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 a 238U-206Pb isochron age of 435±45a with an initial 206Pb/204Pb value of 18.075±0.006,The age of -435 Ma is interpreted to represent the time of limestone diagensis rather than the time of metarmorphic 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 cratos.Becasuse the latest ordovician limestone was involved in the eclogite formation,the continental collision between the Yangtze and Sino-Korean Plates would postdate ordovican.

Marble is associated with ultrahigh pressure eclogite in the Dabie Mountains, EastChina. U-Pb isotope data for the marble define a 238U-206Pb isochron age of 435± 45 Ma withan initial 206Pb/204Pb value of 18. 075±0.006. The age 0f ~ 435 Ma is interpreted to represent the time of limestone diagenesis rather than the time of metamorphic resetting accompa-nied by the formation of the ultrahigh pressure eclogites at Triassic. The paleontologic andstratigraphic studies also favor a local excursion in the carbon isotopic composition of the latestOrdovician water within a sedimentary basin between the Sino-Korean and Yangtze cratons.Because the latest ordovician limestone was involved in the eclogite formation, the continentalcollision between the Yangtze and Sino-Korean plates would postdate Ordovician.