Karst bauxite deposits of north Hussainiyat area, western desert, Iraq : an overview

الملخص EN

The North Hussainiyat karst bauxite deposits in the Western Desert of Iraq are the only known bauxite resources in Iraq.

They were discovered by Iraq Geological Survey in 1990 as few meters to 35 m thick lenses in fossil karsts of various sizes in the Ubaid Formation (early Lower Jurassic), associated with bauxitic kaolinite, kaolinite, flint-clay and quartz sandstone.

Some strongly bauxitic profiles reach up to 100 m in thickness.

They are pisolitic or massive in texture and composed of boehmite, gibbsite, kaolinite and accessory amounts of anatase.

The bauxite lenses are sandwiched between the underlying bottom sandstone and kaolinitic mud rocks and the overlying top clay, which is dominated by kaolinite, quartz and goethite.

Geochemical data suggest that the immobile elements such as Al2O3, TiO2, Cr, Zr, and Ni were enriched, while SiO2, Fe2O3, CaO, MgO, Zn, Co, Ba, Mn, Cu and Sr were depleted during the bauxitization process.

The results of various studies strongly suggest that these karst bauxite deposits were derived from the kaolinitic clay deposits of the Hussainiyat Formation (late Lower Jurassic).

The age of these bauxite deposits is controversial; some authors suggest they are of Early Cretaceous (Aptian – Albian) age whereas others believe they are of Lower – Middle Jurassic age and some authors suggested Paleocene – Eocene age based on their pollens and spores content.

High grade bauxites are scarce and most of the deposits are kaolinitic bauxite or bauxitic clays.

The reserves were estimated by about 1.28 m.t., distributed in various karst deposits, and have been used in alum production and refractories, with limited laboratory experiments in alumina extraction.