The nature of Early Palaeozoic Kwangsian orogenic event in the South China Block: constraints from detrital zircons in Cambrian strata

Abstract

ABSTRACT The tectonic nature of Early Palaeozoic Kwangsian orogeny in the South China Block (SCB) is still debated, due to controversy whether there was a Cambrian ocean between the Yangtze Block and the Cathaysia Block. Similarly, continental affinities of the SCB with India and Australia in East Gondwana during the Cambrian are also controversial. Herein, we present detrital zircon U-Pb geochronology of Cambrian sandstone samples from the southern SCB. Cambrian samples (including our new samples and published samples) from the Cathaysia Block and the Yangtze Block show similar detrital zircon age spectra with one prominent age cluster of ~1000-900 Ma and several subordinate age groups, as well as similar cumulative proportion curves (CPC). Such signatures, together with other geological records, suggest that a Cambrian ocean did not exist between the Cathaysia Block and the Yangtze Block, and that Early Palaeozoic Kwangsian orogeny resulted from an intra-continental collision. Cambrian samples from the SCB have much more similar detrital zircon age spectra and CPC to those from Himalaya and Qiangtang than those from Australia, but detrital zircons in Cambrian samples from the SCB, Himalaya, Qiangtang and Australia have a similar prominent age group of ~1000-900 Ma. Thus, the SCB were likely located between Australia and India during the Cambrian, receiving sediments both from India and Australia.