鸭绿江河口及近岸海域沉积物中重矿物组成、分布及其沉积动力学意义
Heavy mineral distributions and their implications for sediment dynamics in the Yalu Estuary and its adjacent sea area
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摘要: 通过研究鸭绿江河口和近岸海域沉积物的重矿物分布和区域组合特征,同时以重矿物作为示踪物,分析了河口区底部沉积物的运动状况。研究结果表明,研究区的重矿物主要分为两种组合,一是黑云母-普通角闪石-绿帘石组合,二是由不稳定的矿物普通角闪石、较稳定矿物绿帘石和石榴石以及金属矿物(包括磁铁矿、钛铁矿和赤褐铁矿)组成,该组合又可分为四个亚组合。不稳定矿物与稳定矿物含量的比值变化、推移质潮周期输运率和净输运方向计算以及断面的粒度分布特征表明,鸭绿江河口10m等深线以北地区的底部沉积物主要向上游地区输运。这一结论与以往分析结果有很大不同,这主要是由于鸭绿江流域受到了人类活动,尤其受水利工程和人工挖沙的影响而出现的一种自我调节机制。此外,重矿物分析的初步结果还表明,鸭绿江河口10m等深线以南的沉积物主要向下游输运,而近岸地区的沉积物可能由东西两端向中间输运,但是由于受到研究资料的限制,以上结论还有待于通过其他研究方法进一步验证。从北黄海东西两个地区的重矿物分布来看,北黄海西部地区的石榴石和电气石等稳定重矿物含量要大于东部地区的,而白云石和云母等不稳定矿物的含量要小于东部的。综合对比北黄海西部与北黄海东部、南黄海北部和南部来看,前者与后三者最大的区别就是沉积物中没有自生黄铁矿。Abstract: The chatacteristics of heavy mineral composition and distribution were analyzed in the surface sediment of the Yalu Estuary and its adjacent sea area,and its seabed sediment movement was also discussed.Results indicate that there exist two types of heavy mineral assemblages in the study area,one is biotite-hornllende-epidote,and another can be divided int of our sub-types,is composed of hornllende,epi-dote,and metal minerals(magnetite,ilmenite,hematite and limonite) .Variations of stable heavy mineral and unstable heavy mineral contents,seabed sediment transportrate and direction,and sectional distribution of grain size show that the estuarine seabed sediments in the north of 10 m isobath are transported landwards.This pheno menon is distinct from previous studies,is mainly caused by sel-fadjustment of the Yalu River catchments associating with human activities,especially large hydraulic project construction and sand dredging.Furt hermore,results of heavy mineral analysis also indicates that the estuarine seabed sediments in the south of 10 misobath are mainly directed seaw ards,and the sediments of the adjacent sea area of the Yalu Estuary are transported from the east,as well as the west to the medium.However,these conclusions still need to be furt hertestified using the method of geochemistry and sediment dynamics.Stable heavy mineral contents of garne and tourmalin in the west of the northern Huanghai Sea are larger than those in the east of the northern Huang hai Sea according to the comparison of heavy mineral distributions between these two areas.The mostevident difference among the east of the northern Huanghai Sea from the west of the northern Huanghai Sea,the south and the north of the southern Huanghai Sea,is that autogenetic pyrite does not occur in the sediments of the east of the nor thern Huanghai Sea.
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Key words:
- heavy mineral /
- mineral assemblage /
- sediment dynamics /
- Yalu River
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