SHRIMP U-Pb dating of intrusive alaskite in the Fanjigshan Group and alaskite basal conglomerates: constraints on the deposition of the Xiajiang Group

Abstract：The deposition of the Xiajiang Group represents a new rift in late Neoproterozoic. The determination of the age of the Xiajiang Group is of great importance for the study of the Neoproterozoic tectonic movement. A suite of Neoproterozoic alaskite intruded into the Fanjiangshan Group and was covered by the Xiajiang Group, which developed large quantities of alaskite basal conglomerate. However, the alaskite zircon U-Pb age of 835±5 Ma will constrain the starting time of the deposition of the Xiajiang Group and the upper limit of the deposition of Fanjiangshan Group. Combined with the bentonite zircon U-Pb age of 814±6 Ma of the Jialu Formation in Xiajiang Group and considering the age of the Wuling Movement, the authors hold that the deposition age of the Xiajiang Group is not older than the age of the alaskite basal conglomerates.