High-Pressure Melting of (Mg,Fe)SiO ₃ -Perovskite

Abstract

of Ca2+ is at a maximum and a minimum, respectively, and Kd is the dissociation constant of fura 2-AM for Ca2+ (240 nM). The value of b, which determines the degree of asymmetry, was 1.2. TEA was added by perfusion of 5 ml of a modified BSS solution containing 100 mM TEA and low NaCI (50 mM). Other components were not changed (see above for BSS composition). Bombsein was applied by addition of 1 ml of BSS plus 2 gM bombesin to a dish containing 1 ml of BSS (final bombesin concentration = 1 p.M). Solution were applied within 0.5 cm of the cells whose responses were measured.

A simulation study of induced failure and recrystallization of a perfect MgO crystal under non-hydrostatic compression; application to melting in the diamond-anvil cell

“…where T 0 is the value of temperature measured in the center of hot spot and r 0 is an adjustable parameter that can be determined either by assuming certain temperature at the border of the sample [slightly higher than room temperature (A. Zerr, personal communication)] or from reported values of temperature gradients (Boehler et al 1990;Boehler and Zerr 1994;Heinz et al 1994;Shen 1994). The stresses were calculated with the use of temperature distributions shown in Figure 2a.…”

“…It is appreciated that such inhomogeneous heating influences the precision of temperature measurements (Heinz et al 1994;Boehler and Zerr 1994). This, in our opinion, is not the only consequence of inhomogeneous heating.…”

The viscosity structure of the mantle

“…It is generally accepted that the creep strength of a mineral is inversely related to its melting temperature. While there is a difference of opinion concerning the approach to this difficult laboratory experiment [Heinz et al, 1994;Boehler and Zerr, 1994], the measured very high melting temperature of perovskite could prove to be the most important constraint on lower mantle viscosity be cause, many of the estimates from surface observations only constrain the average viscosity over a broad region of the lower mantle. The high melting temperature for perovskite provides a physical explanation for a high viscosity lower mantle.…”

Axial temperature gradients in dielectric samples in the laser‐heated diamond cell

“…This is a concern because accurate temperature measurements are essential to determining melting points and other thermophysical quantities. Recent disagreements in melting temperatures heighten the need to address such potential sources of bias [e.g., Heinz et al, 1994;Boehler and gert, 1994;Jeanloz and Kaynet, 1996].…”