Abstract
Supposedly mid-Archaean (c. 3.3 Ga) granulite-grade marbles from the Gumbu Group, Central Zone, Limpopo Belt (South Africa) have anomalously high δ13C values (+4.6 to +7‰) interpreted as minimum values for their limestone protoliths. Such elevated δ13C values are unknown in any Archaean carbonate worldwide, but occur in Palaeoproterozoic (c. 2.4–2.1 Ga) carbonates; for example, on the adjacent Zimbabwe and Kaapvaal cratons. This suggests that the Central Zone contains a previously unrecognized Palaeoproterozoic cover sequence, contrary to the prevailing view. This conclusion is supported by zircon U–Pb sensitive high-resolution ion microprobe ages from two metasediments, which, in addition to c. 2.02 Ga metamorphic zircon overgrowths, contain detrital zircons no older than c. 2.68 Ga, and some possibly as young as c. 2.2 Ga. The recognition of post-3.3 Ga metasediments in the Central Zone requires a major revision of models of the tectonic evolution of the Limpopo Belt.
- © 2003 The Geological Society of London
INDIVIDUALS
Log in using your username and password
PURCHASE SHORT-TERM ACCESS
Pay Per Article - You may access this article (from the computer you are currently using) for 1 day for US$30.00
Regain Access - You can regain access to a recent Pay per Article purchase if your access period has not yet expired.