Geological setting and timing of the world-class Sn, Nb-Ta and Li mineralization of Manono-Kitotolo (Katanga, Democratic Republic of Congo)

摘要

The Central African Mesoproterozoic Kibara belt in Katanga (DRCongo) forms a metallogenic province that hosts a variety of granite-related mineralization, rich in cassiterite, columbite-tantalite, wolframite/ferberite, spodumene and beryl. This mineralization is mainly present in pegmatites and quartz veins that are thought to be associated with the youngest granite generation in the Kibara belt (i.e., so-called "E-group" granite generation). Manono-Kitotolo is one of the world's largest Sn, Nb-Ta and Li mineralized pegmatites, with a large resource of spodumene, columbite-tantalite and cassiterite still remaining. Mineralized pegmatites have intruded along the foliation in the Mesoproterozoic metasedimentary rocks and dolerites of the Manono-Kitotolo area. The pegmatites have been emplaced very late during the climax of the Kibaran orogeny, probably during the transition from orogenic collapse to extensional tectonics, based on their structural position. The emplacement of the pegmatites resulted in an intense alteration of the doleritic and metasedimentary host-rocks, resulting in muscovitization, tourmalinization and silicification. A mineralogical and geochemical zonation typical for granitic pegmatites has been identified that was affected by metasomatic/hydrothermal alteration, mainly albitization and greisenization. The latter alteration is associated with the main phase of cassiterite mineralization. A first stage with Nb-Ta, Li and minor Sn, however, already formed pre-alteration, directly associated with pegmatite crystallization. Ar-40-Ar-39 muscovite dating of unaltered pegmatites resulted in ages of 938.8 +/- 5.1 Ma and 934.0 +/- 5.9 Ma. These ages are overlapping with the U-Pb age of the Nb-Ta mineralization (940 +/- 5.1 Ma), also giving new temporal constraints on the fertile E-group granite generation in the KIB. The Ar-40-Ar-39 muscovite age of a mineralized greisen is 923.3 +/- 83 Ma, which is younger but still partly within error of the Ar-40-Ar-39 ages of the unaltered pegmatites. Based on the partial overlap in age, but also on field and paragenetic relationships and the stable isotope composition of the fluids, this greisenization and associated cassiterite mineralization can still be linked to the pegmatite crystallization. (C) 2015 Elsevier B.V. All rights reserved.