SHRIMP U-Pb and Sm-Nd dating of the gabbro and syenite from the Hongge ore district in western Panzhihua and its geological significance

Adopting the SHRIMP U-Pb and Sm-Nd method, this paper reported the dating results of the bedded ore-bearing gab-bros and alkaline syenites from the Hongge ore district in western Panzhihua area.The results show that the zircons from gabbro in Hongge have ages of 258.4±4.1Ma, 1841±34Ma and 2487±12Ma, the Sm-Nd isochron age of the gabbro, pyroxene and apatite sam-ples is 253±14Ma, while the zircon U-Pb age of alkaline syenite is 257.2±1.5Ma.These data show that the zircon U-Pb age (258Ma) of the typical mafic rock is similar to the Sm-Nd isochron age of the same samples, and also similar to the zircon U-Pb age of syenite.Considering the close relationship between layered gabbro and alkaline syenite rock in space and in time, it is suggested that both of them resulted from Permian Magmatism, but 1841Ma and 2487Ma zircon might have been magmatic zircon and inherit-ed zircons, which originated from the basement.These data imply the existence of Paleo-Petrozoic or even Archean materials in the lower part of Kangdian axis magmatic rock belt or the crystalline basement.