Potential of Sentinel-2 MSI data in targeting rare earth element (Nd3+) bearing minerals in Esfordi phosphate deposit, Iran

Abstract

Modern-day devices, transport, and green energy require growing supply of rare earth elements (REEs), which subsequently provide the basics for attempts on developing the efficient and innovative methods for their detection and exploration. Remote sensing data / techniques provide great possibilities to quick and non‑destructive exploration of such deposits, even in relatively unreachable and socially sensitive places. The diagnostic absorption features of REEs are generated in the visible to shortwave infrared (VNIR-SWIR) region of the electromagnetic spectrum, among which, the most prominent absorption features of neodymium (Nd), which could be a key pathfinder for REEs, are displayed in the VNIR region. This study assesses the capability of the Sentinel-2 MSI data for detecting absorption feature of Nd from space. This process was successfully examined and verified in the Esfordi phosphate deposit, Central Iran, and resulted the direct mapping of REE (Nd). For this purpose, firstly, the potential of the Sentinel-2 MSI data for detecting REEs was theoretically evaluated, and then, the adaptive coherence estimator (ACE) algorithm was applied for targeting Nd-bearing zones, using the field spectra of apatite as reference. Field works, X-ray diffraction (XRD), spectroscopy, and the geochemical analyses supported the achievements. The results demonstrated that Sentinel-2 MSI can capably detect the 740 nm absorption band of Nd. Generally, this research attained high overall accuracy of 88.64% for the generated map using in situ collected data for verification.

Keywords

• Sentinel-2 MSI
• Rare earth element
• Neodymium
• Subpixel mineral mapping
• Spectroscopy
• Geochemical analyses