| 摘要: |
| 针对冲绳海槽中部热液活动区附近的沉积物岩芯(H9), 利用碱熔法和等离子体发射光谱法对其稀土元素组成进行了分析。结果表明, 在岩芯中稀土元素含量在 75—80 cm 段发生转折, 75 cm以上岩芯段沉积物中稀土元素总量相对较高, 而且稀土元素总量, 尤其是轻稀土元素总量, 与(Fe+Mn)/Al 相关性较好。该段沉积物中稀土元素页岩标准化配分模式呈右倾或近似水平, 突出特征表现为轻稀土间的明显分异和 Eu 的相对富集, 与热液源稀土元素组成极为相似。 与热液流体和热液硫化物相比, 分异程度和Eu正异常程度都较低, 同时, 具有明显的负Ce异常, 与海水的稀土配分模式相类似。 由此可见, 热液活动对该岩芯上段沉积物中稀土元素组成具有重要影响, 一方面表现为热液源物质的直接输入, 另一方面表现为热液颗粒物质沉积过程中对海水中稀土元素的清扫。
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| 关键词: 热液活动, 稀土元素, 冲绳海槽 |
| DOI：10.11693/hyhz201005003003 |
| 分类号: |
| 基金项目:国家自然科学基金项目, 40306009 号 |
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| GEOCHEMICAL CHARACTERISTICS OF THE RARE EARTH ELEMENT COMPOSITIONS IN THE SEDIMENT CORE FROM THE HYDROTHERMAL FIELDS IN OKINAWA TROUGH |
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YU Zeng-Hui, DU Tong-Jun, ZHAI Shi-Kui
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Ocean University of China, Key Lab of Submarine Geosciences and Prospecting Techniques, Ministry of Education, Department of Marine Geosciences
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| Abstract: |
| The compositions of rare earth element (REE) in the sediment core (H9) of the hydrothermal fields at Okinawa trough were analyzed by alkali fusion and ICP-AES. There is a sharp change in the contents of the most rare earth elements at the depth of 75 cm. Total concentrations of the rare earth elements (ΣREE) at the upper 75 cm core sediments are more enrich than those below. The upper 75 cm core sediments show a slight LREE enrichment or weak fractionation under the shale-normalized REE pattern. Significant fractionation among LREEs and positive Eu anomalies are found at the upper 75 cm core sediments, these features are commonly found in hydrothermal fluids and deposits. Core with relatively weak hydrothermal signatures and a negative Ce anomaly shows similarity to the seawater. ΣREE are found positive correlated with the ratio of (Fe+Mn)/Al, the correlation with LREE was found even better. Therefore, hydrothermal activities play an important role in the REE compositions in the upper 75cm core sediments. On one hand, hydrothermal activities involve REE and deposit directly into the sediments. On the other hand, hydrothermal particulates scavenge REE from the seawater to precipitate into the sediments.
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| Key words: rothermal activity, Rare earth element, Okinawa Trough |
