Discrimination of Sericite Phyllic and Quartz-Rich Phyllic Alterations by Using a Combination of ASTER TIR and SWIR Data to Explore Porphyry Cu Deposits Hosted by Granitoids, Kerman Copper Belt, Iran

Abstract

Various mapping methods such as Spectral Angle Mapper, band ratio, and Principal Component Analysis were applied to the Advanced Spaceborne Thermal Emission and Reflection Radiometer data to highlight various hydrothermal alteration minerals (e.g., sericite, kaolinite, epidote and quartz) related to Cu mineralization in the Southern Jabal–Barez Range (SJBR), Kerman province, Iran. The integration of sericite and quartz images with Boolean logic in a geographic information system environment discriminated quartz-rich phyllic hydrothermal alteration from sericitic or sericite phyllic alteration. The mapped hydrothermally altered areas were sampled randomly and studied in the laboratory (microscopic studies, spectral and X-ray diffraction analyses) for data validation. Accuracy assessment of the resulting hydrothermal alteration maps was conducted by using a confusion matrix. The overall accuracy was estimated to be 79.69%. The hydrothermal alteration zones enhanced through this research (i.e., sericite phyllic, argillic, and quartz-rich phyllic) are in good agreement with the known locations of porphyry Cu deposits (PCDs) in the SJBR. Propylitic alteration, as reported and documented from many PCDs, is absent or only poorly developed in the SJBR. The quartz-rich phyllic alteration occurs around the more common sericitic alteration. These findings indicate that the integration of sericite and quartz images is useful for mapping quartz rich-phyllic hydrothermal alteration around PCDs hosted by granitic rocks.