding rock reflect that the metallogenic material source of carbon and oxygen may be the same,and they might come from marine carbonate;the sulfur isotope is characterized by rich heavy sulfur,and sulfur is likely come from marine sulfates.The S in the ore-forming fluid probably comes from Cambrian and Sinian system marine through thermochemical sulfate reduction.For different ore types,ore mineral sources of lead is relatively consistent.The Pb in mining area probably comes from up-crust rocks.Ore structures include banded structure,breccia layer structure,grain structure,which belong to syngenetic sedimentary structure.Ore body with many layers,and thickness size is differ.Wall rock alteration are asymmetric.Based on the analysis of main ore-controlling factors,metallogenic conditions,source of ore-forming materials,ore-forming fluid characteristics,and metallogenic epoch,and comparison of geological characteristics of Nayongzhi lead-zinc deposit with Sedex type Pb-Zn deposits and MVT type Pb-Zn deposits,it can be concluded that Nayongzhi lead-zinc deposit is SEDEX deposit by submarine hydrothermal deposition.