Age constraints on the Palaeoproterozoic Lomagundi-Jatuli Event in Zimbabwe: Zircon geochronology of the Magondi Supergroup

摘要

The ca. 2.2-2.1 Ga Magondi Supergroup on the Zimbabwe Craton in Southern Africa is mainly composed of sedimentary rocks deposited in a rift basin/passive continental margin, which record a unique episode in carbon isotope perturbation called the Lomagundi-Jatuli Event (LJE). This study reports new U-Pb ages of detrital zircons from the Deweras and Lomagundi groups of the Magondi Supergroup, and of igneous zircons from underlying granitoids, to constrain the timing of the LJE and to identify the provenance of the Magondi Supergroup. Most analysed detrital zircon grains range in ages between ca. 2.9 and 2.6 Ga. Three ca. 2.3-2.2 Ga detrital zircons from sandstone of the Deweras Group, with the youngest Pb-207-Pb-206 age of 2,216 +/- 22 Ma, indicate the onset of LJE in the Zimbabwe Craton was almost simultaneous to that in Fennoscandia and the Superior Craton, supporting the global synchronicity of the LJE.