Illiite transformation and rock chemistry: data from the Antola flysch and the Lavagna shales (northern Apennines)
Salvioli-Mariani, Emma; Bonazzi, Achille; Ortalli, Ida; Pedrazzi, Giuseppe
European Journal of Mineralogy Volume 3 Number 1 (1991), p. 147 - 158
published: Feb 21, 1991
manuscript accepted: Sep 3, 1990
manuscript received: Jan 30, 1990
ArtNo. ESP147050301013, Price: 29.00 €
Abstract : Pelitic rocks from the Lavagna Shales and the Antola flysch have been studied to investigate the mineralogical and chemical changes as diagenesis proceeds towards low-grade metamorphism. The contribution of clastic minerals, such as feldspar and muscovite, is not significant in providing potassium for the formation of illite and its transformation to mica. The influence of water solutions in terms of chemical supply and removal is suggested. Mössbauer analysis of 15 samples shows that the distribution of Fe2+ in the octahedral sites of the illite structure is different in the diagenetic and "metamorphic" samples. Moreover, the decreasing Fe3+/Fe2+ ratio with increasing temperature suggests progressive reduction from diagenesis to low grade metamorphism.