Rb-Sr Isotopic Age of Sphalerites from Qingchengzi Stratiform Pb-Zn Ores and Its Implication for the Ore Forming Process

The Qingchengzi orefield, situated in eastern Liaoning Province, northeastern China (123° 37'E, 40° 44'N), is an important region with clusters of Pb, Zn, and precious metal deposits. The orefield contains more than ten PbZn deposits and has a mining history of more than 400 years. Some precious metal (Ag, Au) deposits were recently found in the eastern part of the orefield. The orefield in which the Pb, Zn, Ag, and Au deposits are concentrated is also the location of magmatism of different ages, ranging from Proterozoic, Yindosinian (Triassic) and Yanshanian (Jurassic and Cretaceous). While much work on the origin of these deposits has been carried out, discrepancies as to the ages and the metal sources of the deposits remain (Zhang, 1984; Jiang, 1987; Ding et al., 1992; Liu and Ai, 2001; Xue et al., 2003). Many studies have shown that Rb-Sr dating of sulfide minerals, especially sphalerite and pyrite, can be used to determine the formation age of hydrothermal sulfide mineral deposits (Nakai et al., 1993; Christensen et al., 1995). In this study, we report the results of step-dissolution Rb-Sr dating of sphalerite from the stratiform Pb-Zn ores in Zhenzigou deposits and discuss its implication for the ore forming preocess.