Dating of U-rich heterogenite : new insights into U deposit genesis and U cycling in the Katanga Copperbelt
De Putter, Th.
Earth and related Environmental sciences
Geodynamics and mineral resources
Surface environments and collection management
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The Katanga Copperbelt region of the Democratic Republic of Congo hosts world-class cobalt depositsaccounting for ∼50% of the world reserves. Heterogenite (CoOOH) is the most abundant Co-bearing sec-ondary mineral in the region. Its occurrence is the result of oxidation of Cu Co-sulfides and associated Coreprecipitation in the uppermost part of the deposits, during the Pliocene. In addition to sediment-hostedcopper and cobalt ore deposits, the Katanga Copperbelt also hosts numerous uraniferous mineral occur-rences and deposits, which can be associated with heterogenite. Within these deposits, heterogenite canhave high concentrations of U (up to 3.5%) and Pb (up to ∼4%).In situ SIMS U Pb ages were obtained for heterogenite samples from the U deposits of Shinkolobwe,Kalongwe and Kambove. These analyses yield distinct Neoproterozoic ages, at ∼876 Ma, ∼823 Ma and inthe ∼720 to ∼670 Ma age range. As the geological context prevailing at those times was not favorable forheterogenite formation, these ages most probably record geological events that are not the formation ofthe mineral itself. For instance, the heterogenites could have inherited the U Pb signature of a U-rich min-eral, most likely uraninite, formed and/or yet reworked at ∼876 Ma, ∼823 Ma and in the ∼720 to ∼670 Matime interval and spatially associated with primary Co-sulfides. In this hypothesis, the ages obtained inthis paper are significant for understanding the cycling and re-deposition of U at given moments in theregional geological history.In such context, the ∼876 Ma and the ∼823 Ma age are consistent with syn-early diagenetic concentra-tion of uranium in sediments of the Katanga basin. The ∼720 to ∼670 Ma ages are interpreted as a phaseof U remobilization related to hydrothermal fluid circulation induced by late Nguba proto-oceanic riftingor by early stages of Congo-Kalahari craton convergence, and associated hydrothermal circulation.
CitationDecrée, S.; Deloule, E.; De Putter, Th.; Dewaele, S.; Mees, F.; Baele, J.M.; Marignac, C. (2014). Dating of U-rich heterogenite : new insights into U deposit genesis and U cycling in the Katanga Copperbelt. , Precambrian Research, Vol. 241, 17-28,