Characteristics of the “Mashan Group” and Zircon SHRIMP U-Pb dating of granite in Muling, SA Heilongjiang Province, China: constraint on crustal evolution of the southernmost of Jiamusi Massif.

According to the geological profile from Changxingcun to Xinxingcun in Muling, south of Jiamusi Massif, we suggest that assemblage of formations there shows features of paleo active continental margin. The Mashan Group is the basement of Jiamusi Massif, whereas the Heilongjiang Group represents an accretionary-collision complex containing remnants of oceanic crust. Zircon SHRIMP U-Pb dating on the migmatite from Mashan Group indicates that there is Mesoproterozoic-Neoproterozoic basement in Jiamusi Massif and it has been influenced by ~500Ma metamorphism. The petrological and geochemical studies on the granite, which intruded the Mashan Group, suggest that they are of affinity of S-type granites. The SHRIMP U-Pb dating indicates that the emplacement of granite occurred in Late Cambrian, with a weighted mean age of 486Ma±3Ma, slightly later than previously defined ~500Ma granulite-facies metamorphism of the Mashan Group. Therefore, these granites are syn- or post-collisional intrusive rocks. These data confirmed that the study area underwent a late Fan-African-Early Caledonian collisional orogenesis.