Discovery and geological significance of REE deposit in southern Songxian County, East Qinling, China

[Display omitted] •One REE deposit is firstly discovered in southern Songxian County, China.•The content of REE2O3 in fresh ores reaches the cut-off grade.•The emplacement age of the syenite porphyry is 236.3 ± 2.6 Ma.•REE is hosted in aegirine. East Qinling Orogenic Belt is an important metallogenic belt of China due to its production of an enormous amount of metal mineral resources. Herein, One rare earth element (REE) deposit occurrence is firstly discovered in southern Songxian County, East Qinling, and its geological and geochemical characteristics are reported. The REE ore body occurs as mineral veins in the marginal facies of the syenite porphyry complex, with matrix composed of orthoclase, aegirine and quartz. Zircon geochronological research shows that the emplacement age of the syenite porphyry is 236.3 ± 2.6 Ma (MSWD = 0.77, n = 9). The investigated syenite samples are high-K alkali-rich syenite series alkaline rocks. X-ray diffraction (XRD) analysis of bulk ores and electron probe micro-analysis (EPMA) of mineral reveal that the dark mineral is aegirine, with the chemical formula of (Na0.46K0.26Ca0.10)(Fe0.74Mg0.54)Si2.14O6, and the REE is mainly hosted in aegirine. The total content of REE is high with the rare earth element oxide (REE2O3) between 0.12% and 0.52%, and the REE2O3 content of fresh ores reaches the cut-off grade. The contact features of the REE ore bodies and ore veins with the wall rocks show that REE deposit is magmatic (or post-magmatic) hydrothermal genesis. This finding filled the gap of REE deposits in the East Qinling area, which provides guidance for future geological prospecting.