浙江东南沿海地区中生代火山作用与铅-锌-银的成矿关系

浙江东南沿海发育的中生代酸-中酸性火山岩,属钙碱性和富钾弱碱性岩系,为同源同熔岩浆结晶分异产物;与火山岩系有关的Pb-Zn-Ag矿床产于流纹质火山-侵入杂岩体中,受火山基底断裂和火山构造的双重控制;矿床中硫主要来源于岩浆,Pb、Zn、Ag主要来源于火山基底岩石,部分来源于岩浆,火山热液形成于次火山期后,成矿早期热液具岩浆水与大气降水混合性质,晚期以大气降水为主.

THE MESOZOIC VOLCANISM AND THE Pb-Zn-Ag METALLOGENY ON THE COAST OF SOUTHEASTERN ZHEJIANG PROVINCE

The Early Cretaceous and some late Jurassic, terrestrial acidic, intermediate-acidic volcanic rocks are developed on a large scale in the coastal zone of southeastern Zhejiang province. They belong to cale-alkaline rock series, and in the later stage of magmatic evolution, they change graduaHy to k-rich subaklaine rocks, The characteristics of the trace elements, REE and initial ratios of strontium isotopes indicate that they are the rdsults of crystallization differentiation of the comagmas of the syntectic origin.Over 120 Pb-Zn-Ag deposits, genetically realted to the volcanic and subvolcanic rock series, have been found in this area. Most deposits occur in the rhyolitic volcano-intrusive complexes. The ore deposits and the entire metallogenic zone are controlled obviously by the fault zone which cuts the coastal volcanic basement in coujunction with the volcanic structures. The mineraIization temperature ranges form 200-300℃Based upon the Pb, Zn, Ag, abundances in the volcanics, subvolcanic cks and their basement, and S, O, C, Pb isotopic analyses, we considered that, the sulfur mainly orginated from the magma and partly from the basement rocks, and the Pb, Zn, Ag, were mainly from the bsaement rock and partly from the magmas. The ore-forming hydrothermal solutions were produced after the subvolcanic stage.