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):

Report Date:

1966-08-01

Pagination or Media Count:

69.0

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

Subject Categories:

  • Geology, Geochemistry and Mineralogy
  • Seismology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE