摘要
应用矿物磁测技术对发育于第四纪红土母质上土壤的磁化率（χ），频率依变磁化率（χｆｄ），饱和等温剩磁（ＳＩＲＭ）和矫顽力（ＢＣＫ）进行了研究．结果表明，土壤χ和ＳＩＲＭ的变幅分别为７×１０－８～４７５×１０－８ｍ３ｋｇ－１和８．６×１０－４～３３２．７×１０－４Ａｍ２ｋｇ－１，两者粗略地表明了土壤中亚铁磁性矿物的数量差异．土壤的χｆｄ在４．９％～２３．３％，χｆｄ以及χ和ＳＩＲＭ的粒径分布证明，土壤中的亚铁磁性矿物以次生的超顺磁性颗粒态存在．土壤的磁化和退磁参数则表明具有较高χ的土壤其磁性由亚铁磁性矿物决定，低χ的土壤则是不完整反铁磁性氧化铁的贡献．本研究表明，矿物磁测技术为研究土壤氧化铁的数量、起源和类型提供了一种简便、快速、非破坏性的方法．
Magnetic susceptibility (χ), frequency dependent susceptibility (χ fd ), saturation isothermal remanent magnetisation (SIRM) and coercivity (B CK ) were measured on soils derived from Quaternary red earth to discriminate and characterise ferrimagnatic iron oxide assemblages. The χ ranged from 7×10 -8 to 475×10 -8 m 3·kg -1 and SIRM from 8.6 ×10 -4 to 332.7×10 -4 Am 2·kg -1 . Both χ and SIRM can be used to estimate the ferrimagnetic iron oxide concentration. The χ fd of soils ranges from 4.9 % to 23.3 %, indicating a large proportion of the χ comes from an superparamagnetic component that could be pedogenic. The distribution of χ and SIRM values with respect to the individual particle size fractions suggests that ferrimagnetism derives from secondary iron oxide. The magnetisation and demagnetisation parameters indicate that ferrimagnetic minerals constitute the primary source of χ in soil characterized by higher value of χ and SIRM. The imperfect antiferrimagnetic minerals are significant for soils with a low χ and SIRM. Measurements of magnetic parameters provide a handy, rapid and non destructive method in distinguishing amount, origin and mineralogy of iron oxide in soils.
关键词
磁化率
饱和等温剩磁
氧化铁
第四纪红土
magnetic susceptibility
saturation isothermal remanent magnetisation
iron oxide
Quaternary red earth
