29Si MAS NMR relaxation study of shocked Coconino Sandstone from Meteor Crater, Arizona |
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| Authors: | S. A. Myers R. T. Cygan R. A. Assink M. B. Boslough |
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| Affiliation: | (1) Sandia National Laboratories, Albuquerque, NM 87185, USA, US;(2) Geochemistry Department, Sandia National Laboratories, Albuquerque, NM 87185-0750; Phone: 505-844-7216 (office); Fax: 505-844-7216; E-mail: rtcygan@sandia.gov, |
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| Abstract: | 29Si nuclear magnetic resonance (NMR) spectroscopy was used to characterize the silica phases in a moderately-shocked Coconino sandstone from Meteor Crater, Arizona. The spectra were recorded using direct polarization, magic-angle spinning, and variable delay times in a saturation recovery pulse sequence. Resonances observed at -97.3, -107.1, -113.9 and -191.2 ppm were assigned to a densified hydrous form of amorphous silica (D phase), quartz, coesite and stishovite phases, respectively. The relative percentages were estimated as 1.7, 80.6, 16.4 and 1.3% for the D, quartz, coesite, and stishovite phases. The power-law recoveries of the magnetization for the quartz and coesite phases can be interpreted in terms of their phase geometries. Received: January 3 1997 / Revised, accepted: August 4 1997 |
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