Differential Thermal Analysis Investigation of the High-Low Cristobalite Inversion Under Hydrostatic Pressure to 7 Kbar |
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| Authors: | LEWIS H. COHEN WILLIAM KLEMENT JR. |
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| Affiliation: | Department of Earth Sciences, University of California, Riverside, California 92502;School of Engineering and Applied Science, University of California, Los Angeles, California 90024 |
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| Abstract: | The high-low inversion in polycrystalline cristobalite, synthesized from quartz at 1500°C, was investigated by differential thermal analysis to 7 kbar in hydrostatic apparatus. A region of anomalous curvature ( d2T/dp2 >0) exists to ∼1 kbar; at higher pressure, the low→high and high→low transition temperatures vary linearly with pressure, with slopes of ∼51.1 and 53. 6 deg kbar−1, respectively. Extrapolated 1-bar intercepts are ∼232° and ∼209°C, respectively. It is concluded that high cristobalite is less compressible than low cristobalite near the inversion. The hysteresis between the high→low and low→high transition temperatures decreases with increasing pressure. |
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