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Mafic phyllosilicates in low-grade metabasites; characterization using deconvolution analysis

D. Robinson and R. E. Bevins
Mafic phyllosilicates in low-grade metabasites; characterization using deconvolution analysis
Clay Minerals (June 1994) 29 (2): 223-237

Abstract

The <2 mu m clay fractions from low-grade metabasalts of eastern North Greenland are mixtures of mafic phyllosilicates and celadonite that show complex X-ray diffraction (XRD) patterns. Interpretation of such patterns is difficult and subjective using only visual examination of peak positions and shapes. Deconvolution analysis offers a less subjective means of identifying peak positions for overlapping peaks and is applied to several composite peaks in a pattern; the peaks identified are then rationalized in terms of specific mixed-layer phases. Comparison against NEWMOD patterns of the identified clay mixture provides an additional constraint on the phases identified. Three mafic phyllosilicates, discrete chlorite and two chlorite-smectites with 60:40 and 80:20 proportions are demonstrated in the same XRD pattern. Modelling using NEWMOD of a mechanical mixture between these mineral shows an excellent match to the observed XRD pattern. The recognition in low-grade metabasalts of chlorite and random and different varieties of regular mixed-layer chlorite-smectite offers support for the classical model of a tri-smectite to chlorite transition. This is in contrast to an alternative model proposing smectite and chlorite end-members with corrensite as a discrete phase crystallizing directly without intervening mixed-layer chlorite-smectite.


ISSN: 0009-8558
Coden: CLMIAF
Serial Title: Clay Minerals
Serial Volume: 29
Serial Issue: 2
Title: Mafic phyllosilicates in low-grade metabasites; characterization using deconvolution analysis
Affiliation: University of Bristol, Department of Geology, Bristol, United Kingdom
Pages: 223-237
Published: 199406
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 25
Accession Number: 1996-035606
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: National Museum of Wales, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
Update Code: 199612
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