Digital image processing and geospatial analysis of landsat 7 ETM+ for mineral exploration, Abidiya area, North Sudan

Digital data of Landsat Enhanced Thematic Mapper Plus (ETM⁺7) was used in mineral exploration investigations for the area around Abidiya area, North Sudan. The studied area consists of Precambrian crystalline basement rocks. The oldest geologic unit comprises basic and ultrabasic rocks associated with metacherts overlain by island arc-related metavolcanosedimentary sequences, these units have been overlain by supracrustal metasediments and intruded by magmatic granitic intrusions. Regional structures manifested by the Nakasib suture and Keraf shear zones. Several digital image processing “DIP” techniques applied on the multispectral bands (1, 2, 3, 4, 5 & 7) were demonstrated in the context of geological mapping and mineral exploration. Dual techniques of analyses have been carried-out to enhance and delineate the alteration zones related to gold mineralization. Mineralization zones can be identified by their spectral signatures of the alteration products iron oxides, hydroxyl-bearing minerals, carbonates and quartz-feldspars minerals. Alteration map have been produced based on the band ratio techniques produced from Sabin's band ratio color composite image (bands 5/7, 3/1 and 3/5 in the R G B, respectively). Another alteration map produced by using the Feature Oriented Principal Selection technique (FPCS), named as Crosta alteration color composite image. The Crosta image based on a selective principal component analysis for some bands. Both alteration images have been supervised classified and vectorized. Geospatial analysis of the vectorized layers proved to support the demarcation of the mineralization zones. These zones are aligned with the sheared and metamorphosed basic and ultrabasic and metacherts, and controlled by the shear fractures. The metasomatic replacements associated with the shear activities could be responsible for enhancing the mineralization in this area, which gave high signals in the alteration map.