Clarify the relationship between the land surface temperature and clay minerals using Landsat temporal data, spectral, and XRD data: A case study from some clay quarries southwest Al-Alamin City, Egypt

Clay minerals hold significant economic value due to their extensive industrial applications. This study aims to utilize land surface temperature (LST) data to distinguish and map clay quarries in southwest Al-Alamin City, Egypt, and understand the spectral characteristics of clay minerals using laboratory visible near-infrared (VNIR) spectral data. LST values are retrieved from the thermal infrared bands of Landsat series 5 and 8 data, acquired in August of 1985, 2010, and 2020. The spatial distribution of these values is mapped. The results reveal that LST values increased over time, reaching 37 °C in 1985, 43 °C in 2010, and 44 °C in 2020, primarily due to the exposure and quarrying of clay. Three clay minerals, montmorillonite, kaolinite, and illite, are identified through x-ray diffraction (XRD) analyses. A broad absorption feature near 0.9 μm is recorded in the clay spectral profiles, attributed to the presence of iron, as indicated by x-ray fluorescence (XRF) data. For principal component analysis (PCA) mapping, a combination of PC1, PC2, and PC4 was used for the Deir El-Morair Quarry, while PC1, PC4, and PC5 were employed for the Deir Abuel-Hagif Quarry. The clay spectral profiles showed that band ratio (7/6) effectively discriminates clay from other rocks, while band ratios (5/6 and 5/7) differentiate between iron silicates and clay minerals. The present study successfully identified and mapped the clay quarries using LST, spectra, and XRF data, and the approach can be applied to identify possible clay areas anywhere.