Abstract: A series of strongly-deformed mafic-ultramafic rocks occur at the Kongling high-grade metamorphic terrain in Yan- gtze continenta1 nucleus, scattering in the Miaowan Formation inlayers and podiforms. This metamafic-ultramafic rock associa- tion is of great significance to the early tectonic evolution of Yantgze b1ock. In this study, ID-TIMS whole-rock Sm-Nd isochron dating is carried out for the serpentinized harzburgite and amphibolite from this rock suite. The results indicate that the serpen- tinized harzburgite was formed at1 063土12 Ma, showing that it is feasible to date tiny amount of heavily-altered ultramafic rocks by means of the Sm-Nd isotopic system. The comparatively uniform Nd isotopic composition(with eNd(t) value ranging from6.90 to7.32) indicates that they were formed in a c1osed system. Two-stage Nd moda1 age of 1.13-1.09 Ga is c1ose to their emplacement time, implying an origin of partia1 melting from depleted asthenospheric mantle. Combined with documented workonlate Mesoproterozoic to early Neoproterozoic tectonic-magmatic events in the area, it is suggested that the Yangtze b1ock may have been composed of severa1 microcontinents at that time. There could have been an ocean separating the Yangtze continenta1 nucleus from western Yangtze continenta1 segment.