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Awaleh M.O.,Center Detudes Et Of Recherches Of Djibouti Cerd | Hoch F.B.,Center Detudes Et Of Recherches Of Djibouti Cerd | Boschetti T.,University of Parma | Soubaneh Y.D.,University of Quebec at Rimouski | And 4 more authors.
Journal of Geochemical Exploration | Year: 2015

The Lake Abhe Geothermal Field is located in the South-Western region of the Republic of Djibouti, on the border with Ethiopia. The Lake Abhe geothermal system occurs within a rift basin filled with Pliocene-Quaternary volcanic (mainly basalt) and lacustrine sediments. The thermal water in Lake Abhe geothermal field discharges as hot springs at the bottom of hydrothermal carbonate chimneys distributed along the main faults.Hot springs of Lake Abhe geothermal field as well as ground- and surface waters were sampled and major elements, trace elements, and isotopic (18O/16O, 2H/1H, 3H, 34S/32S, 87Sr/86Sr) compositions were analyzed. Hydrochemical features of the hot springs are dissimilar from those of warm waters: the former are mainly Na-Cl dominated whereas the latter were mostly Na-HCO3-Cl-SO4 and Na-HCO3-Cl. The isotopic composition of sulfur and oxygen in dissolved sulfates suggests equilibrium with anhydrite as the major source of sulfates in the thermal waters.Chemical (mainly Na/K and SiO2), isotope (bisulfate- and anhydrite- water), and multiple mineral equilibrium approaches were applied to estimate the reservoir temperature of the hot springs in the Lake Abhe geothermal field. These different geothermometric approaches estimated a temperature range of the deep geothermal reservoir of 120-160°C. In spite of the relatively wide range, the three different approaches led to a same mean of about 135°C. The hot spring and warm borehole waters from the southwestern part of the Republic of Djibouti showed a possible mixing with hydrothermal waters from the local rift. The negligible tritium content and the low deuterium values (δ2H<-10‰) suggest a deeper circulation and an old age for geothermal water, in comparison with surface waters and the local aquifers recharged by modern precipitations (δ2H>-10‰). © 2015 Elsevier B.V.


Awaleh M.O.,Center Detudes Et Of Recherches Of Djibouti Cerd | Hoch F.B.,Center Detudes Et Of Recherches Of Djibouti Cerd | Kadieh I.H.,Laboratoire Regional | Soubaneh Y.D.,University of Quebec at Rimouski | And 3 more authors.
Journal of Geochemical Exploration | Year: 2015

This paper examines the hydrochemical features of the waters from the Obock coastal geothermal field. As the submarine waters at the ridge, their chemical and isotope composition shows affinities with sea water-basalt interactions at hydrothermal temperature. Moreover, good linear correlations were obtained between hot springs and of sea water sample points when plotting normalized concentrations of elements to chloride (Mg/Cl, SO4/Cl, K/Cl, Ca/Cl, SiO2/Cl) versus concentration of Li/Cl. This would indicate that two end members exist (seawater and reservoir fluid). After extrapolation of the Mg and SO4 concentrations to zero, the obtained value of SiO2 corresponding to the reservoir fluid end member was used to estimate the reservoir temperature by quartz geothermometers. The obtained temperature of 187°C is in good agreement with that obtained from multiple mineral equilibrium approach (180-200°C), cationic geothermometers (172-191°C) and by the evaluation of isotopic equilibrium between water and sulfate molecule (207°C). Summarizing all the employed approaches, a mean temperature of 197±10°C has been estimated.The isotopic δ34S(SO4) signature of the dissolved sulfates in Obock thermal waters confirms that these waters result from the mixture of a hot seawater-derived fluid (absence of sulfates) with cold seawater. However, water isotope data did not exclude the presence of a small contribution from fresh groundwater. © 2015 Elsevier B.V.


Awaleh M.O.,CNRS Institute of Earth Sciences | Awaleh M.O.,Center Detudes Et Of Recherches Of Djibouti Cerd | Hoch F.B.,CNRS Institute of Earth Sciences | Hoch F.B.,Center Detudes Et Of Recherches Of Djibouti Cerd | Farah I.G.,CNRS Institute of Earth Sciences
Journal of Chemical Crystallography | Year: 2013

The bis(methylthio)methane building block was combined with AgX salt where X are weakly or noncoordinating counteranions (X = CF3SO3 - (1), PF6 - (2), SbF6 - (3) and BF4 - (4)) in order to form cationic metal-organic frameworks where the anions only counterbalance the charge of the networks. The crystallographic data of those complexes are: (1) Monoclinic C2; a = 17.3226(2) Å; b = 9.2820(1) Å; c = 29.726(3) Å; β = 93.726(1); V = 4787.59(9) Å3; Z = 4. (2) Monoclinic C2/c; a = 8.2468(4) Å; b = 19.101(1) Å; c = 10.1381(5) Å; β = 107.065(2); V = 1526.7(1) Å3; Z = 4. (3) Monoclinic C2/c; a = 13.2985(4) Å; b = 16.1208(4) Å; c = 8.9804(3) Å; β = 95.883(2); V = 1915.1(1) Å3; Z = 4. (4) Monoclinic C2/c; a = 16.7916(9) Å; b = 9.1090(4) Å; c = 22.670(1) Å; β = 99.676(4); V = 3418.2(3) Å3; Z = 4. The coordination polymer 1 forms channel-like 3D-cationic framework in which the trifluoromethanesulfonate anions are located. The octahedral counteranions, PF6 - (2) and SbF6 - (3), allow the formation of similar cationic cross-linked one-dimensional coordination polymers. Coordination polymers 2 and 3 have hexagonal packing. The tetrahedral counteranion BF4 - (4) gives rise to cationic layer-like coordination network where the tetrafluoroborate anions are inserted between those sheets. Graphical Abstract: Four new silver(I) - coordination polymers have been obtained from the combination of bis(methylthio)methane building block and AgX salt where X are weakly or noncoordinating counteranions (X = CF3SO3 - (1), PF6 - (2), SbF6 - (3) and BF4 - (4)). Those metallosupramolecular compounds have been characterized by elemental analysis, NMR spectroscopy, IR spectroscopy and X-ray crystallography.[Figure not available: see fulltext.] © 2013 Springer Science+Business Media New York.

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