The Regularities Of Mineralization-alteration Facies Zoning And Prospecting Prediction In The Fulaichang Pb-Zn Deposit,Northwest Guizhou Province,China

The Fulaichang Pb-Zn deposit,located in the southwestern margin of Yangtze Plate,which is one of the Pb-Zn deposits representatives of the NW-trending Ziyun-Yadu fault zone.Based on the study of the ore-forming geological characteristics of the deposit,the main line of mineralization-alteration facies zoning is applied.The large-scale structure-alteration facies map and fluid enveloping are applied.Body temperature measurement,mineralization-alteration petrology study and geochemical characteristics of FLD-8 sag,summarizing mineralization-alteration zoning,combining calcite and fluid inclusions in different mineralization stages Petrographics and microscopic thermometry analysis reveals the physicochemical conditions for the formation of different mineralization-alteration facies belts,analyzes the migration characteristics of ore-forming elements and alteration elements,and calculates the mineralization-alteration index of each zone.Finally,the prospecting prediction.The paper mainly achieved the following understanding:1)The ore body mainly exists in the coarse-grained dolomite in the Huanglong Formation(C₂h).The main hydrothermal alterations include dolomitization,pyrolysis,limonite mineralization,and weak silicification.In the ore body and its two sides,strong dolomite,strong pyrite,and strong pyrite mineralization(limonite)coarse-grained dolomite are developed.2)According to the mineral compositions of ores and altered wall rocks,the degree of mineralization and alteration and the distribution characteristics,the zoning regularity of mineralization and alteration has been revealed:from the wall rock to the orebody,there exists the zoning of calcite-dolomitization(I)?strong pyritization-dolomitization zone(II)?lead-zinc mineralization-strong calcification zone(III)?lead-zinc ores zone(IV).The alteration combination of strong dolomitization-strong calcification and strong dolomitization-strong calcification-strong pyritization(limonite)coarse-grained dolomite is an important prospecting indicator.The results of microthermometric data of calcite and quartz inclusions in different mineralization-alteration zones show:from I zone to VI zone,the fluid is characteristiced by moderate-low temperature and low salinity?moderate temperature and low salinity?high-moderate temperature and medium salinity?moderate temperature and moderate-low salinity.3)The analysis of the variation of major elements and Pb-Zn elements in various mineralization-alteration zones shows that:from II zone to III zone,such elements as Zn?Pb?TFe?Mg O,which have a close relationship with ore-forming of Zn-Pb,migrate in as a whole.Meanwile,both iron and Pro iron elements markedly enriched accompanying by the oreformingfluids elements,which indicates that different alteration facies were reformed by the hydrothermal fluids.Mineralization-alteration index(AI),dolomitization index(AI _{Mg O}),pyrite mineralization index(AI _TFe),and lead and zinc mineralization index(AI _Pb,AI _Zn)have the positive correlation with the alteration intensity.Therefore,the mineralization-alteration facies zoning is obviously restricted by the physicochemical conditions of ore-forming fluids.4)The extraction mineralization-alteration index AI>40%indicates pyrite mineralization,sphale zinc mineralization and galena mineralization,and summarized the mineralization-alteration facies zoning rules,and summarized three prospecting indicators,further Nine prospecting targets have been delineated,which provides an important basis for the prediction of concealed mines in the area.