Archean mantle refers to the terrestrial mantle during the Archean eon, which differed both physically and chemically from the modern-day mantle.
The mantle is that part of Earth or other planets between the crust and the core. The upper mantle, from the base of the crust at about 9 km (oceanic) or 30 km (continental) to the transition zone at 660 km, is composed mainly of peridotite, an ultramafic rock mainly composed of olivine, pyroxene, and minor garnet. In the lower mantle, which extends to the core at 2,990 km, the minerals are mainly Mg- and Ca-perovskite ((Mg, Ca)TiO3) and magnesiowüstite ((Mg, Fe)O). The mantle is solid except for localized zones of partial melting, but it convects with velocities of a few tens of centimeters per year.
The Archean mantle differed from the modern mantle in several important ways. Because the main sources of heat – radioactivity, residual heat from accretion, and core crystallization – were more active than today, the mantle...