Geochemistry and geochronology of Carboniferous volcanic rocks in the eastern Junggar terrane, NW China

implication for a tectonic transition

Yuping Su*, Jianping Zheng, William L. Griffin, Junhong Zhao, Huayun Tang, Qiang Ma, Xiangyang Lin

*Corresponding author for this work

Research output: Contribution to journalArticle

105 Citations (Scopus)

Abstract

The Carboniferous tectonic setting of the Junggar terrane, northern Xinjiang, NW China, has long been a matter of debate. Voluminous Carboniferous volcanic rocks are widely distributed in the Karamaili area, the southern part of the eastern Junggar terrane. Early Carboniferous rocks comprise basalts and basaltic andesites, with enrichment of LREE and LILE and depletion of HFSE, and uniformly high ε Nd(t) (+3.7 to +4.0). Late Carboniferous rocks consist of basalts, basaltic andesites, rhyolites and minor dacites, and can be subdivided into basic and felsic groups. The basic rocks are depleted in HFSE, and show variable high ε Nd(t) (+4.8 to +6.9). They have higher Cr and Ni and lower Na 2O, U and Th contents than early Carboniferous basic rocks. The felsic rocks show A-type affinity, with typical enrichment of alkalis, LREE and HFSE and strong depletion in Ba, Sr, Eu and Ti. They have high values of ε Nd(t) and zircon ε Hf(t) (+11.6 to +17.9). New LA-ICPMS zircon U-Pb analyses constrain their emplacement to late Carboniferous time (306.5-314.3Ma).The Carboniferous basic rocks show negative Zr-Hf anomalies and low Th/Ce (<0.07) and Th/La (0.06-0.16), excluding significant crustal contamination during magma evolution. They have low La/Ba (0.03-0.12), Ce/Y (<3) and (Tb/Yb) N (<2) and variable Ba/Th (28-318) and Ba/La (3.1-34), suggesting that they were derived from a main spinel with minor garnet lherzolite mantle source metasomatized by slab-derived fluids. The late Carboniferous felsic rocks were produced when upwelling asthenosphere triggered partial melting of juvenile lower crust. The early Carboniferous volcanism occurred in an island-arc setting related to the southward subduction of the Paleo-Junggar Ocean plate, whereas the late Carboniferous rocks erupted in a post-collisional extensional setting. Thus, a rapid tectonic transition from arc to post-collisional extension may have occurred between early and late Carboniferous, and probably resulted from slab break-off or lithospheric delamination.

Original languageEnglish
Pages (from-to)1009-1029
Number of pages21
JournalGondwana Research
Volume22
Issue number3-4
DOIs
Publication statusPublished - Nov 2012

Keywords

  • carboniferous volcanic rocks
  • mantle metasomatism
  • tectonic evolution
  • slab break-off
  • Eastern Junggar terrane

Fingerprint Dive into the research topics of 'Geochemistry and geochronology of Carboniferous volcanic rocks in the eastern Junggar terrane, NW China: implication for a tectonic transition'. Together they form a unique fingerprint.

Cite this