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

U-Pb zircon data on gneisses indicate a Late Proterozoic protolith at simil ar to 700 Ma at Bixiling and a Late Archean to Early Proterozoic for the Sh uanghe 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 similar to 230 Ma. Rb-Sr and Ar-40-Ar-39 a nalyses of phengite from five gneisses in the Bixiling Complex yield ages a t 198-212 Ma, overlapping the 190-220-Ma age on eclogites. The host gneisse s record a similar metamorphic evolution as the coesite-bearing eclogites s ince both the peak and the retrograde evolution were contemporaneous. This argues for an in situ tectonic relationship.