Au-Ag ORE-MAGMATIC SYSTEM OF VOLCANIC-PLUTONIC ROCK ZONE

The formation of volcanic-plutonic rock zones in inner-are,continental margin and continental tectonic domain shows common characteristics.In Meso-Cenozoic volcanic-plutonic rock zones,are broadly developed Au-Ag mineralizations related to magmatite formations.Calc-alkalic magmatism numerously occurs in the volcanic-plutonic rock zones in island arc,continental margin and inner continent,forming acid,weak acid,and intermediate-basic calc-alkalic volcanic rocks which then are replaced by corresponding magmatites.The Au-Ag mineralization is genetically related to acid to intermediate-basic magmatites with normal to high alkalinity.Generally,subvolcanic rocks and extrusive explorsive-rocks are obviously correlated to endogenetic mineralization.For example,mafic magmatites are commonly associated with Au-Ag-Te mineralization,while sialic magmatites are often paragenetic with Au-Ag-Se mineralization.Geochemically,the mineralizing types are evidently depandent on the alkali in magmatite.For example,if Na₂O/K₂O > 1,correspondingly,the rock's mineralization is Au(with Ag)type;Na₂O/K₂O=1.2~0.8,Ag-Au type;Na₂O/K₂O=0.8~0.4,Au-Ag type;and Na₂O/K₂O < 0.5,Ag(with Au)type.In addition,the magmatite with Na₂O/K₂O > 1.8 is often related to polymetallic mineralization.Flouritization is also related to high-alkali magmatite,such as flourite-telluride-bearing gold deposits associated with alkalic basalt,and flourite-bearing Au-Ag deposit with trachyliparite.