Petrogenesis of Early-Permian sanukitoids from West Junggar, Northwest China : Implications for Late Paleozoic crustal growth in Central Asia

Jiyuan YIN, Wen CHEN, Wenjiao XIAO*, Chao YUAN, Min SUN, Gongjian TANG, Shun YU, Xiaoping LONG, Keda CAI, Hongyan GENG, Yan ZHANG, Xinyu LIU

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)

41 Citations (Scopus)

Abstract

Sanukitoids and their equivalents are rare subduction-related rock types that have been found in modern arc settings and in Late Archean sequences. The investigation of sanukitoids is of particular importance to a better understanding of crust-forming processes and continental growth. In this paper we report zircon U-Pb and Ar-Ar ages and major element, trace element, and Sr-Nd-Hf isotope data for the Bieluagaxi dioritic pluton and dikes from the southern part of the West Junggar, NW China. These rocks formed in the Early Permian and show a remarkable geochemical affinity with Cenozoic sanukitoids of the Setouchi Volcanic Belt of SW Japan with high Mg# (48-73) values, Cr (54-539 ppm), Ni (21-197 ppm) contents and Th/La (0.15-0.37) ratios and low Sr/Y ratios (16-27) and Sr (263-442 ppm) contents. They may be generated by the partial melting of subducting sediments, and subsequent melt-mantle interaction. Additionally, the sanukitoids are also widespread in the Karamay-Baogutu area of West Junggar accompanied by high Sr (average 713 ppm) contents and Sr/Y (50-130) ratios, and low Y (6.9-12.6 ppm) contents. The difference in petrochemical characteristics between the Baogutu-Karamay and Bieluagaxi sanukitoids can be explained by the difference in depth of initial melting, origin composition and fractional crystallization. The Baogutu-Karamay sanukitoids were probably formed under eclogitic conditions, while the Bieluagaxi sanukitoids were at a shallower depth. Moreover, the compositional similarity between continental-crust forming rocks and the Bieluagaxi sanukitoids suggests that the sanukitoids genesis could be closely related to the process of continental crust formation. The Late Carboniferous-Early Permian sanukitoids in the West Junggar may be an indicator of anomalous thermal activity. Ridge subduction may play a crucial role in the evolution and growth of the continental crust in Central Asia.

Original languageEnglish
Pages (from-to)385-397
Number of pages13
JournalTectonophysics
Volume662
Early online date20 Jan 2015
DOIs
Publication statusPublished - 1 Nov 2015
Externally publishedYes

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Keywords

  • Central Asia
  • Crustal growth
  • Late Paleozoic
  • Sanukitoid
  • West Junggar

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