Abstract

Fifteen sandstone samples taken from pre-Cretaceous strata of the Yangtze Block are analysed to constrain the evolution of the South China Block, especially the assembly between the Yangtze and Cathaysia blocks. The results show that the maximum depositional age of the Neoproterozoic Lengjiaxi Group adjacent to the Cathaysia Block is c. 830 Ma, differing from that of the Kunyang and Dahongshan groups (> 960 Ma) on the southwestern margin of the Yangtze Block. The detrital zircons from Palaeozoic samples from the Yangtze Block have similar age populations to those in the Cathaysia Block, and they may originate from the Cathaysia Block according to palaeogeographic, palaeocurrent and former research data. The detrital zircons of Middle–Upper Jurassic sandstones in the southwestern and central Yangtze Block yield dominant age populations at 2.0–1.7 Ga and subordinate groups of 2.6–2.4 Ga, 0.8–0.7 Ga and 0.6–0.4 Ga. The Upper Triassic strata may be derived from the southern Yangtze and North China blocks due to the collisions between the Indosina, South China and North China blocks, whereas the Jurassic sediments may be partly derived from uplift and erosion of the Jiangnan Orogen due to an intracontinental orogeny induced by Pacific subduction towards the Eurasia Plate. The detrital age spectra and provenance data for basement in the South China Block are analysed and compared with each other. The South China Block has affinity with Australia not only in the Columbia supercontinent but also in the Rodinia supercontinent. We infer the existence of an ancient orogen under the western Jiangnan Orogen, which may have occurred during the Columbia age, earlier than the Sibao orogeny. This is supported by seismic profile proof from the SinoProbe.

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