Petrological characteristics of greenstones from the Sanchu belt were determined. The rocks are closely associated with serpentinite masses along the south marginal fault of the belt. A preliminary K-Ar age for the least metamorphosed rock is 120 Ma. They commonly have phenocrysts of plagioclase and olivine, which is totally altered into chlorite and has small euhedral inclusions of chromian spinel. Major-element bulk chemistry indicates they are tholeiitic basalts of MORB affinity. They especially resemble E-type MORB on the basis of chondrite-normalized rare-earth element distribution patterns as well as of Hf-Ta-Th ratios. Relic chromian spinels are enriched with Ti and Fes3+, showing a derivation from within-plate basalt or E-type MORB.Geochemical and mineralogical data indicate that the Sanchu greenstones are most likely E-type MORB.
