Petrogenesis of the Majiari ophiolite (western Tibet, China): Implications for intra-oceanic subduction in the Bangong–Nujiang Tethys. (15th September 2017)

• Record Type: Journal Article
• Authors: Huang, Qiang-tai; Liu, Wei-liang; Xia, Bin; Cai, Zhou-rong; Chen, Wei-yan; Li, Jian-feng; Yin, Zheng-xin
• Is Part Of: Journal of Asian earth sciences. Volume 146(2017)
• Page Start: 337
• Page End: 351
• Publication Date: 2017-09-15
• Subjects: Majiari ophiolite -- Bangong–Nujiang Suture Zone -- Intra-oceanic subduction -- Neo-Tethys -- Tibetan Plateau; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2017.06.008
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: The Majiari ophiolite formed at ca.170.5 Ma and emplaced at ca.112 Ma. Intra-oceanic subduction occurred and northward subduction polarity of the Bangong-Nujiang Tethys is favored. The collision of the North Lhasa and South Qiangtang terranes occurred likely before the Early-Cretaceous. Abstract: The Majiari ophiolite lies in the western Bangong-Nujiang Suture Zone, which separates the Qiangtang and Lhasa blocks in central Tibet. The ophiolite consists of peridotite, gabbro/diabase and basalt. Zircon U-Pb dating yielded an age of 170.5 ± 1.7 Ma for the gabbro, whereas 40 Ar/ 39 Ar dating of plagioclase from the same gabbro yielded ages of 108.4 ± 2.6 Ma (plateau age) and 112 ± 2 Ma (isochron age), indicating that the ophiolite was formed during the Middle Jurassic and was probably emplaced during the Early Cretaceous. Zircons from the gabbro have εHf (t) values ranging from +6.9 to +10.6 and f (Lu/Hf) values ranging from −0.92 to −0.98. Mafic lavas plot in the tholeiitic basalt field but are depleted in Nb, Ta and Ti and enriched in Rb, Ba and Th in the N-MORB-normalized trace element spider diagram. These lavas have whole-rock εNd ( t ) values of +5.9 to +6.6, suggesting that they were derived from a depleted mantle source, which was probably modified by subducted materials. The Majiari ophiolite probably formed in a typical back-arc basin above a supra-subduction zone (SSZ) mantle wedge. Intra-oceanic subduction occurred during the Middle Jurassic and collision of the Lhasa and South Qiangtang terranes likely occurred in the Early Cretaceous. Thus, closure of the Bangong–Nujiang Tethys Ocean likely occurred before the Early Cretaceous.