Chronology of the oldest supracrustal sequences in the Palaeoarchaean Barberton Greenstone Belt, South Africa and Swaziland

A. KRÖNER*, C. R. ANHAEUSSER, J. E. HOFFMANN, J. WONG, H. GENG, E. HEGNER, H. XIE, J. YANG, D. LIU

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)

19 Citations (Scopus)

Abstract

Zircon age data for felsic metavolcanic rocks of the Sandspruit and Theespruit formations, the two oldest supracrustal components in the Palaeoarchaean Barberton Greenstone Belt, show that these two successions are time-equivalent and constitute one single volcanic event at ca. 3530 Ma. The Sandspruit felsic rocks are ubiquitously metasomatized, intensely deformed and intruded by, and tectonically interlayered with, ca. 3450 Ma granitoid sills that are probably part of the Theespruit Pluton. One metasomatized Sandspruit sample contains abundant metamorphic zircons with a weighted mean 207Pb/206Pb age of 3220.1 ± 1.6 Ma, reflecting a widespread metamorphic event in parts of the eastern Kaapvaal craton in South Africa and Swaziland. Several samples of felsic metavolcanic rocks of the Theespruit formation confirm a previously established magmatic emplacement age of ca. 3530 Ma, but slightly older rocks up to 3552 Ma were found in the easternmost exposure of the Theespruit sequence near the South African/Swaziland border and may represent a lower lithostratigraphic level than exposed farther west.Hf-in-zircon isotopic data for most felsic metavolcanic rocks confirm earlier results suggesting that these rocks predominantly originated from melting of a felsic continental basement, possibly related to the oldest, ca. 3660-3550 Ma components of the Ancient Gneiss Complex in Swaziland. However, several Sandspruit samples also suggest that a juvenile source was involved in their generation, perhaps a mafic underplate. We see no evidence in the geochemistry and isotopic signatures of felsic volcanic rocks of the Sandspruit and Theespruit formations for partial melting of a metabasaltic protolith and for Palaeoarchean oceanic crust that formed in connection with subduction. We rather favor a plateau-type setting on older continental crust.

Original languageEnglish
Pages (from-to)123-143
Number of pages21
JournalPrecambrian Research
Volume279
Early online date19 Apr 2016
DOIs
Publication statusPublished - Jul 2016
Externally publishedYes

Fingerprint

felsic rock
greenstone belt
chronology
Rocks
metavolcanic rock
zircon
Melting
Volcanic rocks
protolith
granitoid
Geochemistry
sill
rock
gneiss
oceanic crust
continental crust
pluton
partial melting
craton
volcanic rock

Keywords

  • Felsic volcanism
  • Greenstone Belt
  • Palaeoarchaean
  • South Africa
  • Zircon geochronology

Cite this

KRÖNER, A. ; ANHAEUSSER, C. R. ; HOFFMANN, J. E. ; WONG, J. ; GENG, H. ; HEGNER, E. ; XIE, H. ; YANG, J. ; LIU, D. / Chronology of the oldest supracrustal sequences in the Palaeoarchaean Barberton Greenstone Belt, South Africa and Swaziland. In: Precambrian Research. 2016 ; Vol. 279. pp. 123-143.
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abstract = "Zircon age data for felsic metavolcanic rocks of the Sandspruit and Theespruit formations, the two oldest supracrustal components in the Palaeoarchaean Barberton Greenstone Belt, show that these two successions are time-equivalent and constitute one single volcanic event at ca. 3530 Ma. The Sandspruit felsic rocks are ubiquitously metasomatized, intensely deformed and intruded by, and tectonically interlayered with, ca. 3450 Ma granitoid sills that are probably part of the Theespruit Pluton. One metasomatized Sandspruit sample contains abundant metamorphic zircons with a weighted mean 207Pb/206Pb age of 3220.1 ± 1.6 Ma, reflecting a widespread metamorphic event in parts of the eastern Kaapvaal craton in South Africa and Swaziland. Several samples of felsic metavolcanic rocks of the Theespruit formation confirm a previously established magmatic emplacement age of ca. 3530 Ma, but slightly older rocks up to 3552 Ma were found in the easternmost exposure of the Theespruit sequence near the South African/Swaziland border and may represent a lower lithostratigraphic level than exposed farther west.Hf-in-zircon isotopic data for most felsic metavolcanic rocks confirm earlier results suggesting that these rocks predominantly originated from melting of a felsic continental basement, possibly related to the oldest, ca. 3660-3550 Ma components of the Ancient Gneiss Complex in Swaziland. However, several Sandspruit samples also suggest that a juvenile source was involved in their generation, perhaps a mafic underplate. We see no evidence in the geochemistry and isotopic signatures of felsic volcanic rocks of the Sandspruit and Theespruit formations for partial melting of a metabasaltic protolith and for Palaeoarchean oceanic crust that formed in connection with subduction. We rather favor a plateau-type setting on older continental crust.",
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Chronology of the oldest supracrustal sequences in the Palaeoarchaean Barberton Greenstone Belt, South Africa and Swaziland. / KRÖNER, A.; ANHAEUSSER, C. R.; HOFFMANN, J. E.; WONG, J.; GENG, H.; HEGNER, E.; XIE, H.; YANG, J.; LIU, D.

In: Precambrian Research, Vol. 279, 07.2016, p. 123-143.

Research output: Journal PublicationsJournal Article (refereed)

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T1 - Chronology of the oldest supracrustal sequences in the Palaeoarchaean Barberton Greenstone Belt, South Africa and Swaziland

AU - KRÖNER, A.

AU - ANHAEUSSER, C. R.

AU - HOFFMANN, J. E.

AU - WONG, J.

AU - GENG, H.

AU - HEGNER, E.

AU - XIE, H.

AU - YANG, J.

AU - LIU, D.

PY - 2016/7

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N2 - Zircon age data for felsic metavolcanic rocks of the Sandspruit and Theespruit formations, the two oldest supracrustal components in the Palaeoarchaean Barberton Greenstone Belt, show that these two successions are time-equivalent and constitute one single volcanic event at ca. 3530 Ma. The Sandspruit felsic rocks are ubiquitously metasomatized, intensely deformed and intruded by, and tectonically interlayered with, ca. 3450 Ma granitoid sills that are probably part of the Theespruit Pluton. One metasomatized Sandspruit sample contains abundant metamorphic zircons with a weighted mean 207Pb/206Pb age of 3220.1 ± 1.6 Ma, reflecting a widespread metamorphic event in parts of the eastern Kaapvaal craton in South Africa and Swaziland. Several samples of felsic metavolcanic rocks of the Theespruit formation confirm a previously established magmatic emplacement age of ca. 3530 Ma, but slightly older rocks up to 3552 Ma were found in the easternmost exposure of the Theespruit sequence near the South African/Swaziland border and may represent a lower lithostratigraphic level than exposed farther west.Hf-in-zircon isotopic data for most felsic metavolcanic rocks confirm earlier results suggesting that these rocks predominantly originated from melting of a felsic continental basement, possibly related to the oldest, ca. 3660-3550 Ma components of the Ancient Gneiss Complex in Swaziland. However, several Sandspruit samples also suggest that a juvenile source was involved in their generation, perhaps a mafic underplate. We see no evidence in the geochemistry and isotopic signatures of felsic volcanic rocks of the Sandspruit and Theespruit formations for partial melting of a metabasaltic protolith and for Palaeoarchean oceanic crust that formed in connection with subduction. We rather favor a plateau-type setting on older continental crust.

AB - Zircon age data for felsic metavolcanic rocks of the Sandspruit and Theespruit formations, the two oldest supracrustal components in the Palaeoarchaean Barberton Greenstone Belt, show that these two successions are time-equivalent and constitute one single volcanic event at ca. 3530 Ma. The Sandspruit felsic rocks are ubiquitously metasomatized, intensely deformed and intruded by, and tectonically interlayered with, ca. 3450 Ma granitoid sills that are probably part of the Theespruit Pluton. One metasomatized Sandspruit sample contains abundant metamorphic zircons with a weighted mean 207Pb/206Pb age of 3220.1 ± 1.6 Ma, reflecting a widespread metamorphic event in parts of the eastern Kaapvaal craton in South Africa and Swaziland. Several samples of felsic metavolcanic rocks of the Theespruit formation confirm a previously established magmatic emplacement age of ca. 3530 Ma, but slightly older rocks up to 3552 Ma were found in the easternmost exposure of the Theespruit sequence near the South African/Swaziland border and may represent a lower lithostratigraphic level than exposed farther west.Hf-in-zircon isotopic data for most felsic metavolcanic rocks confirm earlier results suggesting that these rocks predominantly originated from melting of a felsic continental basement, possibly related to the oldest, ca. 3660-3550 Ma components of the Ancient Gneiss Complex in Swaziland. However, several Sandspruit samples also suggest that a juvenile source was involved in their generation, perhaps a mafic underplate. We see no evidence in the geochemistry and isotopic signatures of felsic volcanic rocks of the Sandspruit and Theespruit formations for partial melting of a metabasaltic protolith and for Palaeoarchean oceanic crust that formed in connection with subduction. We rather favor a plateau-type setting on older continental crust.

KW - Felsic volcanism

KW - Greenstone Belt

KW - Palaeoarchaean

KW - South Africa

KW - Zircon geochronology

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M3 - Journal Article (refereed)

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JO - Precambrian Research

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