Chemical diversity of talcs in relation to their origin

Wilamowski Andrzej and Wiewióra Andrzej: Chemical diversity of talcs in relation to their origin. In: Acta mineralogica-petrographica, (45) 2. pp. 35-39. (2004)

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Apart from main constituents, chemical compositions of talc show various elements, such as Fe, Al, Cr, Ni, Mn , alkalies and fluorine. Several analyses of talcs from Egypt (El-Sharkawy 2000) show the rectilinear negative correlation of Si and Fe 3+ suggesting simultaneous substitution of Fe 3 ' both in tetrahedra and in octahedra according to the mechanism MgSi<-»Fe 3 +Fe 3 This wa s veryfied in talks deficient in Si and rich in Fe. Essentially better calculated formulas and agreement of the layer charge with the theoretical value 22 wer e achieved after recalculation of Fe oxidation state according to the above mentioned scheme. The highest Fe 3 contents demonstrate talcs from lowtmperature crystallization environments. The likely explanation is interaction with por e fluids. Chemical compositions of octahedral sheet, plotted in the ternary diagram Mg-Al-Fe+Mn+Ni+Zn , demonstrat e a quite regular grouping of projection points into 3 fields: I. near-stoichiometric talcs around 100 % Mg, II. talcs with elevated Fe+Mn+Ni+Zn contents and III. Mg-Al talcs. Sample s representing all genetic types gather in the first field, in the second dominate talcs from high-pressure and ultramafic environments, and in the third - dolomite-related talcs. T he positive correlation of tetrahedral Al and Na (R2 =0.71) suggests the substitution mechanism involving the tetrahedral sheet and interlayer space: NaAI<->Si. Much weaker correlation shows octahedral Al (R2 =0.50). Sodium content shows positive correlation both with temperature and pressure of talc crystallization. It is likely that high PT-conditions favour incorporating Na into the talc structure.

Item Type: Article
Journal or Publication Title: Acta mineralogica-petrographica
Date: 2004
Volume: 45
Number: 2
ISSN: 0365-8066
Page Range: pp. 35-39
Language: English
Publisher: Department of Mineralogy, Geochemistry and Petrology, University of Szeged
Place of Publication: Szeged
Related URLs:
Uncontrolled Keywords: Földtan, Ásványtan, Kőzettan
Additional Information: Bibliogr.: p. 38-39. ; ill. ; összefoglalás angol nyelven
Subjects: 01. Natural sciences
01. Natural sciences > 01.05. Earth and related environmental sciences
Date Deposited: 2016. Oct. 17. 09:24
Last Modified: 2022. Aug. 24. 15:15

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