U–Pb zircon ages, geochemical and isotopic compositions of granitoids in Songpan-Garze fold belt, eastern Tibetan Plateau: constraints on petrogenesis and tectonic evolution of the basement

• DOI: 10.1007/s00410-006-0095-2
• Publication Date: 2006-05-18T05:53:02Z
• Authors: Hong-Fei Zhang; Li Zhang; Nigel Harris; Lan-Lan Jin; Honglin Yuan
• Keywords: Petrogenesis; Basement

The Songpan-Garze fold belt, located in the eastern part of the Tibetan Plateau, covers a huge triangular area bounded by the Yangtze (South China), the North China and the Tibetan Plateau blocks. In the northeastern part of the Songpan-Garze fold belt, the Yanggon and Maoergai granitoids provide insights into regional tectono-magmatic events, basement nature and tectonic evolution. U-Pb zircon SHRIMP dating shows that the Yanggon and Maoergai granitoids have mag- matic crystallization ages of 221 ± 3.8 Ma and 216 ± 5.7 Ma, respectively. Both the granitoids display adakitic geochemical signatures, suggesting that their magma was derived from partial melting of thickened lower crust. Pb-Sr-Nd isotopic compositions for granitoids reveal that there is an unexposed Proterozoic basement in the Songpan-Garze belt, which has an affinity with the Yangtze block. During development of the Paleo-Tethys ocean, the basement of the Songpan- Garze belt would be a peninsula approaching the Paleo-Tethys ocean from the Yangtze block.