Single-zircon La-ICP-MS Ages of the Longyuanba Pluton in the Eastern Nanling Region and Geological Implication

The Longyuanba pluton in the eastern Nanling Range is an important part of the Nanling granites. However, so far no reliable isotopic dating result is available for this pluton. Based on the interior structures of zircons from the Longyuanba pluton analyzed by the CL technology, in-situ zircon U-Pb dating was performed with La-ICP-MS and reliable age data were obtained. The results show that the Longyuanba pluton was formed in multi-stage magmatism spanning the Indosinian and Yanshanian periods. The main body of the pluton was formed in the Indosinian, especially in the early Indosinian. Single-grain zircon dating for the early Indosinian granites yields ages of 241.0±5.9 Ma and 241.0±1.3 Ma (two samples), for the late Indosinian granite yields 210.9±3.8 Ma, and for the Yanshanian syenite yields 149.4±4.9 Ma. The ages and geneses of the Longyuanba pluton are different from those of the Pitou—Tabei complex pluton located to its east, but are very similar to those of the Zhuguangshan pluton located to its north. When considering the prospect of uranium mineralization in the region, we should consider it with the integration of Zhuguangshan pluton and Longyuanba pluton, and should enhance the exploration on the Longyuanba pluton.