Precise zircon U-Pb and molybdenite Re-Os dating of the Shuikoushan granodiorite-related Pb-Zn mineralization, southern Hunan, South China

摘要

The Shuikoushan ore district, located in southern Hunan Province, South China, contains Pb-Zn-Au mineralization hosted in the Devonian to Triassic strata and Mesozoic granodiorite intrusions. Ore minerals are mainly pyrite, sphalerite, galena and minor molybdenite. Molybdenite, usually intergrown with pyrite, formed during Pb-Zn hydrothermal mineralization. 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). Re-Os isotopic age of seven molybdenite samples yields model ages ranging from 157.5 +/- 2.5 Ma to 161.0 +/- 2.4 Ma, and gives a well-defined Re-187-Os-187 isochron age of 157.8 +/- 1.4 Ma (2 sigma, MSWD = 1.3), indicating the timing of Pb-Zn mineralization in the Shuikoushan ore district at about 158 Ma. This date coincides well with the zircon SIMS U-Pb age of the granodiorite, revealing a genetic association between the Pb-Zn mineralization and the granitic magmatism. Combined with geochronological data published for other Pb-Zn-(Cu) deposits in southern Hunan, it can be concluded that the granodiorite-related Pb-Zn mineralization throughout southern Hunan mainly occurred at 160-156 Ma, rather than 180-170 Ma or 170-160 Ma as considered previously. The Pb-Zn mineralization and major W-Sn mineralization in southern Hunan are coeval and may be related to the same geological event. (C) 2015 Elsevier B.V. All rights reserved.