Abstract: Compositions of major，trace and rare earth elements of the Neogene sandstones and siltstones in Guantao Formation of Nanpu sag are analyzed．The results reveal that most contents of major elements are moderate，SiO₂ and Al₂O₃ contents and their ratios show that most of sandstone samples are arkose or lithic arkose as well as other major elements,with only a few graywackes existing．Contents of mafic elements (Co，Cr，Ni，Sc，V) and large-ion lithophile elements ( LILE) like Rb，Cs，Ba，Sr are similar to that in the upper crust．The unanimous chondrite-normalized REE distribution patterns suggest that sandstones have similar provenance and be formed in the same tectonic settings．Most discrimination diagrams of tectonic settings，such as diagrams of log(K₂O/Na₂O) versus SiO₂，double variants distinction diagrams of major elements，diagrams of Th-Sc-Zr/10 and Th-Co-Zr/10 etc.，show that the provenance of Guantao Formation in Nanpu sag belongs to active continental margin tectonic setting．According to the diagrams of provenance discrimination (such as Th-Hf-Co plot and La/Th-La/Yb plot) and (Gd/Yb)_N ratios，it can be known that the primary materials of sedimentary rocks of Guantao Formation came from the upper continental crust of post-Archaean that were mainly composed of felsic rocks．Compared with REE distribution patterns of intermediate-acidic volcanic rocks and granites from Yanshan orogeny during different times，the results show that source rocks were mainly from intermediate-acidic volcanic rocks and/or granites which were formed during Yanshan movement period inYan-shan orogeny．

Key words: Guantao Formation, sandstone, geochemistry, tectonic setting, provenance, Nanpu sag