Geochemistry and geochronology of charnoenderbites in the Northern Marginal Zone of the Limpopo Belt, Southern Africa, and genetic models

This paper presents petrological and geochemical data combined with zircon U-Pb dating and whole rock Nd model ages for the Northern Marginal Zone (NMZ), Zimbabwe. The granulite terrain of the NMZ comprises enderbites and charnockites as well as their retrograde equivalents. Field relationships and petrological data suggest that the enderbites and charnockites are primary igneous rocks, some of which have been deformed post intrusionally as a result of a ca. 2.6 Ga tectonic event that juxtaposed the NMZ granulites against the amphibolite facies granites and gneisses of the Zimbabwe Craton. Well defined trends of major and trace elements indicate fractionation of clinopyroxene, plagioclase and possibly orthopyroxene to be the mechanism for differentiation of these rocks. The data do not support terrane accretion or continental collision as a reason for Archean crustal thickening of the NMZ and charnoenderbite genesis, but they are in favour of a "soft' continent formation model. -from Authors