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Title:: Depositional Age and Provenance of Yangmu Formation of “Neoproterozoic” Huangsong Group in the Eastern Heilongjiang: Constraints from Zircon U-Pb Geochronology

Author(s):: HAO Wen-li; WANG Feng; XU Wen-liang; TANG Jie; GAO Fu-hong; 1. School of Earth Sciences, Jilin University, Changchun 130061, Jilin, China; 2. Heilongjiang Institute of Geological Sciences, Harbin 150090, Heilongjiang, China

Keywords:: geochronology; Yangmu Fromation; Huangsong Group; zircon; U-Pb dating; depositional age; provenance; Khanka massif

Abstract:: Yangmu Formation in the bottom of Huangsong Group originally defined as Neoproterozoic exposes in the eastern Heilongjiang. LA-ICP-MS zircon U-Pb dating of two-mica quartz schist and late-stage gneissic monzogranite in Yangmu Formation of Huangsong Group was analyzed in order to restrain the depositional age and reveal the provenance. The results show that most of zircons from two-mica quartz schist, which is collected from typical section of Yangmu Formation, are of magmatic orgin, yielding isotopic ages from Paleozoic to Early Mesozoic with the peaks at 248, 263, 270, 290, 318, 326, about 360, 426 Ma, etc., and the formation age of late-stage gneissic monzogranite intruding Yangmu Formation is (221±3)Ma; Yangmu Formation of Huangsong Group deposits during Early-Middle Triassic (221-248 Ma), rather than Neoproterozoic as previously believed. Based on the comparison between the age frequency of detrital zircons in Yangmu Formation and regional geochronological data, the sediment in Yangmu Formation of Huangsong Group is mainly from peripheral Late Paleozoic-Early Mesozoic terrane and minor Early Paleozoic terrane. Furthermore, the Neoproterozoic magmatic zircons identified prove that there might be Neoproterozoic magmatic event in the area, and Meso-Paleoproterozoic detrital zircons identified suggest that there might be ancient Precambrian remnants at or near the surface during Early Mesozoic.