Journal article

Pb- and Nd-isotope systematics of stromatolitic limestones from the 2.7 Ga Ngezi Group of the Belingwe Greenstone Belt: constraints on timing of deposition and provenance

R Bolhar, A Hofmann, J Woodhead, J Hergt, P Dirks

PRECAMBRIAN RESEARCH | ELSEVIER SCIENCE BV | Published : 2002

Abstract

Pb-Pb isochrons have been obtained for stromatolitic limestones from the late Archaean Belingwe Greenstone Belt of Zimbabwe, providing direct age constraints on the deposition of these shallow water marine sediments. Samples from the Manjeri Formation and stratigraphically higher Cheshire Formation yield age estimates of 2706 ± 49 Ma (MSWD = 11.5) and 2601 ± 49 Ma (MSWD = 0.93), respectively. These data are in agreement with published U-Pb zircon and Pb-Pb whole rock ages of associated volcanics, and we, therefore, interpret our Pb-Pb ages as representing the timing of early diagenesis, thus providing a minimum age for carbonate precipitation. A 2543 ± 70 Ma age (MSWD = 5.1) for one sample f..

View full abstract