Neoproterozoic subduction along the Ailaoshan zone, South China: geochronological and geochemical evidence from amphibolite

Yongfeng Cai, Yuejun Wang*, Peter A. Cawood, Weiming Fan, Huichuan Liu, Xiaowan Xing, Yuzhi Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

77 Citations (Scopus)

Abstract

Lenses of amphibolites occur along the Ailaoshan suture zone at the southwestern margin of the Yangtze Block, South China. Petrological, geochemical and zircon U-Pb geochronological data indicate that they are divisible into two coeval groups. Group 1, represented by the Jinping amphibolite, has mg-number of 71-76 and (La/Yb)cn ratios of 7.2-7.7, and displays a geochemical affinity to island arc volcanic rocks. Group 2 amphibolites occur at Yuanyang and are characterized by high Nb contents (14.3-18.4 ppm), resembling Nb-enriched basalts. The epsilon(Nd)(t) values for Group 1 range from -3.45 to -2.04 and for Group 2 from +4.08 to +4.39. A representative sample for Group 1 yields a U-Pb zircon age of 803 7 Ma, whereas two samples for Group 2 give U-Pb zircon ages of 813 +/- 11 Ma and 814 +/- 12 Ma. Petrogenetic analysis suggests that Group 1 originated from an orthopyroxene-rich source and Group 2 from a mantle wedge modified by slab-derived melt. In combination with other geological observations, these amphibolites are inferred to constitute part of an early Neoproterozoic (similar to 815-800 Ma) arc-back-arc basin system. The Neoproterozoic amphibolites and related rocks along the Ailaoshan zone may be the southward extension of the Neoproterozoic supra-subduction zone that developed along the western margin of the Yangtze Block. (C) 2014 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)13-28
Number of pages16
JournalPrecambrian Research
Volume245
Early online date1 Feb 2014
DOIs
Publication statusPublished - May 2014

Keywords

  • Ailaoshan zone
  • Amphibolite
  • Zircon U-Pb dating
  • Petrogenesis
  • Neoproterozoic subduction
  • Zircon U-PB
  • Back-arc basin
  • Scientific-drilling project
  • Northwestern yangtze block
  • Bimodal volcanic-rocks
  • River shear zone
  • A-type granites
  • Tectonic evolution
  • Crustal evolution
  • Jiangnan orogen

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