Os was separated from the sample digest by modified single-stage distillation of osmium tetraoxide (Os O(g) was trapped in a mixture of 0.05% thiourea in 0.05 M sodium hydroxide.An anion-exchange column was used to separate Re from excess Mo in the solution remaining after distillation.Following systematic Re–Os dating of molybdenite from 13 deposits and comparisons with two previously dated deposits, we have recognized that the molybdenum mineralization in the East Qinling–Dabie belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks.Three pulses of granitoid magmatism and Mo mineralization are recognized corresponding to significant tectonic events in the East Qinling–Dabie belt.In order to determine the precise age of Pb–Zn mineralization and further understand the relationship between magma emplacement and hydrothermal mineralization in the ore district, molybdenite Re–Os dating and zircon SIMS U–Pb dating were undertaken.The zircon U–Pb dating reveals that the granodiorite intrusion was emplaced at 158.8 ± 1.8 Ma (MSWD = 0.40).
An analytical method was developed for Os–Re dating of molybdenite.
Analyses were made over a period of 18 months, using four different calibrations of two different spike solutions.
The age of this standard reproduces at a level of ±0.13%.
Ore minerals are mainly pyrite, sphalerite, galena and minor molybdenite.
Molybdenite, usually intergrown with pyrite, formed during Pb–Zn hydrothermal mineralization.