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Durham University

Department of Earth Sciences

Profile

Publication details for Professor Yaoling Niu

Zhou, S., Mo, X.X., Zhao, Z.D., Qiu, R.Z., Niu, Yaoling, Guo, T.Y. & Zhang, S.Q. (2010). 40Ar/39Ar Geochronology of post-collisional volcanism in the middle Gangdese Belt, southern Tibet. Journal of Asian Earth Sciences 37(3): 246-258.

Author(s) from Durham

Abstract

40Ar-39Ar step heating experiments on eleven mineral separates have been conducted on
eight volcanic rocks and a granite-porphyry dike from the Yangying and Wuyu basins in the middle
Gangdese Belt, southern Tibet. New radiometric ages for sanidine and biotite separates in four volcanic
rock samples from Yangying ranges from 10.32 ± 0.07 Ma to 11.40 ± 0.11 Ma, whereas plagioclase and
biotite separates from a stratigraphic section of the Gaza Cun Formation in the Wuyu basin give ages
from 12.57 ± 0.08 Ma to 13.2 ± 0.2 Ma. A granite porphyry which cuts the lower part of the Gaza Cun
Formation gives an age of 11.09 ± 0.07 Ma, and a dacite from the margin of Wuyu basin gives an age of
15.48 ± 0.11 Ma. These age data, in conjunction with geochemical data, suggest that the mid-Miocene
post-collisional volcanic rocks from these two basins have both similarities and difference in their
petrogenesis. The high [Sm/Yb]N (> 7) ratio and high Sr concentration (423 to 1065 ppm) in both
suites are consistent with their parental melts derived from partial melting of eclogitized lower crust.
However, the Yangying samples are more evolved than the Wuyu samples as manifested by lower MgO,
Sr/Sr*, Eu/Eu*, and normative plagioclase. It is likely that the source material for the Yangying suite is
likely more enriched in K2O than that of the Wuyu suite, perhaps has a greater contribution from
metasomatized lithospheric mantle.
It is apparent that the post-collisional volcanism in southern Tibet occurred spatially scattered and
temporally within a short period in each volcanic basin.