皖东五河—凤阳地区钱台子金矿床黄铁矿标型特征及S-Pb同位素组成

Typomorphic characteristics and S-Pb isotopic composition of pyrite in the Qiantaizi gold deposit,Wuhe-Fengyang area,eastern Anhui Province

钱台子金矿床是皖东蚌埠隆起区东端的小型矿床,通过微观矿物分析、载金矿物黄铁矿电子探针分析以及硫化物S-Pb同位素组成研究,探讨钱台子金矿床的成矿物质来源,分析其成矿机制。研究表明,钱台子金矿床黄铁矿中Co/Ni含量比的平均值为2.53,为岩浆热液成因黄铁矿,成矿热液具有中高温性质;硫化物δ34 S介于1.3‰~6.8‰之间;Pb同位素μ值为9.22~10.10,对比围岩与区域花岗岩类,说明成矿作用与岩浆活动有关,矿石铅与围岩铅同源。结合前人的研究,认为钱台子金矿床形成于扬子克拉通沿北西方向俯冲于华北克拉通之下造山期后的持续伸展背景下,而拆沉作用与壳幔相互作用导致的大规模岩浆活动促成了该金矿的形成。

The Qiantaizi gold deposit is a small deposit located at the eastern end of the Bengbu uplift in eastern Anhui.In this paper,the source of its ore-forming materials and metallogenic mechanism were discussed through microscopic mineral analysis,electron probe analysis of gold-bearing pyrite and S-Pb isotopic composition of sulfide.The results show that the average Co/Ni content ratio of pyrite in the Qiantaizi gold deposit is 2.53,suggestive of its magmatic hydrothermal origin,and its ore-forming hydrothermal fluids of medium-high temperature.Theδ34 S value of sulphides is between 1.3‰and 6.8‰,and theμvalue of Pb isotopes is between 9.22 and 10.10.The comparison between surrounding rock and regional granitites shows that mineralization is related to magmatic activity and that lead in ore is homologous to lead in surrounding rock.Combined with previous data,it is concluded that the Qiantaizi gold deposit was formed under the background of continuous extension after the Yangtze Craton subducted under the North China craton in the NW direction during the orogenic period,and the large-scale magmatism caused by the interaction between crust and mantle contributed to the formation of the gold deposit.