Age of Kongjia-Yinshan volcanic basin in Dexing, Jiangxi Province：evidence from zircon U-Pb chronology

Abstract：The Yinshan lead-zinc polymetallic deposit, a giant volcanics-associated hydrothermal ore deposit, is located in Dexing area, northeast Jiangxi Province. The volcanic and sub-volcanic rocks in the Kongjia-Yinshan basin, which constitute the host rocks of the ore deposit, are usually regarded as part of the Upper Jurassic Ehuling Formation, whose exact age, however, remains in question. The dacite porphyry associated with Yinshan volcanic rocks was dated by LA-ICP-MS U-Pb zircon geochronology. The precise geochronologic data indicate that the Kongjia-Yinshan volcanic basin was formed at (181.3±2.1)Ma. The fossil records and stratigraphic contact relationships suggest that the Ehuling Formation formed in late Jurassic. It is thus concluded that the early Jurassic volcanic and sub-volcanic rocks in the Kongjia-yinshan basin are not the component part of the Ehuling Formation. This result is of significance for the study of the regional geological evolution and the regional metallogenic system in this area.