Geochemical and zircon isotopic evidence for extensive high level crustal contamination in Miocene to mid-Pleistocene intra-plate volcanic rocks from the Tengchong field, western Yunnan, China

摘要

SHRIMP zircon Pb/U dating of Cenozoic volcanic rocks in the Tengchong area, western Yunnan Province, China, shows that the dadte and andesitic breccia lavas from Qushi village were intruded at 480 10 ka and 800 40 ka, respectively. Moreover, Pb/U dating of trachyandesite from Tuantian village and olivine basalt from Wuhe village give weighted mean (PbID)-Pb-206/U-238 ages of 2.82 +/- 0.08 Ma and 12.28 +/- 030 Ma. Corrections for initial Th-230 disequilibrium of zircon were used for the former two younger ages.