Optimización de anomalías en un depósito de fosfatos de Marruecos mediante el método del sombreado

Abstract

Shading is a powerful tool for the enhancement of edges in all kind of images. Given the azimuth and elevation of an illumination source we can calculate the reflectance from the different surfaces provided by the data, helping its interpretation. Shading has become a standard tool in the interpretation of geophysical potential field data. In the Oulad Abdoun phosphate basin, the presence of sterile hardpan (caliche) -so-called "disturbances"- are hard to detect during the geophysical exploration surveys and their presence interfere with the phosphate extraction. The resistivity of the sterile hardpan is above 200 m in contrast to the 80 to 150 m for the phosphate-rich mineralization. In this paper a Schlumberger resistivity survey over an area of 50 hectares is presented. Based in the resistivity data and after direct geological evidence, we conclude that the geological models were successfully obtained from the analysis of the shaded maps of the "disturbances". A new field procedure was tested to map the extension and edges of the "disturbances" anomalies. As a result, the phosphate reserves were improved and better constrained.