瓯江口泥质区细粒级矿物物源示踪研究

The process of transport and deposition of terrigenous constituents in the continental shelf area has been a hot topic in marine geology research. Previous studies have shown that the coastal areas of Zhejiang and Fujian developed a large-scale muddy area under the influence of the Yangtze River since the Holocene. In recent years, more and more studies have shown that the contribution of small and medium rivers to muddy sediments cannot be neglected. However, it is difficult to quantify the difference between them and the Yangtze River. Based on the grain size of 32-64μm in sediments, this study analyzes the mineral assemblages and chemical compositions of the amphibole and garnet mineral particles in the Oujiang River, the Yangtze River and the Core D04 from the muddy area offshore Oujiang Estuary. Extract the effective source identification index and build a mathematical model to calculate quantitatively the contributions of Oujiang and the Yangtze River on the muddy area. Revealing the changes since the Holocene. This will help to reveal the source changes in the muddy area, deepen the understanding of the sediment fluxes and the source and sink processes of the small and medium rivers, and the evolution of the mud deposits along Zhe-Min coast.

陆源碎屑物质的入海通量及在陆架地区的搬运和沉积过程是当前海洋地质学研究的热点。以往的研究表明在长江物质影响下，全新世以来浙闽沿岸发育了较大规模的泥质区。最近几年来越来越多的研究表明中小河流对泥质沉积的贡献不容忽视，但很难定量判别它们与长江的差异。本项目拟从32-64μm粒级入手，开展瓯江、长江以及瓯江口泥质区D04孔沉积物碎屑矿物组合、角闪石和石榴石单矿物颗粒化学分析，研究瓯江和长江矿物组成特征，提取有效的物源判别指标，建立瓯江和长江物质端元；进而构建数学模型，定量计算瓯江和长江对瓯江口泥质区的物质贡献，揭示瓯江口泥质区全新世以来的物源变化特点。该研究对于深化认识中小河流的物质通量、源汇过程及浙闽泥质区形成演变具有重要意义。

在长江物质影响下，全新世以来浙闽沿岸发育了较大规模的泥质区。但越来越多的研究表明中小河流对泥质沉积的贡献不容忽视，但很难定量判别它们与长江的差异。本项目分析了瓯江和长江端元矿物组成特征，通过构建数学模型，定量计算了瓯江和长江对瓯江口泥质区的物质贡献，揭示瓯江口泥质区全新世以来的物源变化特点。D04孔岩心物质来源以长江物质为主，瓯江物质为辅，物质贡献比例分别为79.2%和10.0%，其它物源组分含量约10.7%。瓯江贡献自下而上呈逐渐增加的趋势，但是长江贡献呈现减少的趋势。这与海岸线变化、长江三角洲及温州湾发育、气候变化和人类活动有关。在距今2.1-3.7ka期间，由于流域的开垦能力差，沉积物供应大大减少，导致沉积速率低。自2ka开始，长江流域和瓯江流域的人类活动得到加强，导致更多的水土流失被输送到研究区域。由于距瓯江河口的距离缩短，上部（DU1）接收的瓯江沉积物要多于下部单元（DU2和DU3）。本项目成果将有助于加深对大河和沿岸中小河流对泥质沉积的认识。