Abstract:

Garnet peridotites from the Chinese Continental Scientific Drilling project(CCSD-PP1)have less magnesian olivine(Fo_91.5), and lower-Cr garnet than the cratonic mantle xenoliths reflected by those from the Paleozoic Mengyin kimberlites(garnet-facies)and the Cenozoic Hebi basalts(spinel-facies).  The CCSD-PP1 diopsides have low HREE contents and sinusoidal to LREE-enriched patterns.  These features, and their high Mg/Si, and low CaO and Al₂O₃contents indicate that the CCSD-PP1 peridotites represent a moderately refractory mantle protolith.  Details of mineral chemistry indicate that this protolith experienced complex metasomatism by asthenosphere-derived melts/fluids in Mesoproterozoic, and subsolidus re-equilibration involving fluids/melts derived from the subducted Yangtze continental crust during ultrahigh-pressure(UHP)metamorphism in Early Mesozoic.  Tectonic extension of the subcontinental lithospheric mantle(SCLM)of the North China Craton and exhumation of the Sulu UHP rocks in Early Mesozoic induced the early upwelling of asthenosphere.

Key words: Sulu orogen, CCSD-PP1 peridotite, mantle composition, tectonic intrusion, North China Craton