| 小兴安岭河流沉积物源的异质性——重矿物与碎屑锆石U-Pb年代学约束 |
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| 关键词:Lesser Xing’an Range river sediments provenance tracing heavy minerals detrital zircon U-Pb geochronology |
| 基金项目:本文由黑龙江省自然科学基金项目(编号: ZD2023D003)、国家自然科学基金项目(编号: 42171006)和哈尔滨师范大学学术创新项目(编号: XKB202314)联合资助。 |
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| Heterogeneity of Sediment Sources in Rivers of the Lesser Xing’an Range: Constraints from Heavy Minerals and Detrital Zircon U-Pb Geochronology |
| River sediments preserve abundant geological information about their source regions. A detailed analysis of their compositional characteristics is crucial for understanding provenance signatures and the controlling mechanisms of sediment transport and deposition. The complex tectonic and magmatic evolution of the Lesser Xing’an Range offers an ideal natural laboratory for investigating the “source-to-sink” processes of river sediments. In this study, modern sediments from the Hulan, Chalin, Balan, and Tangwang Rivers were analyzed. Heavy mineral composition, detrital zircon LA-ICP-MS U-Pb geochronology were employed to systematically investigate provenance characteristics and their responses to regional tectonic-magmatic events. Additionally, the reliability and stability of detrital zircon age data in reconstructing such events were evaluated through reproducibility analyses.The results demonstrate the following: (1) Heavy mineral assemblages exhibit spatial variations in amphibole, epidote, and ilmenite contents, primarily governed by the lithological composition and exposure of source rocks, with additional influences from tectonothermal intensity, hydrodynamic sorting, and provenance dilution; (2) Detrital zircon age spectra reveal three prominent age groups: ~190 Ma (230–100 Ma), ~250 Ma (300–230 Ma), and ~470 Ma (500–400 Ma), which correspond to major tectonic-magmatic events in the Lesser Xing’an region, confirming a strong source-to-sink coupling; (3) Sediments from all four rivers are predominantly composed of 230–100 Ma zircons (66.67%–98.25%), while the proportion of Early Paleozoic zircons (500–400 Ma) in the Tangwang River (15.32%) is significantly higher than in the Hulan (4.27%), Chalin (5.74%), and Balan (0.88%) Rivers. This spatial variability is attributed to the differing exposures of coeval bedrock within the drainage basins; (4) Reproducibility analysis based on T and K models indicates that detrital zircons from low-frequency depositional cycles exhibit higher fidelity in recording igneous source signals compared to those from high-frequency cycles; (5) The identified zircon age peaks effectively record regional tectonic events: ~470 Ma is associated with subduction of the Paleo-Asian Ocean, ~250 Ma corresponds to its final closure, and ~190 Ma reflects both the subduction of the Mongol–Okhotsk Ocean and the initiation of Paleo-Pacific Plate subduction.This study confirms that in the small river systems of the Lesser Xing’an Mountains, heavy mineral assemblages and detrital zircon U-Pb geochronology serve as effective proxies for tracing source rock characteristics and spatial heterogeneity. Furthermore, detrital zircons from low-frequency cycles may serve as reliable indicators for reconstructing tectonic-magmatic events in the source region. However, provenance interpretation must consider a range of factors, including the distribution of parent rocks, hydrodynamic conditions, and sediment mixing processes. In systems with complex lithological compositions or significant grain-size sorting effects, a multi-proxy approach to provenance analysis is essential. |
| ZHANG Chong,SUN Lei,WANG Yanru,XIE Yuanyun,WEI Zhenyu,LIU Haijin,WANG Yehui,QI Haodong,WU Peng,ZHANG Yan.2026.Heterogeneity of Sediment Sources in Rivers of the Lesser Xing’an Range: Constraints from Heavy Minerals and Detrital Zircon U-Pb Geochronology[J].Acta Geoscientica Sinica,47(4):868-884. |
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