Neoproterozoic to Cambrian granitoids of northern Mozambique and Dronning Maud Land Antarctica: Implications for the assembly of Gondwana

The field relationships, petrography, whole rock major, trace element and radiogenic isotope chemistry and geochronology of Cambrian Granites granites from the Nampula Terrane (NT) Mozambique are reported. These data are compared with published data from Neoproterozoic to Cambrian granites from Central Dronning Land (CDML). Age comparisons include data from the Cabo Delgado/Namuno Terrane of northern Mozambique (CDNMT). Whereas there is significant overlap in the chemistry and ages of the granites from the NT, compared to those from CDML and CDNMT, indicating their possible genesis within the same broad orogenic event, subtle differences in mineralogy, chemistry and age are seen. These differences include subsolvus peraluminous mica-dominated granites with ages < ∼530 Ma in all three areas but concentrated in the NT, in contrast to dominantly metaluminous hypersolvus charnockitic syenogranites with ages > ∼530 Ma in CDML and CDTNM, but absent from the NT and western Sverdrupfjella. The differences between the two granite varieties are inferred to reflect differences in tectonic setting during genesis, with the marginally older CDML and CDTNM granites/charnockites resulting from decompression dehydration melting, dominantly of amphibole in the hanging wall of a mega-nappe. In contrast the marginally younger NT granites were generated dominantly from dehydration melting of mica in the footwall of the mega-nappe structure. Geophysical data indicate the thickened crust underlying the mega nappe in DML extends far in to Antarctica indicating much of East Antarctica may be underlain by allochthonous crust.