Geological and Hydrogeological Conditions for Forming Uranium Occurrences in the Froqlos–Jabal Abou Rabah Region, Palmyrides, Syria

This paper focuses on determining the favorable geological and hydrogeological conditions for forming uranium occurrences in the Froqlos–Jabal Abou Rabah region, Palmyrides, Syria. Eighty rock samples from this area were analyzed by spectrometric gamma-ray technique to determine the radioactive concentrations of eU and eTh, and of %K. Uranium concentrations in shallow and deep groundwaters were also determined. High uranium concentrations were registered owing to the presence of phosphatic outcrops in the study region. The uranium migration trends and its remobilization were analyzed through the analysis of the behavior of eU, eTh, and their ratio. A positive relationship between eU and eU/eTh, and a negative relationship between eTh and eU/eTh in geological formations of different ages supports the secondary remobilization of uranium. The role of groundwater movement in transportation and redeposition of uranium mineralization is discussed: deep waters are less oxidizing than near-surface waters, and do not appear to have significantly remobilized uranium. This indicates that the source of secondary uranium mineralization is surficial or near surficial, and is mainly related to the leaching of outcropping phosphatic layers. Integration of the results with established radioactive and geological sections reveals four radioactive anomalous zones: north Froqlos, Kherbet Hannora, northwestern flanks of Jabal Abou Rabah (Kherbet Al-Hajar), and the northwestern limit of the Ghuntor depression. The high uranium concentration in north Froqlos is because of its original presence in the phosphate beds and extensive fracturing, which allows groundwaters to penetrate and remobilize the uranium. High uranium concentrations in the other three locations are caused by the presence of evaporites and capillary action, which draws solutions upwards and causes redeposition as surface crusts (gypcrete). © 2010 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved. Sommaire Le present article traite de l’evaluation de conditions geologiques et hydrologiques propices a la formation de mineralisations uraniferes dans la region de Froqlos–Jabal Abou Rabah, dans les Palmy-rides, en Syrie. Quatre vingt echantillons de roche provenant de cette region ont ete analyses par la methode de la spectrometrie aux rayons gamma afin de mesurer les valeurs en equivalents d’elements radioactifs eU, eTh et %K. Les concentrations en uranium dans des eaux souterraines superficielles et profondes ont egalement ete mesurees. Des concentrations fortes en uranium ont ete notees dans la region a l’etude; ces dernieres sont expliquees par la presence d’affleurements de roches phosphatees. Le comportement migratoire de l’uranium et sa remobilisation ont ete etudies par l’analyse de la variation d’eU, eTh et leur ratio. Une relation positive entre eU et eU/eTh et une relation negative entre eThe et eU/eTh dans les formations geologiques d’âges varies favorise la remobilisation de l’uranium. Le role de la circulation de l’eau souterraine dans le transport et la re-deposition de l’uranium est discute : les eaux profondes sont moins oxydantes que les eaux plus superficielles et ne semblent pas avoir remobilise significativement l’uranium. Ceci indique que la source de la mineralisation en uranium secondaire est a la surface ou a faible profondeur, et qu’elle est principalement associee au lessivage des affleurements de roches phosphatees. L’integration de nos resultats avec ceux en provenance de sections geologiques et radiometriques bien connues fait ressortir quatres zones radioactives anomales: Froqlos nord, Kherbet, Hannora, les flancs nord-ouest du Jabal Abou Rabah (Kherbet Al-Hajar), et la bordure nord-ouest de la depression de Ghuntor. Les fortes concentrations en uranium a Froqlos nord resultent de sa presence initiale dans les horizons phosphates, et de la fracturation considerable qui permet a la penetration des eaux souterraines de remobiliser l’uranium. Les fortes concentrations en uranium des trois autres localites resultent de la presence d’evaporites et a l’action capillaire, qui permet le mouvement des solutions vers la surface et cause leur re-deposition sous forme de croutes superficielles (gypcrete). © 2010 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.