皖东凤阳地区中家山铅锌(金银)矿床硫铅同位素组成及意义

中家山铅锌(金银)矿床位于蚌埠隆起东部。通过矿石微观矿物分析、主要金属矿物电子探针分析及硫化物硫、铅同位素组成分析,探讨中家山铅锌(金银)矿床的成矿物质来源,初步分析了其成矿机制。研究表明,中家山铅锌(金银)矿床黄铁矿接近变质成因类型,Ag以类质同象形式存在,并可能包含银黝铜矿等独立银矿物,闪锌矿具有层控型特征;硫化物δ(³⁴S)值介于4.2×10^-3~6.1×10^-3之间,正向偏离陨石硫,显示多源的特征。矿床的成矿物质可能来源于地幔或围岩;铅同位素μ值为9.23~9.39,说明矿石铅来源于深部地壳或者上地幔,成矿作用与岩浆活动有关,成矿物质具有壳幔混源特征。矿床的形成可能与中高温热液作用有关,岩体岩浆源区为古老的下地壳物质,强烈的壳幔作用会有幔源物质底侵,成矿元素丰度较高的变质基底地层(五河群)部分熔融和幔源物质的加入。

S-Pb isotopic composition of Zhongjiashan Pb-Zn (Au-Ag) deposit in Fengyang area, eastern Anhui province and its significance

The Zhongjiashan lead-zinc(gold-silver)deposit is located at the eastern end of the Bengbu uplift.Based on identification of ore minerals under microscope,electron probe analysis of the main metal minerals and analysis of S,Pb isotopes of sulfides source material of the ore deposit is discussed and the metallogeneic mechanism analyzed.The results shows that pyrite of the deposit is close to the metamorphic pyrite.Ag exists in the form of isomorphism and possibly there is independent silver mineral,such as silver tetrahedrite.Sphalerite has stratabound characteristics.Value ofδ(³⁴S)of the sulphide is 4.2×10^-3~6.1×10^-3 and is positively deviated from meteoric sulphur that is characteristic of multiple sources.The ore-forming material may come from the mantle,or partly from the surrounding rock.Lead isotopeμvalue is 9.23~9.39,indicating that the ore lead comes from the deep crust or upper mantle,the mineralization is related to magmatic activity,and the ore-forming material is characterized by crust-mantle mixed source.Formation of the deposit may be related to the high temperature hydrothermal process.The source area of magmatic rock body is consisted of palaeo lower crust material.Strong crust-mantle process resulted in the mantle material diaper,partial melt of the ore element-rich metamorphic basement strata(Wuhe Group)and incorporation of mantle material.