The Eclogite–Garnetite transformation in the MORB + H₂O system

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• 作者：Kazuaki Okamoto ; Shigenori Maruyama
• 关键词：Eclogite– ; garnetite transformation ; UHP experiments ; Jadeite ; Ca-perovskite ; Na₂(Ca ; Mg ; Fe²⁺)Si₅O₁₂-component in garnet
• 刊名：Physics of the Earth and Planetary Interiors
• 出版年：2004
• 出版时间：16 August 2004
• 年：2004
• 卷：146
• 期：1-2
• 页码：283-296
• 全文大小：358 K

文摘

To decipher phase relations of oceanic crust in the coldest slab at the mantle transition zone, multi-anvil experiments were conducted in the MORB+H₂O system at pressures of 10–19 GPa, and temperatures of 700–1500 °C. Garnet and stishovite were recognized in all run charges. Above 15 GPa, garnet drastically increases NaSi (Na₂MSi₅O₁₂) component (M = Ca, Mg, Fe²⁺), jadeite occurs instead of omphacite. Na-, K-hollandite containing 7 mol % NaAlSi₃O₈ and Ca-perovskite with 60 mol % CaTiO₃, were observed at P>17 GPa. With decomposition of omphacite and increase of modal ratio of garnet, there is a sharp increase of density at 440 km. The density increase due to appearance of Ca-perovskite at 570 km, is estimated approximately 100 km shallower than that of previous estimation.