ASTER Analysis for Locating REE-Bearing Granites in Arid Regions: Example from the Arabian Shield

The world’s increasing demand for rare earth elements (REEs) highlights the potential for using new multispectral remote sensing techniques to define new exploration targets in arid regions, such as the Kingdom of Saudi Arabia (KSA), Egypt, and regions of central and western China. Although REEs cannot be detected by satellite multispectral instruments, REEs-bearing alkaline granites can be identified on ASTER imagery. Herein, we develop a new ASTER band ratio scheme to delineate mineralization-related features of the Ghurayyah REE-bearing peralkaline granite in the northwestern KSA. The Ghurayyah peralkaline stock is located at the intersection of a NW striking segment of the Najd-fault system, and an E-W striking fault. It is surrounded to the north and west by metavolcanics, from east by the Jabal Dabbagh alkali granite, and from the south by monzogranite. The mineralogical composition of granitic rocks resulted in spectral variation and causes absorption features at different wavelengths in the shortwave infrared (SWIR). The newly developed band ratios were constructed from (b6 + b8)/(b6 − b8) in red; (b6 + b8)/b4 in green, and (b7 − b9)/(b7 + b9) in blue, enabling the discrimination between the Ghurayyah REE-bearing peralkaline granite, Jabal Dabbagh alkali granite, monzogranite, and metavolcanics. Future work will be carried out to perform higher-resolution drone-based hyperspectral imaging for new high-resolution mapping and evaluate the existing REE deposits, emphasizing field spectral measurements to identify the spectral reflectance of REEs mineralized zones and the absorption features of monazite, columbite-tantalite, and aeschynite- (Y), coupled with rock sampling for petrographical, spectral, and geochemical analyses. These methods have great potential for locating REEs-bearing peralkaline granites in the Arabian shield and elsewhere, such as arid portions of central and western China and adjacent regions.