Abstract: The geochemical unit is identified by factor classification in Tahe area, Heilongjiang Province and geological mapping of thinly-covered areas is studied according to the theoretical geochemical meaning of each unit and its relationship to the corresponding geological units. Geochemical information is extracted sufficiently from regional geochemical data and the studied area is divided into five geochemical units with clear geological and geochemical meanings. Among these, the assemblage of Be, Nb, Sn, Y and Rb shows the distribution of the Paleozoic intrusive bodies and acid or alkali volcanic rocks. The assemblage of Co, TFe, Cr, Ni, V, Ti, MgO corresponds to the distribution of the Proterozoic intrusive and metamorphic rocks and Paleozoid basic rocks. The assemblage of SiO₂, K₂O and Na₂O reflects the Paleozoic intrusive bodies,the acid or alkali volcanic rocks, and the sedimentary rocks. The forth type, Al₂O₃, Li and F, implicates the distribution of Mesozoic volcanic rocks. And the fifth assemblage, CaO, Sr and Ba, largely corresponds to the Mesozoic sedimentary rocks, implying a steady deposit environment probably dominated by bio-deposition. Furthermore, The NE, NW, SN and EW faults in the area under study are deduced and recognized based on the element distribution and their boundary trends.

Key words: regional geochemical data, factor classification, geological mapping, geochemical unit