Thèse de doctorat : Géosciences : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

No description available.

No description available.

The Karku unconformity-type uranium deposit is located in the Proterozoic Pasha-Ladoga Basin in western Russia. The deposit is located in basinal sandstones near a reverse fault that offsets the unconformable contact with underlying graphite-bearing biotite schist basement rocks. Meteoric water-sourced diagenetic fluids altered sandstones outside mineralized zones, producing clay assemblages of interstratified illite-smectite with minor dickite and Fe-rich chlorite, and fluid isotopic compositions of d18O = 3.3‰ to 6.0‰ and dD = -55‰ to -44‰ at 130°C. Altered sandstones within zones of mineralization include a clay mineral assemblage of Fe-rich chlorite with minor illite, and fluid isotopic compositions of d18O = 6.0‰ to 12.7‰ and dD = -8‰ to -4‰ at 210°C, caused by seawater-derived fluids related to ore formation. In addition, a Mg-chlorite occurring with uraninite in the mineralized lenses was identified. Dating of Karku uraninite using U/Pb isotope systematics from LA-MC-ICP-MS, LA-HR-ICP-MS, and SIMS gave upper-intercept ages of 1467 ± 39 Ma, 1459 ± 74 Ma, and 1302 ± 150 Ma respectively. The lower-intercept age of all methods was around 300 Ma. A formation model for the Karku uranium deposit is proposed based on the results of this study and incorporating previously published. Early, low-temperature diagenesis resulted in cementation of distal, basin-marginal sandstones by mixed-layer illite-smectite clays, preventing later, higher-temperature diagenetic alteration in this unit. Sandstones towards the centre of the basin allowed the circulation of higher-temperature basinal fluids that later flowed along the unconformity to the graphitic schist unit. A fault intersecting this unit facilitated the mixing of basement and basinal fluids, causing uraninite to precipitate at the unconformity. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-09-12 17:10:28.124

Sandstone-type uranium deposits are among the most economic sources of uranium. Despite their significance, the tabular deposits on the Colorado Plateau and roll-front deposits in Nebraska have not been studied adequately. There are important differences between the tabular Colorado Plateau and Nebraska roll-front deposits, including their ore mineralogy, distribution and habit of ore-bodies, alteration, and mechanisms of ore deposition. The U-Pb ages of uranium minerals from the Colorado deposits indicate four stages of mineralization, spanning from the early Oligocene to late Pliocene. Uranium and V minerals include coffinite, montroseite and carnotite and are associated with both biogenic and non-biogenically precipitated sulphides. Two generations of coffinite mineralization from the Three Crow roll-front deposit in Nebraska were identified. This mineralization precipitated during the early Pliocene and late Miocene. The U-Th activity ratios of U minerals suggest a net accumulation of uranium within the limbs of the roll-front. Evolving oxidation fronts are implied by multiple sulphide generations as indicated by their delta 34S compositions.

Thèse 3e cycle--Pétrologie et minéralogie--Nancy I, 1983. / Bibliogr. p. 325-342. Résumé en français et en anglais.

Thèse 3e cycle--Géologie structurale, métallogénie--Institut national polytechnique de Lorraine, 1984. / Bibliogr. p. 189-196. Résumé en anglais.

Thèse 3 cycle--Pétrologie, géochimie, métallogénie--Paris VI, 1982. / Bibliogr. p. 259-266. Résumés en français, anglais et espagnol.

Th. 3e cycle--Agro-éco-pédol.--Nancy 1, 1983. N°: 249.

Th. univ.--Géochimie de la surface--Poitiers, 1986. / Bibliogr. p. 129-137.