Journal of the Mineralogical Society of Korea (한국광물학회지)

The Mineralogical Society of Korea (한국광물학회)
권호 표지

A Phase Transformation Study on Amorphous Diopside ($CaMgSi_2O_6$)

비정질 투휘석($CaMgSi_2O_6$)에 대한 상변이 연구

  • 김영호 (경상대학교 기초과학부 (지구환경과학 전공), 경상대학교 기초과학연구소)
  • Published : 2003.06.01
Download PDF
⟨ Previous Next ⟩

Abstract

A phase transformation study on a synthetic amorphous diopside, $(Ca,Mg)SiO_3$has been carried out up to ∼30 GPa, and ∼$1000^{\circ}C$ using a diamond anvil cell and YAG laser heating system, respectively. A starting amorphous material shows a direct transition to cubic $(Ca,Mg)SiO_3$perovskite at high pressure, which contradicts to the crystalline diopside phase transformation sequence disproportionating into mixtures of the orthorhombic$ MgSiO_3$perovskite and the cubic $CaSiO_3$perovskite phases. This discrepancy might be due to the different starting materials as well as the temperature variations at each specific experiment performed. The present phase transfor mation sequence would modify the mineralogical assemblage in the Earth transition region and the lower mantle depending upon the pressure, temperature and the oxygen partial pressure.

한성 비정질 투휘석$(Ca,Mg)SiO_3$에 대한 상변이 연구를 압력은 다이아몬드앤빌기기를 이용하여 ∼30 GPa까지, 온도는 약(YAG) 레이저 가열기기를 이용하여 ∼$1000^{\circ}C$에서 조사(scanning)하여 시행하였다. 비정질 투휘석은 고온-고압 하에서 곧바로 등축정계에 속하는 단상의 $(Ca,Mg)SiO_3$페롭스카이트 결정구조로 상변이 하였다. 이러한 결과는 고온-고압 하에서 사방정계에 속하는 $MgSiO_3$페롭스카이트 상과 등축정계에 속하는 $CaSiO_3$페롭스카이트 상으로 분리되는 상변이를 하는 결정질 투휘석의 상변이 계통과는 큰 차이를 보이고 있다. 이러한 차이는 출발시료의 차이점이나 특히 온도가 상변이에 큰 영향인자로 작용하여 기인한 것으로 판단된다. 이러한 강변이 관계는 맨틀의 온도, 압력 및 산소분압 차이 등에 의해 맨틀전이대나 하부맨틀을 구성하는 광물상의 조합에 영향을 줄 수 있다.

Keywords

References

  1. Anderson, D.L. (1989) Composition of the Earth, Science, 243, 367-370.
  2. Anderson, D.L. and Bass, J.D. (1986) Transition region of the Earth's upper mantle, Nature, 320(6060), 321-328.
  3. Barnett, J.D., Block, S., and Piermarini, G.J. (1973) An optical florescence system for quantitative pressure measurement in diamond anvil cell, Rev. Sci. Instrum., 44, 1-9.
  4. Bass, J.D. and Anderson, D.L. (1984) Composition of the upper mantle, geophysical tests of two petrological models, Gephys. Res. Lett., 11, 237-240.
  5. Finger, L.W. and Ohashi, Y. (1976) The thermal expansion of dioside to 800 $^{\circ}C$ and a refinement of the crystal structure at 700 $^{\circ}C$, Am. Mineral., 61, 303-310.
  6. Irifune, T., Susaki, J.I. Yagi, T., and Sawamoto H. (1989) Phase transformations in diopside CaMgSi2O6 at pressures up to 25 GPa, Geophys. Res. Lett., 16(2), 187-190.
  7. Ito, E. and Matsui, Y. (1978) Synthesis and crystal chemical characterization of $MgSiO_3$ perovskite, Earth & Planet. Sci. Lett., 38, 443-450.
  8. Kim, Y.H. (1994) A study of phase transitions on natural diopside under high pressure, Jour. Geol. Soc. Korea, 30(2), 159-167.
  9. Klein, C. and Hurlbut Jnr, C.S. (1985) Manual of Mineralogy, 19th ed., John Wiley & Sons, NY, p 595.
  10. Knittle, E. and Jeanloz, R. (1987) Synthesis and equation of state of (Mg,Fe)$SiO_3$ perovskite to over 100 GPa, Science, 235, 668-670.
  11. Levin, L. and Prewitt, C.T. (1981) High pressure study of diopside, Am. Mineral., 66, 315-323.
  12. Levin, L., Weidner, D.J., and Prewitt, C.T. (1979) Elasticity of diopside, Phys. Chem. Mineral., 4, 105-113.
  13. Liu, L.G. (1987) New silicate perovskites, Geophys. Res. Lett., 14(11), 1079-1082.
  14. Mao, H.K., Yagi, Y., and Bell, P.M. (1978) Mineralogy of the Earth’s deep mantle: Quenching experiments on mineral compositions at high pressure and temperature, Carnegie Yearb 1977-1978, 502-504.
  15. Mao, H.K., Chen, L.C., Helmley, R.J., Jephcoat, A.P., Wu, Y., and Bassett, W.A. (1989) Stability and equation of state of $CaSiO_3$ perovskite to 134 GPa, J. Geophys. Res., 92(B12), 17889-17894.
  16. Matsui, M. and Busing, W.R. (1983) Calculation of the elastic constants and high-pressure properties of diopside, CaMgSi2O6, Am. Mineral., 69, 1090-1095.
  17. Ming, L.C. and Bassett, W.A. (1974) Laser heating in the diamond anvil press up to 2000 $^{\circ}C$ sustained and 3000 $^{\circ}C$ pulsed at pressures up to 260 kilobars, Rev. Sci. Instrum., 45, 1115-1118.
  18. Ming, L.C. and Manghnani, M.H. (1978) Isothermal compression of bcc transition metals to 100 kbar, J. Appl. Phys., 49(1), 208-212.
  19. Reid, A.F. and Ringwood, A.E. (1975) High-pressure modification of $ScAlO_3$ and some geophysical implications, J. Geophys. Res., 80, 3363-3370.
  20. Ringwood, A.E. and Major, A. (1971) Synthesis of majorite and other high pressure garnets and perovskite, Earth & Planet. Sci. Lett., 12, 411-418.
  21. Tamai, H. and Yagi, T. (1989) High-pressure and high-temperature phase relations in $CaSiO_3$ and CaMgSi2O6 and elasticity of perovslite-type $CaSiO_3$, Phys. Earth & Planet. Inter., 54, 370-377.
  22. Yagi, T. Mao, H.K., and Bell, P.M. (1978) Structure and crystal chemistry of perovskite-type $MgSiO_3$, Phys. Chem. Mineral., 3, 97-110.
  23. Yagi, T. Akaoki, M. Shimomura, O. Tamai, H., and Akimoto, S. (1987) High pressure and high temperature equations of state of majorite, Highpressure research in mineral physics, edited by M.H. Manghnani and Y. Syono, 141-148.