The metamorphic evolution of mafic rocks in the Tugela Terrane, Natal Belt, South Africa

Abstract

New petrological and mineral chemical data indicate a clockwise P-T path for medium-to high-grade metamorphic mafic rocks in different thrust sheets of the Tugela Terrane within the Mesoproterozoic Natal Belt in KwaZulu-Natal (eastern South Africa). Three metamorphic stages are distinguished: (i) an early upper amphibolite-to lower granulite-facies metamorphic event (M 1) is indicated by rare relics of clinopyroxene; (ii) mineral chemical and textural equilibration during M 2 at calculated pressure-temperature conditions of 4.5 to 6 kbar and 693 to 750°C; and (iii) partial diffusional resetting of mineral compositions during subsequent uplift and exhumation (M 3) under lower amphibolite-to greenschist-facies conditions. No major differences were noted in the tectonothermal regimes at which each of the respective thrust sheets were deformed suggesting that the Tugela Terrane was a homogenous package and experienced uniform P-T conditions. The new data acquired in this study contribute to an improvement in the ongoing development of a tectono-thermal and geodynamic model for the Natal Belt.

Multiple origins of charnockite in the Mesoproterozoic Natal belt, Kwazulu-Natal, South Africa

“…All three terranes experienced multiple deformational events and are characterized by pervasive E-W trending fabrics and northwardverging overall structure (Talbot and Grantham, 1987;Mendonidis and Strydom, 1989;Thomas, 1989;Jacobs et al, 1993;McCourt et al, 2006;Bisnath et al, 2008). However, the timing of the events in the different terranes was not coeval as shown in Fig.…”

“…2. Multiple metamorphic events have been reported from each terrane and metamorphic textures suggest that metamorphism coincided with the deformation events (Mendonidis, 1989;Mendonidis et al, 2002;Mendonidis and Grantham, 2003;Bisnath et al, 2008). Metamorphic grade generally increases from greenschist facies in Figure 2 Graphical tabulation of the Natal Metamorphic belt lithologies for which there are published U/Pb zircon emplacement ages, sorted according to the age scale on the left (after .…”

A New U-Pb Zircon Age for the Portobello Granite From the Southern Part of the Natal Metamorphic Belt

“…However, the timing of the events in the different terranes was not coeval as shown in Figure 2. Multiple metamorphic events have been reported from each terrane and metamorphic textures suggest that metamorphism coincided with the deformation events (Mendonidis, 1989;Mendonidis et al, 2002;Mendonidis and Grantham, 2003;Bisnath et al, 2008). Metamorphic grade generally increases from greenschist facies in the north to granulite facies in the south (Matthews, 1972;McCourt et al, 2006).…”

“…Large plutons of a rapakivi-charnockitic association collectively called the Oribi Gorge Suite (Thomas, 1988a;Thomas et al, 1993b;Grantham et al, 2001;Eglington et al, 2003) punctured both the Margate and Mzumbe Terranes at about 1.06 Ga ( Figure 2) indicating that these two terranes were juxtaposed by that date Eglington, 2006). All three terranes experienced multiple deformational events and are characterized by pervasive eastwest trending fabrics and northward-verging overall structure (Talbot and Grantham, 1987;Mendonidis and Strydom, 1989;Jacobs et al, 1993;McCourt et al, 2006;Bisnath et al, 2008). However, the timing of the events in the different terranes was not coeval as shown in Figure 2.…”