System Enstatite–Diopside–Jadeite

摘要: Pyroxenes rank high among the most important rock-forming minerals and, because of their optimal chemical and structural complexity, are useful for geothermobarometry. Natural pyroxenes stable at relatively low pressures Earth’s crust shallow upper mantle can contain a large number components [387]. With increasing pressure, solubility some decreases, which leads to simplification pyroxene chemistry. At above 10 GPa, content tetrahedral Al becomes negligible, eliminates Tschermak components, (Ca,Mg,Fe)Al2SiO6. In stability field stishovite higher than 9 Eskola (Ca,Mg,Fe)0.5AlSi2O6, also become negligible [242], partial molar volume SiO2 in structures is larger unit-cell [10]. The Fe expected be low, bulk Fe/(Fe + Mg) ratio an average only about 0.1, partitioned least into pyroxenes. NaPx component could present GPa [15], but may require unusual compositions with excess Na over Al. That leaves three major necessary consider composition deep mantle: enstatite, diopside, jadeite. further increase these transform majoritic garnet, dominant phase transition zone. Hence, relations ternary system enstatite-diopside-jadeite particularly estimating mineralogy, chemistry, structure mantle.