PRECAMBRIAN SUPERCONTINENTS AND THE GROWTH RATE OF THE LITHOSPHERIC MANTLE

Geophysical data on the thickness of the continental sublithospheric mantle are used to calculate the growth rate of the lithosphere since middle Archean. The calculations are based on: (a) the global seismic tomography models (of S. Grand and of N. Shapiro and M. Ritzwoller) and on (b) global thermal model for the continental lithosphere, complemented by a global database on the tectono-thermal ages of the continents (Artemieva, 2006). The results constrained by both tomography and thermal models indicate that a large volume of sublithospheric mantle has been formed already in the Archean. A pronounced discrepancy between the growth rate of lithospheric mantle and the growth rate of juvenile crust at pre-2.5 Ga can be attributed to a high rate of crustal recycling in the Archean. A correlation of the lithosphere growth rate and global anorogenic magmatic events is used to argue that peaks in anorogenic magmatism correspond to the time of formation of Precambrian supercontinents, with the first sizable supercontinents being formed as early as 2.8-2.7 Ga.