Physicochemical Conditions during the Formation of Dalingkou Ag-Pb-Zn Deposit,Zhejiang Province

On the basis of mineral paragenesis and the chemistry and homogenization temperatures of fluidinclusions,the physicochemical parameters were calculated for the formation of the DalingkouAg-Pb-Zn deposit in Zhejiang.From the early to the late stage of mineralization the ore-formingtemperature veriation was found to be 298.5℃→267.0℃→217.6℃→167.3℃,with a corre-sponding pH change of 3.0～5.8→6.1→6.7→5.0～7.3.The pressure changed from 403.8 to128.5 atm,and logf;-9.9→-11.2→<-15;logf;<-44→-45.6～-42.6→>-44.2;and logf;around-1.55.In conjunction with geological observations,the deposit is considered to be of meso-epithermalorigin,i.e.,it was formed after continental volcanic-subvolcanic activity.The major factors affectingore precipitation are the decreasing temperature and the increasing pH of ore-forming solutions.