XVI Reunión Científica de la Sociedad Española de Arcillas - Libro ...

Comunicaciones SEA 2001 – Baeza (Jaén)
SOCIEDAD
ESPAÑOLA DE ARCILLAS
FLUOR CONTENT OF HEAVY CLAYS FROM THE
LITHOSTRATIGRAPHIC UNIT “ARGILAS DE AVEIRO”(PORTUGAL)
AND ITS RELATIONSHIP WITH CLAY COMPOSITION AND TEXTURE
Coroado J a , Marques J b , Rocha F c , Gomes C c
a
Instituto Politécnico de Tomar. Escola Superior de Tecnologia de Tomar. Portugal.
b
Centro Tecnológico da Cerâmica e do Vidro. Coimbra. Portugal.
c
Dpto. de Geociencias. Universidade de Aveiro. Portugal.
Heavy clays belonging to the “Argilas de Aveiro” (AA) formation whose age is
attributed to Upper Cretaceous were studied in what concerns their mineralogy
and texture. Also, their content in fluor (F) was assessed and discussed with
regard to clay composition and texture.
Introduction
The thorough knowledge of raw materials properties is of paramount
importance in any industrial process. In heavy ceramics production it is very
useful to know the mineralogical, chemical and textural compositions of clay raw
materials. In the case of volatiles, such as F, S and Cl, their assessment and the
identification of their bearing minerals is important to predict and minimise
negatives impacts that may affect direct or indirectly either the production of
ceramic materials or the natural environment. The present study deals with F
determination and the characterization of clays sampled in outcrops of the
“Argilas de Aveiro” (AA) formation, Upper Cretaceous, included in the sheet 16-C
(Vagos) of the geologic map of Portugal, scale 1/50000, clays which are used in
the region for structural ceramics.
Materials and methods
The studied clays were sampled in active quarries from Vagos (VGS), Nariz
(NRZ), Bustos (BST) and Fonte de Grou (FTG), covering a large area of the AA
formation. Mineral composition was determined by X-ray diffraction (DRX), grain
size distribution analysis were carried out by wet sieving (fractions >63µm) and by