Accession Number : AD0642925

Title :   SHEAR STRENGTH, POLYMORPHISM, AND MECHANICAL BEHAVIOR OF OLIVINE, ENSTATITE, DIOPSIDE, LABRADORITE, AND PYROPE GARNET: TESTS TO 920C AND 60 KB.

Descriptive Note : Environmental research papers,

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS

Personal Author(s) : Riecker,R. E. ; Rooney,T. P.

Report Date : AUG 1966

Pagination or Media Count : 69

Abstract : Four hundred and seventeen shear and compression tests were completed on five minerals: olivine, enstatite, diopside, labradorite, and pyrope garnet. These minerals are assumed to represent the principal constituents of an upper mantle rock model. Petrographic examination and x-ray analyses indicate that the minerals deform cataclastically at low pressures and temperatures, with intragranular flow beginning at 30 kb normal pressure. Temperature enhances ductility, indicated at high pressures by x-ray line broadening on diffraction patterns and the appearance of kink bands in thin sections. Two phenomena of geophysical importance have been discovered during shear testing: (1) dehydration of less than 5 percent by volume of serpentine weakens dunite by more than 30 percent as the temperature is raised from 300C to 520C; (2) orthorhombic enstatite readily inverts to monoclinic polymorph under the influence of shear stress at all pressures and the temperatures to 920C and 50 kb. The inversion is accompanied by a small, rapid change in volume, sufficient to yield seismic energy for the production of a moderate earthquake. (Author)

Descriptors :   (*ROCK FORMING MINERALS, MECHANICAL PROPERTIES), (*MINERALS, MECHANICAL PROPERTIES), (*SEISMIC WAVES, MINERALS), GARNET, SILICATES, MAGNESIUM COMPOUNDS, IRON COMPOUNDS, CALCIUM COMPOUNDS, FELDSPAR, ALUMINUM COMPOUNDS, SHEAR STRESSES, CRYSTAL STRUCTURE, DEFORMATION, PETROGRAPHY, X RAY DIFFRACTION, DUCTILITY, MICROSTRUCTURE

Subject Categories : Geology, Geochemistry and Mineralogy
      Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE