Review of uranium in the Jordanian phosphorites : distribution, genesis and industry

Abstract EN

Phosphorites are well-known, worldwide, to accommodate a substantial amount of U relative to other sedimentary rocks. This is due to a great extent to the crystal structure of apatite (carbonate flour apatite, francolite) where U substitutes Ca. Phosphorites form in shallow marine environments through the accumulation of planktonic fossils debris on the sea floor in areas characterized by upwelling currents.

Once the organic-rich sediments are buried below the sea floor and the organic matter is decomposed, PO4 is released to the interstitial solutions.

These PO4-rich solutions either precipitate phosphorites directly (authigenic) or the solutions react with pre existing sediments and transform them to phosphorites (early diagenentic).

The Jordanian deposits are dominantly of the former type.

Consequently, phosphorites are also well known to be associated with high percentage of organic matter which makes them a good source rock for petroleum. In Jordan, phosphorites are wide spread from its extreme NW to the SE.

Uranium contents are not the same in each locality. It is not also the same in each bed in the same locality.

In Al-Kora Basin, NW Jordan, U ranges between 60-379 ppm (parts per million or g / ton) with an average of 153 ppm.

In Ruseifa, just east of Amman, the range is 132-195 ppm and average of 123 ppm.

Central Jordan phosphorites (Al-Abiad and Al-Hasa) have a lower U %.

The range is 34-190 ppm with an average of 105 ppm.

Eshidiyya Basin has a much less U concentration.

The range is 7-125 ppm with an average of 70 ppm.

However, a recent work on the uppermost phosphorite horizon, the A0, in Eshidiyya Basin proved the presence of a 3 m thick bed with 242 ppm U.

Furthermore, certain phosphorite horizons are known to have much more than the average U in that locality ; e.

g.

in Al-Kora Basin, the average U is 153 ppm while certain horizons have up to 379 ppm U, the uppermost bed in Ruseifa has up to 195 ppm while the average is 123 ppm, and in Eshidiyya the A0 has 242 ppm while the average of the lower horizon (A1-3) average is 70 ppm.

Obviously, if the U is to be extracted from the phosphorite, the horizons with higher concentrations of U should be explored and used. Uranium sticks to francolite in its behavior from precipitation in the marine environment, through mining and beneficiation, and the fertilizer industry.

1) There is a significant high correlation coefficient between CaO and P2O5 in the hundreds of samples analyzed.

2) Fines (clays) produced when washing the ore have very little U and consequently, washing water for the last 45 years has not contaminated groundwater with U in central Jordan.

3) Uranium is concentrated in the phosphoric acid then into diammonium phosphate (DAP) in the fertilizer industry and not in the phosphogypsum.