A Kaapvaal craton debate: Nucleus of an early small supercontinent or affected by an enhanced accretion event?

Eriksson, P.G.; Banerjee, Santanu; Nelson, David R.; Rigby, Martin J.; Catuneanu, Octavian; Sarkar, S.; Roberts, Ralph J.; Ruban, Dmitry A.; Mtimkulu, Mtimkulu N.; Raju, P. V. Sunder

doi:10.1016/j.gr.2008.08.001

Cited by 63 publications

(34 citation statements)

References 92 publications

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“…Moreover, the P-T conditions determined by Rigby et al (2008a) to be 'intermediate' between the amphibolite facies conditions reported by Zeh et al (2005a) and the granulite facies conditions of Zeh et al (2004) and Rigby (2009) are now bracketed in terms of their age, and collectively this data may suggest that the metamorphic field gradient hypothesis proposed by Rigby et al (2008a) is a valid concept and that metamorphic conditions across the Central Zone of the Limpopo Belt at 2.0Ga varied predictably. However, this hypothesis is dependent on the reliability of the P-T conditions determined by different workers using different methods (Perchuk et al, 2008versus Zeh & Klemd, 2008and Rigby, 2009. If the P-T estimates produced by the pseudosection approach (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…If the P-T estimates produced by the pseudosection approach (e.g. Zeh et al 2004;2005a;Rigby et al, 2008a andRigby, 2009) are correct then the field gradient hypothesis remains a valid concept. However, if the local equilibrium estimates of Boshoff et al (2006) and Perchuk et al (2008) are correct then the hypothesis may be flawed.…”

Section: Methodsmentioning

confidence: 99%

“…Conversely, the Central Zone (CZ) forms a unique and distinct supracrustal block, which is bound to the north and south by the Magohapote and Triangle Shear Zone and Zoefontein-Palala Shear Zones respectively. The P-T-t evolution of the CZ of the Limpopo Belt is a vast and contentious issue too lengthy to be discussed here, however, the reader is referred to Perchuk et al (2008), Zeh & Klemd (2008) and Rigby (2009) Figure 1B). Field relationships indicate the (meta)syenites intruded into the Alldays gneiss (Brandl & Pretorious, 2000).…”

Section: Geological Contextmentioning

confidence: 99%

“…McCourt & Armstrong, 1998; Kroner et al, 1998;Bumby et al, 2001;Bumby & van der Merwe, 2004; Zeh et al, 2007; Millonig et al, 2008; Perchuk et al, 2008; Van Reenen et al, 2008; Gerdes & Zeh, 2009; Zeh et al 2009) and one in the Palaeoproterozoic (e.g. Jaeckel et al, 1997; Holzer et al, 1998; Kroner et al, 1999; Zeh et al, 2004; Rigby et al, 2008b;Chudy et al, 2008;Eriksson et al, 2009; Gerdes & Zeh, 2009; Rigby et al, 2010; Eriksson et al, 2010a and b; Millonig et al, 2010) and without robust geochronological constraints it is not clear in which event the metasyenites were metamorphosed. Additionally, due to this uncertainty, the existence of the proposed metamorphic field gradient by Rigby et al (2008a) is, at present, mere speculation.…”

Section: Introductionmentioning

confidence: 99%

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SHRIMP dating of titanite from metasyenites in the Central Zone of the Limpopo Belt, South Africa

Rigby¹,

Armstrong²

2011

Journal of African Earth Sciences

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SHRIMP dating of titanite from metasyenites in the Central Zone of the Limpopo Belt yields a mean 207 Pb/ 206 Pb age of 2010.3 +/-4.5 Ma calculated from twenty-three analyses. This age, combined with petrographic and field observations, suggests the metamorphism in the syenites occurred during the regional Palaeoproterozoic event.Keywords: Limpopo Belt; SHRIMP; titanite; geochronology; Palaeoproterozoic. IntroductionA unique body of (meta)-syenite intrudes the Alldays Gneiss and outcrops in an elongate, 6.25 x 1.25 km body WNW of Alldays within the Central Zone of the Limpopo Belt, South Africa (Fig 1a + b). A recent study by Rigby et al. (2008a) reveals the metasyenites underwent a metamorphic evolution characterized by a maximum pressure of 7-8 kbar and ~770 o C. The subsequent retrograde path involved a simultaneous P-T decrease along a decompression-cooling path to 4 kbar and ~550 o C. These P-T estimates are 'intermediate' between the high-grade conditions reported by Zeh et al. (2004) and Rigby (2009) for metapelites near Messina and the amphibolite-facies conditions reported by Zeh et al. (2005a,b) and Chudy et al. (2008) for rocks from the Venetia area. Collectively, this data led Rigby et al. (2008a) to postulate the existence of a metamorphic field gradient. However, there are two main tectonometamorphic episodes known in the Central Zone of Limpopo Belt, one in the Neoarchean (e.g. McCourt & Armstrong, 1998; Kroner et al., 1998;Bumby et al., 2001;Bumby & van der Merwe, 2004; Zeh et al., 2007; Millonig et al., 2008; Perchuk et al., 2008; Van Reenen et al., 2008; Gerdes & Zeh, 2009; Zeh et al. 2009) and one in the Palaeoproterozoic (e.g. Jaeckel et al., 1997; Holzer et al., 1998; Kroner et al., 1999; Zeh et al., 2004; Rigby et al., 2008b;Chudy et al., 2008;Eriksson et al., 2009; Gerdes & Zeh, 2009; Rigby et al., 2010; Eriksson et al., 2010a and b; Millonig et al., 2010) and without robust geochronological constraints it is not clear in which event the metasyenites were metamorphosed. Additionally, due to this uncertainty, the existence of the proposed metamorphic field gradient by Rigby et al (2008a) is, at present, mere speculation. In this short communication we present new U-Pb SHRIMP data obtained from titanite in the metasyenites to delineate their age and support the metamorphic field gradient hypothesis.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Geological Contextmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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SHRIMP dating of titanite from metasyenites in the Central Zone of the Limpopo Belt, South Africa

Rigby¹,

Armstrong²

2011

Journal of African Earth Sciences

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“…One camp argues that the data collectively indicate that the CZ underwent deformation and metamorphism at ca. 2.0 Ga (Kamber et al 1995; Holzer et al, 1995;Holzer et al, 1998;Kroner et al 1999;Schaller et al 1999;Zeh et al 2004;Zeh et al, 2005a,b;Eriksson et al, 2009). Conversely, Van Reenen et al (1987), McCourt and Vearncombe (1992), Roering et al (1992), McCourt and Armstrong (1998), Bumby et al (2001), Bumby and Van der Merwe (2004) advocate that the CZ and the entire Limpopo Belt formed during a single, Neoarchean, high-grade event that was initiated by the collision of the Kaapvaal and Zimbabwe cratons.…”

Section: Introductionmentioning

confidence: 99%

Conflicting P–T paths within the Central Zone of the Limpopo Belt: A consequence of different thermobarometric methods?

Rigby

2009

Journal of African Earth Sciences

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a b s t r a c tA single metapelitic sample from the Verbaard locality, near Messina was investigated in order to construct a P-T path and moreover, highlight pertinent contradictions in the current P-T database. Interpretations based on P-T pseudosections, garnet isopleth thermobarometry and mineral mode/isopleth modelling indicate that the mineral assemblages, textures and zonations developed in the metapelite formed along a single clockwise P-T path. The metamorphic evolution is characterized by an early high-pressure phase at 10-11 kbar/800°C, followed by a simultaneous pressure decrease and temperature increase to $8/850°C and subsequent retrogression via decompression-cooling to 4-5 kbar at T < 650°C. Growth zoning in garnet provides evidence for an earlier, prograde history, however, as potential melt-loss was not accounted for this must be deemed speculative. The results of this study agree entirely with that of [Zeh, A., Klemd, R., Buhlmann, S., Barton, J.M. 2004. Pro-and retrograde P-T evolution of granulites of the Beit Bridge Complex (Limpopo Belt, South Africa); constraints from quantitative phase diagrams and geotectonic implications. Journal of Metamorphic Geology 22, 79-95], who adopted a similar approach to thermobarometry i.e. pseudosections. The results are, however, inconsistent with recent publications that argue for a twofold, metamorphic history defined by two decompression-cooling paths (DC1 $2.6 Ga and DC2 $2.0 Ga) that are separated by an isobaric heating path ($2.0 Ga). The disparity in the results obtained from different workers can be explained by an examination of the thermobarometric methods employed. The methodology employed to derive the twofold, polymetamorphic P-T path appears to be erroneous. At present, the most reliable and robust method for determining P-T paths is the pseudosection approach to thermobarometry. Future modelling of Limpopo Belt granulites should adopt this strategy and ensure potential melt-loss is taken into account. Alternatively, this potential problem can be avoided altogether by investigating rocks of mafic composition.

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Archaean granulite facies metamorphism at the Singhbhum Craton–Eastern Ghats Mobile Belt interface: implication for the Ur supercontinent assembly

et al. 2011

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In this study, we investigate the geological significance and the antiquity of lower crustal granulite facies metamorphism from the Rengali Domain, which lies in between the Singhbhum Craton in the north and the Eastern Ghats Mobile Belt in the south. Petrographic, mineral compositional, metamorphic reaction history and geothermobarometric studies of two representative metapelite granulite samples reveal widespread biotite melting at peak granulite facies metamorphic conditions of 7.8 ± 0.13 kbar, 849 ± 31°C and subsequent melt extraction, producing a mixture of residual granulites and melts in the Rengali Province. Depending on local bulk rock compositional variations, biotite melting produced peak metamorphic assemblages of garnet + cordierite in the more aluminous compositional domain, while garnet + orthopyroxene + cordierite resulted in domains of intermediate alumina. During post-peak cooling, there were localized developments of biotite + sillimanite + quartz symplectites replacing garnet and cordierite and biotite + quartz intergrowths after orthopyroxene. Application of garnet-orthopyroxene and garnet-biotite Fe-Mg exchange thermometers to co-existing garnet rim and symplectitic biotite show the extent of cooling to 610-660°C. Electron microprobe geochronology of texturally well constrained monazites indicates the timing of peak granulite metamorphism at 3057 ± 17 Ma and its metamorphic reheating at 2781 ± 16 Ma. The present findings when collated with available geological and geophysical data appear to indicate that the studied granulites and the associated granite gneisses, charnockite and enderbite suite of rocks of the Rengali Domain are part of the exhumed lower continental crust of the Singhbhum Craton. The significance of this Neoarchaean orogenesis in the 'Ur' supercontinent assembly is discussed.

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A Kaapvaal craton debate: Nucleus of an early small supercontinent or affected by an enhanced accretion event?

Cited by 63 publications

References 92 publications

SHRIMP dating of titanite from metasyenites in the Central Zone of the Limpopo Belt, South Africa

SHRIMP dating of titanite from metasyenites in the Central Zone of the Limpopo Belt, South Africa

Conflicting P–T paths within the Central Zone of the Limpopo Belt: A consequence of different thermobarometric methods?

Archaean granulite facies metamorphism at the Singhbhum Craton–Eastern Ghats Mobile Belt interface: implication for the Ur supercontinent assembly

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