Study of reflectance of Precambrian detritic rocks for structural analysis in the visible and near-infrared

Abstract

Image processing of Thematic Mapper data in the Schist-Greywacke Complex (Central Iberian Hesperian Massif, Spain) suggests effects connected to both thermal metamorphism and shear-zone related dynamic metamorphism. Fabric analysis on thin section of rock samples define more intensive deformation in areas with distinct spectral features in the imagery. This is confirmed by ground structural data and laboratory spectra of soil samples. Laboratory spectra in the visible and near-infrared on different surfaces of the same sample, referring to its fabric elements, offer differences in reflectance. Dark rocks present a more favourable response to weak dynamic metamorphic effects on reflectance. The quantity and quality of organic matter content in rocks is believed to be responsible for changes in reflectance corresponding to effects produced by thermal metamorphism and dynamic metamorphism. Thus, reflectance shown by imagery and laboratory data proves to be a useful tool for mapping areas with different deformation intensity and variable attitude in space of structural elements as a guide line in exploration of structural variations for geological mapping.