CONTINENTAL GROWTH DURING A 1.9-GA SUPERPLUME EVENT

Abstract

The growth of juvenile continental crust during a possible superplume event at 1.9-Ga occurred chiefly in the form of new arc systems (esp. continental-margin arcs), which were accreted to cratons during supercontinent formation at 1880-1840 Ma. Although oceanic plateaus may have been widespread during the superplume event, they are not a major component of juvenile crust. A possible reason is that they did not attain sufficient thickness to resist subduction during the superplume event. To explain the significant increase in continental growth at 1.9 Ga, recycling rate of continental crust back into the mantle must have decreased relative to the extraction rate of crust from the mantle. A major contributing factor to a decrease in crustal recycling may have been a decrease in sediment subduction rate. Because of a probable high sea level at 1.9 Ga, more sediment was stored on cratons and was not available for subduction.