冲绳海槽北部沉积岩芯的地球化学特征:对热液活动的响应

Geochemical characteristics of sedimentary core in the northern Okinawa Trough: Response to hydrothermal activity

  • 摘要: 冲绳海槽由于独特的地理位置与地质构造,成为研究西太平洋边缘海沉积“源-汇”过程、古环境演化以及极端系统的理想天然实验室。本研究选取冲绳海槽北部的西部陆坡区HOBAB1-S10沉积岩芯为研究对象,开展了AMS 14C定年,完成了粒度、主微量元素、稀土元素、总有机碳、总氮、δ13Corg、δ15N分析,研究了MIS3-LGM期间研究区域的物质来源及其贡献,最终探讨了海槽中的热液活动对沉积物地球化学特征的影响。结果表明,45~22.5 ka期间,本区沉积物来源稳定。 (La/Sm)UCC与(Gd/Yb)UCC判别图表明,S10岩芯的沉积物主要来源于黄河;31~32 ka期间,沉积物中Cu、Zn、Co、U、As等元素明显富集,比背景值高出1~2个数量级,表明除陆源物质外,可能还存在其他物源。样品的高Mo/Mn比值(平均值5.71)证实了冲绳海槽北部可能存在热液活动和物质输入。本研究为研究冲绳海槽热液活动的影响机制以及今后在海槽北部开展热液活动勘探工作提供了理论依据。

     

    Abstract: Due to its unique geographical location and geological structure, the Okinawa Trough has become an ideal natural laboratory for studying the "source sink" processes, paleoenvironmental evolution, and extreme systems of sedimentation in the western Pacific marginal seas. In this study, we selected the HOBAB1-S10 sedimentary core from the western slope area of the northern Okinawa Trough as the research object and conducted AMS 14C dating. We analyzed the grain size, major and trace elements, rare earth elements, total organic carbon, total nitrogen, δ13Corg, and δ15N, studied the material sources and their shares during MIS3-LGM, and finally explored the influence of hydrothermal activity in the trough on the geochemical characteristics of sediments. Results indicate that during the period of 45~22.5 ka, the material source in this area was stable. The values of (La/Sm) UCC and (Gd/Yb) UCC indicate that the sediment in Core HOBAB1-S10 comes mainly from the Yellow River. During the period of 31~32 ka, elements of Cu, Zn, Co, U, and As were significantly enriched in sediments, which were 1-2 orders of magnitude higher than the background values, indicating that there may be additional source contributions besides terrestrial materials. The high Mo/Mn ratio of the samples (average 5.71) indicated the possibility of hydrothermal activity and material input in the northern Okinawa Trough. This study provided a theoretical basis for studying the mechanism of hydrothermal activity in the Okinawa Trough and for future exploration of hydrothermal activity in the northern Okinawa Trough.

     

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