Multichronometric evidence for an in-situ origin of the ultrahigh-pressure metamorphic terrane of Dabieshan, China

Chavagnac, V., Jahn, B., Villa, I.M., Whitehouse, M.J. and Liu, D. (2001) Multichronometric evidence for an in-situ origin of the ultrahigh-pressure metamorphic terrane of Dabieshan, China. Journal of Geology, 109 (5), 633-646.

Abstract

U-Pb zircon data on gneisses indicate a Late Proterozoic protolith at approx. 700 Ma at Bixiling and a Late Archean to Early Proterozoic for the Shuanghe sheet within the ultrahigh-pressure metamorphic terrane of Dabieshan (China). U-Pb zircon and Sm-Nd dates on the gneisses of the Shuanghe sheet constrain a metamorphic peak at approx. 230 Ma. Rb-Sr and 40Ar-39Ar analyses of phengite from five gneisses in the Bixiling Complex yield ages at 198212 Ma, overlapping the 190220-Ma age on eclogites. The host gneisses record a similar metamorphic evolution as the coesite-bearing eclogites since both the peak and the retrograde evolution were contemporaneous. This argues for an in situ tectonic relationship.

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