Detrital zircon U–Pb ages of the Palaeozoic Natal Group and Msikaba Formation, Kwazulu-Natal, South Africa: provenance areas in context of Gondwana
2016
The Natal Group and Msikaba Formation remain relatively poorly understood with regards to
their provenance and relative age of deposition; a much-needed geochronological study of
the detrital zircons from these two units was therefore undertaken. Five samples of the
Durban and Mariannhill Formations (Natal Group) and the Msikaba Formation (Cape
Supergroup) were obtained. A total of 882 concordant U–Pb ages of detrital zircon
populations from these units were determined by means of laser ablation inductively
coupled plasma mass spectrometry (LA-ICP-MS). Major Neoproterozoic and secondary
Mesoproterozoic detrital zircon age populations are present in the detrital zircon content
of all the samples. Smaller contributions from Archean-, Palaeoproterozoic-, Cambrian- and
Ordovician-aged grains are also present. Due to the presence of a prominent major
population of 800–1000 Ma zircons in all the samples, late Stenian – Tonian ancient
volcanic arc complexes overprinted by Pan-African metamorphism of Mozambique, Malawi and
Zambia, along with areas of similar age within Antarctica, India and Sri Lanka, are
suggested as major sources of detritus. The Namaqua–Natal Metamorphic Complex is suggested
as a possible source of minor late Mesoproterozoic-aged detritus. Minor populations of
Archean and Palaeoproterozoic zircons were likely sourced from the Kaapvaal and Grunehogna
Cratons. Post-orogenic Cambrian – Lower Ordovician granitoids of the Mozambique Belt
(Mozambique) and the Maud Belt (Antarctica) made lesser contributions. In view of the
apparent broad similarity of source areas for the Natal Group and Msikaba Formation, their
sedimentation occurred in parts of the same large and evolving basin rather than localized
in small continental basins, and the current exposures merely represent small erosional
relicts.
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