Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
American Mineralogist house ad
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
American Mineralogist; February 2004; v. 89; no. 2-3; p. 396-404
© 2004 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
Right arrow Citation Map
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 (5)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Fleet, M. E.
Right arrow Articles by Liu, X.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

A new rare earth disilicate (REE2Si2O7; REE = Dy, Tm, Lu; type-L): Evidence for non-quenchable 10 GPa polymorph with silicon in fivefold trigonal bipyramidal coordination?

Michael E. Fleet* and Xiaoyang Liu

Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada

Correspondence: * E-mail: mfleet{at}uwo.ca

A new structure type (L) is reported for disilicates of the middle and heavy rare earth elements (REE) quenched from 10 GPa, 1600–1700 °C. Crystal data are: triclinic, space group P, Z = 6; Dy2Si2O7: a = 6.5971(3), b = 6.6504(2), c = 18.0582(6) Å, {alpha} = 83.791(2), ß = 88.653(2), {gamma} = 88.498(2)°, V = 787.2 Å3, and Dx = 6.242 g/cm3; Tm2Si2O7: a = 6.5499(2), b = 6.5876(2), c = 17.8916(7) Å, {alpha} = 83.828(1), ß = 88.368(1), {gamma} = 88.152(2)°, V = 766.9 Å3, and Dx = 6.574 g/cm3; Lu2Si2O7: a = 6.5240(2), b = 6.5553(2), c = 17.7909(6) Å, {alpha} = 83.977(2), ß = 88.074(2), {gamma} = 87.846(2)°, V = 755.8 Å3 , and Dx = 6.830 g/cm3. The type-L structure comprises linear trisilicate [Si3O10]8– and orthosilicate [SiO4]4– ions cross linked by REE3+ in one sevenfold and five eightfold coordinated positions (to 3.0 Å), and is assembled from alternating (001) strips of the type-B structure of REE2Si2O7 and a sheared structure containing structural elements found in the type-B structure but with Si distributed with 50% occupancy over two face-sharing tetrahedra. The geometry of these half-occupied tetrahedra is consistent with decomposition of a SiO5 trigonal bipyramid during quenching of the pressure.






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