南海西北部表层沉积物元素地球化学空间多尺度变化与机制研究

发布时间：2018-06-02 11:56

本文选题：空间多尺度变化 + 常、微量元素　；参考：《中国地质大学》2016年博士论文

【摘要】：元素地球化学是示踪物源与沉积环境的重要手段,对于资源勘查与环境评价具有重要的指示意义。本文基于南海西北近海获得的880个站位的表层沉积物常、微量元素以及3251个站位粒度数据,利用因子克里格分析和粒径趋势分析等方法,开展空间不同尺度的元素地球化学、沉积动力学研究,旨在揭示沉积物在不同空间尺度上的自然变化规律与人为活动影响特征。主要取得以下几点认识：利用表层沉积物粒度数据,分析了砂-粉砂-粘土的含量及分布特征,结合沉积物粒径参数特征及水动力条件,将研究区划分为四类沉积环境：(Ⅰ)近岸粗H粒砂质沉积区；(Ⅱ)北部湾中部至海南岛西部以及粤西沿岸至海南岛东北部海域的泥质区； (Ⅲ)琼州海峡及东西出口砂质沉积区；(Ⅳ)残留沉积区。基于多元地统计分析的沉积物粒径趋势分析显示,局部尺度上(半径约33km)研究区大致存在A-R等18个较小范围的粒径“汇聚中心”,分布于各类型的沉积环境中,反映了河流输入、地形、海流等多种因素的控制作用。区域尺度上(半径80km),大致存在A'-Ⅰ’等9个较大范围的粒径“汇聚中心”,空间上与Ⅰ、Ⅱ型沉积环境较为一致，且汇聚中心空间展布具有明显的方向性,显示了区域性环流的控制作用。根据常微量元素的相关性分析,选择Al2O3,Fe2O3,MgO,MnO,TiO2,P2O5,K2O,Na2O与Mz组(常量元素组),Ni,Zn,Pb,Cu,Cd，，Cr与Mz组(微量元素组),CaO-Sr组,SiO2-砂组等四组组分分别进行了因子克里格分析。结果显示,常量元素组、微量元素组、SiO2-砂均存在三种尺度的空间结构：块金尺度、变程为70km球状结构(局部尺度)和变程为160km的球状结构(区域尺度)。而CaO-Sr则表现为块金尺度、变程为120km球状结构(局部尺度)和变程为250km的球状结构(区域尺度),明显不同于其他元素的空间结构,归因于CaO的海洋自生属性。常量元素组在局部、区域尺度上,均主要受控于陆源粘土组分以及水成Fe-Mn氧化物组分。局部尺度上,两种组分具有类似的空间分布特征,主要分布在河流的入海口及其近海的海湾、港口等Ⅰ类近岸的粗粒沉积环境,与粒径趋势汇聚中心A,E,G,J,N,P相对应,显示了陆源河流输入的控制作用；Fe-Mn氧化物组分还受到河流入海后碱性、氧化的海水影响产生自生沉淀,导致了Fe-Mn氧化物组分的空间分布比陆源粘土类组分更为接近陆地。区域尺度上,陆源粘土类组分呈现环陆地分布、向海降低的特征,高值区分布于Ⅰ型近岸粗粒沉积环境,推测为海平面上升时期的陆源粘土组分沉积在低海平面时粗粒组分之上形成的。Fe-Mn组分高值区主要分布于Ⅱ型泥质区以及Ⅲ型琼州海峡东出口等水动力较强的地区,对应了区域尺度上粒径汇聚中心A',B',C',G',H',I',指示了区域性环流与氧化还原环境的控制作用。Si02-砂组与CaO-Sr组分别代表了陆源硅质粗粒组分和海洋生物组分,两者空间分布的尺度效应不明显,Si02主要分布在Ⅰ、ⅢH型高能的沉积环境,反映了水动力条件控制作用；CaO主要分布在远离陆地的较深海域,与水深正相关分布,指示了水深对生物类组分的控制。微量元素组在局部尺度上主要受人为活动的影响,Pb,Cd是人为活动影响的指标元素,分别约8.4%和6.5%的站位富集系数已达到中等富集-显著富集的程度,表明Pb,Cd可能已受到人为污染,且高值区分布的防城港、廉州湾、江洪湾、海口湾、湛江港、雷州湾、博鳌港、八所港等人类活动密集、工业或交通发达的地区是可能污染区。微量元素在区域尺度上主要为陆源粘土类吸附组分,空间分布上表现出自陆地向海增加的特征,高值区主要分布于Ⅱ类泥质沉积环境,对应了区域尺度上粒径汇聚中心A',B',C',G',H',I',与区域性环流的影响有关。Cd独特的地球化学性质使其在区域尺度上成为一个独立的主成分,高值区主要分布在琼州海峡、海南岛西南沿岸海域以及漠阳江南部海域,推测是低海平面时近源的陆源碎屑沉积以及海陆相互作用的结果。综上所述,研究区自然的陆源组分具有局部尺度(70km)和区域尺度(160km)两种尺度的空间变化；局部尺度上,中小型河流的陆源输入是最主要的控制因素,水深、地形、海流、氧化还原环境对沉积物的搬运、沉积具有重要作用；区域尺度上,海平面升降以及区域性海洋环流是主控因素。海洋生物组分主要表现为区域尺度上(250km)的空间变化,水深是主要的控制因素。人为影响组分则表现为局部尺度(70km)上的空间变化,主要受控于局部人为污染源的输入。
[Abstract]:Elemental geochemistry is an important means of tracer source and sedimentary environment. It has important directive significance for resource exploration and environmental evaluation. Based on the surface sediments, trace elements and 3251 station size data of 880 stations in the northwest offshore of the South China Sea, the methods of factor Craig analysis and particle size trend analysis are used. In order to reveal the characteristics of natural variation and human activities in different spatial scales, the study of the geochemical and sedimentary dynamics of different spatial scales aims to reveal the characteristics of the natural variation and human activities in different spatial scales. The characteristics of diameter parameters and hydrodynamic conditions are divided into four types of sedimentary environments: (I) the coarse H granular sandy sedimentary area in the near shore; (II) the mud area in the middle of the north bay to the west of Hainan Island and the coastal area of the west of Guangdong to the northeast of Hainan Island; (III) the Qiongzhou Strait and the eastern and Western sand sediment area; (IV) residual sedimentary area. The statistical analysis of sediment grain size trend analysis shows that there are roughly 18 smaller size "convergence centers" of A-R in the study area on the local scale (radius about 33km), which are distributed in various types of sedimentary environments, reflecting the control effect of various factors such as river input, terrain and sea current. The region scale (radius 80km) is roughly A'- I 'and other 9 larger size distribution centers, which are more consistent with the sedimentary environment of type I and II, and have obvious directionality in the distribution center space, showing the control of regional circulation. According to the correlation analysis of the constant trace elements, Al2O3, Fe2O3, MgO, MnO, TiO2, P2O5, K2O, Na2O and Mz group (constant element) Group Ni, Zn, Pb, Cu, Cd, Cr and Mz group (microelement group), CaO-Sr group, SiO2- sand group and other four groups respectively, the factor Craig analysis. The results show that the constant element group, microelement group, SiO2- sand have three kinds of spatial structure: the bulk gold scale, the variable range is the 70km spherical structure (local scale) and the spherical structure of 160km. While CaO-Sr is a massive gold scale, the variable range is 120km spherical structure (local scale) and the spherical structure of 250km (regional scale), which is obviously different from the spatial structure of other elements, which is attributed to the marine authigenic attribute of CaO. The constant element group is mainly controlled by the land source clay components and water on the local and regional scales. Fe-Mn oxide components. On the local scale, the two components have similar spatial distribution characteristics, mainly distributed in the river entrance to the sea and its Offshore Bay, the port and other near shore coarse sedimentary environment, corresponding to the grain size trend convergence center A, E, G, J, N, P, showing the control effect of the land source river input; Fe-Mn oxide component. It is also influenced by the alkaline and oxidizing seawater after the river enters the sea, which produces autogenic precipitation, which leads to the spatial distribution of Fe-Mn oxide components closer to the land than the land-based clay components. The high value area of.Fe-Mn components formed on the low sea level coarse clay components at low sea level is mainly distributed in the type II argillaceous zone and the east exit of type III Qiongzhou Strait, which corresponds to the A', B', C', G', H', I', indicating regional circulation and oxidation, which indicates regional circulation and oxidation. The control effect of the reduction environment.Si02- sand group and CaO-Sr group represent the land source siliceous coarse grain components and the marine biocomponents respectively. The scale effect of the spatial distribution is not obvious. Si02 mainly distributes in the sedimentary environment of type I, III H high energy, which reflects the control of hydrodynamic conditions; CaO is mainly distributed in the deep sea away from the land, and the water is mainly distributed in the water. The deep positive correlation distribution indicates the control of the water depth to the biological components. The microelement group is mainly influenced by human activities on the local scale. Pb and Cd are the index elements of the human activities. The enrichment coefficient of the stations of about 8.4% and 6.5%, respectively, has reached the degree of medium enrichment and significant enrichment, indicating that Pb and Cd may have been polluted by human beings and are high. Fangchenggang, Lian Zhou Bay, Jiang Hong Wan, Haikou Bay, Zhanjiang port, Leizhou Bay, Leizhou Bay, Boao port, and eight ports are concentrated in human activities. The industrial or traffic developed areas are possible pollution areas. The trace elements are mainly land-based clay adsorption components on the regional scale, and the space distribution shows the characteristics of increasing from land to sea, and high value area owners It should be distributed in type II argillaceous sedimentary environment, corresponding to A', B', C', G', H', I' at regional scale. The unique geochemical properties of.Cd related to the influence of regional circulation on the regional scale make it an independent principal component on the regional scale, and the high value area is mainly distributed in the Qiongzhou Strait, the southwestern coastal waters of Hainan Island and the south of the south of the south of desert Yang. It is presumed to be the result of the land-based clastic deposition and sea land interaction of the near source at low sea level. To sum up, the natural terrestrial components of the study area have two spatial variations of the local scale (70km) and the regional scale (160km); on the local scale, the land source input of the small and medium rivers is the most important control factor, the depth of water and the land. Shape, current and redox environment play an important role in sediment transport and deposition; on regional scale, sea level fluctuation and regional ocean circulation are the main controlling factors. The marine biological components are mainly the spatial variations on the regional scale (250km), the water depth is the main control factor. The human influence group is represented as the local scale (70 The spatial variation of KM is mainly controlled by the input of local anthropogenic pollution sources.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P736.41

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