Located in the east segment of Harlik, the Omoertage alkaline intrusion (OMTG) was emplaced in Xiaopudong calc-alkaline granitic pluton during the Late Paleozoic. The purplish red OMTG alkaline granites exhibit uniform micrographic texture and contain typical alkaline ferromagnesian minerals such as arfvedsonite and aegirine and accessory minerals like zircon, ilmenite and fluorite. Geochemically, the alkaline granites are rich in silicon, alkalis, iron, and poor in calcium and magnesium, and show enrichment of Rb, Cs, Th, U and Zr and depletion of Ba, Sr, P and Ti. They also have relatively high concentrations of Nb, Ta, Hf, Ga, and display high (10⁴ Ga/Al) values (3.41~3.65) and strong Eu depletions (δEu=0.30~0.33). Zircon saturation temperatures of OMTG alkaline granites vary from 940 to 952℃, which is in agreement with the characteristics of typical A-type granite. Zircon LA-ICP-MS U-Pb dating yielded a mean age of 288.9±1.6 Ma, indicating that the alkaline intrusion was formed during the Early Permian. The OMTG granites have high εHf(t) values (+8.7~+12.5) and young one-stage Hf model ages (600~430 Ma). The alkaline granites also show higher Y/Nb ratios (2.92~3.17), suggesting that they belong to the A2 type granite. An integrated study of the tectonic setting and geochemical characteristics show that the OMTG A2-type granite experienced fractional crystallization by the alkaline magma which was produced by the partial melting of Neoproterozoic-Early Paleozoic juvenile crust induced by slab break-off after post-collision events.