Triassic collision in the Paleo-Tethys Ocean constrained by volcanic activity in SW China

Jian Wei Zi, Peter A. Cawood, Wei Ming Fan, Yue jun Wang, Eric Tohver, Thompson Campbell McCuaig, Tou Ping Peng

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118 Citations (Scopus)

Abstract

A suite of collision-related Triassic volcanic rocks cropping out within the Jinshajiang-Ailaoshan orogenic belt in SW China offers insights into closure of the Paleo-Tethys and associated terrane/continent collision. Combined geochemical and Sr-Nd isotopic data for samples from the Jinshajiang segment demonstrate that the lower part of the volcanic suite is dominated by high-Si rhyolites (the Pantiange Formation) derived through crustal anatexis; whereas the upper units (the Cuiyibi Formation) are characterized by basalts alternating with intermediate-felsic lavas that share similar Sr-Nd isotopic signatures, and may have originated from partial melting of subduction-enriched lithospheric mantle. SHRIMP U-Pb analyses on zircons yield ages of 247-246. Ma for the rhyolites of the Pantiange Formation, and ages ranging from ca. 245. Ma to 237. Ma for the basaltic and intermediate-felsic samples from the overlying Cuiyibi Formation. These data, integrated with other geologic evidence (e.g., stratigraphic record), suggest an Early-Middle Triassic timing of terrane-continent collision along the Jinshajiang and Ailaoshan sutures with the 247-246. Ma Pantiange high-Si rhyolites representing the early magmatic products generated by this event. The development of the 245-237. Ma bimodal volcanism was associated with subsidence and deep-marine sedimentation. We interpret this as reflective of an extensional setting within an evolving collisional orogen, probably related to oblique convergence along the collisional zone. Triassic volcanic rocks with similar geochemical signatures and ages have been identified along the > 1000. km length of the Jinshajiang-Ailaoshan suture zone. The Indochina block to the south of the suture records 250-240. Ma tectonothermal activity. Taken together, these relationships suggest that initial collision and amalgamation of the Qamdo-Simao terrane (Indochina) with the Yangtze Block (South China) along the Jinshajiang-Ailaoshan and Song Ma sutures probably took place in the Early Triassic following consumption of the Paleo-Tethys Ocean.

Original languageEnglish
Pages (from-to)145-160
Number of pages16
JournalLithos
Volume144-145
DOIs
Publication statusPublished - Jul 2012
Externally publishedYes

Keywords

  • Collisional orogenesis
  • Jinshajiang orogenic belt
  • Paleo-Tethys
  • Triassic volcanism

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