Contribution A L’etude Geologique Petrographique Et Geochimique Des Granites Du Massif De Filfila (skikda, Algerie)

Résumé: Located about 20 km east of Skikda, the Filfila granitoids of Langhian age appear in a tectonic window through the allochthonous and constitute two small massifs (North massif and South massif) of Tertiary age and elongated in the direction WNW-ESE, in accordance with the general orientation of the structures of the region. These granites intersect the four tectonic units (sedimentary and metamorphic formations) and develop significant medium-grade contact metamorphism. They are classically considered to be the result of evolution by fractional crystallization. The detailed petrographic study of these rocks has made it possible to distinguish several varieties of granites according to the proportion of the minerals which contain them: granite with tourmaline, granite with biotite and granite with topaz and which have the same mineralogical association. However, the petrographic composition of the two massifs is relatively homogeneous, which are generally light gray rocks with medium or coarse grains, made up of quartz, feldspar potassium, plagioclase, tourmaline and mica. Geochemical studies of the major elements of the massif have shown that the granites of Filfila are less rich in colored minerals, more siliceous and more potassium than their counterparts from Petite kabylie. The peraluminous and crustal character of the rocks allowed us to relate it to the "S" type granitoid. While the dispersion of the analyzes in the diagrams for the majority of the elements and especially the alkalines, can be explained by the intensity of the phenomena of alteration, hydrothermal.

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