Calculating Mass Balance Per Degree for the Aleutian Crust Using a Novel Method

Abstract

Several global volumetric balances have been carried out for intraoceanic arcs and continental arcs in an attempt to tabulate the global sources and sinks for continental and island-arc crust. However, these balances are flawed in that they cannot recognize geochemical differences in the crust produced by different arcs or different parts of arcs, and that they cannot properly account for sedimentary erosion. In this paper, I calculate a longitudinal degree-by-degree mass balance for the Aleutian arc, emphasizing the shift from basaltic magma production in the east/central Aleutians to andesitic juvenile continental crust production in the west Aleutians. I also calculate for the first time the sedimentary erosion of the Aleutians. I then carry out a more general volumetric balance for the Aleutians historically, which makes clear that there could not have been a steady state for magmatic production throughout the lifetime of the Aleutian arc, or else not enough crust would have been produced. Finally, I calculate that the Aleutians produced approximately 2,500,000 km\(^{3}\) of juvenile continental crust since inception, but lost around 1,000,000 km\(^{3}\) of continental crust through sedimentary erosion, leaving the Aleutians as a small source for continental crust.