论金矿床成矿年代的确定——以丹东地区成岩成矿Rb-Sr、U-Pb同位素年代为例

U-Pb, Rb-Sr Isotopic Dating of the Diagenesis and Mineralization of Gold Deposits in the Dandong Area

丹东地区是中国重要的金矿集中区,到目前为止还没有较准确的成岩成矿年代数据报道。本文采用Rb-Sr等时线法和单颗粒锆石U-Pb法分别测出了丹东三股流花岗岩成岩年龄为131±5Ma和129±3Ma,因此三股流花岗岩综合同位素年龄定为130 Ma。五龙金矿主成矿阶段石英流体包裹体Rb-Sr等时线年龄为120±3Ma。这一组年龄数据理顺了该地区构造—岩浆—成矿的时序关系,对中国东部金矿成矿对比研究提供了有效的年龄数据。Sr、Nd同位素的示踪结果表明三股流花岗岩的成岩物质与下地壳物质有关。三股流花岗岩和矿体(含金石英脉)相似的Sr同位素初始比值,说明成矿和成岩物质可能来自深部同一岩浆源区。

Dandong is one of the important gold deposit concentration areas in China. But, up to the present, accurate age data on the diagenesis and ore-forming have not been reported. In this study, the Sanguliu granite from the Dandong area yields a U-Pb zircon age of 131±4. 5 Ma and a Rb-Sr isochron age of 129±2.9 Ma, and thus the comprehensive isotope age of the Sanguliu granite is defined to be 130 Ma. The Rb-Sr isochron age of the fluid inclusion in Au-bearing quartz veins of the Wulong gold deposit at the main metallogenic stage is 120 it 3Ma. This age group sets up the time-order relationship of structure-magma-mineralization in this region. This work provides valid age data for the comparative study of gold deposits in eastern China. The features of Sr and Nd isotopes display that the diagenetic material of the Sanguliu granite comes from the lower crust. Similar initial ratios of Sr isotopes between the Sanguliu granite and the orebodies suggest that the diagenetic and metallogenic materials may have originated from the deep comagmatic region.