Crustal growth during island arc accretion and transcurrent deformation, Natal Metamorphic Province, South Africa: New isotopic constraints

Christopher J. Spencer, Robert J. Thomas, Nick M W Roberts, Peter A. Cawood, Ian Millar, Simon Tapster

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The Natal Metamorphic Province consists of, from north to south, the Tugela, Mzumbe, and Margate Terranes. These were accreted to the southeastern margin of the Kaapvaal Craton in the late Mesoproterozoic, and followed by intrusion of a large suite of A-type granitoid bodies. New U-Pb data from zircon, titanite, and monazite further constrains the temporal framework of these geological events.The Tugela and Mzumbe Terranes record protracted magmatism in an island arc complex from ~1200. Ma to 1160. Ma, followed by the accretion of these terranes onto the southern margin of the Kaapvaal Craton at ~1150. Ma. Arc magmatism in the Margate Terrane continued until ~1120. Ma and was followed by extension and bimodal volcanism immediately prior to accretion to the Kaapvaal/Mzumbe continental margin at ~1090. Ma. This accretion was accompanied by high-pressure and high-temperature metamorphism, juxtaposition of the Mzumbe and Margate Terranes along the Melville Thrust, and the formation of a number of syntectonic intrusive units derived from melting of the pre-existing arc crust. After accretion, extensional collapse is evidenced by the intrusion of mafic/ultramafic and alkaline intermediate magmatic suites at ~1085. Ma, resulting from mafic underplating and/or lower crustal delamination. Nd and Hf isotopic data imply the magmatic rocks of the Natal Metamorphic Province were derived from relatively juvenile continental crust, initially generated by island arc magmatism and subsequently reworked during the accretion event(s). The combined Kaapvaal-NMP region (the southern margin of the enlarged Kalahari Craton) then experienced extensive sinistral transcurrent deformation centred along a series of discrete steep shear zones that are found from the Kaapvaal cratonic margin to the southernmost portion of the Natal Metamorphic Province. This deformation is accompanied by low-pressure, (ultra)high-temperature metamorphism, isobaric cooling, and intrusion of the voluminous A-type Oribi Gorge Suite porphyritic granites and charnockites throughout the Mzumbe and Margate Terranes.

Original languageEnglish
Pages (from-to)203-217
Number of pages15
JournalPrecambrian Research
Volume265
DOIs
Publication statusPublished - 1 Aug 2015
Externally publishedYes

Keywords

  • Accretion
  • Crustal growth
  • Natal orogeny
  • Oblique collision
  • Zircon U-Pb-Hf

Cite this

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title = "Crustal growth during island arc accretion and transcurrent deformation, Natal Metamorphic Province, South Africa: New isotopic constraints",
abstract = "The Natal Metamorphic Province consists of, from north to south, the Tugela, Mzumbe, and Margate Terranes. These were accreted to the southeastern margin of the Kaapvaal Craton in the late Mesoproterozoic, and followed by intrusion of a large suite of A-type granitoid bodies. New U-Pb data from zircon, titanite, and monazite further constrains the temporal framework of these geological events.The Tugela and Mzumbe Terranes record protracted magmatism in an island arc complex from ~1200. Ma to 1160. Ma, followed by the accretion of these terranes onto the southern margin of the Kaapvaal Craton at ~1150. Ma. Arc magmatism in the Margate Terrane continued until ~1120. Ma and was followed by extension and bimodal volcanism immediately prior to accretion to the Kaapvaal/Mzumbe continental margin at ~1090. Ma. This accretion was accompanied by high-pressure and high-temperature metamorphism, juxtaposition of the Mzumbe and Margate Terranes along the Melville Thrust, and the formation of a number of syntectonic intrusive units derived from melting of the pre-existing arc crust. After accretion, extensional collapse is evidenced by the intrusion of mafic/ultramafic and alkaline intermediate magmatic suites at ~1085. Ma, resulting from mafic underplating and/or lower crustal delamination. Nd and Hf isotopic data imply the magmatic rocks of the Natal Metamorphic Province were derived from relatively juvenile continental crust, initially generated by island arc magmatism and subsequently reworked during the accretion event(s). The combined Kaapvaal-NMP region (the southern margin of the enlarged Kalahari Craton) then experienced extensive sinistral transcurrent deformation centred along a series of discrete steep shear zones that are found from the Kaapvaal cratonic margin to the southernmost portion of the Natal Metamorphic Province. This deformation is accompanied by low-pressure, (ultra)high-temperature metamorphism, isobaric cooling, and intrusion of the voluminous A-type Oribi Gorge Suite porphyritic granites and charnockites throughout the Mzumbe and Margate Terranes.",
keywords = "Accretion, Crustal growth, Natal orogeny, Oblique collision, Zircon U-Pb-Hf",
author = "Spencer, {Christopher J.} and Thomas, {Robert J.} and Roberts, {Nick M W} and Cawood, {Peter A.} and Ian Millar and Simon Tapster",
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Crustal growth during island arc accretion and transcurrent deformation, Natal Metamorphic Province, South Africa : New isotopic constraints. / Spencer, Christopher J.; Thomas, Robert J.; Roberts, Nick M W; Cawood, Peter A.; Millar, Ian; Tapster, Simon.

In: Precambrian Research, Vol. 265, 01.08.2015, p. 203-217.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Crustal growth during island arc accretion and transcurrent deformation, Natal Metamorphic Province, South Africa

T2 - New isotopic constraints

AU - Spencer, Christopher J.

AU - Thomas, Robert J.

AU - Roberts, Nick M W

AU - Cawood, Peter A.

AU - Millar, Ian

AU - Tapster, Simon

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N2 - The Natal Metamorphic Province consists of, from north to south, the Tugela, Mzumbe, and Margate Terranes. These were accreted to the southeastern margin of the Kaapvaal Craton in the late Mesoproterozoic, and followed by intrusion of a large suite of A-type granitoid bodies. New U-Pb data from zircon, titanite, and monazite further constrains the temporal framework of these geological events.The Tugela and Mzumbe Terranes record protracted magmatism in an island arc complex from ~1200. Ma to 1160. Ma, followed by the accretion of these terranes onto the southern margin of the Kaapvaal Craton at ~1150. Ma. Arc magmatism in the Margate Terrane continued until ~1120. Ma and was followed by extension and bimodal volcanism immediately prior to accretion to the Kaapvaal/Mzumbe continental margin at ~1090. Ma. This accretion was accompanied by high-pressure and high-temperature metamorphism, juxtaposition of the Mzumbe and Margate Terranes along the Melville Thrust, and the formation of a number of syntectonic intrusive units derived from melting of the pre-existing arc crust. After accretion, extensional collapse is evidenced by the intrusion of mafic/ultramafic and alkaline intermediate magmatic suites at ~1085. Ma, resulting from mafic underplating and/or lower crustal delamination. Nd and Hf isotopic data imply the magmatic rocks of the Natal Metamorphic Province were derived from relatively juvenile continental crust, initially generated by island arc magmatism and subsequently reworked during the accretion event(s). The combined Kaapvaal-NMP region (the southern margin of the enlarged Kalahari Craton) then experienced extensive sinistral transcurrent deformation centred along a series of discrete steep shear zones that are found from the Kaapvaal cratonic margin to the southernmost portion of the Natal Metamorphic Province. This deformation is accompanied by low-pressure, (ultra)high-temperature metamorphism, isobaric cooling, and intrusion of the voluminous A-type Oribi Gorge Suite porphyritic granites and charnockites throughout the Mzumbe and Margate Terranes.

AB - The Natal Metamorphic Province consists of, from north to south, the Tugela, Mzumbe, and Margate Terranes. These were accreted to the southeastern margin of the Kaapvaal Craton in the late Mesoproterozoic, and followed by intrusion of a large suite of A-type granitoid bodies. New U-Pb data from zircon, titanite, and monazite further constrains the temporal framework of these geological events.The Tugela and Mzumbe Terranes record protracted magmatism in an island arc complex from ~1200. Ma to 1160. Ma, followed by the accretion of these terranes onto the southern margin of the Kaapvaal Craton at ~1150. Ma. Arc magmatism in the Margate Terrane continued until ~1120. Ma and was followed by extension and bimodal volcanism immediately prior to accretion to the Kaapvaal/Mzumbe continental margin at ~1090. Ma. This accretion was accompanied by high-pressure and high-temperature metamorphism, juxtaposition of the Mzumbe and Margate Terranes along the Melville Thrust, and the formation of a number of syntectonic intrusive units derived from melting of the pre-existing arc crust. After accretion, extensional collapse is evidenced by the intrusion of mafic/ultramafic and alkaline intermediate magmatic suites at ~1085. Ma, resulting from mafic underplating and/or lower crustal delamination. Nd and Hf isotopic data imply the magmatic rocks of the Natal Metamorphic Province were derived from relatively juvenile continental crust, initially generated by island arc magmatism and subsequently reworked during the accretion event(s). The combined Kaapvaal-NMP region (the southern margin of the enlarged Kalahari Craton) then experienced extensive sinistral transcurrent deformation centred along a series of discrete steep shear zones that are found from the Kaapvaal cratonic margin to the southernmost portion of the Natal Metamorphic Province. This deformation is accompanied by low-pressure, (ultra)high-temperature metamorphism, isobaric cooling, and intrusion of the voluminous A-type Oribi Gorge Suite porphyritic granites and charnockites throughout the Mzumbe and Margate Terranes.

KW - Accretion

KW - Crustal growth

KW - Natal orogeny

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