Abstract: The Middle Jurassic sandstones in the Mohe Basin,Heilongjiang are characterized by high contents of SiO₂ and low contents of Fe₂O₃,FeO and MgO,LREE enrichment,HREE depletion and slightly negative Eu anomaly.The geochemical signatures of major and trace elements and REEs,in integration with the discrimination diagrams for tectonic settings have mirrored that the Middle Jurassic deposits were derived from the continental island arcs and active continental margins.The Palaeozoic complexes on the northern margin of the Ergun block may be regarded as the main provenance of the basin.