废黄河口门外砂质海滩粒度和重矿物特征及其成因机理分析

Characteristics of grain size and heavy minerals of sandy beach outside the abandoned Yellow River Estuary and its genetic mechanism

为研究黄河南流变迁过程中物质沉积分异作用下的产物,进而追踪废黄河沉积物在江苏沿海以及南黄海的运移状况,测量废黄河口门外砂质海滩沉积物粒级组成及特征参数,分析各样品重矿物含量及种类特征;结合与废黄河陆上沉积物的对比,探讨在不同沉积分异作用下重矿物沉积特征。结果表明:砂质海滩沉积物平均粒度Φ为 2.67(0.16 mm),分选较好,为微负偏,具有海滩砂粒度特征;陆域样沉积物粒度跨度大,以粉砂组分为主,为河流沉积特征。另外,对海滩砂样进行广粒级重矿物(Φ为 1~6)分析,重矿物含量在极细砂和粗粉砂粒级中最高,不同粒级形成不同的矿物组合,砂粒级重矿物组合为黑云母+普通角闪石+褐铁矿,粉砂粒级则为钛铁矿+石榴子石+普通角闪石;砂质海滩样品广粒级重矿物质量分数为 3.66%,其中Φ为 3~4 (0.125~0.063 mm)的粒级重矿物质量分数高达 15.66%,比重大且稳定性较高的矿物在此粒级中富集,表明海滩重矿物分选强烈。

To study the products under the influence of material sedimentation in the process of the Yellow River’s southward transition and track the migration process of the abandoned Yellow River sediments in the South Yellow Sea, the grain size compositions were measured, and the characteristic parameters of sediments in the sandy beach outside the abandoned Yellow River estuary, the heavy mineral content, and the characteristics of each species sample were analyzed. In addition to comparing the land sediments on the abandoned Yellow River estuary, char- acteristics of heavy mineral deposition under different sedimentary conditions were evaluated. The results show that the sandy beach sediments had an average grain size Φ of 2.67 (0.16 mm), which were well sorted and slightly negative skewness, and was characterized by beach sand grain size. The land size sediments had a large particle size range and were mainly composed of silt components, a feature of river sedimentation. In addition, the beach sand samples were analyzed for multiple-window (Φ was within 1~6) heavy minerals. The heavy mineral content was highest in the fine sand and coarse silt grades. Different grades had different mineral combinations. The heavy mineral combination of sand grade was biotite + hornblende + limonite, and that of silt was ilmenite + garnet + hornblende. The weight content of the sandy beach wide-grained heavy mineral was 3.66%, and very fine sand (0.125~0.063 mm) fractions had a heavy mineral weight content of 15.66%. The minerals with higher specific gravity and higher sta- bility were enriched in the fine sand grade of sandy beach samples, indicating that the heavy minerals in the beach are strongly sorted.