Energy Citations Database

Bibliographic Citation

 
Document
For copies of Journal Articles, please contact the Publisher or your local public or university library and refer to the information in the Resource Relation field.
For copies of other documents, please see the Availability, Publisher, Research Organization, Resource Relation and/or Author (affiliation information) fields and/or Document Availability.
Title Chemistry and structure of a natural ferri-aluminum tschermakitic pyroxene produced by pyrometamorphism
Creator/Author Cosca, M.A. ; Peacor, D.R. ; Essene, R.J.
Publication Date1985 Jan 01
OSTI IdentifierOSTI ID: 6874595
Report Number(s)CONF-8510489-
Other Number(s)CODEN: GAAPB
Resource TypeConference
Specific TypeJournal Article
Resource RelationGeol. Soc. Am., Abstr. Programs ; Vol/Issue: 17; 98. annual meeting of the Geological Society of America; 28 Oct 1985; Orlando, FL, USA
Research OrgUniv. of Michigan, Ann Arbor (USA)
Subject580400 -- Geochemistry-- (-1989); POWDER RIVER BASIN-- METAMORPHIC ROCKS;PYROXENES-- CRYSTAL STRUCTURE;PYROXENES-- GEOCHEMISTRY;PYROXENES-- STRUCTURAL CHEMICAL ANALYSIS; ALUMINIUM COMPOUNDS;CHEMICAL COMPOSITION;COAL SEAMS;COMBUSTION;COMBUSTION PRODUCTS;FIRES;IRON IONS;LEAST SQUARE FIT;MAGNESIUM COMPOUNDS;METAMORPHISM;OVERBURDEN;PYROLYSIS PRODUCTS;TITANIUM COMPOUNDS;WYOMING
Related SubjectALKALINE EARTH METAL COMPOUNDS;CHARGED PARTICLES;CHEMICAL REACTIONS;CHEMISTRY;COAL DEPOSITS;FEDERAL REGION VIII;GEOLOGIC DEPOSITS;IONS;MAXIMUM-LIKELIHOOD FIT;MINERAL RESOURCES;MINERALS;MONTANA;NORTH AMERICA;NUMERICAL SOLUTION;OXIDATION;OXYGEN COMPOUNDS;RESOURCES;ROCKS;SILICATES;SILICON COMPOUNDS;THERMOCHEMICAL PROCESSES;TRANSITION ELEMENT COMPOUNDS;USA;WYOMING
Description/Abstract Natural combustion of thick coal seams in the Powder River Basin, Wyoming has produced large areas of baked, to partially melted and fused sediment, termed paralava.^Slag-like paralava occurring within thin coal-ash zones contains phenocrysts of clinopyroxene ranging in composition from diopside (CaMgSi/sub 2/O/sub 6/) to near end-member ferri-aluminum-Tschermaks (CaFeAlSiO/sub 6/); the latter compositions are the first natural occurrence of a pyroxene previously known only through experimental synthesis.^The authors selected a Fe/sup 3 +/-rich pyroxene from the paralava of composition: (Ca/sub 1.01/Na/sub .01)(Fe/sup 3 +//sub .65/Mg/sub .18/Al/sub .10/Ti/sub .03/Fe/sup 2 +//sub .02/) (Al/sub .79/Si/sub 1.21/)O/sub 6/ for which a least-squares structure refinement indicates that only silicon and aluminum are present in tetrahedral sites with aluminum occupying 36 percent of those sites, in close agreement with the authors interpretation of the microprobe analyses.^The fact that there is no Fe/sup 3 +/ in the tetrahedral sites is surprising in light of the temperatures at which paralavas form (>1200/sup 0/C), and because other investigators have identified tetrahedrally coordinated Fe/sup 3 +/ by Moessbauer techniques in synthetic pyroxenes along the join CaFeAlSiO/sub 6/-CaTiAl/sub 2/O/sub 6/, in ferri-diopside and in synthetic CaFeAlSiO/sub 6/.^The authors attribute the absence of tetrahedral Fe/sup 3 +/ to the high activity of aluminum and/or a sufficiently long cooling interval for the interchange of Fe/sup 3 +/ and Al on the Mg and Ti sites.^The observed space group C2/c requires disorder of Si and Al, although short-range order is possible.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 553
System Entry Date2001 May 13

Top