Chinese Science Bulletin

, Volume 49, Issue 12, pp 1272–1278 | Cite as

Discovery of the boninite series volcanic rocks in the Bangong Lake ophiolite mélange, western Tibet, and its tectonic implications

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Abstract

The boninite series volcanic rocks, mainly composed of basaltic andesite, andesitic lava breccia and andesite porphyrite, were recognized for the first time in the Bangong Lake ophiolite mélange, western Tibet. These rocks have a strong boninitic affinity, with high SiO2 (55.61%–59.23%, weight percent), MgO (6.63%–13.08%, 9.13% on average (weight percent)), Al2O3/TiO2 ratios (36–54), Mg# (0.61–0.74), Ni (116 ppm on average) and Cr (354 ppm on average), low TiO2 (0.23%–0.39%, weight percent), and strong LILEs enrichment relative to the depleted HFSEs. Cl-chondrite normalized (La/Gd)N and (Gd/Yb)N ratios of about 1.70 and 0.83, respectively, produce prominent “U-shaped” normalized REE (rare earth element) patterns. Such a close compositional affinity to boninite indicates that these volcanic rocks were formed in a forearc setting produced by the intra-oceanic subduction.

Keywords

ophiolite mélange boninite intra-oceanic subduction Bangong Lake Tibet 

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Copyright information

© Science in China Press 2004

Authors and Affiliations

  • Shi Rendeng
    • 1
  • Yang Jingsui
    • 1
  • Xu Zhiqin
    • 1
  • Qi Xuexiang
    • 1
  1. 1.Laboratory of Continental Dynamics of Ministry of Land and Resources of China, Institute of GeologyChinese Academy of Geological SciencesBeijingChina

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