冲绳海槽中北部表层沉积物地球化学特征及其对陆源、热液源输入的指示

Geochemical characteristics of surface sediments from the central-northern Okinawa Trough and their implications for terrestrial and hydrothermal inputs

  • 摘要: 通过对127个表层沉积物常微量元素及稀土元素组成的系统分析,探讨了冲绳海槽中北部沉积物的来源与控制因素,揭示了沉积物元素组成对陆源输入和热液源信号的指示意义。结果表明,研究区沉积物主要由SiO2、CaO和Al2O3组成,占沉积物总量的54.25%~78.11%。R型因子分析表明,陆源碎屑输入是控制沉积物元素组成的首要因素,其次为火山、热液、自生沉积作用。依据常微量元素组成将研究区沉积物分为3类,即陆源碎屑主导型、生物碳酸盐主导型以及混合型:Ⅲ类沉积物以陆源碎屑为主导,富含Si、Al、K、Ti、Li、Be、Sc、Cu、Pb、Zn等元素;Ⅱ类以极富Ca和Sr为特征,受生物碳酸盐控制;Ⅰ类代表陆源碎屑与生物成因组分的混合。稀土元素(La/Sm)UCC-(Gd/Yb)UCC判别证实黄河源是冲绳海槽中北部沉积物最主要的来源,而长江、东海陆架黏土及火山、热液等物质在局部区域亦有贡献。仅在热液活动区附近,表层沉积物呈现Cu、Pb、Zn等亲铜元素的富集及弱Eu正异常,进一步证实热液源信号的空间局限性。本研究为深入理解冲绳海槽中北部沉积物组成与来源提供了重要的地球化学依据。

     

    Abstract: By analyzing major, trace, and rare earth elements (REEs) in 127 surface sediment samples, we investigated the sources and controlling factors of sediments in the central-northern Okinawa Trough, and explores the significance of element composition as indicators of terrigenous input and hydrothermal signals. Results indicate that the sediments in the study area are composed mainly of SiO2, CaO, and Al2O3, taking 54.25% to 78.11% of the total mass. R-mode factor analysis revealed that terrigenous clastic input is the primary factor con element composition, followed by volcanic/hydrothermal alteration, biogeochemical processes, and authigenic sedimentation. Based on compositional characteristics, the sediments were classified into three types. Cluster III sediments are dominated by terrigenous detrital and are enriched in elements such as SiO2, Al2O3, K2O, TiO2, Li, Be, Sc, Cu, Pb, and Zn; Cluster II sediments are characterized by extremely high CaO and Sr contents, reflecting the dominance of biogenic carbonates; and Cluster I represents a mixture of terrigenous detrital and biogenic components. Discrimination of (La/Sm)UCC-(Gd/Yb)UCC confirmed that the Yellow River is the most important sediment source in the central-northern Okinawa Trough, while the Yangtze River, East China Sea shelf clays, and volcanic-hydrothermal activities exert localized influences. Sediments near hydrothermal areas show enrichment of chalcophile elements (e.g., Cu, Pb, Zn) and weak positive Eu anomalies, indicating spatially-restricted hydrothermal contributions. This study provided key geochemical evidence for deeper understanding of sediment composition and provenance in the central-northern Okinawa Trough.

     

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