Early Neoproterozoic assembly and subsequent rifting in South China: Revealed from mafic and ultramafic rocks, central Jiangnan Orogen

Yuejun Wang, Yuzhi Zhang, Peter A. Cawood, Yongzhi Zhou, Feifei Zhang, Xue Yang, Xiang Cui

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The assembly time and process of the South China Block and its subsequent breakup remain controversial. This paper presents a set of new mineral chemical, zircon U-Pb geochronological, elemental and Sr-Nd-Hf-O isotopic data of the Group 1 Yiyang pillow basalt, Group 2 Aikou and Xinyu mafic–ultramafic rocks, and Group 3 Yuanling-Anjiang gabbro-diabase from the central Jiangnan Orogen. Group 1 is ∼830 Ma high-Mg subalkaline basalt with the mineral assemblage of clinopyroxene, epidote, chlorite and minor plagioclase. It shows arc-like geochemical signatures and derived from a wedge source recently infiltrated by recycled component. Group 2 is mainly characterized by peridotite, pyroxenite, gabbro and diabase and crystallized at ∼791–780 Ma. It has zircon εHf(t) and δ18O values of −0.4∼+5.6 and +4.99∼+5.90‰, respectively. The Group 2 rocks geochemically resemble OIB-like high-Nb/Nb-enriched basalt and originated from an OIB-like origin with the ultramafic rocks being the cumulates of the mafic magma. Group 3 contains normal zoned clinopyroxene and mainly formed at ∼780–786 Ma. It has 87Sr/86Sr(t) = 0.7066–0.7116, εNd(t) = −2.5∼−0.3, zircon εHf(t) = −6.6∼−1.0 and δ18O = +6.06∼+6.65‰, originated from the lithosphere-asthenosphere interaction. These data synthetically reflect the South China Block being created by an early Neoproterozoic accretionary orogen along the periphery of Rodinia and transformed into lithospheric extensional regime since ∼785 Ma in response to Rodinia breakup. Along the Jiangnan Orogen, the Paleo-Huanan Ocean was completely closed by ∼830 Ma. The Yangtze with Cathaysia blocks finally amalgamated at ∼810 Ma and subsequent rifting of the united SCB occurred at ∼785 Ma, respectively.

Original languageEnglish
Article number105367
Pages (from-to)1-26
Number of pages26
JournalPrecambrian Research
Volume331
DOIs
Publication statusPublished - 1 Sep 2019

Keywords

  • Arc-like high-Mg pillow basalts
  • Early Neoproterozoic assemblage
  • Elemental and Sr-Nd-Hf-O isotopic compositions
  • Initial rifting
  • Mineral chemical compositions
  • OIB-like mafic and ultramafic rocks
  • South China

Cite this

Wang, Yuejun ; Zhang, Yuzhi ; Cawood, Peter A. ; Zhou, Yongzhi ; Zhang, Feifei ; Yang, Xue ; Cui, Xiang. / Early Neoproterozoic assembly and subsequent rifting in South China : Revealed from mafic and ultramafic rocks, central Jiangnan Orogen. In: Precambrian Research. 2019 ; Vol. 331. pp. 1-26.
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abstract = "The assembly time and process of the South China Block and its subsequent breakup remain controversial. This paper presents a set of new mineral chemical, zircon U-Pb geochronological, elemental and Sr-Nd-Hf-O isotopic data of the Group 1 Yiyang pillow basalt, Group 2 Aikou and Xinyu mafic–ultramafic rocks, and Group 3 Yuanling-Anjiang gabbro-diabase from the central Jiangnan Orogen. Group 1 is ∼830 Ma high-Mg subalkaline basalt with the mineral assemblage of clinopyroxene, epidote, chlorite and minor plagioclase. It shows arc-like geochemical signatures and derived from a wedge source recently infiltrated by recycled component. Group 2 is mainly characterized by peridotite, pyroxenite, gabbro and diabase and crystallized at ∼791–780 Ma. It has zircon εHf(t) and δ18O values of −0.4∼+5.6 and +4.99∼+5.90‰, respectively. The Group 2 rocks geochemically resemble OIB-like high-Nb/Nb-enriched basalt and originated from an OIB-like origin with the ultramafic rocks being the cumulates of the mafic magma. Group 3 contains normal zoned clinopyroxene and mainly formed at ∼780–786 Ma. It has 87Sr/86Sr(t) = 0.7066–0.7116, εNd(t) = −2.5∼−0.3, zircon εHf(t) = −6.6∼−1.0 and δ18O = +6.06∼+6.65‰, originated from the lithosphere-asthenosphere interaction. These data synthetically reflect the South China Block being created by an early Neoproterozoic accretionary orogen along the periphery of Rodinia and transformed into lithospheric extensional regime since ∼785 Ma in response to Rodinia breakup. Along the Jiangnan Orogen, the Paleo-Huanan Ocean was completely closed by ∼830 Ma. The Yangtze with Cathaysia blocks finally amalgamated at ∼810 Ma and subsequent rifting of the united SCB occurred at ∼785 Ma, respectively.",
keywords = "Arc-like high-Mg pillow basalts, Early Neoproterozoic assemblage, Elemental and Sr-Nd-Hf-O isotopic compositions, Initial rifting, Mineral chemical compositions, OIB-like mafic and ultramafic rocks, South China",
author = "Yuejun Wang and Yuzhi Zhang and Cawood, {Peter A.} and Yongzhi Zhou and Feifei Zhang and Xue Yang and Xiang Cui",
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Early Neoproterozoic assembly and subsequent rifting in South China : Revealed from mafic and ultramafic rocks, central Jiangnan Orogen. / Wang, Yuejun; Zhang, Yuzhi; Cawood, Peter A.; Zhou, Yongzhi; Zhang, Feifei; Yang, Xue; Cui, Xiang.

In: Precambrian Research, Vol. 331, 105367, 01.09.2019, p. 1-26.

Research output: Contribution to journalArticleResearchpeer-review

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T1 - Early Neoproterozoic assembly and subsequent rifting in South China

T2 - Revealed from mafic and ultramafic rocks, central Jiangnan Orogen

AU - Wang, Yuejun

AU - Zhang, Yuzhi

AU - Cawood, Peter A.

AU - Zhou, Yongzhi

AU - Zhang, Feifei

AU - Yang, Xue

AU - Cui, Xiang

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AB - The assembly time and process of the South China Block and its subsequent breakup remain controversial. This paper presents a set of new mineral chemical, zircon U-Pb geochronological, elemental and Sr-Nd-Hf-O isotopic data of the Group 1 Yiyang pillow basalt, Group 2 Aikou and Xinyu mafic–ultramafic rocks, and Group 3 Yuanling-Anjiang gabbro-diabase from the central Jiangnan Orogen. Group 1 is ∼830 Ma high-Mg subalkaline basalt with the mineral assemblage of clinopyroxene, epidote, chlorite and minor plagioclase. It shows arc-like geochemical signatures and derived from a wedge source recently infiltrated by recycled component. Group 2 is mainly characterized by peridotite, pyroxenite, gabbro and diabase and crystallized at ∼791–780 Ma. It has zircon εHf(t) and δ18O values of −0.4∼+5.6 and +4.99∼+5.90‰, respectively. The Group 2 rocks geochemically resemble OIB-like high-Nb/Nb-enriched basalt and originated from an OIB-like origin with the ultramafic rocks being the cumulates of the mafic magma. Group 3 contains normal zoned clinopyroxene and mainly formed at ∼780–786 Ma. It has 87Sr/86Sr(t) = 0.7066–0.7116, εNd(t) = −2.5∼−0.3, zircon εHf(t) = −6.6∼−1.0 and δ18O = +6.06∼+6.65‰, originated from the lithosphere-asthenosphere interaction. These data synthetically reflect the South China Block being created by an early Neoproterozoic accretionary orogen along the periphery of Rodinia and transformed into lithospheric extensional regime since ∼785 Ma in response to Rodinia breakup. Along the Jiangnan Orogen, the Paleo-Huanan Ocean was completely closed by ∼830 Ma. The Yangtze with Cathaysia blocks finally amalgamated at ∼810 Ma and subsequent rifting of the united SCB occurred at ∼785 Ma, respectively.

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KW - Initial rifting

KW - Mineral chemical compositions

KW - OIB-like mafic and ultramafic rocks

KW - South China

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