1. Geochemistry and geochronology of the amphibolite blocks in ophiolitic mélanges along Bangong-Nujiang suture, central Tibet
- Author
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Ching-Hua Lo, Qing-Gao Zeng, Wei-Liang Wang, and Jonathan C. Aitchison
- Subjects
Basalt ,Back-arc basin ,Metamorphic rock ,Geochronology ,Geochemistry ,Geology ,Suture (geology) ,Structural basin ,Ophiolite ,Earth-Surface Processes - Abstract
Amphibolites occur as blocks within serpentinite-matrix melange at Dong Tso and Lagkor Tso in the Gertse area of central Tibet, where they are associated with the Bangong-Nujiang suture (BNS). Geochemical data shows amphibolites have similar MORB or arc-like MORB geochemical characteristics. Lagkor Tso amphibolites show greater arc affinity, whereas those from Dong Tso amphibolites are more MORB-like. These characteristics are similar to basalts from continental back-arc basin settings. Hornblendes from the amphibolites dated by the 40 Ar/ 39 Ar single-grain laser fusion technique show similar metamorphic ages ∼170–177 Ma, which is interpreted to represent the timing of the main metamorphic event experienced in this region. We suggest that the western and middle sectors of the BNS contain the remnants of a short-lived back-arc basin (the Bangong-Nujiang ocean), which partly opened and closed in the Middle Jurassic.
- Published
- 2008
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