Pyrite Rb-Sr geochronology, LA-ICP-MS trace element and telluride mineralogy constraints on the genesis of the Shuangqishan gold deposit, Fujian, China

Abstract

The Shuangqishan gold deposit is the largest gold deposit in the Dehua ore cluster of Fujian Province. The gold orebodies are located in the metamorphic rock of Neoproterozoic Daling Formation. Representative genetic models of Shuangqishan gold deposit include epithermal gold deposit, orogenic gold deposit and granitoid-related gold deposit. Based on the comprehensive research of pyrite Rb-Sr geochronology, telluride mineralogy and pyrite LA-ICP-MS trace element, we intend to discuss the genesis of the Shuangqishan gold deposit. The Rb-Sr isotopic dating of gold-bearing pyrite indicates thatmineralization age of the Shuangqishan gold deposit is 153.5 ± 2.4 Ma, which is the same as that of the granite porphyry dyke (zircon U-Pb age = 153.4 ± 1.2 Ma) in the mining area. The main gold-bearing mineral is native gold, with a fineness of >920, additional gold-bearing mineral is electrum, with a fineness of 677 ~ 741. The gold-bearing polymetallic sulphide quartz veins contain a large amount of tellurbimuth (Bi2Te3), rucklidgeite (PbBi2Te4) and tetradymite (Bi2Te2S). The Shuangqishan gold deposit’s characteristic combination of Au-Bi-Te elements is analogous to that of typical magmatic-hydrothermal deposit. The estimated log f Te2 versus log f S2 conditions of telluride mineralization at 250 °C are –13.0 ~ –9.5, –14.7 ~ –10.5, respectively. LA-ICP-MS trace element analysis of gold-bearing pyrite shows that the pyrite is As-poor and has high content of Te, Bi, Pb, Co and Ni, but has low content of Au and As. The typical As-poor pyrite indicates that the Shuangqishan gold deposit is the magmatic hydrothermal gold deposit. Te displays a high positive correlation with Bi and Pb, indicating that Te, Bi and Pb occur as Bi-telluride micro-inclusion in pyrite. Our research shows that the Shuangqishan gold deposit is the magmatic hydrothermal gold deposit formed in the late Jurassic.