Concordant ages for the giant Kipushi base metal deposit (DR Congo) from direct Rb–Sr and Re–Os dating of sulfides |
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| Authors: | Jens Schneider Frank Melcher Michael Brauns |
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| Institution: | 1.Département de Minéralogie,Université de Genève,Geneva,Switzerland;2.Bundesanstalt für Geowissenschaften und Rohstoffe,Hanover,Germany;3.CEZ Arch?ometrie GmbH,Mannheim,Germany;4.Geodynamics and Geofluids Research Group, Afdeling Geologie,Katholieke Universiteit Leuven,Heverlee,Belgium |
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| Abstract: | We report concordant ages of 451.1 ± 6.0 and 450.5 ± 3.4 Ma from direct Rb–Sr and Re–Os isochron dating, respectively, of
ore-stage Zn–Cu–Ge sulfides, including sphalerite for the giant carbonate-hosted Kipushi base metal (+Ge) deposit in the Neoproterozoic
Lufilian Arc, DR Congo. This is the first example of a world-class sulfide deposit being directly dated by two independent
isotopic methods. The 451 Ma age for Kipushi suggests that the ore-forming solutions did not evolve from metamorphogenic fluids
mobilized syntectonically during the Pan-African-Lufilian orogeny but rather were generated in a Late Ordovician postorogenic,
extensional setting. The homogeneous Pb isotopic composition of the sulfides indicates that both Cu–Ge- and Zn-rich orebodies
of the Kipushi deposit formed contemporaneously from the same fluid system. The sulfide Pb isotope signatures in combination
with initial 87Sr/86Sr and 187Os/188Os ratios defined by the isochrons point to metal sources located in the (upper) crust. The concordant Re–Os and Rb–Sr ages
obtained in this study provide independent proof of the geological significance of direct Rb–Sr dating of sphalerite. |
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| Keywords: | Kipushi Base metals Copperbelt Congo Rb– Sr isotopes Re– Os isotopes Pb isotopes |
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