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GEOREF RECORD

The occurrence and chemistry of epidote-clinozoisites in mafic gneisses from the Ruby Range, southwestern Montana

P. S. Dahl and L. M. Friberg
The occurrence and chemistry of epidote-clinozoisites in mafic gneisses from the Ruby Range, southwestern Montana
Contributions to Geology (1980) 18 (2): 77-82

Abstract

Optically and chemically zoned epidote-clinozoisite occurs here as a retrograde mineral in Precambrian mafic gneisses. Computer-corrected electron microprobe analyses place the chemical boundary between epidote and clinozoisite at 15.45 + or - 1.55 mole% pistacite (Fe (super 3+) /(Fe (super 3+) + Al (super vi) ). Zoning profiles indicate that epidote-clinozoisite crystals formed during a single episode in which: 1) T declined gradually (in the range 745 degrees -550 degrees C) ; and/or 2) fO (sub 2) increased. Superimposed on these changes were local and relatively minor T-fO (sub 2) fluctuations, as indicated by oscillatory Al-Fe (super 3+) zoning in single crystals. These physicochemical variations probably characterize conditions that prevailed in mafic gneisses during the post-2700 m.y. uplift event.


ISSN: 0010-7980
Coden: WUGGAO
Serial Title: Contributions to Geology
Serial Volume: 18
Serial Issue: 2
Title: The occurrence and chemistry of epidote-clinozoisites in mafic gneisses from the Ruby Range, southwestern Montana
Affiliation: Kent State Univ., Dep. Geol., Kent, Ohio, United States
Pages: 77-82
Published: 1980
Text Language: English
Publisher: University of Wyoming, Laramie, WY, United States
References: 16
Accession Number: 1981-008826
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. table, sketch maps
N45°19'60" - N45°34'60", W112°30'00" - W111°30'00"
Secondary Affiliation: Univ. Akron, Dep. Geol., Akron, Ohio, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1981
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