Palaeomagnetic constraints on the Position of the Congo craton ca. 765 Ma

With Michael Wingate and Sergei Pisarevsky

Samples collected from the Lwawu volcanic sequence in 2000 by Wingate, De Waele and Banda, in the far northwestern corner of Zambia (Mwinilunga area), have been the subject of a palaeomagnetic study.

The Lwawu (or Luakela) volcanics occur along a NE-SW oriented belt in between the (par)autochtonous sequences of the northwestern foreland of the Lufilian belt. They are of very low metamorphic grade, and occur parallel to the under- and overlying strata of the Kundelungu and Mwashya groups.

The entire Neoproterozoic sequence lies unconformably on granites and gneisses which have been dated by Armstrong (SHRIMP U-Pb) at ca. 2500 Ma and ca. 2000 Ma. No "Kibaran" aged basement has been recognised in NW Zambia, and the basement is interpreted to form part of the Congo craton (refer to Key et al., 2000, Journal of African Earth Sciences).

The volcanics themselves have been dated at 765 Ma by Armstrong on the Canberra SHRIMP, and therefore provide an excellent target for a Palaeomagnetic study (refer to Key et al., 2000, Journal of African Earth Sciences).

Samples collected from a total of eight sites have yielded two separate remanences, which will help constrain the position of the Congo craton at around 760 Ma and possibly at the peak of Lufilian orogeny at 550 Ma.

The data will be compared and contrasted with poles obtained from the Gagwe lavas and the Mbozi alkaline complex in Tanzania.

Michael Wingate sampling with a portable drill