Shock Effects in Carbonate Minerals and Rocks.
Final rept. 1 Jan-30 Jun 78,
CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB
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The ESR spectra of Mn in naturally and laboratory shocked calcite crystals and coral core samples were studied and variations in several spectral parameters were found to be correlative with shock pressure. The amount of splitting in the central transition hyperfine component peaks was observed to decrease in the upper levels of the Cactus Crater core and in core samples shocked in the laboratory to progressively higher pressures. A comparison of the splitting amplitude between the two types of samples allows pressure assignments to the Cactus core of 3.3 GPa at 8m. or - 5m. and 2.0 GPa at 13m. or - 5m. Unshocked coral core samples showed no splitting amplitude variation with depth. Results from coral subjected to a long duration pressure pulse in the Misers Bluff TNT experiment are generally inconsistent. Laboratory shocked single crystal calcite showed similar decreases in hyperfine peak splitting but at pressure levels three times greater than those producing comparable coral sample spectra. The decrease in peak splitting is interpreted to reflect small increases in cation-anion distances produced by mechanical energy input during the shock process. Another parameter, the non-central to central transition peak amplitude, is observed to decrease with increasing pressure in spectra of single crystal calcite, and may provide a means of empirically correlating very low less than 4.5 GPa shock pressure levels in calcite. Author
- Geology, Geochemistry and Mineralogy