ENVIONMENTAL IMPLICATION OF THE COLOR INDEX OF THE PLINTHITIC RED EARTH IN JINHUA-QUZHOU BASIN

The plinthitic red earth is a kind of deposit with red clay matrix decorated by a large number of irregular light-colored stripes. It needs a special color expression system. The color index of L^*(lightness), a^*(redness), b^*(yellowness) and ΔE(color difference between the red matrix and white reticulation) of the red substrates, light-colored stripes and full sample from Jiangtang (JT) section, Tangxi (TX-LSD) section and Luodian(LD) section in Jinhua-Quzhou basin were measured respectively by K-Minolta CR-400. The results show that:(1)the plinthitic red earth needs a special color expression system due to its special stripe-structure. The system includes the colors of the bulk sample, red matrix, light-colored stripe and color difference. Different color system has specific environmental implications. The factors which caused the color variation are complicated; (2) The color of bulk sample, in general, may indicate the tendency of reticulation forming process, the higher the redness (a^*), the more the content of Fe₂O₃、Al₂O₃ and the less the SiO₂/R₂O₃ ratio (or the stronger the desilica-allitization), but the value is not stable due to random sampling; (3) The color of red matrix can well indicate the level of redness and its changes; and the color of light-colored stripe can well indicate the trend of change of plinthitic red earth in section; (4) The new color index-color difference (ΔE) can indicate the trend and phase of reticulation, the higher the color difference, the stronger the forming process of the reticulate structure. Environmental implication can be better indicated with the new system.