U-Pb dating of marble associated with eclogite from the Dabie Mountains, East China

Marble is associated with ultrahigh pressure eclogite in the Dabie Mountains, East China. U-Pb isotope data for the marble define a238U-206Pb isochron age of 435 ± 45 Ma with an initial206Pb/204Pb value of 18.075 ± 0.006. The age of ∼435 Ma is interpreted to represent the time of limestone diagenesis rather than the time of metamorphic resetting accompanied by the formation of the ultrahigh pressure eclogites at Triassic. The paleontologic and stratigraphic studies also favor a local excursion in the carbon isotopic composition of the latest Ordovician water within a sedimentary basin between the Sino-Korean and Yangtze cratons. Because the latest Ordovician limestone was involved in the eclogite formation, the continental collision between the Yangtze and Sino-Korean plates would postdate Ordovician.