Low Mantle Perovskite:Solid Solution, Spin State of Iron and Water Solubility  

作　　者：LI Lin LI Qing LI Sheng-Rong 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences Beijing [2]Institute of Science Research, China University of Geosciences Beijing [3]School of Earth Sciences and Resources, China University of Geosciences [4]School of Earth Sciences and Resources, China University of Geosciences Beijing

出　　处：《Acta Geologica Sinica(English Edition)》2014年第6期1884-1894,共11页地质学报（英文版）

基　　金：partly supported by projects from JSPS KAKENHI (Grant No. 18340167);MEXT KAKENHI (Grant No. 20103002);NSFC (Grand No.90914002);China Geological Survey (Grant No. 1212011220926);the Ministry of Education of China (Grant No. 20130022110003)

摘　　要：Silicate perovskites（（Mg, Fe）SiO 3 and CaS iO 3） are believed to be the major constituent minerals in the lower mantle. The phase relation, solid solution, spin state of iron and water solubility related to the lower mantle perovskite are of great effect on the geodynamics of the Earth＇s interior and on ore mineralization. Previous studies indicate that a large amount of iron coupled with aluminum can incorporate into magnesium perovskite, but this is discordant with the disproportionation of（Mg,Fe）SiO 3 perovskite into iron-free MgS i O3 perovskite and hexagonal phase（Mg0.6Fe0.4）SiO 3 in the Earth＇s lower mantle. MnS iO 3 is the first chemical component confirmed to form wide range solid solution with Ca SiO 3 perovskite and complete solid solution with MgS i O3 perovskite at the P-T conditions in the lower mantle, and addition of Mn Si O3 will strongly affects the mutual solubility between Mg Si O3 and CaS iO 3. The spin state of iron is deeply depends on the site occupation of the Fe3＋or Fe2＋, the synthesis and the annealing conditions of the sample. It seems that the spin state of Fe2＋ in the lower mantle perovskite can be settled as high spin, however, the existence of intermediate spin or low spin state of Fe2＋ in perovskite has not been clarified. Moreover, different results have also been reported for the spin state of Fe3＋ in perovskite. The water solubility of the lower mantle perovskite is related with its composition. In pure Mg SiO 3 perovskite, only less than 500 ppm water was reported. Al–Mg Si O3 perovskite or Al–Fe–MgS iO 3 perovskite in the lower mantle accommodates water of 1100 to 1800 ppm. Further experiments are necessary to clarify the detailed conditions for perovskite solid solution, to reliably analyze the valence and spin states of iron in the coexisting iron-bearing phases, and to compare the water solubility of different phases at different layers for deeply understanding the geodynamics of the Earth＇s interior and ore mineralization.Silicate perovskites（（Mg, Fe）SiO 3 and CaS iO 3） are believed to be the major constituent minerals in the lower mantle. The phase relation, solid solution, spin state of iron and water solubility related to the lower mantle perovskite are of great effect on the geodynamics of the Earth＇s interior and on ore mineralization. Previous studies indicate that a large amount of iron coupled with aluminum can incorporate into magnesium perovskite, but this is discordant with the disproportionation of（Mg,Fe）SiO 3 perovskite into iron-free MgS i O3 perovskite and hexagonal phase（Mg0.6Fe0.4）SiO 3 in the Earth＇s lower mantle. MnS iO 3 is the first chemical component confirmed to form wide range solid solution with Ca SiO 3 perovskite and complete solid solution with MgS i O3 perovskite at the P-T conditions in the lower mantle, and addition of Mn Si O3 will strongly affects the mutual solubility between Mg Si O3 and CaS iO 3. The spin state of iron is deeply depends on the site occupation of the Fe3＋or Fe2＋, the synthesis and the annealing conditions of the sample. It seems that the spin state of Fe2＋ in the lower mantle perovskite can be settled as high spin, however, the existence of intermediate spin or low spin state of Fe2＋ in perovskite has not been clarified. Moreover, different results have also been reported for the spin state of Fe3＋ in perovskite. The water solubility of the lower mantle perovskite is related with its composition. In pure Mg SiO 3 perovskite, only less than 500 ppm water was reported. Al–Mg Si O3 perovskite or Al–Fe–MgS iO 3 perovskite in the lower mantle accommodates water of 1100 to 1800 ppm. Further experiments are necessary to clarify the detailed conditions for perovskite solid solution, to reliably analyze the valence and spin states of iron in the coexisting iron-bearing phases, and to compare the water solubility of different phases at different layers for deeply understanding the geodynamics of the Earth＇s interior and ore mineralization.

关 键 词：solid solution spin state of iron water solubility PEROVSKITE low mantle 

分 类 号：P618.47[天文地球—矿床学]