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Precambrian |
1 Tectonics Special Research Centre, Department of Applied Geology, Curtin University of Technology, PO Box U1987, Perth, Western Australia, 6845 s.wilde{at}curtin.edu.au
2 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China
3 Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China
SHRIMP U-Pb zircon analyses from eight samples of metamorphosed intermediate to felsic volcanic rocks from the lower, middle and upper ‘subgroups’ of the Wutai sequence in the North China Craton define a weighted mean 207Pb/206Pb age of 2523 ± 3 Ma. Although individual rock ages range from 2533 ± 8 Ma to 2513 ± 8 Ma, all overlap within the error of the mean and do not support a stratigraphic interpretation for the sequence, since variations within individual previously assigned ‘formations’ in the sequence match the total age range. Contrary to previous interpretations, there is no correlation in age with metamorphic grade. These features highlight the need to reformulate stratigraphic schemes when defining the Precambrian geology of the North China Craton. The similarity in age between volcanic rocks of the Wutai Complex and higher-grade gneisses of the adjacent Fuping and Hengshan complexes supports the view that all three complexes represent portions of a Late Archaean arc complex that was tectonically dismembered and then re-assembled. There is no Fuping or Wutai orogeny in this, its type area: all three complexes were deformed and metamorphosed during collision of the eastern and western blocks of the North China Craton in the Lüliang orogeny c. 1.8 Ga ago.
