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Brook, G.A.; Railsback, L.B.; Marais, E. |
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Title |
Reassessment of carbonate ages by dating both carbonate and organic material from an Etosha Pan (Namibia) stromatolite: Evidence of humid phases during the last 20ka |
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2011 |
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Quaternary International |
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229 |
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1 |
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24-37 |
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Previous research on lacustrine stromatolites from Etosha Pan in Namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating. These ages suggested that the basin was likely not subject to extensive flooding during the last ca. 40ka. This study shows that AMS radiocarbon ages for the carbonate of a stromatolite from Poacher’s Point are 15–21ka older than ages for organic material in the stromatolite structure. Calibrated ages range from 30 to 40ka for carbonate and 3–19ka for the organic residue. The new ages, together with petrographic and isotopic data for the stromatolite, have provided important new information on past flooding of Etosha Pan including evidence of prolonged lacustrine conditions during the Holocene Climatic Optimum. |
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THL @ christoph.kuells @ brook_reassessment_2011 |
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110 |
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Ammar, F.H.; Deschamps, P.; Chkir, N.; Zouari, K.; Agoune, A.; Hamelin, B. |
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Title |
Uranium isotopes as tracers of groundwater evolution in the Complexe Terminal aquifer of southern Tunisia |
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Journal Article |
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2020 |
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Quaternary International |
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547 |
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33-49 |
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CT southern Tunisia, Holocene, Mixing, Radicarbon, Uranium isotopes, Water-rock interaction |
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The Complexe Terminal (CT) multi-layer aquifer is formed by Neogene/Paleogene sand deposits, Upper Senonian (Campanian-Maastrichtian limestones) and Turonian carbonates. The chemical composition and isotopes of carbon and uranium were investigated in groundwater sampled from the main hydrogeological units of the (CT) aquifer in southern Tunisia. We paid special attention to the variability of uranium contents and isotopes ratio (234U/238U) to provide a better understanding of the evolution of the groundwater system. Uranium concentrations range from 1.5 to 19.5 ppb, typical of oxic or mildly reducing conditions in groundwaters. The lowest concentrations are found southeast of the study area, where active recharge is supposed to take place. When looking at the isotope composition, it appears that all the samples, including those from carbonate levels, are in radioactive disequilibrium with significant 234U excess. A clear-cut distinction is observed between Turonian and Senonian carbonate aquifers on the one hand, with 234U/238U activity ratios between 1.1 and 1.8, and the sandy aquifer on the other hand, showing higher ratios from 1.8 to 3.2. The distribution of uranium in this complex aquifer system seems to be in agreement with the lithological variability and are ultimately a function of a number of physical and chemical factors including the uranium content of the hosting geological formation, water-rock interaction and mixing between waters having different isotopic signatures. Significant relationships also appear when comparing the uranium distribution with the major ions composition. It is noticeable that uranium is better correlated with sulfate, calcium and magnesium than with other major ions as chloride or bicarbonate. The 14C activities and δ13C values of DIC cover a wide range of values, from 1.1 pmc to 30.2 pmc and from −3.6‰ to −10.7‰, respectively. 14C model ages estimated by the Fontes and Garnier model are all younger than 22 Ka and indicate that the recharge of CT groundwater occurred mainly during the end of the last Glacial and throughout the Holocene. |
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THL @ christoph.kuells @ ammar_uranium_2020 |
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119 |
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Constantinou, C.; Udluft, P. |
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Mapping the availability and dynamics of groundwater recharge. Part 2: Case studies from Mediterranean Basins |
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2000 |
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Proceedings of Third Congress on Regional Geological Cartography and Information Systems |
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163-168 |
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THL @ christoph.kuells @ Constantinou2000mapping |
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61 |
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Udluft, P.; Külls, C. |
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Title |
Mapping the availability and dynamics of groundwater recharge. Part 1: modelling techniques |
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2000 |
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Proceedings of the Third Congress on Regional Geological Cartography and Information Systems |
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337-340 |
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THL @ christoph.kuells @ Udluft2000mapping |
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64 |
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Love, A.J.; Shand, P.; Karlstrom, K.; Crossey, L.; Rousseau-Gueutin, P.; Priestley, S.; Wholing, D.; Fulton, S.; Keppel, M. |
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Geochemistry and Travertine Dating Provide New Insights into the Hydrogeology of the Great Artesian Basin, South Australia |
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2013 |
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Procedia Earth and Planetary Science |
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7 |
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521-524 |
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GAB springs, Great Artesian Basin, Helium isotope data, Uranium series dating |
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While of great national and societal significance, and importance in its own right, the Great Artesian Basin of Australia is an iconic example of a continental scale artesian groundwater system. New geochemical, hydrological, and neo-tectonic data suggests that existing models that involve recharge in eastern Australia, relatively simple flowpaths and discharge in springs in the western margin require modification. New geochemical data indicate a small volume flux of deeply derived (endogenic) fluids mixing into the aquifer system at a continental scale. Neo- tectonic data indicates active tectonism today that provides a fluid pathway through faults for the deeply sourced endogenic fluids to discharge in GAB travertine depositing springs. |
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1878-5220 |
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THL @ christoph.kuells @ love_geochemistry_2013 |
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122 |
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Lach, P.; Cathelineau, M.; Brouand, M.; Fiet, N. |
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In-situ Isotopic and Chemical Study of Pyrite from Chu-Sarysu (Kazakhstan) Roll-front Uranium Deposit |
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2015 |
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Procedia Earth and Planetary Science |
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13 |
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207-210 |
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LA-ICP-MS, pyrite, roll-front, SIMS, sulfur isotopy, traces elements, uranium |
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Pyrite is common in roll-front type uranium deposit in Chu-sarysu basin, Kazakhstan. Combined in-situ microstructural, isotopic and chemical analysis of pyrite indicates variation in precipitation conditions and in fluid composition. Broad-scale δ34S heterogeneity indicates a complex multi-facet evolution. First generation authigenic framboïdal aggregates are biogenic as demonstrated by the lowest δ34S values of -48‰ to -28‰. The latest generation pyrites are probably hydrothermal with greater δ34S variation (-30‰ to +12‰). This hydrothermal pyrite commonly displays variable enrichment of several trace elements especially As, Co and Ni. Strong variation in δ34S values and variable trace element enrichment is interpreted in terms of continuous variations in fluid composition. |
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1878-5220 |
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THL @ christoph.kuells @ lach_-situ_2015 |
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182 |
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Hu, K.; Wang, Q.; Tao, G.; Wang, A.; Ding, D. |
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Title |
Experimental Study on Restoration of Polluted Groundwater from in Situ Leaching Uranium Mining with Sulfate Reducing Bacteria and ZVI-SRB |
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2011 |
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Procedia Earth and Planetary Science |
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2 |
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150-155 |
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In situ leaching of uranium, nitrate radical, sulfate radical, Sulfate-Reducing Bacteria (SRB), Zero Valent Iron (ZVI) |
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In the case of in situ leaching of uranium, the primitive geochemical environment for groundwater is changed since leachant is injected into the water beaving uranium deposit. This increases the concentration of uranium and results in the groundwater contamination.Microbial reduction technology by Sulfate reducing bacteria and Zero Valent Iron were employed to treat uranium wastewater. The experiments were conducted to evaluate the influence of anion (sulfate and nitrate) on dealing with uranium wastewater. Experimental results show that the utilization of both SRB system and ZVI – SRB system to process uranium wastewater is affected by sulfate ion and nitrate ion. As the concentration of sulfate radical is lower than 4000mg/L, sulfate-reducing bacteria has no influence on precipitated uranium. However, as the concentration of sulfate is more than 6,000mg/L, uranium removal rate decreases significantly, from 80% to 14.1%. When adding sulfate radical on ZVI – SRB system to process uranium wastewater, its uranium removal rate is higher than SRB system. Low concentration of nitrate contributes to reduction metabolism of SRB. High concentration of nitrate inhibits the growth and metabolism of SRB and affects the treatment efficiency of uranium wastewater. When the concentration of nitrate reaches 1500mg/L, uranium removal rate is less than 0.1%. Nevertheless, as the concentration of nitrate is lower than 1000mg/L, uranium removal rate could reach more than 75%. As existence of nitrate radical, uranium removal rate of SRB by adding ZVI is higher than that without adding. |
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THL @ christoph.kuells @ hu_experimental_2011 |
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202 |
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Merembayev, T.; Yunussov, R.; Yedilkhan, A. |
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Title |
Machine Learning Algorithms for Stratigraphy Classification on Uranium Deposits |
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2019 |
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Procedia Computer Science |
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150 |
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46-52 |
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classification, geophysics logging data, machine learning, stratigraphy, uranium deposit |
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Machine learning today becomes more and more effective instrument to solve many particular problems, where there are difficulties to apply well known and described math model. In other words – it is a great tool to describe non-linear phenomena. We tried to use this technique to improve existing process of stratigraphy, and reduce costs on site by applying computer leaded predictions on the basis of existing on-field collected data. Article describes usage of machine learning algorithms for stratigraphy boundaries classification based on geophysics logging data for uranium deposit in Kazakhstan. Correct marking of stratigraphy from geophysics logging data is complex non-linear task. To solve this task we applied several algorithms of machine learning: random forest, logistic regression, gradient boosting, k nearest neighbour and XGBoost. |
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1877-0509 |
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THL @ christoph.kuells @ merembayev_machine_2019 |
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113 |
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Frey, S.; Külls, C.; Schlosser, C. |
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New Hydrological Age-Dating techniques using cosmogenic radionuclides Beryllium-7 and Sodium-22 |
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2011 |
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Proc. IAEA Conf. Monacco |
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THL @ christoph.kuells @ Frey2011new |
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48 |
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Hamutoko, J.; Mapani, B.; Ellmies, R.; Bittner, A.; Külls, C. |
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A fingerprinting method for the identification of uranium sources in alluvial aquifers: An example from the Khan and Swakop Rivers, Namibia |
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2014 |
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Physics and Chemistry of the Earth, Parts A/B/C |
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72 |
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34-42 |
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Pergamon |
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THL @ christoph.kuells @ Hamutoko2014fingerprinting |
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