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Science 11 March 1977:
Vol. 195. no. 4282, pp. 990 - 991
DOI: 10.1126/science.195.4282.990
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Articles

First Occurrence of the Garnet-Ilmenite Transition in Silicates

LIN-GUN LIU 1

1 Research School of Earth Sciences, Australian National University, Canberra, A.C.T., Australia

Pyrope garnet (Mg3Al2Si3O12) has been found to transform to an ilmenite-type phase at a loading pressure between 240 and 250 kilobars and at about 1000° to 1400°C in a diamond-anvil press coupled with laser heating. The lattice parameters for the ilmenite-type phase of (Mg.75 Al.25)(Si.75 Al.25)O3 are a0 = 4.755 ± 0.002 and c0 = 13.360 ± 0.005 angstroms. The zero-pressure volume change associated with the garnet-ilmenite transition is calculated to be –7.1 percent. This result verifies the prediction that pyrope garnet would transform to the ilmenite structure at high pressure first suggested in 1962 by Clark et al. and Ringwood.

Submitted on October 8, 1976


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Crystal Chemistry of Silicon--Oxygen Bonds at High Pressure: Implications for the Earth's Mantle Mineralogy.
R. M. Hazen, R. M. HAZEN, and L. W. FINGER (1978)
Science 201, 1122-1123
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A Fluorite Isotype of SnO2 and a New Modification of TiO2: Implications for the Earth's Lower Mantle.
L. G. Liu and L.-G. LIU (1978)
Science 199, 422-425
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