Affiliation:
1. School of Civil Engineering and Architecture West Yunnan University of Applied Sciences Dali 671006 China
2. School of Earth Sciences and Resources China University of Geosciences (Beijing) Beijing 100080 China
3. Library West Yunnan University of Applied Sciences Dali 671006 China
4. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 100080 China
Abstract
AbstractIn this study, zircon U–Pb dating of volcanic rocks from the Zhongba ophiolite of the Yarlung Zangbo Suture Zone (YZSZ) in southern Xizang (Tibet) yielded an age of 247±3 Ma. According to whole rock geochemical and Sr–Nd–Pb isotopic data, the Early Triassic samples could be divided into two groups: Group 1 with P‐MORB affinity, showing initial 87Sr/86Sr ratios of 0.70253–0.70602, ɛNd(t) values of 4.2–5.3, (206Pb/204Pb)t ratios of 16.353–18.222, (207Pb/204Pb)tratios of 15.454–15.564, and (208Pb/204Pb)t ratios of 35.665–38.136; Group 2 with OIB affinity, showing initial 87Sr/86Sr ratios of 0.70249–0.70513, ɛNd(t) values of 4.4–4.9, (206Pb/204Pb)t ratios of 17.140–18.328, (207Pb/204Pb)t ratios of 15.491–15.575, and (208Pb/204Pb)t ratios of 36.051–38.247. Group 2 rocks formed by partial melting of the mantle source enriched by a former plume, and assimilated continental crustal material during melt ascension. The formation of Group 1 rocks corresponds to the mixing of OIB melts, with the same components as Group 2 and N‐MORBs. The Zhongba Early Triassic rocks belong to the continental margin type ophiolite and formed in the continental–oceanic transition zone during the initial opening of the Neo‐Tethys in southern Xizang (Tibet).