Direct evidence of transformation from smectite to palygorskite:TEM investigation  

作　　者：CHEN Tianhu1,,XU Huifang2,LU Anhuai3,XU Xiaochun1,PENG Shuchuan1 2 &YUE Shucang1 1.College of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,China 2.Department of Geology and Geophysics,University of Wisconsin,Madison,WI53706,USA 3.Department of Geology,Peking University,Beijing 100871,China Correspondence should be addressed to Chen Tianhu(email: [e-mail] or [e-mail]) 

出　　处：《Science China Earth Sciences》2004年第11期985-994,共10页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.40072017).

摘　　要：Palygorskite clays sampled from palygorskite clay deposits in Jiangsu and Anhui provinces were investigated by transmission electron microscopy (TEM). Many intergrowth phenomena of special ultra-microstructure between smectite and palygorskite were found. The ultra-microstructure indicates that palygorsite fiberrous crystals grow along (001) of primary smectite through structural transformation and decomposition of the primary smectite. According to field investigation and X-ray diffraction (XRD) analyses, the transformation mechanism and process can be described as: formation of smectite from basalt weathering deposited in localiza- tion basin; evaporation of lake water in aridity environment causing pH increase and concentra- tion of magnesium ion in interstice water of sediment smectite in the lake basin. Under alkaline conditions, magnesium ion occupied interlayer positions of the smectite. Because of the misfit between magnesium octahedral sheet and smectite layer, magnesium ion interaction with smec- tite layers caused the smectite to transform into palygorskite, and resulted in the formation of smectite and palygorskite complex particulates, and even smaller secondary smectite crystal plates. The transformation of smectite structure resulted in the formation of nanometer minerals with large specific surface area and excellent property of physics and chemistry in smec- tite-palygorskite mixing clay. The results from TEM investigation are important for understanding properties of palygorskite clay and application.Palygorskite clays sampled from palygorskite clay deposits in Jiangsu and Anhui provinces were investigated by transmission electron microscopy (TEM). Many intergrowth phenomena of special ultra-microstructure between smectite and palygorskite were found. The ultra-microstructure indicates that palygorsite fiberrous crystals grow along (001) of primary smectite through structural transformation and decomposition of the primary smectite. According to field investigation and X-ray diffraction (XRD) analyses, the transformation mechanism and process can be described as: formation of smectite from basalt weathering deposited in localization basin; evaporation of lake water in aridity environment causing pH increase and concentration of magnesium ion in interstice water of sediment smectite in the lake basin. Under alkaline conditions, magnesium ion occupied interlayer positions of the smectite. Because of the misfit between magnesium octahedral sheet and smectite layer, magnesium ion interaction with smectite layers caused the smectite to transform into palygorskite, and resulted in the formation of smectite and palygorskite complex particulates, and even smaller secondary smectite crystal plates. The transformation of smectite structure resulted in the formation of nanometer minerals with large specific surface area and excellent property of physics and chemistry in smec-tite-palygorskite mixing clay. The results from TEM investigation are important for understanding properties of palygorskite clay and application.

关 键 词：palygorskite  smectite  transmission electron microscopy  X-ray diffraction  NANOMETER mineralogy. 

分 类 号：P578[天文地球—矿物学]