Abstract:Hongshiquan area is located in the western part of Longshoushan. This paper makes a detailed petrographic and geochemical analysis of the alaskite to explore its petrogenesis, characteristics of magma source area and tectonic background. The results show that the Hongshiquan alaskite has high SiO2 (67.46% ~ 75.56%), rich Al2O3 (11.46% ~ 14.80%), lean MgO (0.11% ~ 0.99%), low TFe2O3 (0.53% ~ 1.10%), aluminum saturation index (A / CNK) is 0.86 ~ 1.12, and total alkali (ALK) is 8.58% ~ 10.91%, which belongs to quasi aluminum-weak peraluminous alkaline granite. The trace element samples are relatively rich in U, Rb elements, and relatively depleted in P, Nb, Ba, and Ti elements. The rare earth elements are relatively rich in light rare earth (15.9 × 10-6 ~ 197.79 × 10-6), relatively deficient in heavy rare earth (2.43 × 10-6 ~ 32.85 × 10-6), and the overall EU negative anomaly. The above geochemical characteristics indicate that Hongshiquan alaskite has the characteristics of I-type granite. The comprehensive analysis shows that the post-collision extension environment of Hongshiquan alaskite may be due to the magma bottom invasion of mantle-derived magma, which generates a large amount of thermal energy, resulting in partial melting of the crustal material.