Aerogravity and remote sensing observations of an iron deposit in Gara Djebilet, southwestern Algeria

• Detection of iron ore deposits (SW Algeria) by Landsat 8 OLI images.
• Investigation of iron ore by 2-D and 3-D modeling of gravity data.
• The estimated tonnage of the iron ore at Gara Djebilet is 2.37 billion tonnes.

The Gara Djebilet iron ore region is one of the most important regions in Africa. Located in the southwestern part of Algeria at the border with Mauritania, the Gara Djebilet region is characterized by steep terrain, which makes this area not easily accessible. Due to these conditions, remote sensing techniques and geophysics are the best ways to map this iron ore. The Gara Djebilet formations are characterized by high iron content that is especially rich in hematite, chamosite and goethite. The high iron content causes an absorption band at 0.88 μm, which is referred to as band 5 in the Operational Land Imager (OLI) Landsat 8 images. In this study, we integrated geological data, aerogravity data, and remote sensing data for the purpose of mapping the distribution of the Gara Djebilet iron deposit.Several remote sensing treatments were applied to the Landsat 8 OLI image, such as color composites, band ratioing, principal component analysis and a mathematical index, which helped locate the surface distribution of the iron ore. The results from gravity gradient interpretation techniques, 2-D forward modeling and 3-D inversion of aerogravity data provided information about the 2-D and 3-D distribution of the iron deposit. The combination of remote sensing and gravity results help us evaluate the ore potential of Gara Djebilet. The estimated tonnage of the iron ore at Gara Djebilet is approximately 2.37 billion tonnes with 57% Fe.