Late Archaean to early Proterozoic granitoid magmatism and high-grade metamorphism in the central Limpopo belt, South Africa

Jaeckel, P.; Kröner, Alfred; Kamo, Sandra L.; Brandl, G.; Wendt, Jobst

doi:10.1144/gsjgs.154.1.0025

Cited by 156 publications

(75 citation statements)

References 33 publications

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“…However, many studies have demonstrated that there is a very strong likelihood that these data represent true zircon crystallization ages when: (1) the 207 Pb/ 206 Pb ratio does not change with increasing temperature of evaporation and/or (2) repeated analyses of grains from the same sample at high evaporation temperatures yield the same isotopic ratios within error. Comparative studies by evaporation, conventional U-Pb dating, and ion-microprobe analysis have shown this to be correct (Kröner et al, 1991Cocherie et al, 1992;Jaeckel et al, 1997;Karabinos, 1997).…”

Section: Methodsmentioning

confidence: 87%

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Miller

Alene

Sacchi

et al. 2003

Precambrian Research

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Juvenile continental crust of the Arabian-Nubian Shield (ANS) formed within a Neoproterozoic supercontinent cycle. Subsequent late Neoproterozoic deposition overlapped a series of dramatic climatic events that are unparalleled in subsequent Phanerozoic time, as proposed by the "Snowball Earth" hypothesis. In particular, extreme negative δ 13 C excursions coincident with glacial diamictite and cap carbonate sequences imply that profound carbon flux changes accompanied widespread glacial transitions (Snowball Events). Such a succession appears to be partially preserved in metasediments of the diamictite-bearing Tambien Group of northern Ethiopia (Negash syncline). Here, a pronounced negative carbon excursion from values of +7 to −2 per mil accompanies the transition to diamictite deposition. New zircon evaporation dates from granites intruding the base of the sequence but post-dating early deformation of the entire sequence suggest that the Tambien Group is older than 613 Ma, and therefore diamictite genesis is incompatible with younger Marinoan, Varanger, or "Ediacaran" glacial intervals. Syn-tectonic granites elsewhere within the region date between 750 and 800 Ma and provide an older age constraint for the Tambien Group. The limestone sequence underlying the diamictite has an average 87 Sr/ 86 Sr composition of 0.7066, which supports either a middle (ca. 750-740 Ma) or late (ca. 725-720 Ma) Sturtian age. Combined Sr and C isotopic compositions of the limestones and the upper age constraint from the granite ages provide a compelling argument that the Tambien Group sediments are ∼720-750 Ma or a little older and strongly support the prospect that the Negash diamictite is the product of Sturtian glaciation. If so, these are the first Sturtian Snowball Earth sequences identified in the ANS.

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Section: Methodsmentioning

confidence: 87%

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Miller

Alene

Sacchi

et al. 2003

Precambrian Research

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“…Historically, the metamorphic, magmatic and deformational characteristics of the Limpopo mobile belt (LMB) have been attributed to an Alpine-Himalayan style collision event between the Zimbabwe and Kaapvaal cratons at c. 2.7-2.6 Ga (Rigby et al 2008a and references therein). However, in the late 1990's the first reports of the now ubiquitous Paleoprotorozoic age for metamorphism in the Central zone (CZ) started to emerge (Barton and Sergeev 1997;Jaeckel et al 1997;Holzer et al 1998;Kröner et al 1999), and this ultimately led Holzer et al (1998) to conclude that the "Limpopo orogeny" formed as a result of the oblique collision between the Kaapvaal and Zimbabwe cratons at c. 2.0 Ga. An Archean-only versus a Paleoproterozoic-only collision is, however, an oversimplication that is inconsistent with recent studies, which have unequivocally demonstrated that the LMB has a long and protracted evolution spanning over 700 My of Earth history (Barton et al 2006;Boshoff et al 2006;Zeh et al 2007;Zeh et al 2008;Millonig et al 2008;Van Reenen et al 2008;Perchuk et al 2008;Chudy et al 2008;Gerdes and Zeh 2009). The CZ is characterized by discrete metamorphic and magmatic activity which is attributable, in part, to a Neoarchean event (Millonig et al 2008;Van Reenen et al 2008;Gerdes and Zeh 2009), and a final c. 2.0 Ga overprint (Zeh et al 2004;Zeh et al 2005;Zeh et al 2007;Perchuk et al 2008;Rigby et al 2008b;Van Reenen et al 2008;Chudy et al 2008;Rigby 2009).…”

Section: Kaapvaal As Part Of a >C 20 Ga Supercontinent -Evidence Formentioning

confidence: 99%

The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?

Eriksson

Rigby

Bandopadhyay

et al. 2011

International Geology Review

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“…The D2/M2 event is characterized by the presence of numerous orthogneisses, designated to include the Alldays, Singelele, Zanzibar, Bulai and Zoetfontein Gneisses, which belong to a 2734-2604 Ma age group (Jaeckel et al, 1997;Kröner et al, 1999;Zeh et al, 2007). Kröner et al (1999) suggest that the orthogneiss precursors were emplaced into the already ductile and deformed gneisses of the oldest group.…”

Section: P-t-t Evolution Of the Central Zonementioning

confidence: 99%

“…The timing of the last high-grade metamorphic event (D3/M3) is constrained by the dating of metamorphic minerals (Holzer et al, 1998;Boshoff et al, 2006;Van Reenen et al, 2008;Gerdes and Zeh, 2009), metamorphic overgrowths on igneous or detrital zircons (Barton and Sergeev, 1997;Buick et al, 2006) and igneous zircons from either late-stage granitoids or anatectic sweats (Jaeckel et al 1997;Kröner et al, 1999;Zeh et al, 2007;Van Reenen et al, 2008). The petrological investigations of Zeh et al (2004) provide evidence to suggest that pelitic rocks of the BBC underwent a single prograde evolution at ca.…”

Section: P-t-t Evolution Of the Central Zonementioning

confidence: 99%

“…Whereas, the relative timing, style and extent of metamorphic activity in CZ has, over the years, come into question by numerous workers (e.g. Harris and Holland, 1984;Droop, 1989;Hisada and Miyano, 1996;Jaeckel et al, 1997;Holzer et al, 1998;Kröner et al, 1998Kröner et al, , 1999Smit et al, 2001;Van Reenen et al, 2004;Zeh et al, 2004;Zeh et al, 2005a,b;Hisada et al, 2005;Boshoff et al, 2006;Zeh et al, 2007;Rigby et al, 2008b;Gerdes and Zeh, 2009;Van Reenen et al, 2008;Perchuk et al 2008) who have defined different P-T paths. This has ultimately led to a great deal of controversy surrounding the tectonic evolution of the Limpopo Belt (Rigby et al, 2008a).…”

Section: Introductionmentioning

confidence: 99%

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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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Late Archaean to early Proterozoic granitoid magmatism and high-grade metamorphism in the central Limpopo belt, South Africa

Cited by 156 publications

References 33 publications

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield

The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?

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

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