Organic-rich Albian deposits as the origin of hydrocarbon-contaminated phosphates, southeastern Constantine Basin, Algeria

International audienceThe southeastern Constantine Basin, from its phosphatic layers (Djebel Onk, Bled El Hadba, Negrine) and its hydrocarbon resources, constitutes a promising area for mining and oil research of northern Algeria. The presence of organic matter (OM), micro-organisms and phosphate particles in the Upper Albian deposits would correspond to layers of source rock for hydrocarbons. The facies characterizing this stage correspond to marine deposits of which OM related to the formation of these hydrocarbons in a relatively reducing environment. Such layers, with TOC rates varying from 0.50% to 11.53%, seem comparable to Paleocene-Eocene phosphatic layers, and thus economically exploitable with an average content of P2O5 of 16%. A stratigraphic, structural and paleogeographic overview are based on geochemical and petrographic data. Such data were analyzed and indicate that Albian layers are at the origin of a phosphate layer with organic support, e.g. radiolarians and diatoms, covered by a sedimentation inducing hydrocarbon production. They are found at subsurface among the Upper Cretaceous sedimentary pile, as it can be mentioned in several oil exploration wells. This is related to their lower location compared to the northern part of the basin where the Upper Cretaceous formations are eroded, suggesting maturation temperatures much higher southwards, and thus corroborating the link with burial sedimentary levels

LES SEDIMENTS ALBIENS DU SUD-EST CONSTANTINOIS: SOURCES DE NIVEAUX A GAZ ET A PHOSPHATE POTENTIELS

International audienceLes sédiments albiens du bassin sud-est constantinois ont vu une période géologique de grandesplateformes péricontinentales envahies par des mers peu profondes plus ou moins fermées, favorables àl’accumulation de la matière organique (MO). La répartition dans l’espace de ces niveaux albiens à l’échellestratigraphique du bassin est très large, ayant des structures et des épaisseurs importantes riches en MO eten phosphate (P2O5). Ces sédiments argilo-sableux albiens présentent un taux en carbone organique total(TOC) assez élevé [0.50%-11.53%] et une concentration moyenne en P2O5 de 16%.Les ressources de ces réservoirs en hydrocarbures et en phosphates emmagasinées dans ces niveaux sontéconomiquement exploitables. La récupération des phosphates et des hydrocarbures pourrait être assuréerespectivement par méthodes conventionnelle d’enrichissement et non conventionnelle (biolixiviation)pour une meilleure valorisation. Cette dernière méthode est sensiblement peu polluante et peu coûteuse.A plus forte raison, ces sédiments sont de bons candidats pour la production de phosphate et de gaz deschistes. Néanmoins, l’exploitation des ressources non conventionnelles présente un risque decontamination des nappes phréatiques superficielles, en raison de possibles erreurs techniques lors de leurexploitation, ce qui leur incombe une mauvaise réputation

LES SEDIMENTS ALBIENS DU SUD-EST CONSTANTINOIS: SOURCES DE NIVEAUX A GAZ ET A PHOSPHATE POTENTIELS

International audienceLes sédiments albiens du bassin sud-est constantinois ont vu une période géologique de grandesplateformes péricontinentales envahies par des mers peu profondes plus ou moins fermées, favorables àl’accumulation de la matière organique (MO). La répartition dans l’espace de ces niveaux albiens à l’échellestratigraphique du bassin est très large, ayant des structures et des épaisseurs importantes riches en MO eten phosphate (P2O5). Ces sédiments argilo-sableux albiens présentent un taux en carbone organique total(TOC) assez élevé [0.50%-11.53%] et une concentration moyenne en P2O5 de 16%.Les ressources de ces réservoirs en hydrocarbures et en phosphates emmagasinées dans ces niveaux sontéconomiquement exploitables. La récupération des phosphates et des hydrocarbures pourrait être assuréerespectivement par méthodes conventionnelle d’enrichissement et non conventionnelle (biolixiviation)pour une meilleure valorisation. Cette dernière méthode est sensiblement peu polluante et peu coûteuse.A plus forte raison, ces sédiments sont de bons candidats pour la production de phosphate et de gaz deschistes. Néanmoins, l’exploitation des ressources non conventionnelles présente un risque decontamination des nappes phréatiques superficielles, en raison de possibles erreurs techniques lors de leurexploitation, ce qui leur incombe une mauvaise réputation

A DFT investigation of some (formally) redox isomerization reactions of bis(pentalenyl)iron and bis(azulenyl)iron

International audienc

Haptotropic shifts in mononuclear complexes of substituted pentalenes: A DFT investigation of the [CpFe(C8H4R2)]q (R = H, Me, NH2, CF3, CN ; q = −1, 0, +1) series

International audienceThe haptotropic migration of Fe from the unsubstituted ring to the substituted one in the pentalenic complexes [CpFe(η5-1,3 C8H4R2)]q (q = +1, 0, −1) has been investigated by the means of DFT calculations in the case of R = H, CH3, NH2, CF3 and CN. The low energy pathway is a least-motion one-step process in the cationic case. In the anionic series, it is a two-step process involving an intermediate in which the metal moiety is η3-bonded in an exocyclic way to the pentalene ligand. The activation barriers and the preference for the Fe coordination on one ring rather on the other one is investigated with respect to the donor or acceptor abilities of R. The effect of changing q on the haptotropic situation is analyzed in terms of redox molecular switching

Extraction of uranium from an unconventional deposit by the radiometric emission method: Application to the phosphate deposit of Dj. Onk, eastern Algeria

International audienceUranium is an element that exists in the phosphate deposits of Dj. Onk. It turns out that this radioactive element replaces the calcium (Ca2+) cations in the apatite network of the phosphated material, as it can precipitate directly because of the reducing nature of the phosphate medium. The determination of uranium in phosphates allowed to demonstrate its presence with an average content of 48 ppm. Its existence in phosphates may cause an environmental problem, following the formation of phosphogypsum heaps from the industrial production of fertilizers. Radioactivity, which is a physical property appropriate to this unstable chemical element, and its characteristics can be used to recover it by optimal selection: radiometric separation. This method is based on the emission of radiation using the natural radioactivity of a chemical element. It is ecologically clean with secondary production of uranium from a phosphate deposit that can exceed 25,000 tons

On the structure and fluxionality of mononuclear complexes of naphthalene: A DFT investigation of (naphthalene)MCp (M = Sc, V, Mn, Fe, Ni) and related complexes

International audienceThe coordination modes of naphthalene to a MCp metal moiety has been investigated in the series of first-row transition metals. Depending on the electron-richness of M, the coordination modes of naphthalene in the ground state configuration can be η2, η4 or η6. The η3 or η10 coordination mode are also possible in high-energy minima which are predicted to be reaction intermediates in haptotropic migration mechanisms interconverting degenerate ground state structures. Except for the M = Sc case, all the inter-ring haptotropic exchanges occur through a transition state or intermediate in which the metal moiety is bonded in an exocyclic way to the naphthalene ligand

Extraction of uranium from an unconventional deposit by the radiometric emission method: Application to the phosphate deposit of Dj. Onk, eastern Algeria

International audienceUranium is an element that exists in the phosphate deposits of Dj. Onk. It turns out that this radioactive element replaces the calcium (Ca2+) cations in the apatite network of the phosphated material, as it can precipitate directly because of the reducing nature of the phosphate medium. The determination of uranium in phosphates allowed to demonstrate its presence with an average content of 48 ppm. Its existence in phosphates may cause an environmental problem, following the formation of phosphogypsum heaps from the industrial production of fertilizers. Radioactivity, which is a physical property appropriate to this unstable chemical element, and its characteristics can be used to recover it by optimal selection: radiometric separation. This method is based on the emission of radiation using the natural radioactivity of a chemical element. It is ecologically clean with secondary production of uranium from a phosphate deposit that can exceed 25,000 tons

Extraction of uranium from an unconventional deposit by the radiometric emission method: Application to the phosphate deposit of Dj. Onk, eastern Algeria

International audienceUranium is an element that exists in the phosphate deposits of Dj. Onk. It turns out that this radioactive element replaces the calcium (Ca2+) cations in the apatite network of the phosphated material, as it can precipitate directly because of the reducing nature of the phosphate medium. The determination of uranium in phosphates allowed to demonstrate its presence with an average content of 48 ppm. Its existence in phosphates may cause an environmental problem, following the formation of phosphogypsum heaps from the industrial production of fertilizers. Radioactivity, which is a physical property appropriate to this unstable chemical element, and its characteristics can be used to recover it by optimal selection: radiometric separation. This method is based on the emission of radiation using the natural radioactivity of a chemical element. It is ecologically clean with secondary production of uranium from a phosphate deposit that can exceed 25,000 tons

Purification of phosphate Mineral of South-Eastern Constantine deposit (Algeria)

International audienc