摘要
20061406 Chen Ming (Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China) Forming Conditions of Ringwoodite in Meteorites: Clues to Finding Terrestrial Ringwoodite (Earth Science Frontiers, ISSN 1005-2321, CN 11-3370/P, 12(1), 2005, p.23-27, 4 illus. , 18 refs. )olivine Ringwoodite, a high-pressure polymorph of olivine, is an important mineral predominating in the transition zone of the Earth mantle. Natural ringwoodite has been found only in the shock-produced veins of chondritic meteorites. No terrestrial ringwoodite has yet ever been found. The pressure and temperature history of shock veins in meteorites and their mineral assemblages indicate that quenching of shock veins under pressure plays a key role in preserving ringwoodite from a reverse transformation to olivine. Time duration of up to ten seconds was estimated to be necessary for the quenching of ringwoodite. No geological process on the Earth could bring ringwoodite from the transition zone of the mantle to the surface of the Earth in such a short time period. To look for terrestrial ringwoodite, one should find those rocks or minerals available for keeping ringwoodite under high pressure, especially when the rocks and minerals are still under high temperature.
20061406 Chen Ming (Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China) Forming Conditions of Ringwoodite in Meteorites: Clues to Finding Terrestrial Ringwoodite (Earth Science Frontiers, ISSN 1005-2321, CN 11-3370/P, 12(1), 2005, p.23-27, 4 illus. , 18 refs. )olivine Ringwoodite, a high-pressure polymorph of olivine, is an important mineral predominating in the transition zone of the Earth mantle. Natural ringwoodite has been found only in the shock-produced veins of chondritic meteorites. No terrestrial ringwoodite has yet ever been found. The pressure and temperature history of shock veins in meteorites and their mineral assemblages indicate that quenching of shock veins under pressure plays a key role in preserving ringwoodite from a reverse transformation to olivine. Time duration of up to ten seconds was estimated to be necessary for the quenching of ringwoodite. No geological process on the Earth could bring ringwoodite from the transition zone of the mantle to the surface of the Earth in such a short time period. To look for terrestrial ringwoodite, one should find those rocks or minerals available for keeping ringwoodite under high pressure, especially when the rocks and minerals are still under high temperature.
