Sm-Nd dating of eclogites from the main drill hole of the Chinese Continental Scientific Drilling Project and outcrops in the southwestern Sulu terrane, eastern China

Abstract：Sm-Nd ages of from eclogites in the mainhole of the Chinese Continental Scientific Drilling (CCSD) Project and outcrops in the southern ultrahigh-pressure terrane were determined. The data points of whole rock, garnet and omphacite of each sample all plot on a line. Except for sample B210R186, the other five samples eclogites give very close Sm-Nd isochron ages, ranging between 202.6 and 219 Ma. These Sm-Nd ages are similar to those (SHRIMP U-Pb ages 200 - 220 Ma) of zircon retrogressive rims from the country rock——gneisses, suggesting that the Sm-Nd isotope system of garnet in eclogites analyzed in the study might be reset during the isothermal decompressional retrogressive stage and close during the retrograde transition to amphibolite facies. Therefore the Sm-Nd whole rock-mineral isochron ages of 202.6-219 Ma determined in this paper should be interpreted as representing the retrograde ages of the isothermal decompressional retrogressive stage during exhumation of the South Sulu eclogite, rather than the ultrahigh-pressure metamorphic ages of the Sulu terrane.