Magmatic mingling origin of adamellite: zircon U-Pb dating and Hf isotopes evidence of microgranular dioritic enclaves and host rocks from Yangtianhu adamellite of Qitianling, South China

Abstract：A large number of directional microgranular dioritic enclaves occur in Yangtianhu adamellite of Qitianling composite body. Microgranular dioritic enclaves，which commonly show cloudleted and sub-rounded shapes, display igneous textures and are from meter to centimeter in size. These enclaves are darker in color and finer in granularity than their hosting adamellite. Based on an analysis of the inner structural CL images of zircons, this paper discusses U-Pb ages and Hf isotopes of zircons from the host adamellite and mafic microgranular enclaves by using in situ zircon analysis of LA-ICP-MS and MC-ICP-MS. The ages of （157.2±3.7）Ma from host adamellite and （168.6±3.5） Ma from enclaves were obtained, respectively. The Yangtianhu adamellite intrusion was formed by the mingling between the partial melting products from the crustal materials and the magma derived from the mantle.