Spontaneous combustion of coal seams can produce very high temperature (generally between 600 and 850 °C, even reach to 1000 °C), which greatly changes the properties of the surface loess layer, such as its magnetic susceptibility and chromaticity. In order to study a fast, effective and nondestructive method to determine the influence range of coal seam spontaneous combustion zone, and to provide important clues for the development and utilization of coal seam and burnt rock, the mass-specific magnetic susceptibility (χ) and redness chromaticity (Δa) of loess samples were measured after heating to 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C or 900 °C in a furnace. The results show that the redness chromaticity of loess increases linearly with temperature in the range of 300–900 °C, and the mass-specific magnetic susceptibility decreases suddenly above 700 °C. These changes in mass-specific susceptibility and redness chromaticity with temperature are related to the degree of iron compounds conversion.

煤层自燃会产生很高的温度（一般在600～850℃之间，甚至达到1000℃），极大地改变了表层黄土层的磁化率和色度等性质。为研究一种快速、有效、无损的确定煤层自燃区影响范围的方法，为煤层和烧岩的开发利用提供重要线索，质量比磁化率（χ）和红度色度 (Δ a) 的黄土样品在炉中加热至 100 °C、200 °C、300 °C、400 °C、500 °C、600 °C、700 °C、800 °C 或 900 °C 后测量。结果表明，黄土的红度色度在300～900℃范围内随温度呈线性增加，质量比磁化率在700℃以上突然下降。质量特异性磁化率和红度色度随温度的这些变化与铁化合物的转化程度有关。