Ultrasound Resonance Measurements and Expansivity Measure- ments at 2000 K: Velocities of Sound at Mantle Temperatures

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The objective of this work is to advance the capability of measurement techniques towards the ultimate objective which is to: Measure the temperature dependence of the elastic constants (and velocities) of high pressure phases of mantle minerals in the temperature range of the lower mantle. The objectives of this work are to 1) advance the temperature capability of elastic constant measurements from 1800 K to 2000 K, 2) to decrease the size of the sample measured to sub-millimeter size, 3) to measure iron-bearing minerals at these high temperatures, and 4) to measure the thermal expansivity between 1500 K and 2000 K on a variety of mantle minerals. The methods employed will be to 1) use old and new techniques of resonance ultrasound on small single crystals of various shapes, and 2) to construct a laser interferometer capable of high temperature dilametric measurement. The significance of this work, is that it will allow a higher certainty of isolating the mineralogy of the earth's lower mantle, and that it will greatly augment the thermodynamic database which will be useful for geochemistry and mineralogy.