长江与黄河碎屑石榴石的元素组成及其物源示踪应用

It's one hotspot to identify the source compositions in sedimentary geochemistry study by using the chemical compositions of single grains. However,little work of mineralogical chemistry has been done on the source identification of Chinese rivers and marginal sea sediments.In the project, the composition analysis of single grain garnet of Changjiang and Huanghe rivers will be used in revealing the constraints of chmical compositions of garnets, and the source indicators of Changjiang and Huanghe will be obtained by the correlation function and discriminant function calculation. The characheristical garnent assemblages will be used in source identification of the surface sediments of the South Yellow Sea on the bases of the result and former work. Therefore, the relative garnet supply of the two rivers will be discussed in the quantitative provenance analysis. Our work will offer an idea in studying the source indication and quantitative provenance analysis of East China marginal sea sediments.

利用单颗粒标型矿物的化学组成来研究物源已成为目前沉积地球化学研究的热点之一，而在我国河流和边缘海沉积物的源汇研究中应用较少。本项目拟采用单颗粒碎屑石榴石矿物化学组成分析方法，研究长江和黄河端元主要粒级的石榴石元素组成特征，探讨其化学组成的主要控制因素，通过相关函数和判别函数分析，提取特征的石榴石组合作为物源示踪因子；在前期研究基础上选择南黄海作为实验靶区应用石榴石组合进行物源示踪，探讨长江和黄河对研究区石榴石的相对贡献。该研究将为探索我国陆架海晚第四纪沉积物的物源研究提供一种新的思路和方法。

长江和黄河沉积物的单颗粒碎屑石榴石组合具有明显差异，可以应用于陆架中河流沉积物的物源示踪。长江流域主体是年轻的扬子地块―华夏地块，石榴石源岩以中低级变质岩为主，呈高Mn低Mg特征；黄河流域主要分布在太古宙—元古宙古老的华北地块，石榴石源岩以中高级变质岩或超基性岩为主，呈高Mg相对低Mn特征。由于部分长江和黄河沉积物流域源岩的相同性，二者部分碎屑石榴石组成相近，但总体上完全可以区分它们不同的碎屑石榴石组成特征。金沙江和窟野河可分别作为长江和黄河的特征物源区，它们不同的标型石榴石组成为海区识别长江和黄河沉积物奠定了基础。