SHRIMP U-Pb zircon dating of the Ordos Basin basement and its tectonic significance

SHRIMP U-Pb zircon Pb-207/Pb-206 ages were obtained from two drill cores from the basement of the Ordos Basin. A garnet-sillimanite-biotite-plagioclase gneiss (QI1-1) from the western Ordos Basin basement yielded an average age of 2031 +/- 10 Ma. Based on the mineral assemblages, the source material of the gneiss is speculated to be pelitic-felsic system. A gneissic two-mica granite (Long1-1) from the eastern Ordos Basin basement yielded an average age of 2035 +/- 10 Ma. The zircons from both samples exhibit magmatic growth pattern. The shapes of the zircons suggest that the zircons should crystallize from a granitic of felsic volcanic terrain. The ages and the characters of zircons are consisitent with the other researches in the Ordos Basin and indicate that the basement of the Ordos Basin had experienced an intensive magmatic epsode during the late Paleoproterozoic period. The date from this study suggest the possible existences of a Paleoproterozoic mobile tectonic belt in the region. The reconstruction of such a belt is critical for understanding the tectonomagmatic evolution of the western block of the North China Craton.