The Halinudeng pluton is located in the northern margin of Alxa area.LA-ICP-MS U-Pb dating of zircons from the pluton yields an age of 284.0±1.8 Ma,indicating that the formation of this pluton is Permian instead of Silurian as previous considered.The main rock types of the pluton include biotite-plagioclase granites and biotite monzogranites,with high SiO2(67%-72%),CaO(2.2%-4.4%) and Al2O3(14.5%-17.2%).Geochemical characteristics indicate that they are metaluminous-weakly peraluminous(A/CNK=0.90-1.07) and calc-alkaline to high-K calc-alkaline rocks(Na2O=3.7%-4.3%,K2O=2.1%-2.9%),assuming characteristics of I-type granite.The rocks have lower REE contents(35.2×10-6-130.6×10-6) with relative enrichment of LREE and positive Eu anomaly(δEu=1.04-1.90).The primitive mantle normalized trace element patterns are characterized by the enrichment of the LILE(K,Rb,Ba,Sr) and depletion of the HFSE(Ta,Nb,P,Yb,Y),showing the features of arc granites.It is considered that the northern margin of Alxa might still have had some arc-related magmatic activities during the Early Permian period.