PALYGORSKITE DEPOSITS AND OCCURRENCES IN IRAQ: AN OVERVIEW

Abstract

Numerous palygorskite deposits and showings have been recorded and studied in Iraq. They range in age from Maastrichtian to Holocene, and are found in about 10 different formations. The Iraqi deposits are of sedimentary origin, deposited in marine, lagoonal, lacustrine, fluvial, and pedogenic environments as well as epigenetic fillings of fractures and veins. The majority was formed by the alteration of precursor minerals and to a lesser extent by direct precipitation from solution. The marine black shale deposits of the Upper Cretaceous Safra Beds of the Digma Formation and Lower Paleocene Traifawi Member of the Akashat Formation represent important palygorskite resources in the Western Desert of Iraq. Moreover, palygorskite is the dominant clay mineral in the lagoonal facies of the Tayarat Formation (Upper Cretaceous) in the Southern Desert. Other occurrences in the desert include thin palygorskite-rich claystone horizons in the lagoonal deposits of the Nfayil Formation, (Middle Miocene), and thin lenses of palygorskite-rich claystones in the fluvial deposits of the Zahra Formation (Pliocene – Pleistocene). In the Najaf – Karbala region, palygorskite is the dominant clay mineral in the fluvial and lacustrine mudstones of the Injana Formation (Upper Miocene), and in the sandy claystone lenses in the fluvial deposits of the Dibdibba Formation (Pliocene – Pleistocene). In the northern parts of Iraq, palygorskite veins and fracture-fill deposits are recorded in the sandstones of the Injana Formation, near Jabal Maqlub area, forming one of the most peculiar palygorskite showings in Iraq. In the Shikhan area, another interesting showing was recorded within the fluvial deposits of the Gercus Formation (Eocene). Furthermore, palygorskite forms the main clay mineral in the Holocene deposits of the Ahwar region of the Mesopotamia, as well as in the Recent soils of Iraq in general.