| 摘要: |
| 利用X 射线物相分析、扫描电镜及能谱分析等方法分析了长江和黄河入海沉积物矿物颗粒形态特征及不同粒级的碳酸盐矿物百分含量分布。结果表明, 长江和黄河入海沉积物的碳酸盐矿物含量均在9%左右, 差异不大。长江碳酸盐矿物含量在粗粒级较高, 随着粒度变细波动式降低, 黄河碳酸盐矿物含量则随粒度变细而逐步增加; 黄河方解石含量高而白云石低, 长江的情况正好相反。长江和黄河入海沉积物中的白云石颗粒大多比较完整, 侵蚀沿完全解理面发生, 菱面体形态明显。长江白云石上可以见到大量的磨蚀和溶蚀形态。黄河白云石保存较好, 侵蚀程度较低, 磨蚀和碰撞形态明显, 溶蚀形态很少, 发现典型的马鞍状白云石颗粒。长江和黄河的方解石均遭受强烈侵蚀。长江方解石溶蚀特征特别明显, 深入矿物颗粒内部。黄河方解石侵蚀深度相对浅表, 侵蚀形态多为磨蚀、碰撞和溶蚀等物理和化学综合侵蚀特征。长江某些方解石表面布满细小鲕状方解石颗粒, 似为局部自由空间的胶体-陈化成因特征。黄河方解石呈现多个次生微晶集合体, 显示其黄土粘粒空隙胶结物成因形态。碳酸盐矿物的菱面体形态和菱面体完全解理所特有的60°和120°交角, 是其电镜下的最佳识别特征。长江和黄河沉积物物源、流域风化强度以及矿物晶体结构本身的特点, 是两河沉积物中碳酸盐矿物含量及颗粒形态差异的主要影响因素。
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| 关键词: 长江与黄河, 沉积物, 碳酸盐矿物, 形态特征, 风化 |
| DOI：10.11693/hyhz200906002002 |
| 分类号: |
| 基金项目:国家重点基础研究发展(973)计划项目, 2002CB412404 号 |
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| CARBONATE MINERALS IN ESTUARY SEDIMENTS OF THE CHANGJIANG (YANGTZE RIVER)AND HUANGHE (YELLOW RIVER): THE CONTENT, MORPHOLOGY, AND INFLUENTIAL FACTORS |
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YANG Zuo-Sheng1,2, WANG Hai-Cheng1,2, QIAO Shu-Qing3
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1.College of Marine Geosciences, Ocean University of China;2.Key Laboratory of Seafloor Science and Exploration Technology (KLSSET), Ocean University of China;3.Key Laboratory of Sedimentation and Environmental Geology,First Institute of Oceanography, State Oceanic Administration
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| Abstract: |
| Sediment samples were collected in estuaries of the Changjiang (Yangtze River) and the Huanghe (Yellow River) for studying carbonate minerals, their morphologic features, and influential factors by gain size analysis, XRD, SEM with EDX. The result shows that the percentage content of carbonate minerals occupied about 9% of the total major minerals, which is similar for the two rivers. The calcite content in the Huanghe sediment is higher than the dolomite, and vice versa in the Changjiang samples. Morphological study on the carbonate minerals illustrates that the shapes of the dolomite grains from the two river sediments are mostly well crystallized in general, except for minor cleavages and erosion/dissolution in the Changjiang samples. Calcite grains in all the samples were strongly eroded. The surface morphology was mostly resulted from the joint effect of grinding and dissolving under physical and chemical weathering processes. Some Changjiang calcite grains are covered with tiny oolites of colloid origin, while Huanghe calcite grains often consist of needle-like micro-crystals as aggregates resulted from secondary viscous origin in loess vacancies. The specific rhombic shape and the rhombic cleavage angles of 60° and 120° are characteristic for identification of the carbonate grains under SEM. Differences in provenance and weathering intensity are major influential factors responsible for the differences in the carbonate contents and their grain morphological features.
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| Key words: Changjiang (Yangtze River), Huanghe (Yellow River), Sediments, Carbonate mineral, Morphology, Weathering |
