The application of advanced space-borne thermal emission and reflection (ASTER) radiometer data in the detection of alteration in the Chadormalu paleocrater, Bafq region, Central Iran

Abstract

Ore deposits are often produced by fluid flow processes that alter the mineralogy and chemistry of the country rock. One of the main objectives in developing a multi-spectral and hyperspectral sensor is to detect the optical characteristics of the Earth’s surface using hundreds of spectral bands. All previous studies show that remote sensing can recognize alteration to different degrees, using different spatial and spectral resolution sensors. The ASTER sensor measures reflected radiation in VNIR, SWIR and TIR electromagnetic energies. It is cheap and easily available. The alteration minerals in the Precambrian Chadormalu area (Chadormalu paleocrater and the related iron oxide deposit) have been investigated in the field and have been successfully detected by applying IARR (Internal Average Relative Reflectance), FCC (False Color Composite), Decorrelation-stretch, MNF (Minimum Noise Fraction Transform), correlated filter and MEM (Mathematical Evaluation Method) techniques on ASTER imageries. Sodic, potassic, and silicic–phyllic alteration patterns can be distinguished. This study shows that the capability and accuracy of the MEM method is better than 2 × 2 correlated filter techniques. Results indicate that pervasive hydrothermal ore-forming processes were important in the study area. Judging from the assemblage of alteration minerals, the Chadormalu iron deposit is an end-member of the Kiruna type – Iron oxide (Cu–Au) ore deposit continuum.