Constraints from zircon U-Pb ages, O and Hf isotopic compositions on the origin of Neoproterozoic peraluminous granitoids from the Jiangnan Fold Belt, South China

Jun Hong Zhao*, Mei Fu Zhou, Jian Ping Zheng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

84 Citations (Scopus)

Abstract

Zircon textures and micro-chemical compositions precisely record the origin and petrogenesis of granitoids, which are crucial for evaluating crustal growth and reworking, thermal and geodynamic evolution. Zircons in peraluminous granitoids from the three largest 820 Ma complexes (Guibei, Yueyang and Jiuling) in the Jiangnan Fold Belt in South China are used to constrain their sources and petrogenetic processes. Zircons in the Guibei granitoids have complex internal structures. Nearly all magmatic and inherited zircons have similar εHf (-6.8 to +5.6) and δ18O values (8.8-11.6 ‰) and dominantly lie between εHf evolution vectors for a crust created between 1.7 and 2.1 Ga, suggesting that the Guibei granitoids were produced by partial melting of recycled heterogeneous supracrustal material. However, the Yueyang granitoids contain zircons with high εHf (-0.5 to +9.7) and relatively low δ18O values (5.9-8.4 ‰) and two-stage model ages of 1.1-1.8 Ga, and thus may have been formed by melting of mafic rocks from the lower crust. The Jiuling granitoids and their enclaves contain more complex zircons with more variable εHf (-7.2 to +9.7) and δ18O values (7.0-10.6 ‰), and lie along the mixing trend between the above-proposed infracrustal and supracrustal granitoids. Therefore, the Neoproterozoic peraluminous granitoids in the Jiangnan Fold Belt were produced by melting and mixing of continental crust. Compared with extremely low (≤4 ‰) and negative δ18O values of Neoproterozoic igneous zircons formed in its northern active continental margin, the high δ18O peraluminous granitoids in the southeastern Yangtze Block are considered to have been formed by melting of hydrothermally unaltered continental crust triggered by asthenosphere upwelling in the Nanhua back-arc basin.

Original languageEnglish
Pages (from-to)1505-1519
Number of pages15
JournalContributions to Mineralogy and Petrology
Volume166
Issue number5
DOIs
Publication statusPublished - Nov 2013
Externally publishedYes

Keywords

  • Hafnium isotope
  • Neoproterozoic
  • Oxygen isotope
  • Peraluminous granitoid
  • South China
  • Zircon

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