Restricting the deposition age of the Kanas Group of Altai tectonic belt and its implications

The Kanas Group consists of thick epimetamorphic terrigenous clasolite, which occurs widely in the north of the Altai-Qinghe ductile shear belt, northwest of the Chinese Altai tectonic belt. The deposition age of the Kanas Group is controversial so that the tectonic implications of it have been existing different opinions. U-Pb dating of detrital zircons from the Kanas Group yields the youngest detrital zircons age of 550 +/- 18Ma, as the maximum deposition age of the Kanas Group, together with the magma crystallization age of 523 +/- 19Ma for the metamorphosed granite that invaded into the Kanas Group, as the minimum deposition age of the stratum. Therefore, the deposition age of the Kanas Group can be constrained to be Late Sinian to Early Cambrian (523 similar to 550Ma). The sedimentary characteristics of the Kanas Group show that it deposited in a passive continental margin, which indicates the existence of Precambrian continental crust basement in Altai tectonic belt.