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Statistical microanalysis applied to garnet growth zoning and to cordierite fluid content
Author(s) -
PAQUET J.,
DELAY F.,
LEMAGUER D.
Publication year - 1989
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.1989.tb00615.x
Subject(s) - cordierite , electron microprobe , zoning , geology , mineralogy , microprobe , electron probe microanalysis , homogeneity (statistics) , analytical chemistry (journal) , materials science , chemistry , mathematics , statistics , chromatography , composite material , ceramic , political science , law
An analytical study to evaluate quantitatively weak zoning of a garnet from a high‐grade kinzigite has been performed with an electron microprobe. The technique consists of the reconstruction of a profile step‐by‐step by successive analyses performed during relatively long counting times (30 s), along a radial profile of 2,500 μm length. The successive analytical data along this profile are statistically treated by Fisher's test and compared with the χ 2 values (Pearson's law). These statistical tests were applied to assess microprobe stability and analysis homogeneity, and as a consequence to assure high credibility of the radial variations of the garnet. From core to rim, and for each element, zoning appears as the radial juxtaposition of stationary Poissonian samples. These samples being associated, the garnet appears to be constituted of successive concentric domains with stationary compositions. Different substitutions between Mg, Fe, Mn and Ca are evidenced. Such an analytical approach to chemical zoning can be useful for understanding growth mechanisms, and the possible diffusion reactions with the environment at each growth step. In addition, such a procedure can be used to evaluate accurately the fluid content of cordierite, and to appreciate the nature of the fluids concerned. As an example, the fluid content of a cordierite from a similar high‐grade kinzigite has been evaluated.