关键词: 桦南隆起, LA-ICP-MS U-Pb定年, 晚古生代花岗岩, 马家街群, 佳木斯地块

Abstract: LA-ICP-MS zircon U-Pb dating of the Meizuo granite in eastern Heilongjiang Province is carried out in order to determine the age and to discuss the tectonics environment of the Majiajie Group’s contact metamorphism. The present results show that the zircons from the granite have clear oscillatory zones，their Th/U ratio is between 0.12-1.04，and their weighted average ²⁰⁶Pb/²³⁸U age is （259.0±3.6） Ma（n=14，MSWD=5.9）. This shows that the crystalline age of the Meizuo granite is the Middle Permian. This age is also same as the age of the Qingshan, Chushan and Chaihe granites in the southern Jiamusi block, and the common geochemical characteristics(enrichment of light REEs， depletion of heavy REEs，negative Eu anomaly and obvious depletion in Nb, Ta, Sr and Ti) of these granites show that they are volcanic arc granites of crust derivation. They are probably related to the subduction of the Paleo-Asia Oceanic plate, and their intrusion resulted in the contact metamorphism of the Majiajie Group. The determination of the Meizuo granite’s crystallization age not only reveals that the contact metamorphism age of the Majiajie Group is the Later Permian, but also provides new evidence for the Paleozoic tectonic evolution of the Jiamusi block.

Key words: Huanan uplift, LA-ICP-MS U-Pb dating, Late Paleozoic granite, Majiajie Group, Jiamusi block