Characteristics of the "Mashan Group" and zircon SHRIMP U-Pb dating of granite in Muling area, southeastern Heilongjiang Province, China: constraint on crustal evolution of the south-ernmost of Jiamusi Massif
Characteristics of the "Mashan Group" and zircon SHRIMP U-Pb dating of granite in Muling area, southeastern Heilongjiang Province, China: constraint on crustal evolution of the south-ernmost of Jiamusi Massif
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作者：
Liu Dun-yi
根据佳木斯地块南部穆棱长兴村至新兴村地质剖面，认为该处地层组合具有古活动大陆边缘特征。马山群是佳木斯地块的基底，而黑龙江群则代表了包含洋壳残余物的增生-碰撞杂岩。马山群混合岩锆石SHRIMP U-Pb定年表明佳木斯地块存在中元古代—新元古代基底，并受~500Ma变质作用的影响。对侵入马山群的花岗岩进行的岩石学和地球化学研究表明，它们具有S型花岗岩的亲和性。 SHRIMP U-Pb测年表明花岗岩侵位发生于晚寒武世，加权平均年龄为486Ma±3Ma，略晚于先前定义的马山群麻粒岩相变质作用~500Ma。因此，这些花岗岩是同碰撞或碰撞后侵入岩。这些数据证实，研究区经历了晚范-非洲-早加里东期碰撞造山作用。
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 paleoactive 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 Mas- sif 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 gran- ulite-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.