The enrichment mechanism of rare earth elements in ion-adsorption rare earth deposits is a hot topic in ore deposit studies. Comprehensive zircon U-Pb geochronology and whole-rock major and trace element analyses were carried out on the fresh granites from 3 drill hole in the ion-adsorption rare earth deposit of the Guidong pluton in Shaoguan, northern Guangdong. The granites are mainly composed of quartz, potash feldspar, plagioclase and biotite, and are mainly of monzogranite and syenogranite in lithology. Zircon U-Pb dating of two monzogranites and one syenogranite show that their formation ages are 160±1 Ma, 162±1 Ma and 160±2 Ma, respectively, indicating that the western part of the Guidong pluton is formed concentrated at the Early Yanshanian (~160 Ma). These granites are peraluminous to strongly peraluminous, with high alkali content. The syenogranite is highly fractionated, featured by high SiO2 content, low Zr/Hf ratio, and enrichment of K and Rb. It is suggested that the Guidong Yanshanian granites are aluminous A-type granite, which may be derived from the biotite dehydration partial melting of late Paleoproterozoic tonalite under anhydrous conditions, and the syenogranites are the product of intense fractional crystallization of monzogranites. Compared with the adjacent Dadaonshan granites, it is proposed that the intense fractional crystallization of alkaline felsic melts may play an important role for the formation of HREE-enriched ion-adsorption rare earth deposits.