DETECTION OF HIGH-PRESSURE SILICA POLYMORPHS IN WHOLE-ROCK SAMPLES FROM A METEOR CRATER,ARIZONA, IMPACT SAMPLE USING SOLID-STATE SILICON-29 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY |
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Authors: | Wang-Hong Yang R. James Kirkpatrick Norma Vergo John McHone Tryggvi I. Emilsson Eric Oldfield |
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Abstract: | High-resolution solid-state silicon-29 nuclear magnetic resonance spectroscopy using “magic-angle” sample-spinning can readily detect the presence of the high pressure silica polymorphs coesite and stishovite in whole-rock samples from a Meteor Crater, Arizona, impact sample, and yields accurate coesite/stishovite ratios. Such determinations are being carried out by partially suppressing (saturating) intense quartz signals (which have long spin-lattice relaxation times) by means of short experimental recycle-times. This method enhances the signal-to-noise ratios of coesite and stishovite (which have relatively short spin-lattice relaxation times). For the sample examined, the coesite/stishovite ratio is about 27. |
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