Abstract
In 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,εNd(t)values of 4.2-5.3,(206Pb/204Pb)t ratios of 16.353-18.222,(207Pb/204Pb)t ratios 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,εNd(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).
基金项目
National Natural Science Foundation of China(91955206)
National Natural Science Foundation of China(41603038)
Second Tibetan Plateau Scientific Expedition and Research program(2019QZKK0803)
Scientific Research Foundation for Advanced Scholars,West Yunnan University of Applied Sciences(2022RCKY0004)
Yunnan Fundamental Research Projects(202301AT070012)
国家科技期刊平台
NSTL
万方数据