【作者】 管章志；

【导师】 师育新；

【作者基本信息】 华东师范大学 ， 自然地理学， 2007， 硕士

【摘要】 粘土矿物普遍存在于各种类型的沉积物和沉积岩中，作为次生矿物，粘土对环境的变化极为敏感，因而粘土矿物的沉积分异、组合特征、矿物成分及其含量和矿物的结晶度都从不同的角度记录了粘土矿物的形成过程中各种环境因素的变化。本文选择长江下游的巢湖流域和太湖流域的澄湖作为研究区域，以巢湖流域表层土样、ALE、AC4、AC5、CH以及澄湖的SC6、SC7等柱样为主要研究对象。通过对沉积物中的粘土矿物参数指标的实验分析，同时结合了ALE、CH柱样的粒度特征和CH的测年数据，提取了沉积物记录的过去环境信息。并在查阅大量文献资料的基础上，探讨了流域环境对粘土矿物的组份、形成、晶体结构及其分布特征的影响。1、巢湖现代沉积的粘土矿物，主要为伊利石(53.69～64.51％)、高岭石(17.9～23.18％)、蛭石(8.27～14.2％)、绿泥石(4.37～5.58％)和蒙皂石(2.86～3.39％)五种，粘土矿物的组合类型为伊利石—高岭石—蛭石—绿泥石—蒙皂石型，伊利石的Kubler指数为0.4，结晶度较差，粘土矿物的这种组合类型及伊利石的结晶度表明是强风化作用的产物；巢湖硬粘土层中粘土矿物也为上述五种，含量分别为73.58％，14.74％，4.15％，4.52％和3.01％。粘土矿物的组合类型为伊利石—高岭石—蛭石+绿泥石+蒙皂石型，伊利石的Kubler指数为0.23，伊利石结晶度较高，这些指示了巢湖硬粘土形成时受到风化作用的强度比现代弱。2、澄湖现代河湖相沉积物中，粘土矿物组分主要为伊利石(70.77％)、绿泥石(12.64％)、高岭石(10.74％)、蒙皂石(4.25％)和蛭石(1.6％)五种，组合类型为伊利石—绿泥石+高岭石—蒙皂石+蛭石型，伊利石的Kubler指数平均为0.22，伊利石结晶度较高，澄湖河湖相沉积物粘土矿物的组合类型及伊利石的结晶度表明是一种弱风化的环境。澄湖硬粘土层中，粘土矿物组分主要为伊利石(52.3％)、高岭石(21.97％)、蛭石(12.35％)、绿泥石(10.68％)和蒙皂石(4.25％)五种，组合类型为伊利石—高岭石—绿泥石+蛭石—蒙皂石型，伊利石的Kubler指数分别为0.19。通过和我国黄土中粘土矿物的对比，澄湖硬粘土层中伊利石和蒙皂石的含量低于我国黄土中伊利石和蒙皂石的含量，而硬粘土层中高岭石和蛭石的含量又远高于黄土，表明这层硬粘土经历了一定强度的淋滤和水解作用。3、长江下游湖泊沉积的粘土矿物在形成过程中，由于受流域的气候、地质环境等的共同作用，从而形成了以伊利石—高岭石—绿泥石—蛭石—蒙皂石为主要特征的矿物组合类型。长江下游山区中火成岩及基性岩等广泛分布，地质岩性较复杂，风化碎屑中的云母或长石绢云母化形成的大量伊利石，所以流域沉积粘土矿物中伊利石的含量一般在53.6—70.77％之间。流域气候湿润，淋滤和水解作用强，粘土矿物处于脱硅失钾的阶段，土壤的富铝化特征明显，导致流域沉积物中高岭石的含量一般在10.74—20.92％之间，高于黄河流域的10％，但低于华南地区的20％。本流域化学风化作用占主导地位，蒙皂石的Na~+、Ca~+从层间位置上剥离，不利于蒙皂石的形成和保存，流域内蒙皂石的含量仅为2.86—4.25％。绿泥石属于岩石初期风化阶段的风化产物，杭埠河上游龙河口水库ALE柱样沉积物中的绿泥石含量较高，达到23.9％，是上游流域区域上游山区土壤发育程度不高的象征。4、长江下游湖泊中粘土矿物的分布与水动力和晶体结构特征有关。在水动力强的河口区域高岭石和蛭石含量普遍较高，而伊利石、蒙皂石的含量较低；在水动力较弱的湖心或流域下游区域，伊利石、蒙皂石的含量较高，而高岭石和蛭石含量却较低。在河口水动力较强的区域，水体的矿化度高，絮凝作用强，晶粒粗大的高岭石(粒径约为0.2nm)和蛭石类矿物来说容易先在这里沉淀下来，晶粒细小呈鳞片状的伊利石(粒径约0.1nm)、蒙皂石(粒径约0.01nm)等不易沉积，长时间悬浮于水体中，使得伊利石、蒙皂石等可以运移到离河口较远的湖心区域沉积。5、巢湖CH柱样中沉积物自底部向上，蒙皂石的含量是在减少，高岭石的含量、K／S(高岭石含量／蒙皂石含量)的比率以及伊利石的Kubler指数都是在增加的，这些特征均指示了巢湖流域近千年来的气候是在向湿润方向变化的。特别是在60～25cm层位(约15世纪到18世纪中叶)，K／S出现谷值对应巢湖处于平水期，流域降水少，淋滤作用弱。更多还原

【Abstract】 Clay minerals are distributed in different types of deposits and sedimentary rocks. As secondary minerals they are highly sensitive to environmental changes. The characteristics of clay mineral such as sedimentary differentiation, composition and assemblage, crystallinity and stable isotope have recorder the information of environmental change during the processes of clay minerals formation.This article selects Chaohu Lake basin and Chenghu Lake of Taihu Lake basin in Lower Reaches of the Yangtze River as the study area. So we attempted to study the past environmental evolution from the samples which including surface soil of Hangbu River catchment, ALE ,AC4,AC5 and CH core of Chaohu Lake catcgment,SC6 and SC7 core of Chenghu Lake et al. A large number of date have been obtained by systematical measure of clay mineral,content of grain size and ²¹⁰Pb dating to calculate sediment of CH core. By statistical analysis of these date from the sediments we discussed the clay mineral composition, formulation, crystal texture and distribution characters which had been influenced by the environment of the catchments.1、The dominate clay mineral of recent sedimentation in Chaohu Lake are illite （53.69-64.51%） ,kaolinite（17.9-23.18%）, vermiculite（8.27-14.2%）, chlorite （4.37 -5.58%） and smectite（2.86-3.39%）,The clay minerals composition character is Illite-kaolinite-vermiculite-chlorite-smectite, Illite’s Kübler index is 0.4, illite crytsallinity is very low,which are strongly-weathering products;The clay mineral in hard clay are also the five mineral, the minerals quantity are 73.58%, 14.74%, 4.15%, 4.52% and 3.01%.The composition character is Illite-kaolinite-vermiculite+chlorite +smectite, illite’s Kübler index is 0.23, illite crytsallinity is high,which all showed that the clay minerals had undergone a stronger weathering than recent.2、The dominate clay minerals of recent sedimentation of Chenghu are illite （70.77%）,chlorite（12.64%）,kaolinite（10.74%）,smectite（4.25%）,vermiculite（1.6%）,the minerals composition characters are all illite-chlorite+kaolinite-vermiculite +smectite, Illite’s Kübler index are 0.22, illite crytsallinity are high,which showed a weakly-weathering environment; In the hard clay band, the dominate clay minerals are illite（52.3%）, kaolinite（21.97%）, vermiculite（12.35%）, chlorite（10.68%） , smectite （4.25%）, the minerals composition characters are illite-kaolinite-chlorite+ vermiculite-smectite, Illite’s Kübler index are 0.19. Througe comparing with Chinese loess’s, Illite and semctite quantity in the hard clay band under Chenghu Lake bed were lower than Chinese loess’s, but kaolinite and vermiculite quantity wes higher than Chinese loess’s, which reflected this hard clay band had experienced a strong eluviation and hydrolyzation.3、The formation of clay minerals in Lower Reaches of the Yangtze River had been influenced by the climate, geologic environment et al. The clay minerals composition character is Illite-kaolinite-chlorite-vermiculite-smectite.There were large of area igneous rock, bedrock et al, In mountain district in the Lower Reaches of the Yangtze River, the rocks of the Geologic are very complex. There are many micas in the weathering rocks fragments, those micas are effloresced to number of illite, So illite quantity is among the 53.66-70.77%.The climate of this area is humid and warm, the eluviation and hydrolyzation are very strong, the clay minerals are in the dissilicon and diskalium phase, soils are rich in kaolinite,the quantity is among the 10.74-20.92% in the sediments, which is higher than Huanghe River’s 10% and at the same time lower than south of China’s 20%.This area, chemistral weathering is dominant, the Na⁺, Ca⁺ are deprived from the smectite’s crystalline layer. So the semectite quantity is only 2.86-4.25%.Chlorite is the sedentary production of the incipient weathering stage. In the upper reaches of Hangbu River, the chlorite high quantity is 23.9%, which is the soil lowerly-development symbol.4、The clay minerals distribution has intimate relationship with hydrodynamics and crystalline structure. In the river estuary area, the hydrodynamics is more intensity, the kaolinite and vermiculite quantity are higher, the illite and semectite quantity are lower; but in the center area of the lake, the hydrodynamics is poorer, the kaolinite and vermiculite quantity are lower, Illite and semectite quantity are higher. In the river estuary area, the water salinity is high and flocculating agent is strong, kaolinite（about 0.2nm） and vermiculite’s crystal grain are coarse ,so they deposit easily. Illite（about 0.1nm） and semectite（about 0.01nm）’s crystal grain are very fine , they can be suspended in the water for long time, so they can be transported to the center lake where is far away from the river estuary.5、 In the CH core, from the botton to top, smectite quantity is very low and decreased, but kaolinite quantity, K/S（kaolinite quantity / smectite quantity ）ratio and illite’s Kiibler index are increasd. Those characteristics had reflected that the Chaohu Lake’s climate was gradually warm and humid. Especially, at the 60-25cm phase, Curve of the K/S ratio appeared a lower segments, which reflect that Chaohu Lake was in the usual discharged period ,At this period Chaohu basin wes lack of rain and the eluviation weakened.更多还原