Research On Geochronological Framework Of The Quanji Group And Precambrian Tectonic Affinity Of The Quanji Massif, North Qaidam

Precambrian sedimentary cover the Quanji Group lies angularly unconformably over the Delingha Complex and the Dakendaban Group, which constitute the metamorphic basement of the Quanji Massif, North Qaidam.Many researchers thought that the age of the Quanji Group was the Nanhua Period to Sinian Period, and the lower limit age was about 760 Ma, and the Quanji Group was the result of the breakup of the Columbia supercontinent. The Quanji Massif is a fragment detached from the Tarim Craton, and its tectonic thermal events and property are identical or similar to the North China Craton from the Era Neoarchean to Paleoproterozoic, responding to assembly events of the Columbia supercontinent. They probably ever interacted with each other, and have tectonic affinity. But the Quanji Massif and the Tarim Craton share a same geological evolution history with the Yangtze Craton after Neoproterozoic.Choosing the Quanji Group exposed in three places to research, we confirm two parallel unconformity surfaces within the Quanji Group. Ascertaining the age of the Quanji Group by means of the LA-MC-ICPMS zircon U-Pb dating, fossils and regional sedimentary feature correlation, we redefine the Quanji Group. The redefined Guanji Group contains the Mahuanggou Formation, the Kubaimu Formation, the Shiyingliang Formation and the Hongzaoshan Formation. And they belong to the Changcheng System. The lower limit age of the Quanji Group is restricted at about 1.78 Ga. The Quanji Massif is one component of the southwestern North China Craton, and the Quanji Group is the Aulacogen sedimentary sequence after the breakup of the Columbia supercontinent.