Le Massif D Ebelekan : Un Granite À Tantale Dans Le Sud-est Du Hoggar Central (algerie )

Résumé: The Ebelekan meant is situated in the farthest south-eastern part of central Hoggar (Algeria) in the Issaiane terrane , displaced along megashear zones during the Pan-African orogeny ( 750Ma-55! Ma). It is a small cupola hosted within a regional megacrystic biotite granite. A perphyntic albite-topaz-protolithionite microgranite, with accessory minerals of zircon, mona; :e. uranothorite and ferrocolumbite, crops out to the north of the cupola . The latter is caprei with a thin greisen lens and is composed of albite-topaz-zinnwaldite granite with fine-grained reticulated texture and "snow ball" quartz (and an overlying banded alpitepegmatite formed by layers of quartz-micas-topaze with colored alpite and of quartz-micastopazemicrocline pink colored pegmatite). The mica composition is varying: enriched in Li and Mn in the aplite, and in Fe in the pegmatite. Accessories include zircon, monazite, columbite tantalite, wodginite, Ta - rich cassiterite and rutile . The albite-topaz-zinnwaldite granite is peraluminous, characterized by high F, Li, A1203, Si02, Na20 (with Na20>K20),Ga, Rb, Nb, Ta, Sn contents and very low Ti02, MgO, CaO, P205, V,Cr, Co, Ni, Sr, Ba and W. It has many features in common with topaz-bearing and rare metal granites described in the world and would belong to low-P subtype of topaz granites or phosphorus-poor type of Ta-bearing granites. Nevertheless, it is distinct from them in its more peraluminous character , its very depleted REE with fractionated pattern and a weak negative Eu anomaly. The main Nb-Ta carriers follow a Mn- suite : manganocolumbite-n- anganotaBtalitewodginite-titanowodginite-cassiterite, product of aF-rkh melt.The mineralogical composition of the granite reveals a strong pegmatitic affinity . The Ebelekan granite is a Ta- granite and a potential economic ore for this element .

Publié dans la revue: Bulletin du Service Géologique de l'Algérie