The Mineralogy And Magnetic Susceptibility Characteristics Of Iron Oxides In Ancient Paddy Soils

The origin of agriculture is the most significant research subject which focused attention by the archaeologists in the world. Research on original soils of rice cultivation is the important content of exploring the development of human society and the progress of agricultural civilization. Frequent oxidation-reduction alternative affection in main soil forming process of paddy soils has caused especial form transform of soil iron oxides. The ironoxide morphology has close relations with the stability and development stages of paddy soil. This study took the ancient paddy soil profile of Sanlonggang village. Liyang Plain, as research objective.Analyzed the form of iron with different diametes particle, the form of clay minerals and iron minerals compared and studied the soil iron form characteristics and magnetic susceptibility features in current cultivation paddy soil and buried ancient paddy soil by using Atomic absorption spectrophotometry,sedimenration-siphon and X-ray diffractometry.The results obtained were list as follows:1) The explicit variation of the different form Fe was observed in buried ancient paddy soil and current paddy soil in Liyang Plain, for 16.96-28.82g/kg and 16.25-33.03g/kg in total iron,0.96-11.13g/kg and 0.91-13.27g/kg in free iron,0.002-0.756 g/kg and 0.002-0.807g/kg in amorphous iron,0.69-10.60g/kg and 0.4-12.61g/kg in crystal iron.Except for amorphous iron, proportions of all others in buried ancient paddy soil outnumber those in current paddy soil. The change trend turns to be increasing with the increase of the section depth.2) The mineral composition of ancient paddy soil is the same with current paddy soil.They both consist of minerals of illite,kaolinite and vermiculite. The current paddy soil and ancient paddy soil have high illite crystallinity. The illite crystallinity of ancient paddy soil is better than that in current paddy soil. The mineral form of iron oxides in ancient paddy soil are consist of goethite, magnetite,hematite and lepidocrokite. The intensity of diffraction peak of goethite and hematite is higher than all others in the ancient paddy soil.3) The magnetic susceptibility of ancient paddy soil in PB and PC profile range from 5.3×10-8/m3·kg-1-6.0×10-8/m3·kg-1 and 6.0×10-8/m3·kg-1-7.3×10-8/m3·kg-1. The magnetic susceptibility of cureent paddy soil in PB and PC profile range from 7.3×10-8/m3·kg-1-33.1×10-8/m3·kg-1 and 8.0×10-8/m3·kg-1-25.3×10-8/m3·kg-1Based on the analysis results of magnetic susceptibility, the typical characteristics of the soil magnetic susceptibility in ancient paddy soil have been summer-ized systematically.The results show that:the magnetic susceptibility of the current paddy soil is higher in the ancient paddy soil. XLF has positive correlation with SIRM,SOFT,HIRM and have good indication of the magnetic soil particle. The XFD of ancient paddy soil and current paddy soil are more than 10%,indicating that most the magnetic minerals of ancient paddy soils are SP super paramagnetic particle.