Birth of the Kaapvaal tectosphere 3.08 billion years ago.
The crustal remnants of Earth's Archean continents have been shielded from mantle convection by thick roots of ancient mantle lithosphere. The precise time of crust-root coupling (tectosphere birth) is poorly known but is needed to test competing theories of continental plate genesis. Our mapping and geochronology of an impact-generated section through the Mesoarchean crust of the Kaapvaal craton indicates tectosphere birth at 3.08 +/- 0.01 billion years ago, roughly 0.12 billion years after crust assembly. Growth of the southern African mantle root by subduction processes occurred within about 0.2 billion years. The assembly of crust before mantle may be common to the tectosphere.
Moser
D E
DE
Geology and Geophysics Department, University of Utah, 135S 1460E, Salt Lake City, UT 84112-0111, USA. demoser@mines.utah.edu
Flowers
R M
RM
Hart
R J
RJ