Tectonic significance of the Dongqiao ophiolite in the north-central Tibetan plateau: Evidence from zircon dating, petrological, geochemical and Sr–Nd–Hf isotopic characterization. (February 2016)

• Record Type: Journal Article
• Authors: Liu, Tong; Zhai, Qing-guo; Wang, Jun; Bao, Pei-sheng; Qiangba, Zhaxi; Tang, Suo-han; Tang, Yue
• Is Part Of: Journal of Asian earth sciences. Volume 116(2016)
• Page Start: 139
• Page End: 154
• Publication Date: 2016-02
• Subjects: North-central Tibet -- Bangong–Nujiang suture zone -- Dongqiao ophiolite -- Geochemistry and isotope -- Zircon U–Pb ages; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2015.11.014
• Languages: English
• ISSNs: 1367-9120

Abstract

Highlights: The systematic petrological, geochemical, geochronological and Sr–Nd–Hf isotopic compositions of the Dongqiao ophiolite. The age of the Dongqiao ophiolite is ca. 188 Ma, and it was formed in the late Early Jurassic. The Dongqiao ophiolite was a typical SSZ-type ophiolite and was formed in an initial fore-arc oceanic basin. The Bangong–Nujiang Tethys Ocean probably existed as a fore-arc oceanic basin during the Late Triassic to Early Jurassic. Abstract: The Dongqiao ophiolite occurs in the central segment of the Bangong–Nujiang suture zone, in north-central Tibet, China. It is still debated on the tectonic setting of the Dongqiao ophiolite despite after more than 30 years' studies. The Dongqiao ophiolite has a complete section of a typical ophiolite, composed of harzburgite, dunite, layered and isotropic gabbros, pillow and massive basalts, as well as radiolarian chert. Whole-rock geochemical analyses show that harzburgite displays a broad U-shaped REE pattern and has a fore-arc affinity, whereas basalts show affinities of E-MORB, OIB and IAB. The basalts were probably formed in different tectonic settings, that is, mid-ocean ridge, oceanic island and island arc. The gabbros and basalts are characterized by positive ε Nd ( t ) (+1.6 to +6.7) and ε Hf ( t ) (+8.1 to +13.9) values. Zircon U–Pb dating yielded ages of 188 ± 1 Ma for the layered gabbro and 181 ± 1 Ma for the amphibole gabbro. The new ages and the published age data of the Dingqing and Dong Co ophiolites led us to conclude that the Bangong–Nujiang Ocean existed from the Late Triassic to Early Cretaceous. The new geochemical data also suggested that the Dongqiao ophiolite was a typical SSZ-type ophiolite formed in an initial fore-arc oceanic basin. Fore-arc ophiolites are probably widely distributed along the Bangong–Nujiang suture zone. If so, the Tethys Ocean of the Bangong–Nujiang area probably existed as a fore-arc oceanic basin during the Late Triassic to Early Jurassic.