Re-Os Geochronology of Molybdenite from Yuanzhuding Porphyry Cu-Mo Deposit in South China

摘要

The Yuanzhuding porphyry Cu-Mo deposit, discovered in 2008, is located within the southern segment of the Chenzhou-Huaiji fault belt, South China. The deposit is hosted within the Upper Cambrian neritic facies sandstone and shale formation that is the strata of the axis and wings of within the Yuanzhuding anticline. Both of the porphyry and exo-contact zone contain Cu-Mo mineralization. Economic orebodies occur mainly in the exo-contact zone around the porphyry. We dated 11 molybdenite samples obtained from two borehole cores of the deposit, using the Re-Os method. Analyses of eight molybdenite samples from borehole ZK12-112 yield a Re-Os isochron age of 157.3 ± 4.3 Ma (2σ), and analyses of 11 samples from boreholes ZK12-112 and ZK16-104 yield a Re-Os isochron age of 155.6 ± 3.4 Ma (2σ). These isochron ages are within the error of the Re-Os model ages, demonstrating that the age results are reliable and that the Yuanzhuding porphyry Cu-Mo deposit formed during the late Middle Jurassic. The formation age of the Yuanzhuding Cu-Mo deposit is similar to the age of intermediate-acid rocks and W-Sn polymetallic deposits along the Chenzhou-Huaiji fault belt. This concordance suggests the same geodynamic process to the igneous activity and related mineralization, raising the potentiality of the porphyry Cu-Mo mineralization in the belt.