| Project/Area Number |
11440162
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Petrology/Mineralogy/Science of ore deposit
|
|---|
| Research Institution | Gakushuin University |
|---|
Principal Investigator |
AKAOGI Masaki Gakushuin University, Department of Chemistry, Professor, 理学部, 教授 (30126560)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
KOJITANI Hiroshi Gakushuin University, Department of Chemistry, Research Associate, 理学部, 助手 (60291522)
SUZUKI Toshihiro Gakushuin University, Department of Chemistry, Research Associate, 理学部, 助手 (40235974)
|
|---|
| Project Period (FY) |
1999 – 2001
|
| Project Status |
Completed (Fiscal Year 2001)
|
| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
|
|---|
| Keywords | high-pressure transition / calorimetry / lower mantle / slab / perovskite / ilmenite / garnet / プロブスカイト / 玄武岩 / 熱測定 / カルシウムフェライト / メジャーライト |
|---|
| Research Abstract |
High-pressure phase relations of minerals consisting of MORE and pyrolite in slabs subducting into the lower mantle were investigated up to pressure-temperature conditions of the uppermost lower mantle. Calorimetric measurements were also performed, and phase relations were determined using the obtained thermodynamic data. Main results are as follows.
(1) High-pressure phase relations in the systems MgAl_2O_4-NaAlSiO_4 and MgAl_2O_4-CaAl_2O_4 were clarified up to 30 Gpa, and a new phase with hexagonal symmetry was found. Structural analysis of the hexagonal phase showed that this phase has a new structure related to calcium-ferrite structure. This phase may be an important host of alkali elements and aluminum in the lower mantle. Phase transitions in NaAlSiO_4 were also examined by high-pressure experiments and calorimetry, and the phase boundary for transition to NaAlSiO_4 calcium ferrite was determined.
(2) Phase relations in the system Mg_4Si_4O_<12>-Mg_3Al_2Si_3O_<12> were examined at 1000 ℃ up to 27 Gpa. It was clarified that garnet solid solution transforms to ilmenite solid solution which further transforms to perovskite solid solution. Enthalpies of the garnet-ilmenite-perovskite transitions were measured, and the phase boundaries were calculated. Based on the results, it was established that the garnct-ilmcnitc-pcrovskitc transitions occur in pyrolite in subducting slabs at the uppermost lower mantle.
(3) Enthalpies of perovskite solid solutions in the systems CaSiO_3-CaTiO_3 and CaSiO_3-CaGeO_3 were measured, and the enthalpy was estimated for CaSiO_3 perovskite which cannot be recovered at ambient conditions. Phase relations of CaSiO_3 perovskite, one of major constituent minerals of the lower mantle, were thermodynamically calculated.
|
