辽东湾海岸带沉积物碎屑矿物分析及其环境意义

发布时间：2018-09-04 16:36

【摘要】：海洋沉积物沉积特征和物质来源的研究是海洋地质学的一项重要内容，也是研究近代沉积作用的核心问题之一。综合运用沉积物的粒度、碎屑矿物和粘土矿物、元素地球化学、同位素示踪和生物组合等分析判别方法可探讨沉积环境和物源。本文通过对研究区表层样、柱状样碎屑沉积物的重、轻矿物组合特征，沉积物的单粒级（极细砂0.063-0.125mm）等研究，探讨了辽东湾沉积物的物质来源和沉积环境。对研究区38个海岸带表层样，43个河流样，14根岩芯柱状（鉴定271个样品）沉积物样品进行了综合分析，运用矿物学、粒度分析和沉积动力学手段，研究了表层沉积物矿物组成、扩散运移趋势，并选取多种矿物指标运用系统聚类分析方法进行矿物组合分区，从而深入探讨沉积物物质来源、沉积环境等内容。研究区表层沉积物极细砂粒级与重矿物含量对比分析表明二者之间存在明显的负相关性。极细砂含量也可反映水环境条件，在辽河、大凌河等河口区沉积物以细质组分为主，水能相对较弱，而在辽东湾东岸沉积物粒度较粗，海岸水动力作用较强。矿物分析表明研究区共统计了41种重矿物，重矿物主要有角闪石、绿帘石、石榴石、磁铁矿、钛铁矿和榍石等；轻矿物约11种主要为石英、长石（以斜长石为主）。应用Q型聚类分析将研究区表层沉积物划分出3个矿物区；一区，老铁山—复州湾北，优势矿物组合为金属矿物-角闪石类-帘石类，金属矿物以钛铁矿为主，特征矿物为石榴子石，复州河及沿岸冲刷可能为其主要物源；二区，复州湾北—营口，优势组合矿物为角闪石类-金属矿物-帘石类，，金属矿物中磁铁矿含量高，特征矿物为榍石、锆石，明显受到大辽河及沿岸短源河流物质影响；三区，营口—秦皇岛，其优势矿物组合为角闪石类-帘石类-金属矿物，褐铁矿是金属矿物中主要组分，特征矿物为石榴子石、磷灰石，辽河、大凌河对其贡献作用突出，六股河有所贡献。根据海岸地貌与重矿物含量关系本区分作三种沉积环境重矿物分布区：河口型、港湾型、海岛型。对14个柱样的岩性特征研究显示，柱样中从表层到底层极细砂的含量波动，反映水动力的变化。重矿物分析表明，研究区不稳定矿物含量较高，柱样中的自生黄铁矿含量变化能指示沉积环境的氧化还原条件与分选作用变化。结果显示辽东湾两侧岸段水动力相对较强，湾顶水能较弱，与粒度分析得出的结论基本一致。
[Abstract]:The study of sedimentary characteristics and material sources of marine sediments is an important part of marine geology and one of the core issues in the study of modern sedimentation. The sedimentary environment and provenance can be discussed by using the methods of grain size, clastic minerals and clay minerals, element geochemistry, isotopic tracer and bioassemblage. In this paper, the material source and sedimentary environment of sediments in Liaodong Bay are discussed by studying the characteristics of heavy and light mineral assemblages of surface samples and columnar clastic sediments, and the single grain size (0.063-0.125mm) of sediments in the study area. The mineral composition of surface sediments was studied by means of mineralogy, granularity analysis and sedimentation dynamics, including 14 core columnar samples (identified 271 samples) from 38 coastal zone surface samples and 43 river samples. The trend of diffusion and migration, and the systematic cluster analysis method are used to divide the mineral assemblage, so as to discuss the source of sediment material and the sedimentary environment and so on. The comparative analysis of the ultrafine sand grade and heavy mineral content in the surface sediment in the study area shows that there is an obvious negative correlation between them. The content of very fine sand can also reflect the water environmental conditions. In Liaohe, Dalinghe and other estuaries, the sediment is mainly composed of fine components and relatively weak in water energy, while in the eastern coast of Liaodong Bay, the grain size of sediment is relatively coarse, and the coastal hydrodynamic action is stronger. Mineral analysis shows that there are 41 kinds of heavy minerals, including hornblende, verdant, garnet, magnetite, ilmenite and sphene, while 11 kinds of light minerals are mainly quartz and feldspar (mainly plagioclase). The surface sediments of the study area are divided into three mineral areas by using Q cluster analysis: the first area is Laotieshan-Fuzhou Bay, the dominant mineral assemblage is metal mineral, hornblende and curtain, and the main metal mineral is ilmenite. The characteristic mineral is pomegranate, which may be the main material source of Fuzhou River and coastal scour, the dominant assemblage mineral is hornblende, metal mineral and curtain type, and the magnetite content in metal mineral is high, in the second area, in the north of Fuzhou Bay and Yingkou, the dominant assemblage mineral is hornblende, metal mineral and hornblende. The characteristic minerals are sphene and zircon, which are obviously influenced by the Daliaohe River and the short-source fluvial materials along the coast, and the dominant mineral assemblage in the third area, Yingkou-Qinhuangdao, is hornblende, curtain stone and metal minerals, and limonite is the main component of the metal minerals. The typical minerals are pomegranate, apatite, Liaohe and Dalinghe. According to the relationship between coastal geomorphology and heavy mineral content, there are three distribution areas of heavy minerals in sedimentary environment: estuarine type, estuarine type and island type. The study of lithologic characteristics of 14 column samples shows that the contents of very fine sand fluctuate from the surface to the bottom reflecting the change of hydrodynamics. The analysis of heavy minerals shows that the unstable mineral content in the study area is relatively high, and the variation of the content of autogenous pyrite in the column sample can indicate the redox conditions and the separation process of the sedimentary environment. The results show that the hydrodynamic force is relatively strong and the water energy at the top of the bay is relatively weak, which is consistent with the conclusion of grain size analysis.
【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P736.21

【参考文献】