GeoArabia, 2013, v. 18, no. 2, p. 67-94 Gulf PetroLink, Bahrain The eastern Mediterranean phosphorite giants: An interplay between tectonics and upwelling Abdulkader M. Abed ABSTRACT About 20 billion tonnes of world-class, high-grade phosphorite resources occur in a small area of the eastern Mediterranean region, including Jordan, northern Negev (Palestine), northwestern Saudi Arabia, western Iraq, and southeastern Syria. Major deposits were formed during Campanian to Eocene times and contribute significantly to the economic development of these countries, particularly Jordan and Syria. The phosphorite deposits consist mainly of reworked granular material. The phosphate particles are peloids, such as pellets, intraclasts, nodules, coated grains and coprolites, and vertebrate fragments (bone and teeth). The phosphorite sequences are associated with extensive bedded chert, porcelanite, and organic-rich marls. The main phosphate mineral is francolite, a carbonate-rich variety of fluorapatite that has a relatively enhanced uranium content as a result of substitution for calcium in its crystal structure. Two factors are deemed responsible for the deposition of the phosphorites and their associated chert, porcelanite, and marl within this relatively restricted area. The first was a compressional event associated with the initial collision of the oceanic forefront of the Afro-Arabian Plate with the subduction trench of Eurasia that began in Turonian times and continued into the Eocene. This event resulted in gentle folding that produced the Syrian Arc, the Ha’il, Rutba, and Sirhan paleohighs and the Ga’ara Dome, which were loci for the deposition of phosphorites. The second factor was the obstruction and consequent upwelling of oceanic currents by these tectonic highs, enhanced by winds blowing from east to west along the southern platform margin of the Neo-Tethys Ocean. The intense upwelling was associated with the Tethyan Circumglobal Current that flowed along the Afro-Arabian platform on the southern margin of the Neo-Tethys Ocean. In contrast, relatively minor phosphorite deposition took place to the north in southern Europe. The upwelling spread cold, nutrient-rich oceanic water from the deep Neo-Tethys Ocean to the surface, thereby enhancing bioproductivity to produce organic-rich sediments. The subsequent authigenesis of phosphorites, their diagenesis and the reworking and winnowing of the phosphorite-rich sediments, concentrated the materials into economic deposits. Phosphorite deposition ended in the Late Eocene following the final collision of the Afro-Arabian Plate with Eurasia. The sub-aerial exposure of this formerly productive shallow-marine platform was the result of the separation of the Arabian Plate from the African Plate during the mid-Miocene. INTRODUCTION The eastern Mediterranean region and North Africa hold more than half the world’s phosphorite resources, amounting to about 80 billion tonnes of high-grade commercial phosphorites (Jasinski, 2003, 2011; Van Kauwenbergh, 2010). These deposits form part of the Late Cretaceous to Eocene Tethyan Phosphorite Regime that extends through North and northwest Africa, and into parts of the Caribbean and Columbia and Venezuela in northern South America (Lucas and Prévôt, 1975; Bentor, 1980; Notholt, 1980; Abed, 1994; Lucas and Prévôt-Lucas, 1995; Föllmi, 1996; Soudry, et al., 2006). The Tethyan phosphorites, together with the Miocene–Holocene deposits of the USA, account for the majority of the world’s phosphorite resources and production (Notholt, 1980; Notholt et al., 1989). In the Middle East, most of the phosphorite deposits are in Iraq, Jordan, Palestine, Saudi Arabia and Syria, and their production is of primary economic importance to the development of countries with limited oil and gas production; for example, Jordan and Syria. 67 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/18/2/67/4570666/abed.pdf by guest on 30 September 2021 Abed This paper presents an overview of the geology of the Tethyan phosphorite deposits in the Middle East (Figure 1). Its aim is threefold. Firstly, the paper describes and correlates the various phosphorite deposits of the eastern Mediterranean region; secondly, it discusses the regional plate-tectonic setting associated with the formation of the deposits; and thirdly it attempts to explain the presence of giant phosphorite deposits that were formed in a relatively small part of the eastern Mediterranean region in a relatively short period of geological time. Resources and reserves of phosphorites deposits, as of 2010, in the eastern Mediterranean countries (Figure 1) are about 20 billion tonnes and 2.4 billion tonnes, respectively (Table 1) (Van Kauwenbergh, 2010). Both resources and reserves are dynamic and are changing continuously due to increasing exploration activities. For example, the phosphorite resources of Iraq, currently 5.7 billion tonnes, will become 10 billion tonnes when the recently discovered Swab deposits, west of Akashat, are added. Also, grade reductions can significantly increase resources; for example, Iran’s resources at about 170 million tonnes (Mt) at a grade of 20% P2O5 would be increased by 70 Mt if the grade was lowered to 12% P2O5. Iraq and Saudi Arabia have most of the region’s resources with 5.7 billion tonnes and 7.8 36°E4TURKEY 0.14 2° 44°46° 48°50° 52° Mazidagi Kurdagh 36°N 36° SYRIA 2.0 N 0 300 Tehran Med. Rakheime Sea Sawwaneh km Khneifiss 34° Habari-Sirji 34° IRAQ Damascus Akashat / Swab IRAN LEBANON Baghdad Al-Kora 5.7 0.17 JORDAN Ruseifa 32° Umm Jalamid Pabdeh PA1.6LESTINE Amman Oron 1.8 Wu’al / Arqah Zefa Al-Hisa/ Sirhan E’fe Al-Abiyad Thaniyat 30° 7.8 30° Eshidiyya KUWAIT SAUDI ARABIA Paleocene–Eocene deposits Late Cretaceous deposits 28° 28° 36° 38° 40°42° 44°46° 48°50° 52° Figure 1: Location map of the major chert-phosphorite facies (green) and the major phosphorite deposits in the eastern Mediterranean region and adjacent countries, their ages, and total resources (bold numbers in billion tonnes). Red arrow indicates the NNE-trending direction of phosphorite deposition (see also Table 2). Table 1: Resources, reserves and annual production of phosphate (in Mt) in the eastern Mediterranean region and adjacent countries as of 2010 (Van Kauwenberg, 2010; Jasinski, 2011). Annual Country Resources % P O Reserves Destination 2 5 Production Jordan 1,800 28 1,500 6.00 Export: phosph. acid, DAP Palestine, Nejev 1,600 26 200 3.00 Export: phosph. acid, DAP Syria 2,000 25 100 3.70 Export: fertilizers Turkey 136 45 ~ 0.1 Fertilizers Iraq 5,700 22 430 ~ 2 (1989) - Iran 170 20 30 0.1 Fertilizers Saudi Arabia 7,800 20 93 5.00 Export: phosph. acid, DAP Total 19,206 Av. 23.5 2,398 ~19.9 World total 163,000 Av. 22.5 16,000 160 Mainly fertilizers 68 68 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/18/2/67/4570666/abed.pdf by guest on 30 September 2021 Eastern Mediterranean Phosphorite Giants billion tonnes, respectively, although Jordan is the major producer with 6 Mt/year (Table 1). Iraq was producing about 2 Mt in 1989 but this declined to 100,000 tonnes in 2001 and production has now ceased due to the adverse security conditions. Saudi Arabia started production towards the end of 2010 at a rate of about 5 Mt/year. The mined rock phosphate is upgraded by various beneficiation processes usually involving washing, separation, flotation and concentration, depending on the ore. Concentrates need a P2O5 content of more than 30% in order to compete in global markets. Phosphorites, worldwide, have a much higher uranium (U) content than other sedimentary rocks. The average U in phosphorite is 120 ppm compared with 3.5, 0.5 and 2.2 ppm in shale, sandstone and limestone respectively; an enrichment factor of about 30 relative to shale. Certain phosphorite beds in Jordan have as much as 240 ppm U (Abed and Sadaqah, 2013). Uranium can be extracted from some phosphorites as a byproduct during fertilizer production, which adds to their economic importance. Most of the Middle East phosphate production is exported; for example, Jordan exports about 80% of its mined production. Locally, there is production of phosphoric acid and fertilizers such as diammonium phosphate (DAP), monoammonium phosphate (MAP) and triple superphosphate (TSP), depending on the country. The price of the high-grade concentrates (> 70% tricalcium phosphate (TCP)) was fairly constant for many years at between US$40–50/tonne until 2007. A very sharp increase then occurred and the price increased to US$500/tonne. At this time Jordanian concentrates with 70–74% TCP sold for about US$350/tonne whereas those of North Africa reached US$500/tonne. Prices have since declined and are now at about US$100/tonne (Van Kauwenbergh, 2010; Jasinski, 2011). GEOLOGICAL SETTING AND GLOBAL DISTRIBUTION The major Tethyan phosphorites were laid down during the Late Cretaceous to Eocene. During this relatively short time interval the closure of the Neo-Tethys Ocean took place as the Afro-Arabian and Eurasian plates converged (Robertson and Dixon, 1984; Beydoun, 1991; Brew et al., 2001; Sharland et al., 2001; Haq and Al-Qahtani, 2005). These tectonic activities were responsible for setting the scene for the formation of the major phosphorite deposits in the eastern Mediterranean region and throughout the Tethys realm (see Belayouni and Beja-Sassi, 1987; Sheldon, 1988; Abed, 1989; Al-Bassam, 1990). Phosphorites are poorly represented throughout geological history compared to other sedimentary rocks such as limestones, dolomites, sandstones, shales and evaporites. They are restricted in their distribution in space and time and also they show a distinct episodicity (Sheldon, 1981; Riggs, 1986; Balson, 1990). During phosphogenic episodes, phosphorite deposits were distributed on a global scale, whereas in non-phosphogenic periods only minor, local deposits were laid down. Four major depositional episodes are known (Figures 2a, b): 25 a 80 20 ) s Eocene- Cretaceous 60 - 15 40 10 Proterozoic Cambrian Miocene- Holocene Number of deposit c Phosphorite (billion tonnes 20 c 5 iassi Ordovician Permian Tr Devonian Jurassi Carboniferous Silurian 0 0 Period 0 100200 300 400500 Age (Ma) Figure 2: Episodicity of phosphorite deposition.