RARE EARTH ELEMENTS GEOCHEMISTRY  OF SOME PALEOCENE CARBONATE FLUORAPATITES  FROM IRAQ

T. Al-Rawi, Yehya; S. Al-Bassam, Khaldoun; A. Aba-Hussain, Asma

	RARE EARTH ELEMENTS GEOCHEMISTRY OF SOME PALEOCENE CARBONATE FLUORAPATITES FROM IRAQ
Iraqi Bulletin of Geology and Mining
Article 1, Volume 6, Issue 1, 2010, Pages 81-94
Authors
Yehya T. Al-Rawi; Khaldoun S. Al-Bassam; Asma A. Aba-Hussain
Abstract
Marine sedimentary phosphorites of Late Cretaceous, Paleocene and Eocene age are wide spread in the Western Desert of Iraq. The Paleocene deposits (Akashat Formation) are the most extensive in thickness and distribution, and are industrially exploited. They are granular phosphorites composed mostly of ooids and peloids, with accessory amounts of coprolites and fish scales. The cementing material is calcite. The phosphate mineralogy is carbonate fluorapatite (francolite). Rare earth elements, phosphorus and yttrium were analyzed in ten concentrated carbonate fluorapatite samples from the Paleocene phosphorite of Iraq. The concentrated apatites included coprolites, peloids – ooids, bones and teeth. The results show lower REE content relative to average world phosphorites, and the coprolites contained the highest concentrations among the three types of phosphate grains studied, whereas the bioclasts contained the lowest concentrations. The data were normalized relative to average shale and compared to REE patterns of seawater, and average world phosphorites. The REE patterns of the Iraqi Paleocene apatites are relatively depleted in REE, but they show distribution patterns comparable to seawater and average world phosphorites. The seawater pattern with the negative Ce anomaly of the studied apatites reflects the influence of deep seawater on their origin. Variation in the REE content of the various apatite grains was related to their mode of formation, duration of contact with sea water, mass/surface ratio of the grains, as well as to probable diagenetic alterations.

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