试论早子沟金矿成矿作用过程中地幔流体的参与

PARTICIPATION OF MANTLE FLUID WITH GOLD METALLOGENETIC PROCESS IN ZAOZIGOU GOLD DEPOSIT

早子沟金矿地处夏河—合作—岷县区域性深大断裂带南侧,在时空上受断裂和壳幔混合岩浆双重控制。通过对矿床主要控矿因素、矿石稀土地球化学、流体包裹体及S、H、O、Pb同位素的系统研究,在探讨成矿流体来源的基础上,对地幔流体参与金矿成矿作用的可能性进行了探讨。研究表明:矿石稀土元素配分模式表现出轻稀土富集的特征;矿床流体包裹体气相成分主要为H_(2)O和CO_(2),含少量CH_(4)、N_(2)等,液相成分阳离子以Na^(+)、K^(+)为主,含少量Ca^(2+)、Mg^(2+),阴离子以SO_(4)^(2-)、Cl^(-)为主;黄铁矿、辉锑矿矿物的δ^(34)S_(v-CDT)介于-10.30‰~-4.9‰之间,平均-8.33‰,反映成矿作用过程有地层硫的加入;氢、氧同位素显示成矿流体既有岩浆水和地幔初生水的参与,亦有大气降水的加入;矿石铅同位素组成显示铅来源于壳幔的混合。以上说明成矿流体具多源性,暗示地幔流体参与了矿床成矿作用。

Located in the south of Xiahe-Hezuo-Minxian Fault,Zaozigou gold deposit is controlled by fault and crust-mantle mixed magma on spatiotemporal evolution.It is summarized such the deposit characteristic as main ore-controling factors,rare earth geochemistry of ore samples,fluid inclusion,and isotopic data of S,H,O,Pb,meanwhile discussed the participation possibility of earth mantle fluid in the gold mineralization by the study of metallogenetic fluid source.REE partitioning model of ore samples illustrate light REE concentration.The composition of fluid inclusion show that gas phase material are mainly H_(2)O and CO_(2) with a little amount of CH_(4) and N^(2),fluid phase matter are Na^(+),K^(+),Ca^(2+),Mg^(2+),SO_(4)^(2-),Cl^(-).The value of S^(34)S_(v-CDT)is-10.30‰~-4.9‰in pyrite and stibnite sample,which support mineralization was related with participation of crust sulphur material.The study of hydrogen and oxygen isotope revealed that mineralization fluid include both magmatic water and original water from the mantle and meteoric water.Lead isotope composition of ore sample reflect they were mixture of crust and mantle material.