辽宁树基沟铜锌矿床成矿时代-来自斜长角闪片麻岩锆石U-Pb同位素的制约

METALLOGENIC AGE OF SHUJIGOU COPPER-ZINC DEPOSIT IN LIAONING PROVINCE:Constraints from the Zircon U-Pb Isotopes of Plagioclase Amphibolite Gneiss

树基沟铜锌矿是产于华北地台北缘东段花岗-绿岩带中与火山岩有关的块状硫化物矿床.本次运用LA-ICP-MS锆石UPb定年技术获得赋矿围岩斜长角闪片麻岩原岩结晶年龄为2564±2 Ma,可近似代表树基沟铜锌矿成矿时代.根据已发表的幔部锆石U-Pb年龄(2517~2529 Ma),认为树基沟铜锌矿经后期鞍山运动发生变质变形活化迁移.结合赋矿围岩地球化学特征及演化过程,推测树基沟铜锌矿的成因是板块俯冲引起地幔部分熔融形成富含贱金属岩浆,岩浆向上运移、会聚、喷发、固结成岩,后经海水淋滤成矿元素向渗透性差的部位下渗富集,并沿着深渗透性的断裂构造喷出地表,热流体与海水相互作用成矿,而后经变质变形作用的产物.

The Shujigou Cu-Zn deposit of VMS type occurs in the granite-greenstone belt in east section of northern margin of the North China Platform.The crystallization age of 2564±2 Ma for the host plagioclase amphibolite gneiss is obtained with LA-ICP-MS zircon U-Pb dating technique,which can approximately represent the metallogenic age.According to the published mantle zircon U-Pb age(2517-2529 Ma),it is considered that the Shujigou Cu-Zn deposit underwent metamorphism,deformation and remobilization during the later Anshan Orogeny.Combined with the geochemical characteristics and evolution of the host rock,it is inferred that the mineralization is involved with partial melting of mantle to form base metal-rich magma during plate subduction.With upward migration,convergence,eruption,consolidation and diagenesis of the magma,ore-forming elements leached by seawater are infiltrated and enriched in the igneous rocks,which then erupt to the surface along faults with deep permeability.Finally,the hydrothermal fluid is mixed with surrounding seawater,followed by further metamorphism and deformation to form the Cu-Zn deposit.