Abstract: The large-porphyritic alkali-feldspar granite in Mordaga area is the product of the first magmatic activity of Ergun block. Study on the geological and geochemical characteristics of the large-porphyritic alkali-feldspar granite shows that the batholith was formed in Neoproterozoic Era during the continental crust evolution in syn-collision setting. From then on, the Ergun block started its intense collision-accretion period.