Kinematics and age constraints of deformation in a Late Carboniferous accretionary complex in Western Junggar, NW China

Ji'en ZHANG, Wenjiao XIAO*, Chunming HAN, Songjian AO, Chao YUAN, Min SUN, Hongyan GENG, Guochun ZHAO, Qianqian GUO, Chong MA

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)

133 Citations (Scopus)

Abstract

The Karamay area, situated in the eastern part of Western Junggar, Southern Altaids, contains an ophiolitic mélange with ultramafic rocks, gabbro, basalt, chert and limestone, which show typical block-in-matrix structures, and coherent turbidites and tuffs. These lithological associations are interpreted as incoherent and coherent series formed in an accretionary complex. On the basis of detailed field mapping and analyses of the asymmetry of imbricate thrusts, duplexes, tilted structures, shear band cleavages, and the NW-verging inclined to overturned folds, we conclude that the overall movement in the accretionary complex was top-to-the-NW. The youngest tuff involved in the deformation contains detrital zircons that have a U-Pb age (LA-MC ICP-MS) of 308±7Ma. 39Ar-40Ar resistance furnace step-heating of amphibole separates from a diorite dike, which cuts the folded and imbricated rocks in the accretionary prism, yielded a plateau age of 307±2Ma. Consequently, the age of the deformation in the prism is tightly constrained at 307-308Ma, implying that the deformation occurred in an extremely short time-span during SE-ward subduction. Combined contemporaneous occurrence of Baogutu adakite, high-Mg, Sr-enriched and Y-poor dioritic dikes, Miaoergou charnockite, and Maliya mafic rocks, we further suggest the accretionary complex was cut by near-trench volcanic rocks and plutons possibly due to interaction with a spreading ridge.

Original languageEnglish
Pages (from-to)958-974
Number of pages17
JournalGondwana Research
Volume19
Issue number4
Early online date17 Oct 2010
DOIs
Publication statusPublished - Jun 2011
Externally publishedYes

Keywords

  • Accretionary complex
  • Coheret unit
  • Melange
  • Southern Altaids
  • West Junggar

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