Abstract
Composition of the lithospheric mantle beneath the Sino-Korea craton is investigated, using garnet xenocrysts, mantle xenoliths in kimberlites and mineral inclusions within diamonds. It is verified that the lithospheric mantle beneath the Sino-Korea craton is mainly composed of strongly depleted garnet lherzolite and garnet harzburgite, with a very small proportion of eclogite. The Mg number of peridotite olivine ranges from 91.5 to 95.0, with a peak at about 92.5. Estimated Mg/Si ratio ranges from 1.26 to 1.31. Differences of the Sino-Korea cratonic peridotite with the upper mantle in oceanic and off-cratonic regions are significant. Combined with seismic information, we propose that this compositional anomaly of Archean lithospheric mantle is a worldwide phenomenon. Evident differences in chemical composition, thickness and temperature of the present lithosphere in the Sino-Korea craton region with that established in this study show that the extremely refractory lithospheric mantle was replaced by convective mantle after the kimberlite eruption. It seems to be the first locality that detachment of cratonic lithospheric mantle was verified.
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