1. Shenyang Geological Survey, China Geological Survey, Shenyang 110034, China;
2. College of Earth Sciences, Jilin University, Changchun 130061, China

The Saima niobium deposit was a newly discovered REE deposit in Fengcheng area of Liaoning Province. The Ni and Ta ores were mainly reserved in grey-brown and grass-green ijolite syenite bodies. To understand the characteristics and metallogenic background of the deposit, the authors studied the petrography and geochemistry of metallogenic rock bodies. Petrographic studies showed that the rock bodies were mainly composed of orthoclase (Or, 50%), nepheline (Ne, 30%), biotite (Bt, 15%), arfvedsonite (Arf,3%) and aegirine (2%). The rocks underwent weak alteration, which was mainly silicification. Geochemical analysis found that the rocks consist of SiO₂ of 55.86%~63.80%, TiO₂ of 0.36%~0.64% and P₂O₅ of 0.04%~0.11%. The content of A1₂O₃ was more than 15%,which was metaluminous. The rocks were also characterized by high total alkali (K₂O+Na₂O=9.72%~15.51%) and kalium (K₂O/Na₂O=2.42~3.64), with Rittman index (σ=[w(K₂O+Na₂O)]2/[w(SiO₂-43)]) between 6.84 and 17.10. Therefore, the rock bodies belong to the syenite series of potassium-rich, aluminum-partial and alkali-rich. The rocks were enriched in Cs, Rb, Ba and other large ions (LILE) elements but depleted in Nb, Zr, Ti and other high field strength elements (HFSE), as well as P and Ti, with Nb of 34.79×10^-6~106.59×10^-6. The distribution pattern curve of their transitional elements was typical "W" shape. Th and Pb in HFSE were relatively abundant, but with negative Ti anomaly. The total amount of rare earth elements was high but with obvious variation (0.34×10^-6~946.00×10^-6), the LREE/HREE was between 7.20 and 18.48. The light rare earth elements (LREE) of the rocks were enriched and the heavy rare earth elements (HREE) were depleted, and the fractionation of rare earth elements was obvious. The rocks had higher (La/Yb)_N (7.56~39.58) and Nb/Ta (24.56~40.04), but lower (Rb/La)_N (0.31~1.14). There were no obvious Sr and Eu anomalies. The above features indicated that the metallogenic rock bodies of the Saima niobium deposit were formed in the post-collision continental rift environment.