It is offered import information by the a lot of the zircon U—Pb ages, concerning with the Ergun block. It is make clear that the fragmental and magmatic zircon U-Pb age of the Xinghuadukou rock group, just as, 892±220Ma which are come from the two-mica quartz schist in the Lvlin forestry centre, 1000～1100Ma which are come from the garnet two-mica schist bearing staurolite, 816±27Ma which are come from the plagioclase hornblende schist in the Hanjiayuanzhi, 981.0±6Ma～ 820±3Ma which are come from the biotite plagioclase gneissose(it is equal to Fensuishan gneissic complex) in the Hanjiayuanzhi, the Xinghuadukou rock group with the metamorphous hypogene rocks were formed at early of the Neo-Proterozoic Tonian period. The Xinghuadukou rock group was subjected to migmatization generally .As a result, the metomorphous zircon U-Pb age 431.5±1.6～430±16Ma of the migmatization felsic vein, which are come from the Xinghuadukou rock group had established in the eastern Hanjiayuanzhi, and studding the zircon LA-MC-ICPMS HF isotope come from the early Palaeo zoic granites, a lot of the late mountain-building granites forming at the early Caledonian was produced by the melting of crust due to drop in press which were came from the quick going up of the Ergun block with the denudation, and the migmatization of the Xinghuadukou rock group was due to the relic magma at the early Silurian ,after the late mountain-building granites forming at the early Caledonian. According to the 2800 Ma、2600 Ma、2400Ma、2200 Ma、1888Ma which are coming from the some zircon U—Pb ages, there are an old crystalline basement forming at the Neoarchean to Paleo-proterozoic in the Ergun block. It is compared by the character of the petrographic pattern, khondalite series bearing the graphite, that the “Xinghuadukou rock group” emergence in the Mendulihe of the Mohe area with the Masan rock group and the Damahe rock formation of the Xingdong rock group. Base on above mentioned, an old crystalline basement of the Ergun block is setting in the Mendulihe of the Mohe area, and the Xinghuadukou rock group is the producer by the growing at the Neoarchean to Paleo-proterozoic in the continental margin, and it is change in to stable continental segment by the intrusion and the welding in the early Palaeo zoic granites forming at the late mountain-building.