New occurrences of diagenetic faujasite in the Quaternary tuffs of north-east Jordan
Ibrahim, Khalil; Hall, Anthony
European Journal of Mineralogy Volume 7 Number 5 (1995), p. 1129 - 1136
published: Oct 5, 1995
ArtNo. ESP147050705008, Price: 29.00 €
Abstract This paper reports the discovery of new localities of diagenetic faujasite, occurring with phillipsite and chabazite in Quaternary tuffs in north-east Jordan. The distribution of zeolites shows a vertical zonation of a previously undescribed type, in which a phillipsite-chabazite zone occurs at the top and is underlain by a faujasite-phillipsite zone. It corresponds to the sequence of zeolite crystallization: faujasite-phillipsitechabazite. Faujasite is more abundant in the tuffs of the lower zone than at any other locality described hitherto, constituting up to 30 % of the rock. The faujasite occurs as octahedral crystals between 50 and 300 μm in size. At Jabal Aritayn, two generations of faujasite occur in the same sample. The first generation occurs as a lining to cavities and is characterized by a low K content, whereas the second generation occupies the central part of cavities and has a higher K content. The second type is richer in K2O than faujasite from any previously known locality (up to 2.93 %). The Si/(Si+Al+Fe) ratio of the Jordanian faujasites varies between 0.695 and 0.718. The formation of faujasite and the other zeolites is attributed to the alteration and leaching of sideromelane in an open hydrological system by percolating meteoric water.