Mantle source characteristics of magmatic carbonatites from the Himalayan Collision Zone in western Sichuan, SW China; Evidence of Pb-Sr-Nd isotopes

作者：Tian SH^*; Hou ZQ; Yuan ZX; Xie YL; Fei HC; Yin SP; Yi LS; Yang ZM

来源：Acta Petrologica Sinica, 2006, 22(3): 669-677.

• magmatic carbonatite
• Himalayan Collision Zone
• Pb-Sr-Nd isotopes
• mantle source characteristics
• tectonic implication
• western Sichuan

Pb-Sr-Nd isotopes of the Cenozoic carbonatites (WSC) in western Sichuan, east Tibet, China, are presented in this paper. The WSC develop in the eastern Indo-Asian collision zone. The results show that the WSC have extremely low epsilon(Nd)(t) of -3.2 similar to -18.7 and relative high (Sr-87/Sr-86); of 0. 706020 similar to 0. 707923, as well as a wide range of Pb-207/Pb-204 (15.362 similar to 15. 679) and Pb-208/Pb-204 ratios (38.083 similar to 39.202), distinguished from most carbonatites around the world, generated by anorogenic processes. Their Sr-Nd, Pb-Pb, Sr-Pb and Nd-Pb isotopic signatures indicate that most carbonatites were derived from a transitional source between EMI and EMII components, related to recycling of the pelagic/tenigenous sediments with various mass ratios and underlying MORB-like oceanic crust by subduction process in Proterozoic times, whereas some carbonatites underwent Sr-Nd-Pb contamination by crustal materials. Melting of an enriched EMI-EMII mantle source for generating the WSC with coeval potassium-rich magmas was most likely triggered by a Cenozoic asthenospheric mantle diapir formed by subduction of the Indian and Yangtze continental slabs, and took place in the tectonic regime of the transition from transpression to transtension at Eocene/Oligocene boundary in the eastern Indo-Asian collision zone.

• 出版日期2006-3
• 单位中国地质科学院矿产资源研究所; 北京大学