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Detrital monazite in the Tim Mersoï basin, Niger: provenance and contribution to the uranium budget in siliciclastic sediments

Abstract : A detailed study using back-scattered electron imaging and electron-microprobe analysis shows that grains of detrital monazite are present in the Carboniferous, Permian, Triassic and Jurassic sediments of the Tim Mersoï basin, Niger. Despite variations in the size and shape of monazite grains, the U-Th-Pb chemical ages obtained by electron microprobe fall in a narrow range, 425 to 650 Ma. These ages indicate that the monazite grains are issued from the erosion of Pan-African granites and metamorphic rocks from the Aïr Mountains, and probably also from the basement near Zinder and in Nigeria, a hypothesis in good agreement with paleocurrent reconstruction. The uranium content of monazite from sediments is high (up to 1.7 wt% UO2), but low in adjacent rhyolite. Some monazite grains from the sandstone show evidence of alteration, especially to florencite. We conclude that detrital monazite is a major reservoir of uranium in some sandstones from the Tim Mersoï Basin.
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https://hal-insu.archives-ouvertes.fr/insu-00681804
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Submitted on : Thursday, March 22, 2012 - 2:53:58 PM
Last modification on : Wednesday, September 16, 2020 - 4:58:31 PM

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Ibrahim Wagani, Maurice Pagel, Emilie Janots, Edwin Gnos. Detrital monazite in the Tim Mersoï basin, Niger: provenance and contribution to the uranium budget in siliciclastic sediments. The Canadian Mineralogist, Mineralogical Association of Canada, 2011, 49 (2), pp.487-501. ⟨10.3749/canmin.49.2.487⟩. ⟨insu-00681804⟩

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