摘要
河北省石湖金矿位于阜平幔枝构造核部中南段,其围岩主要是太古宇阜平群,是冀西目前已发现的唯一大型金矿。为研究石湖金矿的成矿时代,重点对含金石英脉中锆石进行了阴极发光分析和LA-ICP-MS U-Pb同位素测年。结果表明:锆石形态为自形-半自形,环带特征明显,Th/U比值大多大于0.1,为典型的岩浆锆石。锆石U-Pb年龄主要分为两组,其中一组^(207)Pb/^(206)Pb年龄主要位于(2 569±41)-(2 014±38)Ma之间,年龄数据在谐和图上基本位于一致曲线下方,显示放射成因铅明显有不同程度的丢失,其年龄数据与一致曲线的上交点年龄为(2 492±82)Ma,表示岩浆锆石的结晶年龄,可代表阜平群TTG片麻岩的结晶年龄;另一组^(206)Pb/^(238)U年龄为(136±4)Ma,结合含矿地质体之间的空间位置关系,综合表明石湖金矿主要成矿事件发生在(136±4)Ma之后。石英脉中没有热液锆石,锆石来自围岩。
The Shihu gold deposit, currently the only large gold deposit in the western Hebei, is located in the middle-southern section of Fuping mantle branch and its surrounding rocks are mainly Archean Fuping Group rocks. In order to deeply study the metallogenic age of this gold deposit, this paper focuses the zir- cons from gold-bearing quartz veins with analysis of cathodoluminescence image features and U-Pb ages by LA-ICP-MS. The results show that the zircons mainly display characteristics of magmatic zircon, with idi- omorphic- hypidiomorphic texture and oscillatory zones, main Th/U ratio above 0.1. Two main groups of zircon U-Pb ages were obtained, the 207Pb/206Pb ages of （2 569±41）-（2 014±38） Ma and the 206Pb/238U ages of （136±4） Ma respectively. The first ages are mainly below the discordia, indicating the varying de- gree of losses of radiogenic lead. And an upper intercepted age of （2 492±82）Ma shows the crystallization age of magmatic zircon probably from the Fuping Group TTG gneiss. Combining the second age with the spatial position relation of ore bearing geological bodies, it shows that the main metallogenic events of Shi- hu gold deposit occured after （136±4）Ma. In addition, the hydrothermal zircons have not been found in gold-bearing quartz veins in the current and zircons are from the surrounding rock.
出处
《地质科技情报》
CSCD
北大核心
2017年第3期103-109,共7页
Geological Science and Technology Information
基金
国家自然科学基金项目(40872137)
河北省自然基金项目(D2015403013)
河北省教育厅项目(ZC2016060)
河北地质大学博士基金项目(BQ201320)
关键词
石湖金矿
锆石
U-PB年龄
含金石英脉
幔枝构造
麻棚岩体
阜平群
Shihu gold deposit
zircon
U-Pb age
gold-bearing quartz vein
mantle branch structure
Mapeng granitic intrusion
Fuping Group
