Sr-Nd-Pb isotopic variations of the Cenozoic volcanic rocks from the Qinghai-Xizang Plateau and its adjacent areas

The highlights in the present paper are placed on the spatio-temporal evolution of the Cenozoic volcanic rocks from the Qinghai-Xizang Plateau and its adjacent areas in the light of Sr, Nd and Pb isotopic data issued in recent years. The results of research are generalized as follows. (1) There are gradations from PREMA to EMⅡ for the magmatic sources of the volcanic rocks in central Gangdise, and from the mixed crust-mantle sources in subduction zones through upper crust sources in orogenic zones to lower crust sources in western Gangdise. (2) The magmatic sources in western Qiangtang are represented by depleted mantle-derived rocks. The Nangqian Basin and volcanic sources in Haidong, Dali are relatively deeper, suggesting a mixed source of oceanic asthenospheric mantle and subduction components. The magmatic sources of northern Xizang, western Kunlun and northern Qiangtang are represented by EMⅡ-type enrichment mantle; The Yulinshan ultrapotassic volcanic rocks represent the EMⅡ-type magmatic sources that have been subjected to intense metasomatism of the continental crustal matter. The western Qinling volcanic rocks are derived from the depleted mantle. The Tengchong Cenozoic volcanic rocks occur in the EMⅡ-type enrichment mantle source areas. (3) There are two evolutionary trends for the Cenozoic volcanic rocks from western Qiangtang, Hoh Xil, western Kunlun and Tengchong:towards the EMⅡ type for the Yulinshan, Pulu, Xiongyingtai-Jingyuhu and Tengchong volcanic rocks, and along the 0 Ma mantle-upper crust line for the Quanshuigou, Heishibeihu and Ashikule volcanic rocks. (4) At least four types of magmatic sources may be recognized for the Cenozoic volcanic rocks on the Qinghai-Xizang Plateau and its adjacent areas.