A resistivity survey of phosphate deposits containing hardpan pockets in Oulad Abdoun, Morocco

Abstract

In the great Oulad Abdoun Basin exploitation of a new phosphate deposit was begun after the Grand Daoui horizon was exhausted. Inclusions of sterile hardpan—so-called “disturbances” —are hard to detect and interfere with phosphate extraction. Their resistivity is above 200 Ω-m as against 80 to 150 Ω-m for the phosphate-rich mineral. A Schlumberger resistivity survey over an area of 50 hectares was carried out. Models of the geology were successfully obtained from Fourier analysis. A new field procedure was tested to deal with the presence of disturbances. Estimates of phosphate reserves were improved and better constrained.