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GEOREF RECORD

Chemistry of dark zinnwaldite from Bom Futuro tin mine, Rondonia, Brazil

G. R. Lowell and M. Ahl
Chemistry of dark zinnwaldite from Bom Futuro tin mine, Rondonia, Brazil (in Carbonatite thematic set, A. P. Jones)
Mineralogical Magazine (August 2000) 64 (4(425)): 699-709

Abstract

Physical and chemical properties of lustrous black mica from greisen veins at the Bom Futuro tin mine indicate that it is a relatively Fe-F-rich, Li-poor zinnwaldite with a composition near the midpoint of the polylithionite-siderophyllite join. On the basis of 22 oxygens, the mica contains 1.28-1.73 atoms of Li with an average octahedral occupancy of 5.61 and a filled interlayer site. Compositional variation reflects the net effects of alteration, coupled tetrahedral-octahedral substitutions, and petrogenetic factors related to vein fluid chemistry. Geological constraints and compositional data suggest the Bom Futuro zinnwaldite crystallized at T nearly equal 500 degrees , P nearly equal 1-500 bar, and f (sub O2) nearly equal 10 (super -23) . High Mn-Zn concentrations in the Bom Futuro mica appear to be a feature of Fe-Li micas from evolved anorogenic granitic systems not shared by orogenic counterparts.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 64
Serial Issue: 4(425)
Title: Chemistry of dark zinnwaldite from Bom Futuro tin mine, Rondonia, Brazil
Title: Carbonatite thematic set
Author(s): Lowell, G. R.Ahl, M.
Author(s): Jones, A. P.
Affiliation: Southeast Missouri State University, Department of Geosciences, Cape Girardeau, MO, United States
Affiliation: University College, Department of Geological Sciences, London, United Kingdom
Pages: 699-709
Published: 200008
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
Meeting name: Tenth carbonatite workshop
Meeting location: London, GBR, United Kingdom
Meeting date: 19990219Feb. 19, 1999
References: 30
Accession Number: 2000-066405
Categories: Mineralogy of silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
S13°49'60" - S07°55'00", W66°45'00" - W60°00'00"
Secondary Affiliation: Stockholm University, SWE, Sweden
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200021
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