Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
American Mineralogist Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
American Mineralogist; July 2007; v. 92; no. 7; p. 1112-1118; DOI: 10.2138/am.2007.2255
© 2007 Mineralogical Society of America
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Web of Science (4)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kojitani, H.
Right arrow Articles by Akaogi, M.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

High-pressure phase relations and crystal chemistry of calcium ferrite-type solid solutions in the system MgAl2O4-Mg2SiO4

Hiroshi Kojitani*, Ryosuke Hisatomi and Masaki Akaogi

Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan

Correspondence: * E-mail: hiroshi.kojitani{at}gakushuin.ac.jp

To map the stability field of calcium ferrite-type MgAl2O4–Mg2SiO4 solid solutions, high-pressure phase relations in the system MgAl2O4-Mg2SiO4 were studied in the compositional range of 0 to 50 mol% Mg2SiO4. The calcium ferrite solid solutions are stable above 23 GPa at 1600 °C, and the maximum solubility of Mg2SiO4 component in MgAl2O4 calcium ferrite is 34 mol%. Lattice parameters and unit-cell volume of calcium ferrite-type MgAl2O4 (space group Pbnm) determined by Rietveld analysis are a = 9.9498(6) Å, b = 8.6468(6) Å, c = 2.7901(2) Å, and V = 240.02(2) Å3. Lattice parameters for the MgAl2O4–Mg2SiO4 solid solutions with the compositions of 14, 24, and 34 mol% Mg2SiO4 indicated the following compositional dependency of lattice parameters: a (Å) = 9.9498 + 0.1947·XMg2SiO4, b (Å) = 8.6468 – 0.1097·X Mg2SiO4, and c (Å) = 2.7901 + 0.0086·XMg2SiO4, where XMg2SiO4 is the mole fraction of Mg2SiO4 component. A linear extrapolation of the composition-molar volume relationship gave an estimated volume of 36.49(2) cm3/mol for the hypothetical calcium ferrite-type Mg2SiO4. This value is larger than that of the isochemical mixture of MgSiO3 perovskite and MgO, 35.72(1) cm3/mol. This implies that the mixture of MgSiO3 perovskite and MgO is more stable than the hypothetical calcium ferrite-type Mg2SiO4 under the lower mantle conditions.

Key Words: MgAl2O4 • Mg2SiO4 • calcium ferrite • high pressure • phase relation • Rietveld refinement






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Mineralogical Society of America