Open AccessMinerals of the earth's deep interior
Author(s) -
D. Schiferl,
Yue Zhao,
T. J. Shankland
Publication year - 1998
Language(s) - English
Resource type - Reports
DOI - 10.2172/677030
Subject(s) - diamond anvil cell , mantle (geology) , equation of state , diffraction , structure of the earth , discontinuity (linguistics) , mantle convection , geology , core–mantle boundary , convection , lattice constant , mineralogy , geophysics , thermodynamics , physics , optics , subduction , mathematical analysis , paleontology , tectonics , mathematics
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project addresses the major geophysical issue of the nature of the seismic velocity and density discontinuity at 670 km depth (the boundary between upper and lower mantle with temperature about 1,900 K and pressure about 23 GPa). A phase change at this depth would represent a relatively small barrier to mantle convection through the discontinuity, but compositional change would inhibit thermal convection throughout the mantle. To address this problem the authors measured equation of state parameters in mantle minerals as functions of high P-T using single crystal x-ray diffraction with a unique, new diamond-anvil cell (DAC) at simultaneous high temperature and pressure. Single-crystal diffraction improves absolute accuracy in lattice constants over those from powder diffraction by a factor of 5 to 10. The authors have measured equations of state of orthoenstatite MgSiO{sub 3} and hexagonal boron nitride hBN