Neoproterozoic granitoids from the Phan Si Pan Zone, NW Vietnam: geochemistry and geochronology constraints on reconstructing South China - India Palaeogeography

摘要

Neoproterozoic rocks in the Phan Si Pan Zone, NW Vietnam are considered to be the remnant of the ancient continental crust. They recorded the evolution of the Gondwana supercontinent. A combined study of U-Pb geochronology and Sr-Nd-Hf isotopic geochemistry has been carried out for the Neoproterozoic granites in the Phan Si Pan Zone. Zircon LA-ICP-MS data yield crystallization ages ranging from 758.0 +/- 5.0 to 762.0 +/- 8.1 Ma. The Neoproterozoic granites have variable (Sr-87/Sr-86)(i) ratios of 0.7029 to 0.708 and a wide range of epsilon(Nd)(t) values (-2.02 to 0.04) and of zircon epsilon(Hf)(t) values (-5.1 to 0.0). All these characteristics suggest an origin through partial melting of ancient crustal source rocks with small amount input from the mantle material. Whole-rock Nd and zircon Hf isotopic model ages mostly vary from 1.67 Ga to 1.99 Ga, indicating the existence of the Paleoproterozoic source material in the study area. Neoproterozoic granites in the Phan Si Pan Zone, NW Vietnam have a similar tectonic evolution to those in SW Yangtze, South China.