The stability of annite + quartz: reversed experimental data for the reaction 2 annite + 3 quartz = 2 sanidine + 3 fayalite + 2H2O

Article Abstract:

The reaction 2 annite + 3 quartz = 2 sanidine + 3 fayalite + 2H2O is stable at higher temperatures. The reaction is stable in the temperature range 500-540 degrees celsius (C) at 2 kbar. An increase in the pressure increases the equilibrium temperature. The forward reaction takes place in the stability field of fayalite + sanidine. Reverse reactions form biotite rather than annite. The experimental thermodynamic standard state enthalpy and entropy of annite are similar to those of the redox reaction annite = sanidine + magnetite + H2.

Observations, Chemical equilibrium, Minerals (Geology), Rocks, Rock-forming minerals

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Mixing properties and stability of jadeite-acmite pyroxene in the presence of albite and quartz

Article Abstract:

A study was conducted on the stability and mixing characteristics of synthetic jadeite-acmite pyroxene in the presence of quartz and albite. Results of experiments conducted at 600-900 degrees celsius generally support conclusions by other researchers that jadeite and acmite mixing is ideal. Acmite addition to jadeite was found to enhance the stability of pyroxene by under 300 MPa at a temperature of 900 degrees celsius.

Jadeite (Petrology), Jadeite

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Diffusion-controlled growth of albite and pyroxene reaction rims

Article Abstract:

The effects of water content differences on the kinetics of diffusion-controlled growth of albite (Ab) and enstatite + diopside + spinel rims (Px) are studied using the reaction rim technique. Results show that based on the parabolic rates constants for Ab and Px reaction rims at 1000 degrees Centigrade and 700 MPa, water content has a small impact on grain boundary diffusion rates.

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