In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle

Details In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle

Jan 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001e%26psl.184..567h&link_type=abstract

Earth and Planetary Science Letters, Volume 184, Issue 3-4, p. 567-573.

Physics

44

Scientific paper

Here we report the phase boundary of pyrope garnet (Mg3Al2Si3O12) to Al-bearing silicate perovskite plus corundum, with the highest transition pressure determined by in situ measurements in a multi-anvil apparatus at high temperature. The consistency of the pressure scales by different standards of Au, NaCl, Pt, W, and Mo at high temperature was also evaluated by in situ X-ray measurements. Our results, together with recent in situ measurements of the post-spinel transition in Mg2SiO4 [Irifune et al., Science 279 (1998) 1698-1700] and the ilmenite-perovskite transition in MgSiO3 [Ono et al., Geophys. Res. Lett. (2000) submitted], show that pressures determined in conventional quench experiments [Ito and Takahashi, J. Geophys. Res. 94 (1989) 10637-10646] could have been overestimated by more than 2 GPa at pressures corresponding to the bottom of the transition zone. On the basis of the in situ measurements, the post-spinel transition occurs at a depth (~600 km) that is too shallow to match with the 660-km seismic discontinuity in the Earth's mantle. Therefore, an olivine dominant mantle compositional model may be inconsistent with the seismic observations. Alternatively, we propose a pyroxene-garnet dominant transition zone with an appropriate Al2O3 content (ca. 6-8 mol%), in which majorite garnet transforms to perovskite at the depth of the 660-km discontinuity. Any alternative models would have to consider chemical stratification in the mantle.

Affiliated with

Also associated with

No associations

Rating

In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In situ measurements of the phase transition boundary in Mg3Al2Si3O12: implications for the nature of the seismic discontinuities in the Earth's mantle will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-923364