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The High-Low Quartz Transition up to 10 Kilobars Pressure

A. F. Koster Van Groos and J. P. Ter Heege
The Journal of Geology
Vol. 81, No. 6 (Nov., 1973), pp. 717-724
Stable URL: http://www.jstor.org/stable/30058998
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The High-Low Quartz Transition up to 10 Kilobars Pressure
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Abstract

The high-low quartz transition of a vein quartz and a composite quartz sample were compared at up to 10,000 bars pressure, using a comparative DTA technique. The differences are smaller than 0.2°C, suggesting that such a composite sample may be preferred for use as a DTA thermal standard. The transition temperature ranges from 572.6°C at 1 bar to 825.3°C at 10,000 bars. The best fit of the data is given by two expressions: $T_{p} = 572.5 + 1.55 X 10^{-2}P + 5.465 X 10^{-6}P_{2}$ for the pressure range 1-1,000 bars, and $T_{p} = 567.3 + 2.645 X 10^{-2}P - 6.525 X 10^{-8}P_{2}$ for pressures between 1,000 and 10,000 bars. The change in the rate and sign of the curvature may be explained by a gradual inhibition of the high rate of thermal expansion of low quartz just below the high-low quartz transition when the pressure increases from 1 to about 1,000 bars.

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