<i>P</i>–<i>T</i>–fluid evolution in the Mahalapye Complex, Limpopo high‐grade terrane, eastern Botswana

Hisada, K.; Perchuk, L. L.; Gerya, T. V.; Reenen, Dirk D. van; Paya, B. K.

doi:10.1111/j.1525-1314.2005.00579.x

Cited by 31 publications

(11 citation statements)

References 59 publications

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“…The peak metamorphic P-T conditions agree well with the peak P-T estimates obtained by Droop (1989) and Hisada and Miyano (1996). However, the retrograde path, defined by matrix assemblages, garnet resorption textures, mineral zoning and diffusion patterns (Zeh et al, 2004) requires a simultaneous P-T decrease, in agreement with the DC paths defined by Perchuk et al (2000), Van Reenen et al (2004), Hisada et al (2005) and Rigby et al (2008b) but in stark contrast to retrograde paths defined by ITD (e.g. Droop, 1989;Hisada and Miyano, 1996) and subsequent IBC (Hisada and Miyano, 1996).…”

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

confidence: 78%

“…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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Section: P-t-t Evolution Of the Central Zonesupporting

confidence: 78%

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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“…The relative timing, style and extent of the magmatic and metamorphic activity have, over the years, come into question by numerous workers (e.g. [Harris and Holland, 1984], [Droop, 1989], [Stevens and Van Reenen, 1992a], [Hisada and Miyano, 1996], [Jaeckel et al, 1997], [Holzer et al, 1998], ], [Kroner et al, 1999], [Smit et al, 2001], [Van Reenen et al, 2004], [Zeh et al, 2004], [Zeh et al, 2005], [Hisada et al, 2005] and [Boshoff et al, 2006]) who have defined different pressure-temperature-time (P-T-t) paths for each of the zones. This has ultimately led to a great deal of controversy surrounding the tectonic evolution of the Limpopo Belt.…”

Section: Fig 1 a Geological Map Of The Limpopo Belt And Adjacent Crmentioning

confidence: 99%

“…The metapelitic gneisses are commonly migmatitic, forming predominantly layered and stromatic textures (e.g. [Chavagnac et al, 2001] and [Hisada et al, 2005]). There is some dispute as to whether the BBC forms a supracrustal unit that was deposited on top of the SRG, and its compositional variants (e.g.…”

Section: The Central Zonementioning

confidence: 99%

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A review of the pressure–temperature–time evolution of the Limpopo Belt: Constraints for a tectonic model

Rigby

Mouri

Brandl

2008

Journal of African Earth Sciences

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Published literature argues that the Limpopo Belt can be subdivided into three zones, each with a distinctive geological character and tectono-metamorphic fingerprint. There are currently two contrasting schools of thought regarding the tectono-metamorphic evolution of the CZ. One camp argues that geochronological, structural and prograde pressure-temperature (P-T) evidence collectively indicate that the CZ underwent tectono-metamorphism at ca. 2.0 Ga which followed a clockwise P-T evolution during a transpressive orogeny that was initiated by the collision of the Kaapvaal and Zimbabwe cratons. Deformation and metamorphism consistent with this scenario are observed in the southern part of the NMZ but are curiously absent from the whole of the SMZ. The opposing view argues that the peak metamorphism associated with the collision of the Kaapvaal and Zimbabwe cratons occurred at ca. 2.6 Ga and the later metamorphic event is an overprint associated with reactivation along Archean shear zones. Post-peakmetamorphic conditions, which at present cannot be convincingly related to either a ca. 2.6 or 2.0 Ga event in the CZ reveal contrasting retrograde paths implying either nearisothermal decompression and isobaric cooling associated with a 'pop-up' style of exhumation or steady decompression-cooling linked to exhumation controlled by erosion. Recent data argue that the prograde evolution of the ca. 2.0 Ga event is characterised by isobaric heating prior to decompression-cooling. Contrasting P-T paths indicate that either different units exist within the CZ that underwent different P-T evolutions or that some P-T work is erroneous due to the application of equilibrium thermobarometry to mineral assemblages that are not in equilibrium. The morphology of the P-T path(s) for the ca. 2.6-2.52 Ga event are also a matter of dispute. Some workers have postulated an anticlockwise P-T evolution during this period whilst others regard this metamorphic event as following a clockwise evolution. Granitoid magmatism is broadly contemporaneous in all three zones at ca. 2.7-2.5 suggesting a possible causal geodynamic link. P-T contrasts between and within the respective zones prevent, at present, the construction of a coherent and inter-related tectonic model that can account for all of the available evidence. Detailed and fully-integrated petrological and geochronological studies are required to produce reliable P-T-t paths that may resolve some of these pertinent issues.

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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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P–T–fluid evolution in the Mahalapye Complex, Limpopo high‐grade terrane, eastern Botswana

Cited by 31 publications

References 59 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?

A review of the pressure–temperature–time evolution of the Limpopo Belt: Constraints for a tectonic model

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

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