Geochronological problems related to polymetamorphism in the Limpopo Complex, South Africa

D. D. Van Reenen, R. Boshoff, C. A. Smit, L. L. Perchuk, J. D. Kramers, S. McCourt, R. A. Armstrong

Research output: Contribution to journalArticlepeer-review

68 Citations (Scopus)

Abstract

The integration of new and published geochronologic data with structural, magmatic/anatectic and pressure-temperature (P-T) process information allow the recognition of high-grade polymetamorphic granulites and associated high-grade shear zones in the Central Zone (CZ) of the Limpopo high-grade terrain in South Africa. Together, these two important features reflect a major high-grade D3/M3 event at ~ 2.02 Ga that overprinted the > 2.63 Ga high-grade Neoarchaean D2/M2 event, characterized by SW-plunging sheath folds. These major D2/M2 folds developed before ~ 2.63 Ga based on U-Pb zircon age data for precursors to leucocratic anatectic gneisses that cut the high-grade gneissic fabric. The D3/M3 shear event is accurately dated by U-Pb monazite (2017.1 ± 2.8 Ma) and PbSL garnet (2023 ± 11 Ma) age data obtained from syntectonic anatectic material, and from sheared metapelitic gneisses that were completely reworked during the high-grade shear event. The shear event was preceded by isobaric heating (P = ~ 6 kbar and T = ~ 670-780 °C), which resulted in the widespread formation of polymetamorphic granulites. Many efforts to date high-grade gneisses from the CZ using PbSL garnet dating resulted in a large spread of ages (~ 2.0-2.6 Ga) that reflect the polymetamorphic nature of these complexly deformed high-grade rocks.

Original languageEnglish
Pages (from-to)644-662
Number of pages19
JournalGondwana Research
Volume14
Issue number4
DOIs
Publication statusPublished - Dec 2008

Keywords

  • High-temperature shear zones
  • Limpopo high-grade terrain
  • PbSL and U-Pb age dating
  • Polymetamorphic granulites
  • Southern Africa

ASJC Scopus subject areas

  • Geology

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