METABASITES. CHARACTERIZAT ION US ING DECONVOLUTION ANALYS IS
ABSTRACT: The <2 gm 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 f such patterns i difficult and subjective using only visual examination f peak position...
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| Format: | Text |
| Language: | English |
| Published: |
1993
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.600.1497 http://www.minersoc.org/pages/Archive-CM/Volume_29/29-2-223.pdf |
| Summary: | ABSTRACT: The <2 gm 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 f such patterns i difficult and subjective using only visual examination f 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 o chlorite transition. This is in contrast to an alternative model proposing smectite and chlorite nd-members with corrensite as a discrete phase crystallizing directly without intervening mixed-layer chlorite-smectite. Mafic phyllosil icates are ubiquitous in low-grade metabasites of hydrothermal /geothermal systems |
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