The Hongliugoubei simple mafic—ultramafic intrusion is located in the northeastern margin of Olongbuluck micro block, its wall rock is the Dakendaban Group (Pt1dk) of Palaeoproterozoic and the intrusion mainly composed of melaolivine—gabbro and gabbro. It’s a moderately enriched Fe—Ti—P ferruginous ultrabasic intrusion with m/f value being 2.66 to 3.04.The rocks from Hongliugoubei intrusion is well pervasive cumulatic texture, olivine poikilitic texture and plagioclase poikilitic texture. The crystallization sequence of minerals is olivine olivine + plagioclase + orthopyroxeneorthopyroxene + clinopyroxene + plagioclase. All kinds of the rocks from the intrusion are enriched in light rare earth elements （LREE） and large ion lithophile elements （LILE） and depleted in Nb, Ta. The Geochemistry information indicates that the magma has undergone some degree assimilation and contamination from upper crust. Partial melting process occurs in spinel stable field. SHRIMP zircon U Pb age is 418.3 2.8Ma belonging to late Silurian. The Geochemical characteristics of this intrusion , formation age and regional geological data show that it forms in the extensional (or rifting) environment of ancient continental margin. It also suggests northern margin of Qaidam Basin is extensional during late Silurian to late Devonian.