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Primary uranium sources for sedimentary-hosted uranium deposits in NE China: insight from basement igneous rocks of the Erlian Basin

Abstract : Carboniferous–Permian, Triassic and Jurassic igneousbasement rocks around the Erlian Basin in northeastChina have been investigated through detailed mineralogical,whole-rock geochemistry, geochronological data and Sm–Ndisotope studies. Carboniferous–Permian biotite granites andvolcanic rocks belong to a calc-alkaline association and wereemplaced during the Late Carboniferous–Early Permian (313±1–286 ± 2 Ma). These rocks are characterised by positiveεNd(t) (3.3–5.3) and fairly young TDM model ages (485–726 Ma), suggesting a dominant derivation from partial meltingof earlier emplaced juvenile source rocks. Triassic biotitegranites belong to a high-K calc-alkaline association and wereemplaced during the Middle Triassic (243 ± 3–233± 2 Ma).Their negative εNd(t) (−2 to −0.1) and higher TDM model ages(703–893 Ma) suggest a contribution from Precambrian crustduring the magma generation processes, leading to a strongenrichment in K and incompatible elements such as Th and U.Highly fractionated magmas crystallised in U-rich biotite (upto 21 ppm U) and two-mica granites. In biotite granite, themajor U-bearing minerals are uranothorite and allanite. Theyare strongly metamict and the major part of their uranium(90 %) has been released from the mineral structure and wasavailable for leaching. Mass balance calculations show thatthe Triassic biotite granites may have, at least, liberated ∼14,000 t U/km3 and thus correspond to a major primary uraniumsource for the U deposits hosted in the Erlian Basin.
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https://hal-insu.archives-ouvertes.fr/insu-01321136
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Submitted on : Wednesday, May 25, 2016 - 9:45:32 AM
Last modification on : Thursday, May 28, 2020 - 3:10:07 PM

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Christophe Bonnetti, Michel Cuney, Sylvain Bourlange, Etienne Deloule, Marc Poujol, et al.. Primary uranium sources for sedimentary-hosted uranium deposits in NE China: insight from basement igneous rocks of the Erlian Basin. Mineralium Deposita, Spinger, 2017, 52 (3), pp.297-315. ⟨10.1007/s00126-016-0661-0⟩. ⟨insu-01321136⟩

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