Ages of detrital zircons from the Permian strata in Dashizhai area of Inner Mongolia and their tectonic implications

Abstrac: The authors collected a large number of data about U-Pb ages of zircons through compling the relative probability plot of detrital zircons, briefly discussed the evolution history of the Siberia craton, North China craton, Northeast China micro-block and Dashizhai area of Inner Mongolia. The comparative analysis of ages for the Permian strata in Dashizhai area of Inner Mongolia and the neighboring old blocks can help to study the problem of the source of Permian strata in Dashizhai area of Inner Mongolia. Based on the ages of detrital zircons from the South Siberia craton, North China craton, Northeast China micro-block and the Permian strata in Dashizai area in comparison with zircon ages of blocks in neighboring areas, the authors discussed the provenance and made research on zircons U-Pb chronology. The source of the Permian strata in Dashizhai area of Inner Mongolia was reasonably determined. The study of the ages of detrital zircons shows that detrital zircon ages of Permian strata in Dashizai area of Inner Mongolia can be divided into the Paleozoic age group (500-250 Ma), the central and late Proterozoic age group (1.6-0.8 Ga) and the late Archean age group (2.6-1.7 Ga ), whereas on the northern margin of North China craton and on the southern margin of Siberian craton, zircon U-Pb ages are earlier than 1.6Ga. Both of them fail to reflect the reasonable age information of the Permian strata source in Dashizhai area of Inner Mongolia. The age peaks of the Northeast China micro-block in China are consistent with the age peaks of the Permian strata from Dashizai area, which indicates that the provenance of the Permian strata came from the Northeast China block rather than the northern margin of North China craton and the southern margin of Siberian craton. Large quantities of ages of zircons from old basements indicate the existence of ancient micro-continents in Northeast China that may be independent of Siberia craton and North China craton, which is consistent with the view that there existed an ancient micro-continent in the central Asian orogenic belt. Northeast China block might have consisted of many small blocks after collision, and it then collided with the Siberia craton and the North China craton, with the collision taking place respectively along the Hegenshan-Heihe suture zone and Silas Mulun suture zone.