X-ray Diffraction Analysis Of The Composite Characteristics Of Clay Minerals In The Local Coastal Zone Of Shandong Peninsula

The country has vigorously supported the marine industry in recent years,which has got great achievements in the development of China's marine economy.The construction of Shandong Peninsula Blue Economic Zone is an important part of China's marine development strategy.“The Shandong Peninsula comprehensive geological survey” project is on the agenda,and the combination characteristics and environmental significance of the clay minerals are indispensable basic elements.In this paper,12 samples of surface sediments and the drilling1302 with a length of 5.5 meters obtained from the local coastal zone of the Shandong Peninsula were studied.Clay minerals were extracted by sedimentation method,and the combination characteristics and mineral characteristics of clay minerals were analyzed by X-ray diffraction(XRD)and the effects of XRD test conditions on the results of clay minerals were discussed;Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to observe the morphology and composition of the clay minerals;At the same time,the grain size analysis of drilling samples had been done and correlation analysis of grain size and clay minerals relative contents was carried out;.The main results are as follows:(1)The test conditions of XRD have some impact on the results of the clay minerals.With the increase of power,the diffraction intensity increased,but it's not the bigger the better.The most suitable power is 6kW(voltage-40 k V,current-150mA).In step scanning mode,the step size and preset time determine the scanning speed.The step size affects the resolution,the larger the step size,the lower the resolution;the preset time affects the diffraction intensity,and the diffraction intensity increases with the preset time increases.In continuous scanning mode,the scanning speed affects the diffraction intensity,and the slower the scanning speed,the larger the diffraction intensity;The sampling width mainly affects the resolution,and the larger the sampling width,the lower the resolution.The scanning speed and the sampling width should be reasonably combined.Finally,the most efficient test conditions for clay minerals are as follows: voltage 40 kV,current 150 mA,continuous scanning mode,scanning speed is 8 degrees /min,and sampling width is 0.024°.Scan a sample of clay minerals in 3 minutes and 37 seconds.(2)There are four types of clay minerals in surface sediments: smectite,illite,kaolinite and chlorite.In the samples of Dagu River estuary in Qingdao,illite is the dominant clay mineral(61.0%),followed by kaolinite(16.0%),chlorite(12.2%)and smectite(10.8%).It is characterized by illite-kaolinite-chlorite-smectite assemblage and similar to clay minerals distribution in Jiaozhou Bay.In the samples of Yellow River estuary in Dongying,illite is also the dominant clay mineral(55.3%),followed by chlorite(20.3%),kaolinite(16.1%)and smectite(8.3%).It is characterized by a clay minerals assemblage of illite-chlorite-kaolinite-smectite,which is similar to clay minerals assemblage from the coastal area of Yellow River delta.The Kübler index which is 0.396°2? averagely in Dagu River estuary in Qingdao is higher than Yellow River estuary in Dongying.The crystallinity of illite in Dagu River estuary is poor because of the relatively strong hydrolysis.It has a certain relationship with the annual precipitation which is larger in Qingdao.The chemical index of illite is all less than 0.4.It can be seen that illite is in rich of Fe-Mg,which is the result of physical weathering.(3)The deposits of drilling 1302 are also made of the above four kinds of clay minerals with little feldspar and clastic quarz.In the relative clay mineral content,illite is the dominant(59.1%),followed by chlorite(17.7%),kaolinite(13.8%)and smectite(9.4%).It is characterized by illite-chlorite-kaolinite-smectite assemblage which is similar to clay minerals assemblage from the coastal area of Yellow River delta.The Kübler index which is from 0.312°2? to 0.463°2? is higher than that of the loess of China's inland.The crystallinity of illite is lower too.The chemical index of illite is all less than 0.4.Illite is in rich of Fe-Mg,which is the result of physical weathering.(4)In the sediments of drilling 1302,the contents of illite fluctuated from the bottom to surface,and the contents of smectite and illite have a negative correlation,indicating the cold and dry climatic conditions.The contents of kaolinite changes little from the bottom to surface,showing a trend of small increase.The trend of chlorite contents is similar to that of illite contents.The composition and distribution of clay minerals are mainly controlled by climate,meanwhile,the sediment source and hydrodynamic conditions also have some influence.SEM observations show that: smectite is mostly agglomerated together in the form of cottonwool or flakes;illite is the most common,flaky accumulation or dispersion;chlorite is leaf-like and larger.EDS analysis shows that the clay minerals is characterized by calcium rich smectite;potassium rich and a certain amount of iron and magnesium in illite,which is corresponding to the chemical index of illite.(5)Grain size analysis of drilling 1302 shows that the sediments are mainly sand,silt and clay.The grain size of the sediments from the bottom to the surface followed a coarse-fine-coarse-fine sequence.Additionally,the deposition in drilling 1302 has undergone changes there.The sediments have bad sorting reflecting a weak water dynamic effect at that time.There is almost no correlation between the change in grain size of the borehole sediment and the relative content of clay minerals.