The Luoguhe intrusion, located in MoheCounty, Heilongjiang Province, is mainly composed of mon-zogranite, quartz diorite and granodiorite, with minor dio-rite, tonalite, quartz monzodiorite, quartz monzonite, syeno-granite and alkali-feldspar granite. The intrusion can bedivided into two lithological units, i.e. quartz diorite andmonzogranite units, with affinities to high-K calc-alkalineseries. The quartz diorite unit (SiO2: 54.79%―58.30%Na2O/CaO: 0.79―1.53 and Shand index: 0.77―0.82) belongsto metaluminous rocks. And the monzogranite unit (SiO2:65.29%―66.45%, Na2O/CaO: 1.73―3.43 and Shand index<1.05) can be considered as weakly peraluminous rocks. Theintrusion is characterized by high REE abundance (∑REE =180.2―344.3 μg/g), medium-strong negative Eu anomalies(δ Eu = 0.33―0.82), weak REE fractionation [(La/Yb)N =4.12―10.45], enrichments in Rb, Th, U, K, La, Ce, Nd, HfZr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and TiThese characteristics of major, REE and trace elements in-dicate that the intrusion was formed in a transitional tectonicsetting from compressional to extensional regime, which canbe classified as post-collisional granitoids. SHRIMP U-Pbzircon analyses yield ages of 517±9 and 504±8 Ma for thequartz diorite and monzogranite units, respectively. The dis-covery of Early Paleozoic post-collisional granites in thenorthern margin of the Erguna massif indicates that thenorthern branch of Paleo-Asian Ocean between Siberianplate and Erguna massif was closed in the Early Paleozoicand the Salair orogeny ended ca. 500 Ma ago. The Luoguhe intrusion, located in Mohe County, Heilongjiang Province, is mainly composed of mon-zogranite, quartz diorite and granodiorite, with minor dio-rite, tonalite, quartz monzodiorite, quartz monzonite, syeno-granite and alkali-feldspar granite. The quartz diorite units (SiO2: 54.79% -58.30% Na2O / CaO: 0.79-1.53 ​​and Shand index: 0.77-0.82) belongsto And the monzogranite unit (SiO2: 65.29% -66.45%, Na2O / CaO: 1.73-3.43 and Shand index <1.05) can be considered as weakly peraluminous rocks. Theintrusion is characterized by high REE abundance (ΣREE = 180.2- 344.3 μg / g), medium-strong negative Eu anomalies (δ Eu = 0.33-0.82), weak REE fractionation [(La / Yb) N = 4.12-10.45], enrichments in Rb, Th, U, K, La, Ce , Nd, HfZr and Sm, but strong depletions of Ba, Nb, Ta, Sr, P and Ti These characteristics of major, REE and trace elements in-dicate that the intrusion was formed in a transitional tectonic setting from compressional to extensional regime, which canbe classified as post-collisional granitoids. SHRIMP U-Pbzircon analyzes yield ages of 517 ± 9 and 504 ± 8 Ma for thequartz diorite and monzogranite units, respectively. The dis-covery of Early Paleozoic post-collisional granites in thenorthern margin of the Erguna massif indicates that then northern branch of Paleo-Asian Ocean between Siberianplate and Erguna massif was closed in the Early Paleozoic and the Salair orogeny ended ca. 500 Ma ago.