Detrital zircon provenance of Upper Ordovician and Silurian strata in the northeastern Yangtze Block: Response to orogenesis in South China

Abstract

Upper Ordovician to Silurian strata along the northeastern margin of the Yangtze Block, South China Craton, were deposited in a syn-orogenic basin related to the Early Paleozoic Kwangsian Orogeny in the adjoining Cathaysia Block. U–Pb age data for 450 detrital zircons from six sandstones samples range in age from Archean to the early Paleozoic. All samples have a dominant age peak between 0.8 and 0.9Ga and subordinate peaks around 2.5Ga and 1.8Ga, with the youngest samples also containing zircons between 0.47 and 0.43Ga. The detrital zircon age spectrum is indicative of derivation from the southeast with Precambrian grains derived from the basement of Cathaysia Block and the Early Neoproterozoic Jiang-Shao suture, and Early Paleozoic zircons derived from igneous activity associated with the Kwangsian Orogeny. The restriction of Paleozoic detritus to the latter phases of the Kwangsian Orogeny (which started by 460Ma) suggests progressive exhumation of the Cathaysia Block, perhaps due to thrusting over the Yangtze Block, with the latter remaining a site of active sedimentation during orogenesis.