Nanometer-Size α-PbO 2 -Type TiO 2 in Garnet: A Thermobarometer for Ultrahigh-Pressure Metamorphism
- 14 April 2000
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 288 (5464), 321-324
- https://doi.org/10.1126/science.288.5464.321
Abstract
A high-pressure phase of titanium dioxide (TiO 2 ) with an α-PbO 2 –type structure has been identified in garnet of diamondiferous quartzofeldspathic rocks from the Saxonian Erzgebirge, Germany. Analytical electron microscopy indicates that this α-PbO 2 –type TiO 2 occurred as an epitaxial nanometer-thick slab between twinned rutile bicrystals. Given a V-shaped curve for the equilibrium phase boundary of α-PbO 2 –type TiO 2 to rutile, the stabilization pressure of α-PbO 2 –type TiO 2 should be 4 to 5 gigapascals at 900° to 1000°C. This suggests a burial of continental crustal rocks to depths of at least 130 kilometers. The α-PbO 2 –type TiO 2 may be a useful pressure and temperature indicator in the diamond stability field.Keywords
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