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Ca-Fe (super 3+) -rich, Si-undersaturated buchite from Zelenky, North-Bohemian brown coal basin, Czech Republic

Vladimir Zacek, Roman Skala, Marta Chlupacova and Zdenek Dvorak
Ca-Fe (super 3+) -rich, Si-undersaturated buchite from Zelenky, North-Bohemian brown coal basin, Czech Republic
European Journal of Mineralogy (August 2005) 17 (4): 623-633

Abstract

Si-undersaturated Ca-Fe-rich buchite produced by fossil burning of a coal seam occurs in a porcelanite deposit at Zelenky in the North Bohemian brown coal basin. The buchite is a highly inhomogeneous, dense (D 2.9-3.1 g/cm (super 3) ), strongly magnetic rock composed of melilite, esseneite, spinel-group minerals, hematite, Ca (sub 2) SiO (sub 4) , calcite, aragonite, anorthite, anhydrite, perovskite, baryte and two calcium ferrites. The clinopyroxene has 19-63 mol% of the esseneite component and up to 25 mol% of a hypothetical CaFe (super 3+) Fe (super 3+) SiO (sub 6) end-member due to Fe (super 3+) substitution in tetrahedral sites (up to 0.26 pfu) and also 2-36 mol% of a hypothetical component Ca(Fe (super 2+) ,Mg) (sub 0.5) Ti (sub 0.5) AlSiO (sub 6) due to incorporation of Ti (0.012-0.18 pfu) in the M1 site. The melilite shows a wide compositional variability with gehlenite 21-93, ferrigehlenite 0-34, akermanite 1-49, ferroakermanite 0-25 and soda melilite 0-15 mol%. Srebrodolskite, orthorhombic Ca (sub 2) (Fe (super 3+) Al) (sub 2) O (sub 5) , (sub ) is widely substituted by Si and Ti. Calcium ferrite associated with srebrodolskite, ideally CaFe (super 3+) (sub 4) O (sub 7) , shows extensive variability, and the first natural occurrence of barium hexaferrite, ideally BaFe (super 3+) (sub 12) O (sub 19) , is reported. This buchite originated by fusion of Tertiary clay and residual ash with overlying Quaternary sediments (loess loam with a carbonate horizon) during fossil combustion of a Miocene coal seam.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 4
Title: Ca-Fe (super 3+) -rich, Si-undersaturated buchite from Zelenky, North-Bohemian brown coal basin, Czech Republic
Affiliation: Czech Geological Survey, Prague, Czech Republic
Pages: 623-633
Published: 200508
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 27
Accession Number: 2006-013175
Categories: General mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 8 tables
N49°40'00" - N50°45'00", E13°40'00" - E16°30'00"
Secondary Affiliation: Doly Bilina, CZE, Czech Republic
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200607
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