Zircon U-Pb geochronology of intermediate-acid intrusions in the Shujiadian ore district of the Tongling ore concentration area

Intermediate-acidic intrusive rocks are well developed in Shujiadian area of Tongling region. The intrusive rocks are mainly composed of Shujiadian rock body, Linjiachong rock body and several minor rock bodies around them. The intrusive rocks in the area can be divided into high-K calc-alkaline series and shoshonite series. In this study, the authors carried out LA-ICP-MS zircon U-Pb chronological research on the two main rock bodies. The results show that there existed multiple phases in the intermediate-acidic rock intrusion events in this area. The intrusion ages of the granodiorite porphyry, the pyroxene monzodiorite, the quartz monzodiorite, the granodiorite, the granite porphyry and the felsic vein are between 147.0 Ma and 146.9 Ma, 144.8 Ma, 141.0 Ma, 138.0 Ma, between 130.5 Ma and 124.0 Ma, and 129.4 Ma, respectively. On such basis, the authors consider that the intruding order of the intermediate-acidic magma in this area should be granodiorite porphyry→pyroxene monzodiorite→quartz monzodiorite→granodiorite→granite porphyry or felsic vein.