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珠江口盆地深水区物源与运移机制分析：基于稀土元素和Sr-Nd同位素的研究
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Abstract:
边缘海沉积物对于研究气候变化、古海洋演化和大陆的剥蚀与抬升等方面具有非常重要的指示意义。本研究通过对珠江口盆地深水区Z8站位沉积重力柱的粒度、稀土元素和Sr-Nd同位素的分析，发现研究区沉积粒度较不稳定，平均粒径在19.70 μm左右变化，沉积物成分主要是粉砂，其次是黏土，砂的含量最少。根据沉积粒径可将沉积分为三个阶段：表层的沉积较不稳定阶段、中层的沉积稳定阶段与底层的沉积环境动荡阶段；稀土元素REE平均值为141.50 μg/g，呈现出Eu负异常，轻稀土占总稀土绝大部分比例(均超过75%)；87Sr/86Sr平均值为0.723722，143Nd/144Nd平均值为0.512023，随深度的增加，87Sr/86Sr和εNd均呈现出先增大再减小最后保持稳定的趋势。与不同潜在物源区的稀土元素特征和Sr-Nd同位素的对比分析表明，近万年来，台湾岛为珠江口盆地深水区最大物源，黑潮和深海环流对台湾岛的沉积物运移起到了至关重要的作用；此外，红河、海南岛和湄公河也对研究区的物源有着一定贡献，这主要是依靠东亚季风驱动的表层环流和沿岸流对沉积物进行运移的。值得注意的是，由于珠江是距离Z8站位最近的大陆水系，因此也不能忽略珠江的物源贡献。
The sediments of marginal seas play a very important role in the study of climate change, paleo-ocean evolution and uplift denudation of continents. This study has studied the grain size, rare earth elements and Sr-Nd isotopes of the sedimentary gravity core at the Z8 site in the deep-water area of the Pearl River Mouth Basin and found that the sedimentary particle size in the study area was relatively unstable, with an average particle size of 19.70 μm; the sediment composition was mainly composed of silt, followed by clay, with the least sand content. Sedimentation can be divided into three stages based on the particle size of the sediments: The unstable stage of surface sedimentation, the stable stage of middle sedimentation, and the turbulent stage of bottom sedimentation environment; the average value of the REE (rare earth element) is 141.50 μg/g. There was a negative anomaly of Eu on the REE distribution curve. In addition, LREE (light rare earth element) accounted for the vast majority of REE (over 75%). The average value of 87Sr/86Sr ratio was 0.723722, and the mean value of 143Nd/144Nd was 0.512023, as the depth increases, both 87Sr/86Sr and εNd show a trend of first increasing, then decreasing, and finally maintaining stability. Comparative analysis of REE characteristics and Sr-Nd isotopes with different potential sources showed that Taiwan Island was the largest source in the deep-water area of the Pearl River Mouth Basin over the past ten thousand years, and the Kuroshio and deep-sea current played a crucial role in the sediment migration of Taiwan Island. What’s more, the Red River, Hainan Island and Mekong River also contributed to the provenance of the study area, which were mainly due to the sediment transport by the surface current and coastal current driven by the East Asian monsoon. It is worth noting that since the Pearl River is the nearest continental water system to Z8
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