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Magnesiochloritoid, and the Fe-Mg series in the chloritoid group

Christian Chopin, Eberhard Seidel, Thomas Theye, Giovanni Ferraris, Gabriella Ivaldi and Michele Catti
Magnesiochloritoid, and the Fe-Mg series in the chloritoid group
European Journal of Mineralogy (February 1992) 4 (1): 67-76


In the high-P metamorphic rocks of the Alps, magnesiochloritoid with Mg/(Mg+Fe+Mn) up to 0.82 occurs in association with talc, kyanite, garnet, chlorite, omphacite, phengite, quartz, etc. EPMA results and cell parameters are reported for 22 chloritoids. Magnesiochloritoid from the Monte Rosa massif, Italy, has the formula (Mg (sub 0.65) Fe (sub 0.35) ) (sub 2) Al (sub 4) O (sub 2) (SiO (sub 4) ) (sub 2) (OH) (sub 4) , with a 9.452, b 5.466, c 18.158 Angstrom, beta 101.47 degrees ; Z = 4, D 3.25 g/cm (super 3) ; alpha 1.687, beta 1.690, gamma 1.702, 2V (sub gamma) 40-50 degrees, very faint pleochroism (light blue, grey blue, yellowish). The synthetic Mg end-member grown at 700 degrees C, 33 kbar PH (sub 2) O shows both the monoclinic and triclinic polytypes; the former has a 9.427, b 5.442, c 18.140 Angstrom, beta 101.12 degrees, and the latter has a 9.429, b 5.445, c 9.126 Angstrom, alpha 96.36, beta, 101.12, gamma 90.07 degrees, space group C1 (super -) . The substitution of Mg for Fe results in a decrease of approx 0.8% for a and b, 0.3% for c. The highest substitutions known for Al are 0.3 atom by Fe (super 3+) and 0.6 atom by Cr (super 3+) (pfu).

ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 1
Title: Magnesiochloritoid, and the Fe-Mg series in the chloritoid group
Affiliation: Ecole Normale Superieure, Lab. Geol., Paris, France
Pages: 67-76
Published: 199202
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 2 p.
Accession Number: 1993-025704
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables, 22 anals.
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany
Update Code: 1993
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