Osdating - Nudecamsfree
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).
These molybdenites define a well-constrained Os isochron with an age of 1019 ± 6 Ma, which is interpreted as the age of W(Mo) mineralization.Therefore, the effects of retrograde Namaquan metamorphism extend at least to ∼1020 Ma or, alternatively, these W(Mo) veins were affected by a poorly constrained later event (e.g. An analytical method was developed for Os–Re dating of molybdenite.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.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%.The Tuolugou cobalt–(gold) deposit, in the northeastern margin of the Qinghai–Tibetan plateau and central part of the eastern Kunlun orogenic belt, is the most recently discovered, large, cobalt–(gold) discovery in Qinghai Province, NW China.Exploration to date has identified a cobalt resource of greater than 20,000 t Co, with significant potential for expansion.The East Qinling–Dabie molybdenum belt is part of a larger East–West trending metallogenic belt in eastern China.