Kaolinized rocks on the Island of Lesbos (Greece)

A description is given of the mineralogy and geology of the kaolin deposits of Lesbos (Greece) which are caused by the action of hydrothermal fluids on volcanic rocks, lavas and tuffs, having dacitic, rhyodacitic, latitic, andesitic, etc. chemism. The major deposits are Magaros-Arghenos, Aspres Petr...

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Bibliographic Details
Main Authors: Kanaris G.
Mattias Pier Paolo
Corporate Author: International Kaolin Symposium (10.) (1979) (Budapest)
Format: Article
Published: University of Szeged, Department of Mineralogy, Geochemistry and Petrology Szeged 1980
Series:Acta mineralogica-petrographica 24
Kulcsszavak:Kőzettan, Ásványtan, Földtan
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Online Access:http://acta.bibl.u-szeged.hu/24672
Description
Summary:A description is given of the mineralogy and geology of the kaolin deposits of Lesbos (Greece) which are caused by the action of hydrothermal fluids on volcanic rocks, lavas and tuffs, having dacitic, rhyodacitic, latitic, andesitic, etc. chemism. The major deposits are Magaros-Arghenos, Aspres Petres, Stipsi and Mesotopos; the first three are located in the northern part of the island, near the centre of Petra, the last one near the southern coast and the centre of Mesotopos. Inside these deposits, through diffractometric and thermal (DTA and TG) methods and direct E. M. and S. E. M. observations, the following minerals were detected: kaolinite (type from pM to T), smectite (montmorillonite), a mixed-layer mineral of the I-MO type, open-layer illite, alunite, jarosite, cristobalite and marcasite, surely newly-formed, while quartz and feldspar are to be considered as "residual". On the whole, the deposits of Aspres Petres and Mesotopos show a rather homogeneous mineralogy, where the always present kaolin minerals can be associated with sulphates, alunite and jarosite, or with silica phases, quartz and cristobalite; the remaining deposits, instead, feature a significant "zoning". The latter has kaolin in the central part while, at the periphery, essentially smectitic minerals can be noted, mostly associated with feldspar and sometimes illitic. This diversity of alteration products is to be ascribed to the different degree of alterability and thus of acidity of the fluids altered. Indeed, the different rock permeability due to differentiated porosity and fracturing as well as temperature variations, allow the same fluids to undergo modifications, including the hypothesis of becoming enriched with ions derived from the same rocks subjected to alteration. The chemism of the original rocks does not seem to have determined any substantial influence on the formation of the altered terms. Finally, all the deposits formed "in situ" fall within the typical deposits resulted by the actions of hydrothermal fluids connected with a late volcanism. Additionally, they are arranged along the structural alignments typical of the island and of the adjoining region of Asia Minor (Turkey).
Physical Description:47-64
ISSN:0365-8066