Enrichment of uranium in the uppermost Al-Hisa Phosphorite Formation, Eshidiyya basin, southern Jordan

The Al-Hisa Phosphorite Formation (AHP) in the Eshidiyya basin of south Jordan consists of three members, the lower member accommodates the main high grade commercial phosphorite deposits, followed upwards by the coquinoidal limestone member which is overlain by the uppermost member, the A0 member. The phosphorites in both member are granular (peloidal) type deposits. Uranium (U) and Vanadium (V), in the main phosphorites of the lower member, are 75 and 70 ppm respectively as analyzed in a previous work.The distribution of the analyzed elements in this work is governed by three factors: the phosphorite (P, Ca, Na, U, V, Cd, Zn, and Sr) decreasing upwards from the lower A0 unit to the topsoil, detritals (Al, Si, Fe, Mg, K, Ga, Hf, Nb, Rb, Th, and Zr) increasing upwards, and minor carbonates (Ca, and Sr) with no obvious trend. Uranium is three times more enriched in the upper phosphorite member, the A0, relative to the lower or main phosphorite member, 234 ppm versus 75 ppm respectively. Vanadium is likewise enriched several times in the A0. Both elements, U and V are worth further exploration in the A0 in northern Eshidiyya basin. Thorium, Zr and Hf are relatively low.

► Analysis of 70 samples of the upper member (A0), Al-Hisa Phosphorite Formation, Eshidiyya basin.
► Uranium is associated with phosphorite phase replacing Ca in francolite structure.
► Uranium is enriched up to 3 times in the lowermost A0 compared with the lower member.
► Enrichment is possibly due different factors including, mild leaching at the unconformity.
► It could also be due to a reducing environment within karst pockets at the unconformity.