Central Jordon Uranium Project, CJUP, Hasa Qatrana
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The Central Jordan Uranium Project (CJUP) deposits are located in central Jordon and are distributed over an area of ~40 x 25 km, over 100 km south of Amman and 60 km east of the Israeli border. Uranium also occurs in association with Late Cretaceous phosphorite units at Hasa-Qatrana, immediately to the west over a similar area.
The geology of Jordan is dominated by a post Neoproterozoic platformal environment, and by the Red Sea-Dead Sea rift from the early Miocene to the present.
All of these rocks overlie basement of the Arabian-Nubian Shield, which is exposed on the both sides of the Red Sea, within NE Africa and the Arabian Peninsula.
The geology of Jordan may be summarised as follows:
Proterozoic basement - In Jordan, this basement is only exposed in a small area in the SW of the country. It comprises two main sequences, the lower Aqaba Complex comprising a variably metamorphosed (from 800 to 750 Ma) suite of amphibolite and sillimanite, cordierite, garnet schists and gneisses, intruded by the 640 to 610 Ma Duheila Hornblendic suite and a 625 to 600 Ma suite of calc-alkaline granitoids, a unimodal suite of convergent margin magmas related to closure of the East African Orogen and collision between East and West Gondwanaland. This is overlain by the Araba Complex, separated by a regional unconformity marked by a conglomerate dated at 600 Ma. The Araba Complex is characterised by a 600 to 545 Ma bimodal alkali-calcic to alkali igneous suite related to a post collisional rift suite of granitoids and mafic rocks (Jarrar, Stern, Saffarini and Al-Zubi, 2003).
Lower to Middle Palaeozoic - The basement suite is unconformably overlain by Early Palaeozoic arkosic sandstones, subdivided into the Cambro-Ordovician Ram and Ordovician to Silurian Khrayim groups. The base of this sequence is composed of pebbly arkosic sandstones of the Salib Arkosic Sandstone formation, overlain by dolostone, dolomitic sandstones and shales, of the Burj Dolomite formation, that, in turn, grades upward into a succession of sandstones containing lenses of quartz-pebble conglomerates. Sedimentation ceased during the Silurian
Late Palaeozoic to Mesozoic - Following a hiatus, deposition resumed in the Permian with the the Umm Irna sandstones, the lowest unit of the Permo-Triassic Ramtha Group, which is predominantly composed of sandstones, with an intercalated limestone unit.
The Ramtha Group sandstones grade upward into the Jurassic Azab Group that is also composed of sandstones intercalated with limestones.
These are unconformably overlain by coarse grained clastic sediments of the Lower Cretaceous Kurnub Group, including coarse-grained, poorly sorted and pebbly sandstones, fluvial quartz-arenite sediments and intercalated subordinate thin alluvial mudstone beds. This sequence varies from 50 m in the east of Jordan, to 350 m in the West, reaching a maximum of 600 m to the West of Dead Sea.
The succeeding Upper Cretaceous Ajlun Group is composed of shallow marine platform carbonate (limestone) rocks, intercalated with marine and fluvial siliciclastic rocks in the south and east of Jordan (Powell and Moh'd 2011), with a thickness ranging from zero in the SE to ~800m in the north (Andrews 1992).
Late Cretaceous to Cainozoic - The Late Cretaceous-Eocene Belqa Group, which disconformably overlays the Ajlun Group sedimentary rocks, and occupies the greater part of the Jordan plateau, is dominated by chalk, chert and phosphorite. The regional scale disconformity at the base of the Belqa Group indicates a rapid change to a pelagic or hemi-pelagic ramp setting depositional environment (Burchette and Wright 1992; Powell and Moh'd 2011). In central Jordan, the Belqa group is subdivided into six formations that in stratigraphic order are the:
• Wadi Umm Ghudran formation - cherts and marls.
• Amman Silicified Limestone formation - silicified limestone, which in the northern part of Jordan is not differentiated from the overlying Al Hisa Phosphorite.
• Al Hisa Phosphorite formation: phosphorite, limestone and chert, subdivided into:
- Sultani Phosphorite unit - limestone, light grey cherts and phosphorite.
- Bahiya Coquina unit - Coquina limestone.
- Qatrana Phosphorite units - marl, chalky limestone, blocks chert and phosphorite.
• Muwaqqar Chalk Marl formation - chalks, chalky limestone and marl, intercalated with layers of black oil shale (most commonly in the lower 40% of the section, with limestone concretions towards the top of the formation.
• Umm Rijam Chert formation - limestone intercalated with varicoloured chert, and containing marble lenses. Limestone concretions are abundant at the bottom of the formation.
Metamorphic marbles are distributed in the upper part of the Muwaqqar Chalk Marl formation and the lower part of the overlaying Umm Rijam Chert formation. These marbles occur as hills, and locally coalesce to form continuous ridges, hosted across sharp contacts by unmetamorphosed marls, chalks and limestones. The marbles are vari-coloured, commonly brown, greenish, reddish, white and locally black, and primarily consist of calcite and apatite. They are cut by hydrothermal veins and have experienced varying degrees of low temperature alteration. In addition there are zones of high- and ultra-high temperature (up to 1500°C) low-pressure metamorphic mineral assemblages, including spurrite, wollastonite, ellastadite, diopside and garnet (Khoury et al., 2014) and ~200 mineral species, many of them unique. The formation of these marbles is commonly explained by pyrometamorphism, either caused by the burning of bituminous marls (Khoury et al., 2014) or alternatively by the combustion of deep reservoirs of hydrocarbon gases released via mud volcanoes (Sokol, Novikov, Vapnik and Sharygin 2007, 2010; Novikov et al., 2013; Vapnik and Novikov 2013). Dating of these rocks has identified several episodes of combustion metamorphism during the Miocene (~16Ma), Pliocene (~3Ma) and Pleistocene (1.7-1.0 Ma) (Burg, Starinsky, Bartov and Kolodny 1992; Gur et al., 1995), broadly coinciding with mafic magmatism during the Miocene (23.8 to 21.1 and 12.05-8.08 Ma) and Pleistocene (3.2-1.5 Ma; Steinitz and Bartov 1991; Ibrahim et al., 2003), suggesting the magmatism could have triggered the rapid combustion of hydrocarbons, or at least that these processes are part of the same tectono-magmatic event.
• Wadi Shallala Chalk formation - chalk and claystone
Neogene to Quaternary Basaltic Magmatism - The platform sequence is terminated by basalts and horizons of travertine that cover large areas of the north-eastern part of Jordan, although basalts are rare in central Jordan where they only occur as small subvolcanic intrusions and vents. The latest basalt eruptions occurred in the Pleistocene and are the same age as travertine horizons in central Jordan (Steinitz and Bartov 1991; Ibrahim et al., 2003; Razvalyaev et al., 2005). Large parts of the region underwent major Neogene-Quaternary tectono-magmatic activation, related to the Early Miocene (Ibrahim et al., 2003) Red Sea-Dead Sea rifting episode, separating the Arabian and African plates. Neogene and Quaternary igneous rocks in Jordan are represented by basalts and comagmatic dykes, sills and shallow subvolcanic intrusions (Steinitz and Bartov 1991; Ibrahim et al., 2003). These igneous rocks are predominantly located in the Harrat Ash Shaam Volcanic Field in NE Jordan. Smaller basalt fields are also known along the Dead Sea and in central Jordan, while Barjous (1986) suggests there is a large magmatic crypto-volcanic dome in the Siwaqa area of central Jordan. Three main episodes of basaltic magmatism, have been dated in Jordan (Steinitz and Bartov 1991; Ibrahim et al., 2003), namely:
• 23.8 to 21.1 Ma, which are tholeiitic and basaltic (Ibrahim et al., 2003)
• 12.05 to 8.08 Ma, sodic alkaline olivine basalts (Ibrahim et al., 2003) and
• 3.2 to 1.5 Ma, also sodic alkaline olivine basalts.
Recent paralava dykes have been found cutting marbles, and are spatially associated with pyrometamorphic marbles. They are interpreted to be the result of rocks melting during high-temperature combustion metamorphism, unrelated to the basaltic volcanism in the region (Vapnik et al., 2007).
The principal regional structure in Jordan is the north-south to NNE trending, 360 km long Wadi Araba-Dead Sea Transform fault, which extends from east Africa, across the Red Sea, Gulf of Aqaba and the Dead Sea to southern Turkey. It is accompanied by a series of splays forming east-west and NW-SE striking faults. In central Jordan, the most important faults are the east-west trending Siwaqa and Zarqa Ma'in faults. The Siwaqa strike-slip fault extends for >100 km eastward from the Dead Sea, and is overlain by the 6.0±1.2 Ma Jebel Shihan basalt (Barberi et al., 1979). It has a down throw, mainly towards the south of 50 to 200 m. The Zarqa Ma'in fault, also extends for about 100 km from the Dead Sea, toward the Saudi border in the East, and intersects the Siwaqa Fault. These structures are accompanied by drag folds in their wall rocks. These structures may be involved in distribution of uranium mineralisation in central Jordan, particularly at Khan Azabib, where higher grades and associated gamma anomalies are broadly coincident with these regional faults.
The known uranium mineralisation in Jordan is largely hosted by Upper Cretaceous to Tertiary sediments of the Arabian plate, occurring as two main mineralisation types, namely:
• Surficial mineralisation - characterised by uranium enrichment in weathered rocks exposed at the surface, where although the host rocks are calcareous, there is no evidence of calcrete formation. At the Central Jordan Uranium Project (CJUP) deposit, this mineralisation is mainly concentrated in a thin, ~4.5 m thick layer, the 'Surficial' layer, that is distributed close to the topographic surface and is independent of phosphorite beds. The principal uranium minerals are uranium vanadates, referred as carnotite group minerals. The average uranium grade decreases rapidly below 4 to 5 m, although mineralisation continues to depths of 30 to 40 m, where it is known as the 'Deep' mineralisation.
• Phosphorate-hosted mineralisation includes stratabound accumulations formed by the enrichment of uranium in phosphorites during sedimentation and diagenesis (Dahlkamp 1993), most commonly occurring in the central and southern parts of Jordan, where it is associated with phosphorite beds within the Upper Cretaceous Al Hisa Phosphorite formation. Mineralisation has been modified by weathering of the uraniferous phosphorites, resulting in liberation of uranium from apatite and its transport by supergene processes and reprecipitation as carnotite. The phosphorites of the Belqa Group sedimentary rocks were derived from sea water, either directly by chemical precipitation, or indirectly through biogenic activity (Fleurance et al., 2012), and are related to the great phosphorite deposition event that occurred along the southern margin of the Tethys Ocean during this period.
• Uranium mineralisation also occurs in hydrothermal veins cross-cutting Cambrian rocks exposed along the plate margin within the Dead Sea rift valley (Rabba 2004). However, this type of uranium mineralisation is rare in Jordan, and so far has only been found in the Dana area.
Uranium mineralisation is hosted within the upper sections of the shallowly dipping Muwaqqar Chalk Marl formation, just below its upper contact with the Umm Rijam Chert formation, and occurs within two layers. The best grades are localised within a long narrow layer zone corresponding to the exposed width and strike extent of the upper Muwaqqar Chalk Marl formation, and extending from the surface to a depth of ~4.5 m over widths of up to 1 km or more. This is the 'Surficial' layer (Abzalov et al., 2014). Grades decrease sharply at the base of this high grade layer, although further uranium mineralisation is found as discontinuous lenses that are most abundant at shallow depths, usually from 5 to 30 m below surface, known as the 'Deep' mineralisation (Abzalov et al., 2014).
This layer is hosted by near-surface weathered chalks and marls of the Muwaqqar Chalk Marl formation, which weather to a mixture of powder and small fragments, obliterating the original rock texture, with no organic matter or iron staining, and could in part be transported by wind, water or down-slope creep, and is not necessarily all in situ. This upper zone is underlain by deeply weathered and broken chalky limestone and marl, locally termed saprolite, which varies from completely altered to moderately altered rocks, retaining some of the original rock structure and fabric, grading into bedrock at depth.
The highest grades of uranium occur along the contact between saprolite and mildly weathered to fresh bedrock, and is hosted in both saprolite and underlying weakly weathered Muwaqqar Chalk Marl formation rocks. High grade mineralisation is also commonly observed along contacts with the pyrometamorphic marbles. The mineralisation is mostly overlain by a narrow thickness of barren soil and/or alluvium, although it is locally exposed at the surface.
Uranium mineralisation is very irregularly distributed, occurring as fine-grained disseminations forming zones of variable size and shape, impregnating weakly lithified friable sediments and coating the surfaces of joints and fractures. The principal ore minerals are uranium vanadates, the most common of which are the strelkinite-tyuyamunite series [Na2(UO2)2V2O8•6(H2O)] - [Ca(UO2)2V2O8•3(H2O)] (Khoury et al., 2014). Carnotite [K2(UO2)2(V2O8)•1-3H2O], uraninite [UO2] and uranophane [Ca(UO2)2Si2O7•6H2O] have also been recorded but are much less abundant (Bender 1975; Abzalov 2009).
The uranium content of the mineralisation does not correlate with either vanadium or phosphorous. This implies that either uranium also occurs within minerals other than vanadates, or that there are also uranium-poor vanadium minerals present. It also demonstrates that the secondary uranium mineralisation is not controlled by primary phosphorite layers (Abzalov et al., 2015).
The principal gangue mineral assemblage includes calcite and clay (smectite/illite), with small but variable amounts of halite, apatite, fluorite, gypsum and an intermediate member of the barite-celestine solid solution series [(Ba,Sr)SO4].
Halite is erratically distributed, presumably precipitated from saline groundwater solutions, and typically, occurs locally as small cubic crystals or aggregates within the matrix of the host rock, intergrown with calcite and Mg-bearing clay minerals.
Apatite, which is a widely distributed accessory mineral, is typically found as very small hexagonal crystals, rarely exceeding 25 mm in size, and usually occurs in the matrix between calcite grains. It is locally more abundant and may form aggregates of closely packed crystals.
The Ba-Sr sulphate minerals are also sparingly disseminated throughout the host rocks as small, irregular patches and pockets, with variable Ba and Sr levels, although both are usually present in significant amounts, consistent with their presence as an intermediate member of the barite-celestine solid solution series.
Variable, but minor amounts of fluorite are usually present in the uranium mineralisation, occasionally intergrown with carnotite. It typically forms small aggregates that are inferred to have developed in former open pore spaces in the host rock. It is also locally present within thin coatings that are developed on the surfaces of open fractures or joints.
Cr-rich smectite (volkonskite) also occurs within the uranium mineralisation also contains, most commonly where hosted in hydrothermally altered marbles, although it is also present in unmetamorphosed rocks.
Mineralisation persists beneath the surficial layer, where it is hosted by unmetamorphosed chalks and marls of the Muwaqqar Chalk Marl formation. The mineralogy, texture and composition of this mineralisation is similar to that of the surficial layer, but has a lower average grade. However, high grade uranium mineralisation does occur locally beneath the 'Surficial' layer, with high grade lenses where uranium concentrations have reached 1204 ppm (Abzalov et al., 2014). These high grade lenses are usually <20 m long and are thin. The distribution of uranium within the areas of 'Deep' mineralisation does not correlate with phosphorite beds.
Formation of mineralisation
The surficial uranium mineralisation is spatially associated with a number of features, including the presence of marble units, local and regional faulting, and depressions in the landscape, with very little uranium mineralisation on the hills and ridges of Central Jordan. It is interpreted to have been formed from the liberation of uranium from its primary source (apatite?), and redistributed upward, towards the surface, by supergene processes,where uranium minerals were precipitated at the interface between saprolite and fresh to weakly weathered rocks (Abzalov et al., 2015).
The source of the uranium is apparently the Belqa group sedimentary rocks, most likely the apatite within limestones and phosphorates of the group (Abzalov et al., 2015). Metamorphic processes are suggested to have facilitated the liberation of uranium from apatite, as is suggested by the spatial association of high-grade surficial uranium mineralisation with pyrometamorphic marbles and the concentration of uranium mineralisation around these marble lenses in some instances. Abzalov et al., 2015) suggest that pyrometamorphism due to either the combustion of hydrocarbon gases released via mud volcanoes (Sokol et al., 2007, 2010; Novikov et al., 2013; Vapnik and Novikov 2013) or alternatively caused by the burning of organic rich sediments (Khoury et al., 2014) is the most likely process initiating the liberation of uranium that was subsequently deposited as surficial mineralisation. This broadly coincides with the onset of basaltic magmatism, suggesting that the latter may have triggered combustion metamorphism, producing pyrometamorphic marbles, the liberating uranium from apatite and concentrating redox sensitive elements. Hyperalkaline groundwater, possibly related to the basalts, also participated in the process, remobilising the redox sensitive elements and re-precipitating them into topographic and/or structurally favourable positions. Faults may also have acted as conduits controlling the distribution of remobilised uranium. In summary, the same authors conclude, the uranium deposits of Central Jordan resulted from the interplay of sedimentary, tectonic, and metamorphic events, with the final influence being climatic factors and chemical weathering processes (Abzalov et al., 2015).
Hasa-Qatrana comprises phosphorite hosted uranium mineralisation within the Late Cretaceous Al Hisa Phosphorite formation.
In central Jordan, the Al Hisa Phosphorite formation comprises three units, the Sultani and Qatrana phosphorite units, separated by the Bahiya Coquina unit limestones (Pufahl et al., 2003). The phosphorites of the same formation, which are mined for the production of fertiliser for agriculture in the central Jordan, also contain uranium minerals.
Radiometric surveys show gamma anomalies in central Jordan are commonly coincident with phosphorites of the Al Hisa Phosphorite formation. Uranium enrichment is a common feature of continental-shelf marine margin phosphorites, with syn-depositional uranium capture during precipitation and early diagenetic alteration of apatite grains (Dahlkamp 1993). The synsedimentary origin of the phosphorite-hosted uranium mineralisation creates stratiform ore bodies with uranium in these stratabound orebodies is usually restricted to phosphorite horizons. At the Hasa-Qatrana deposit, uranium mineralisation correlates with phosphorous suggesting both elements are contained in apatite, confirmed by mineralogical studies and SEM trace element analysis which shows that uranium is deported in apatite with an average of 586±110 ppm U from 150 apatite grains analysed (E. Ryan, unpublished data, quoted by Abzalov et al., 2015).
Acid leach tests have also shown that uranium is extracted together with phosphorous, which is in good agreement with the mineralogical studies (Abzalov 2009). Within intensely weathered phosphorites, uranium has been liberated from apatite and was redistributed as a supergene 'carnotite', occurring as yellow stains coating rock surfaces. In general, uranium mineralisation in weathered phosphorites is similar to the surficial mineralisation within the CJUP deposit. It comprises supergene 'carnotite', formed after uranium was liberated from the primary host minerals of the phosphorites and redeposited on rock surfaces or filling voids in porous rocks. Mineral resources of the Hasa–Qatrana prospect have not been estimated to international reporting standards (e.g. JORC 2012). An approximate estimation of exploration targets has been made by Jordanian geologists in 2012 using 441 exploration trenches (Abzalov et al., 2015).
Resource estimates are as follows (Abzalov et al., 2015):
Surficial mineralisation - 67.5 Mt @ 159 ppm U3O8 (10.7 kt U3O8).
Deep mineralisation (mixed surficial and phosphorite) - 201.7 Mt @ 127 ppm U3O8 (25.7 kt U3O8).
Hasa-Qatrana Prospect - 26 kt U3O8.
The details of this summary are derived and paraphrased from: "Abzalov, M.Z., van der Heyden, A., Saymeh, A. and Abuqudaira, M., 2015 - Geology and metallogeny of Jordanian uranium deposits; Transactions of the Institute of Materials, Minerals and Mining and The AusIMM, Section B, Applied Earth Science, v. 124, no. 2, pp. 63-77."
The most recent source geological information used to prepare this summary was dated: 2015.
This description is a summary from published sources, the chief of which are listed below.
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Abzalov, M.Z., van der Heyden, A., Saymeh, A. and Abuqudaira, M., 2015 - Geology and metallogeny of Jordanian uranium deposits: in Trans. IMM (incorp. AusIMM Proc.), Section B, Appl. Earth Sc. v. 124 pp. 63-77|
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