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Les feldspaths potassiques des porphyres de Roffna

ContributorsGysin, Marcel
Published inSchweizerische mineralogische und petrographische Mitteilungen, vol. 43, no. 1, p. 385-405,Pl.I-VIII
Publication date1963
Abstract

K-Felspars of the Roffna-porphyries belong to the group of "triclinic orthoclase". Their optical properties (indicatrix orientation) are similar to those of anorthoclase or of a felspar intermediate between anorthoclase and microcline. Homogenous crystals show 2V values ranging between —76° and —86°. Spotted crystals have a greater range of variation, from — 42° to — 84,5°. Concerning the genesis of the "porphyries", the author suggests that they are of detritic origin, resulting from the erosion of albite-rich rhyolite (quartz-porphyries).

NoteTexte en français avec résumé en anglais
Citation (ISO format)
GYSIN, Marcel. Les feldspaths potassiques des porphyres de Roffna. In: Schweizerische mineralogische und petrographische Mitteilungen, 1963, vol. 43, n° 1, p. 385–405,Pl.I–VIII. doi: 10.5169/seals-33460
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ISSN of the journal0036-7699
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