1.Heilongjiang Geological Science Institute, Harbin 150080, China;

2. Department of Earth Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China

 In order to explore the basement affinity and rock assemblage of the Xing??an block in the eastern sector of the Central Asian orogenic belt, the authors have chosen the previously proposed Precambrian Fengshui?gouhe Group in the Lesser Xing??an Range as the study object, and made a detailed study on the rock assemblage,age and genesis of the Fengshuigouhe Group by means of petrography, zircon LA??ICP??MS U??Pb dating and paleon?tological fossils. The results show that the Fengshuigouhe Group is mainly composed of metamorphic rocks such as leptynite, gneiss, marble, phyllite and schist, among which the protolith age of biotite plagioclase gneiss is 389 ??387 Ma, the protolith age of schistose two?mica andalusite hornstone is (284 ±5) Ma, and that of biotite plagio?clase schist is (261 ±2) Ma. On the basis of the characteristics mentioned above and the Early Permian brachio?pod fossils found in the black hornized sillimanite?, cordierite?bearing two?mica leptynite, it is proved that the Fengshuigouhe Group may be formed in the Late Paleozoic rather than Precambrian, and could be a subduction accretionary complex resulted from the subduction of a Paleo??Asian Ocean branch beneath the Erguna??Xingan block.

Lesser Xingan Range   Fengshuigouhe Group   metamorphic complex    dating
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