Supercontinents, superplumes and continental growth: the Neoproterozoic record

Between 1300 and 500 Ma the Neoproterozoic supercontinent Rodinia aggregated (1300-950 Ma), broke up (850-600 Ma) and a new supercontinent, Pannotia-Gondwana, formed (680-550 Ma). Only c. 11% of the preserved continental crust was produced during this 800 Ma time interval and most of this crust formed as arcs, chiefly continental margin arcs. At least 50% of juvenile continental crust produced between 750 and 550 Ma is in the Arabian-Nubian Shield and in other terranes that formed along the northern border of Amazonia and West Africa. An additional 20% occurs in Pan-African orogens within Amazonia, and c. 16% in the Adamastor and West African orogens. The growth rate of continental crust between 1350 and 500 Ma was similar or less than the average rate of continental growth during the Phanerozoic of 1 km³/a, and this low rate characterizes both formation and breakup stages of the supercontinents. The low rates of continental growth during the Neoproterozoic may be due to the absence of a superplume event associated with either Rodinia or Pannotia-Gondwana. If supercontinent breakup is required to produce a superplume event, perhaps by initiating catastrophic collapse of lithospheric slabs at the 660 km seismic discontinuity, the absence of a Meso-proterozoic-Neoproterozoic superplume event may mean that a Palaeoproterozoic supercontinent did not fully breakup prior to aggregation of Rodinia.