Sr-Nd-Hf-Os isotopic characterizations of the Jiaohe peridotite xenoliths in Jilin province and constraints on the lithospheric mantle age in northeastern China

Abundant peridotitic xenoliths had been found in the Dashihe Cenozoic basalts in Jiaohe of Jilin Province, northeastern China. Petrological and mineralogical investigations indicated that these xenoliths are mostly spinel-bearing lherzolite with minor harzburgite, no garnet-bearing peridolite is found. Petrographic and geochemical data revealed that these xenoliths are fragments of the lithospheric mantle derived from the depth of 40 similar to 60km, constrained by equilibrium temperature. It was also indicated by the temperature calculation that the lithspheric mantle is stratigraphically layered with the lower part composed by fertile lherzolite and the upper part by refractory harzburgite and clinopyroxene-poor lherzolite. Sr-Nd-Hf isotopic data indicated that both of these lithospheric mantle are isotopically depleted, and the Os isotopic data proposed that they were formed during Mesoproterozoic, which is older than the overlying continental crust, showing geochronological decoupling between the crust and mantle. Therefore, we proposed that the studied area had undergone the whole-scale lost of the lithospheric mantle, similar to that taken place in the North China Craton, and then the Mesoproterozoic lithospheric mantle formed elsewhere accreted beneath the area.