Unraveling the record of successive high grade events in the Central Zone of the Limpopo Belt using Pb single phase dating of metamorphic minerals

Holzer, Lorenz; Barton, J. M.; Kramers, Jan D.

doi:10.1016/s0301-9268(97)00058-2

Cited by 175 publications

(126 citation statements)

References 33 publications

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“…Three temporally distinct structural-metamorphic events are recognized within the CZ at 3.24-3.12 Ga (D1/M1), 2.58-2.51 Ga (D2/M2) and 2.03 (D3/M3) (Holzer et al, 1998;Kroner et al, 1999;Zeh et al, 2007;Millonig et al, 2008;Gerdes and Zeh, 2009). …”

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

confidence: 99%

“…SRG sheath folds and type 1 and 2 interference patterns); Hofmann et al, 1998) at ca. 2.6-2.51 is based on Pb stepwise leaching dates from sillimanite and cogenetic garnet, obtained from metapelitic xenoliths within the Bulai Pluton (Holzer et al, 1998). Textural relationships indicate that sillimanite + cordierite + garnet are replacing andalusite, which Holzer et al (1998) interpret to represent a prograde reaction reflecting an anticlockwise low-P/high-T evolution.…”

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

confidence: 99%

“…Holzer (1995) described three generations of such rocks, the oldest being intruded by the Bulai and the youngest cutting the Bulai. Coupled with single zircon ages for other granitoid gneisses (Holzer et al, 1998;Kröner et al, 1999;Zeh et al, 2007;Gerdes and Zeh, 2009) it seems the CZ underwent several pulses of thermal disturbance associated with magmatism and/or tectono-metamorphism between ca 2.7 and 2.5 Ga. This magmatic-metamorphic evolution is broadly contemporaneous with than those reported from the NMZ (2.58-2.7 Ga: Berger et al, 1995) and the SMZ (2.66-2.69 Ga: Kreissig et al, 2001), suggesting a possible causal geodynamic link.…”

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%

“…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%

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

confidence: 99%

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

confidence: 99%

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

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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Petrology and geochronology of sapphirine‐bearing granulites from the Limpopo Complex in eastern Botswana: Implications for Palaeoproterozoic long‐lived high‐pressure/ultrahigh‐temperature metamorphism and rapid exhumation

2022

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The Limpopo Complex in southern Africa is a classic example of Neoarchean collisional orogens with a Palaeoproterozoic thermal overprint. We report new petrological, pressure–temperature (P–T), and geochronological data of sapphirine‐bearing Mg–Al‐rich and pelitic granulites from a metasupracrustal unit (the Beit Bridge Complex [BBC]) in the eastern part of Botswana to constrain its P–T–time evolution. Textural observations and phase equilibria modelling of the peak mineral assemblage of Mg–Al‐rich granulites (K‐feldspar + orthopyroxene [Opx2; Al2O3 up to 8.8 wt.%] + sillimanite [Sil2] + quartz + rutile + biotite [Bt2] + inferred melt) in the NCKFMASHTO system recorded a peak metamorphic condition of >930°C and > 10.3 kbar. A pelitic granulite recorded consistent P–T conditions of 960–980°C and > 10.3 kbar, indicating high‐pressure (HP) and ultrahigh‐temperature (UHT) metamorphism for the BBC in Botswana. Post‐peak retrograde conditions were obtained based on the stability of sapphirine + cordierite symplectite assemblage in the Mg–Al‐rich rocks (820–860°C and 6.4–7.0 kbar) and orthopyroxene [Opx3] + cordierite symplectite assemblage in the pelitic granulite (830–930°C and 4.3–5.8 kbar), indicating near‐isothermal decompression after the peak HP–UHT metamorphism along a clockwise P–T path. Similar HP–UHT metamorphism followed by a near‐isothermal decompression along a clockwise P–T path was reported from different regions of the BBC in South Africa and Zimbabwe (P > 14 kbar and ~1,000°C based on the stability fields of magnesian staurolite and sapphirine + quartz assemblage), although the peak P–T condition is slightly lower in Botswana. Monazite grains with patchy zoning show isochron ages of 2,115 ± 77 Ma for Th‐poor domains, and 2,058 ± 40 Ma and 2,033 ± 34 Ma for Th‐rich domains. Similar ages were obtained from zircon U–Pb geochronology as 2,232–2,135 Ma and 2,010 ± 19 Ma (Th/U = 0.05–0.26). The younger ages (2.0 Ga) probably indicate the timing of near‐peak high‐grade event, while the older ages might indicate a thermal event during the prograde heating stage. The P–T conditions and zircon/monazite ages suggest Palaeoproterozoic long‐lived metamorphism associated with intracontinental transpressional tectonics related to Palaeoproterozoic orogenic events around the united Zimbabwe–Kaapvaal Craton.

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The Kalahari Craton, Southern Africa: From Archean Crustal Evolution to Gondwana Amalgamation

Oriolo

Becker

2018

Regional Geology Reviews

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Unraveling the record of successive high grade events in the Central Zone of the Limpopo Belt using Pb single phase dating of metamorphic minerals

Cited by 175 publications

References 33 publications

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

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

Petrology and geochronology of sapphirine‐bearing granulites from the Limpopo Complex in eastern Botswana: Implications for Palaeoproterozoic long‐lived high‐pressure/ultrahigh‐temperature metamorphism and rapid exhumation

The Kalahari Craton, Southern Africa: From Archean Crustal Evolution to Gondwana Amalgamation

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