Clay-stone Of Illite In The South Of Zhangcun: Characters Of I/S Mixed-layer Minerals

Illite is an important inorganic non-metallic mineral.It is widely used in the industrial fields especially in the ceramic and rubber,paper industry and papermaking and so on. But pure illite clay rocks are relatively rare in the nature.Illite can be transformed into montmorillonite under certain conditions and be transformed firstly into I/S mixed-layer minerals which will affect the minerals properties and process properties of illite.The aim of this paper was to explore occurrence horizon,mineralogical characteristics,chemical composition and characteristics of trace elements of the illite clay rocks in Permian system of study area by using X-ray diffraction(XRD),infrared spectroscopy(IR),scanning electron microscopy(SEM) and so on.The mineralogical characters of I/S mixed-layer minerals with different mixed-layer ratio were studied in detail.Seven stratums illite rocks having industrial exploitation value were found by combining with both field observation including field investigations,sampling,sample hand observation and laboratory analysis including XRD,IR,SEM.The ratio of SIO₂/Al₂O₃ of seven stratums was 1.71-2.75;The contents of Fe₂O₃ were overall high in the whole and the content of trace elements were close to the abundance value of elements in crust.The results of XRD test showed that the major clay minerals in illite clay rocks were illite,I/S mixed-layer minerals,pyrophyllite,serpentine,etc...The IR patterns of illite clay include four types:â‘ illite(I/S mixed-layer) type;â‘¡illite-serpentine type;â‘¢pyrophyllite- serpentine type;â‘£illite-pyrophyllite-serpentine type.The SEM results showed that the shape of various clay minerals monomer was flake with different sizes, the aggregates were different with each other.The mineralogical characteristics of I/S mixed-layer minerals with different mixed-layer ratio were studied by using XRD,IR and SEM.The XRD patterns showed that the character peak with 10(?) value moved to a higher angle with increase of mixed-layer ratio and became smaller thanl0(?) value.The IR spectrums of I/S mixed-layer minerals with mixed-layer ratio of 5%,10%,15%,20%,25%and 30% were analyzed and the results showed that three regions including 3625 cm^-1±, 1200-1000 cm^-1,850-700 cm^-1 in all spectrums had taken place great change regularly. It was confirmed that the shape of IR spectrum was controlled by the replacement degree of Al³⁺ on Sl⁴⁺.The SEM pictures showed that I/S mixed-layer minerals with expansible crystal layer had obvious layered structure with clear border.In the contract, the layer structure of I/S with non-expansible crystal layer was not obvious and its' monomer was in the shape of broken edge appeared as filiform and the aggregate appeared as glass litter illusion.