Identification of High-Pressure Phases of Rocks and Minerals from Hugoniot Data

摘要: Summary Crystal structures which have been proposed as possible high-pressure phases of some rocks and minerals are tested by comparing predictions their pressure–density Hugoniots with shock-wave Hugoniot data. The based on tentatively established systematic variations bulk modulus its pressure derivative density, composition crystal field effects. This procedure avoids the ambiguity extra-polating to zero data do not clearly define a phase. New or more strongly supported interpretations structure obtained in seven 12 cases considered. More than one phase transition seems be involved bronzitite fayalite. Perovskite is likely for highest-pressure bronzitite. Electronic spin transitions Fe2+ Fe3+ seem required explain high densities magnetite haematite phases, also fayalite Mooihoek dunite. Eclogite phase, but approach those isochemical mixture oxides. almandite-pyrope garnet lower zero-pressure density previously inferred, may still ilmenite suggested. exceptionally attained forsterite enstatite ceramics reaffirmed. Forsterite achieve about 10 per cent denser oxides mixture, possibly K2NiF4 structure. Previous Twin Sisters dunite, spinel rutile