New Dating of the Fuling Granite Body with LA-ICP-MS Zircon U-Pb in Jixi,Anhui Province and Their Geological Significance

The Fuling rock body is located in the eastern section of the northern part of the Qinhang metallogenic belt in southern Anhui Province. There are many deposits (spots) that have been explored around it. 2 fresh granite samples in the surface of Fuling rock body have been collected and the zircons analyzed using LA-ICP-MS method in an attempt to determine the relationship between the rock body and mineralization. The weighted average ²⁰⁶Pb/²³⁸U ages for zircons from the coarse-grained K-feldspar granite collected in the transition part of the Xiaochangxi unit is (129.95±0.70) Ma (n=14), MSWD=1.7, which indicates the formation age of the main part of the Xiaochangxi unit. The average ²⁰⁶Pb/²³⁸U ages for zircons from the middle-fine-grained K-feldspar granite collected in the edge of the Fanzhengjian unit is (133.9±1.1) Ma(n=8), MSWD=1.06, which is not in agreement with the formation age of the main part of the Fanzhengjian unit. These results contradict with the geological mapping. Either the rocks cooled gradually from the rim inwards, or the two different ages represent the diagenetic age and the emplacement age respectively. The Fuling rock body is the production of magma activity in the early stage of the late Yanshanian Period (early Cretaceous), which is almost 10 Ma older than previous research results. This dating is more representative of the formation age of the rock body according to the high precision of the Zircon U-Pb technology.