黑龙江东部“新元古代”黄松群杨木组沉积时限和物源组成：来自锆石U-Pb年代学的制约-《地球科学与环境学报》

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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

作者:: 郝文丽; 王枫; 许文良; 唐杰; 高福红; 1. 吉林大学地球科学学院,吉林长春 130061; 2. 黑龙江省地质科学研究所,黑龙江哈尔滨 150090

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

摘要:: 以出露于黑龙江东部地区前人原定为新元古代的黄松群底部杨木组为研究对象,对其中的二云母石英片岩和晚期片麻状二长花岗岩分别进行LA-ICP-MS锆石U-Pb年代学研究,旨在准确限定杨木组的沉积时限并揭示其物源组成。结果表明:采自黑龙江东宁地区黄松群杨木组标准剖面的二云母石英片岩中锆石多为岩浆成因,同位素年龄集中在古生代—早中生代,并且呈现出248、263、270、290、318、326、约360、426 Ma等多个显著的年龄峰值,而侵入到其中的晚期片麻状二长花岗岩的形成时代为(221±3)Ma;黄松群杨木组沉积于早—中三叠世(221~248 Ma),并非前人所厘定的新元古代?基于杨木组碎屑锆石年龄频数和区域地质年代学资料的对比分析,杨木组沉积物主要来源于周边的晚古生代—早中生代地质体以及次要的早古生代地质体。此外,新元古代岩浆锆石的出现证明研究区可能存在新元古代岩浆事件,而中—古元古代碎屑锆石的存在同时暗示早中生代期间该区地表或地表浅部应存在更为古老的前寒武纪残片。

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.