Zoned olivine xenocrysts in a late Mesozoic gabbro from the southern Taihang Mountains: implications for old lithospheric mantle beneath the central North China Craton

Abstract

AbstractZoned olivine grains are abundant in the late Mesozoic Shatuo gabbro (southern Taihang Mountains, central North China Craton). Olivine cores are rich in MgO and NiO, rims are rich in FeO and MnO, and both cores and rims have very low CaO contents. The cores invariably have a high Mg no. (92–94), similar to olivine xenocrysts from Palaeozoic kimberlites in eastern China. The compositional features of these olivines imply that they are xenocrysts rather than phenocrysts, namely, disaggregates of mantle peridotites at the time of intrusion. The compositional similarity of olivine cores to xenocrysts from Palaeozoic kimberlites suggests that the lithospheric mantle beneath the central North China Craton is ancient and refractory in nature, and quite different from eastern China, where the mantle is mainly composed of newly accreted materials resulting from large-scale lithospheric removal and replacement. The contrasting features of the lithospheric mantle beneath the eastern and central North China Craton imply that the large-scale lithospheric removal in Phanerozoic times was mainly confined to the eastern North China Craton.