Abstract: The Haerguole seamount basalt is located in Buqingshan area on the southern margin of the East Kunlun Mountains. Detailed geochemical analysis shows that the Haerguole seamount basalt can be divided into alkaline basalts and subalkaline basalts. The REE distribution patterns of alkaline basalts are similar to those of OIB, w i t h t h e d a t a ∑ L R E E = 6 3 . 8 × 1 0 - 6 ~ 1 7 5 . 3 6 × 1 0 - 6 , ∑ HREE=14.46 × 10- 6~28.56 × 10- 6, ∑ LREE/∑ HREE=4.41~6.14, (La/Yb)N=4.14~6.71, (Ce/Yb)N=3.31~5.12, and δEu=1.03~1.17. The REE distribution patterns of subalkaline basalts are similar to those of N-MORB, with the data ∑LREE=11.07×10-6~29.95×10-6, ∑ HREE=12.56 × 10- 6~25.41 × 10- 6, ∑ LREE/∑ HREE=0.88~1.54, (La/Yb)N=0.29~0.74, (Ce/Yb)N=0.37~0.77 and δEu=1.02~1.22. These geochemical characteristics suggest that the Haerguole basalt is the association of OIB and N-MORB. The OIB of Haerguole seamount basalt was formed in a seamount or an ocean island setting near the mid-ocean ridge, and OIB magma originated from EM Ⅱ- type enriched mantle. The N- MORB was formed in a mid- ocean ridge setting and originated in depleted mantle. These data provide more evidence for the existence of ocean basin in Buqingshan area in Late Paleozoic.