Lu-Hf dating of apatite from the Katanga Copperbelt: age resetting due to post-orogenic fluid migration

Abstract

The Katanga Copperbelt stands out as one of the world’s largest sediment-hosted Cu-Co provinces, contributing to over 68% of global Co and 15% of global Cu production. The age of these sedimentary Cu-Co deposits remains contentious. This paper presents the first Lu-Hf dates for apatite samples from the late diagenetic to syn-orogentic mineralization phase at Luiswishi, yielding ages of ca. 475–470 Ma. This age range is comparable with a previous Re-Os age on bornite (473 ± 4 Ma) from Kamoto and Rb–Sr and Re–Os ages for sulfides (451 ± 6.0 and 450 ± 3.4 Ma) from Kipushi but younger than the hydrothermal diagenetic mineralization (~ 800 Ma) and the mineralization event related to the Lufilian Orogeny (~ 560–500 Ma). The new Lu-Hf ages indicate a post-orogenic fluid migration at ca. 475–470 Ma in the Katanga Copperbelt, causing dissolution and reprecipitation of apatite and likely precipitation of cogenetic sulfides. The rare earth element (REE) contents of the apatite and scanning electron microprobe (SEM) images provide evidence of partial or complete remobilization of earlier high REE-rich to neo-crystalline homogeneous apatite with lower REE content.