| Co-Investigator(Kenkyū-buntansha) |
KARATANI Minako Nihon University, Department of Geosystem Sciences, Assistant, 文理学部, 副手
OKUI Masato Nihon University, Department of Geosystem Sciences, Research Associate, 文理学部, 助手 (50307790)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
A study was carried out on the phase relation in an esseneite-rich region of the pseudo-three-components system diopside(Di)-esseneite(Es)-anorthite(An) under the ambient pressure at several compositions in order to determine the stable field of non-stoichiometric clinopyroxenes. At the composition of Di_<23>Es_<53>An_<24>, crystals of diopside solid-solutions crystallized at 1350 and 1325℃, whereas non-stoichiometric clinopyroxenes appeared at 1300, 1275 and 1250℃. The chemical compositions determined with EPMA are Ca_<0.99>(Al_<0.30>Mg_<0.19>Fe_<0.48>)(Al_<0.22>Si_<1.78>)O_6, Ca_<0.99>(Mg_<0.39>Fe_<0.61>)(Al_<0.43>Si_<1.41>Fe_<0.16>)O_6, Ca_<0.75>(Mg_<0.02>Al_<0.87>Fe_<0.15>)(Al_<0.45>Si_<1.55>)O_6, Ca_<0.74>(Mg_<0.02>Al_<0.80>Fe_<0.17>)(Al_<0.44>Si_<1.56>)O_6 and Ca_<0.73>(Mg_<0.03>Al_<0.79>Fe_<0.19>)(Al_<0.47>Si_<1.53>)O_6 for the products obtained at 1350, 1325, 1300, 1275 and 1250℃, respectively. The phase relations were also explored on the join Di-Es at the compositions Di_<20>
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Es_<80>, Di_<30>Es_<70> and Di_<40>Es_<60>. At 1350℃ stoichiometric crystals of diopside solid-solutions coexist with liquids at all the compositions, while non-stoichiometric clinopyroxenes crystallize at 1325℃ and the lower temperatures. In the case of the composition Di_<30>Es_<70>, chemical analyses gave the formulae Ca_<0.98>(Mg_<0.48>Al_<0.26>Fe_<0.29>)(Al_<0.57>Si_<1.43>)O_6, Ca_<0.75>(Mg_<0.03>Al_<0.81>Fe_<0.16>)(Al_<0.48>Si_<1.52>)O_6, Ca_<0.74>(Mg_<0.02>Al_<0.82>Fe_<0.15>)(Al_<0.48>Si_<1.52>)O_6 and Ca_<0.74>(Mg_<0.04>Al_<0.84>Fe_<0.19>)(Al_<0.44>Si_<1.56>)O_6 for the clinopyroxenes crystallized at 1350, 1325, 1300 and 1250℃, respectively. The differences are quite small between chemical compositions of non-stoichiometric clinopyroxenes obtained at different temperatures from waw materials with different compositions. The non-stoichiometric clinopyroxenes extremely rich in Al and poor in Mg. On the other hand, the stoichiometric clinopyroxenes contain fairly large amounts of Mg and are rich in Fe. With this investigation, the non-stoichiometric clinopyroxenes are shown not to be unique products under high pressure conditions. Less
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