RELATIONSHIP BETWEEN Al-BEARING PHASES NAL AND CFIN THE LOWER MANTLE
K.D. Litasov and E. Ohtani*
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS,3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
* Institute of Mineralogy, Petrology and Economic Geology, Tohoku University, Sendai, Japan
Keywords: Lower mantle, oceanic crust, Al-bearing phases
Pages: 1259-1273
Abstract
Alumina-bearing phases with orthorhombic (phase CF) and hexagonal (phase NAL) structures have been identified in average MORB composition at pressures above 25 GPa. These phases are very similar in structure and composition and can coexist in a single experimental sample. In this paper, we report data on the chemical composition, structure, and stability fields of the CF and NAL phases and study their relationship in the lower mantle. It is shown that these phases are stable at a pressure of 20 GPa and temperatures below 1300
|
