Geochronology of Neoproterozoic syn-rift magmatism in the Yangtze Craton, South China and correlations with other continents: evidence for a mantle superplume that broke up Rodinia

Neoproterozoic granitic intrusions in South China have traditionally been interpreted as related to orogenesis, marking the cratonisation of the Yangtze Block. However, a number of ca. 830-820 Ma granitoids and mafic-ultramafic intrusions unconformably overlain by Neoproterozoic rift successions have recently been reinterpreted as being related to a mantle plume during the breakup of the supercontinent Rodinia. In this paper, we report SHRIMP zircon U-Pb ages from granitoids and gabbros that are closely related to the Neoproterozoic rifting event, and one age from a volcanic unit in the rift successions. We demonstrate that there were two major phases of widespread bimodal magmatism in South China during the Neoproterozoic. The first one, at ca. 830-795 Ma, started before the continental rift but continued into the first two stages of the rifting. The second one, ca. 780-745 Ma, occurred during the later stages of the rifting. Some co-magmatic malic dykes have rare-earth element and trace element distribution characteristic of continental flood basalts. Similar age patterns of Neoproterozoic anorogenic magmatism are recorded in most other Rodinian continental blocks, such as Australia, India, Madagascar, Seychelles, southern Africa and Laurentia. The widespread occurrence and protracted duration (ca. 85 million years) of such anorogenic magmatism. require a large and sustained heat source. We interpret these magmatism as results of a mantle superplume beneath Rodinia, which was responsible for the breakup of the supercontinent during the Neoproterozoic. (C) 2002 Elsevier Science B.V. All rights reserved.