Influence of Particle Size on Magnetic Properties of Soils in Zhejiang Province, China

The relationship between magnetic properties and particle size of soils derived from metamorphic rock, basalt, granite, Quaternary red clay, limestone and mudstone from Zhejiang Province, East China was studied. Based on the variations of the mass magnetic susceptibility (X), anhysteretic remanent magnetization (ARM), and saturation isothermal remanent magnetization (SIRM) with soil particle size, the relationship could be classified into three groups. For the soils derived from metamorphic rock and basalt, magnetic values were the highest in the gravel and coarse sand fractions and decreased with decreasing soil particle size. The soils derived from sedimentary rock had a bimodal distribution of magnetic values, with peaks in 1-0.5 and 0.005-0.000 5 mm fractions. The soil developed on granite was characterized by a peak of magnetic value in 0.001-0.000 5 mm fractions. Frequency-dependent susceptibility (Xfd ) and ratics of magnetic parameters (ARM/X, SIRM/X and SIRM/ARM) of soil particle fractions showed that variations in ferrimagnetic grain size paralleled those in particle size. Xfd peaked in clay fraction and decreased with increasing particle size, irrespective of soil parent materials. The acquisition curves of IRM and demagnetization parameter of different soil particles indicated that there were different magnetic minerals assemblages in different particle fractions.