High temperature centrifuge simulation - New method to study multiphase flow of partially molten zones

Present-day physical theories suggest that the mantle was partially or comp letely molten about 4.5 billion years ago. As is expected, the phase separa tion could result in the stratification of the initially homogeneous mantle into reservoirs of different chemical composition. Because of the poor kno wledge of the physical phenomena connected with the multiphase system diffe rentiation, many aspects of the evolution of partially molten zones remain disputable. In this study the simulation of liquid and crystal separation i n a high- temperature centrifuge was carried out. Experimental simulation w ith the pyroxene + olivine + plagioclase + magnetite + melt mixture demonst rates rite gravitational instability of the polycrystalline framework of pa rtially molten zones. The melt motion in partially molten rocks is thought to be a multiphase flow involving both the melt and individual crystals. A high mobility of plagioclase crystals in the multiphase flow was ascertaine d. It is revealed as the formation of a monomineral plagioclase cumulate ov erlying the accumulated molten layer. The separation and motion of sulfides in the intercrystalline space is shown to be in an intimate relationship w ith the degree of melting of a silicate material. (C) 2000 Elsevier Science Ltd. All rights reserved.