Abstract:

The Cuihongshan deposit is one of important polymetallic deposits in the Lesser Xing’an Range-Zhangguangcai Mountain polymetallic metallogenic belt. The tungsten, molybdenum and zinc resources in this deposit are over large-scale. To determine the metallogenic age of the deposit, Re-Os dating of 7 molybdenite samples from W-Mo ore bodies in the inner contact zone has been completed. The Re content in the molybdenite varies from (0.376 9-0.973 8)×10^-6 and Os content varies from (1.272-3.234)×10^-9. The model age of the molybdenite ranges from (199.0±3.1) Ma to (203.9±3.8) Ma, the weighted mean age is (201.6±1.4) Ma (MSWD is 0.80), and the isochron age is (198.9±3.7) Ma (MSWD is 0.83). Combined the isotopic dating with the regional mineralization characteristics, it’s suggested that the Cuihongshan polymetallic deposit be formed in Early Jurassic period, contemporary with some large-scale porphyry molybdenum deposits as Huojihe and Luming in the Lesser Xing’an Range-Zhangguangcai Mountain metallogenic belt, and they are all resulted from the Early Yanshanian large-scale tectonic-magma-metallogenetic events. According to the molybdenite Re-Os ages and zircon U-Pb ages of some granitic rock bodies in the mine, we can conclude that the monzonite and alkali-feldspar granite were closely related to the W-Mo polymetallic mineralization. The content of Re in molybdenite minerals, together with data on material source of associated intrusion, suggests that the ore-forming materials should be derived mainly from the mixing source of the crust and the upper mantle.

Key words: Re-Os isotopic dating, molybdenite, ore deposit, Lesser Xing’an Range-Zhangguangcai Mountain metallogenic belt, skarn deposit