GEOLOGY OF THE PHOSPHORITE DEPOSITS OF IRAQ | ||
| Iraqi Bulletin of Geology and Mining | ||
| Article 1, Volume 0, Issue 7, December 2017, Pages 25-50 | ||
| Author | ||
| Khaldoun S. Al-Bassam | ||
| Abstract | ||
| Phosphorite deposits of Late Cretaceous and Paleogene age are well known in the Iraqi Western Desert. They are part of the regional phosphorite belt of the Tethys which is best developed in North Africa and East Mediterranean countries and is considered to include the largest marine upwelling-type deposits in the world. The phosphorites of Iraq, as with the other deposits of this belt, are marine sedimentary stratiform deposits, granular in texture, associated with limestone, shale, chert and occasionally sandstone. The phosphorite beds may reach several meters in thickness, and show common features of hardgrounds and bioturbation. Silicification is common in these deposits. They were deposited in several cycles of phosphogenesis, extended from Maastrichtian to Middle Eocene. Most of the Iraqi phosphorite deposits, except those in the Nukhaib area, were laid down west of the Horan High, in successive episodes, culminated in the Paleocene. The phosphate components consist mostly of coated grains (cortoids and ooids), uncoated grains (peloids) and to a lesser extent phosphoclasts (mostly bones) and coprolites. The cementing material is commonly calcite; occasionally silicified. The only phosphate mineral identified is francolite. The P2O5 content of the Iraqi deposits is generally in the range of (18 – 25) %, but typically (20 – 22) %; the main diluent is calcite cement. The phosphorites, as with most upwelling marine deposits, are relatively enriched in F, U, Cd, Sr, Y and REE, which are associated with the phosphate phase. The indicated phosphate resources of Iraq were estimated by about 10 billion metric tones, which put Iraq the second after Morocco in that respect. These resources are divided among several deposits; most of which are bordering the northern and western rims of the Ga'ara Depression. They are: Akashat, Swab, Hirri, Marbat, Dwaima, H3 and Ethna. The bulk of the phosphate resources is found in the Paleocene Akashat Formation. The H3 deposit includes parts of the Late Cretaceous sequence (Digma Formation), whereas the Ethna deposit is merely of Middle Eocene age (Ratga Formation). Among the Iraqi deposits, only Akashat has been developed and exploited since the early eighties of the past century. | ||
| Keywords | ||
| Phosphorites; Stratigraphy; Sedimentation; Mineralogy; Geochemistry; Iraq | ||
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