Using remote sensing techniques and field-based structural analysis to explore new gold and associated mineral sites around Al-Hajar mine, Asir terrane, Arabian Shield

• Different Image processing techniques were used to delineate alteration zones.
• Identifying new mineralized-bearing metamorphic belt.
• Porphyry-type deposit is determined in the Al-Hajar prospect.
• Alteration zone, hydrothermal breccia, Iron gossans and Jasper are mineral indicatores.
• Mineralizations and alterations are generally shear zone controlled.

Modern earth resource satellites provide huge amounts of digital imagery at different resolutions. These satellite imageries are considered one of the most significant sources of data for mineral exploration. Image processing techniques were applied to the exposed rocks around the Al-Aqiq area of the Asir terrane in the southern part of the Arabian Shield. The area under study has two sub-parallel N–S trending metamorphic belts of green-schist facies. The first belt is located southeast of Al-Aqiq, where the Al-Hajar Gold Mine is situated. It is essentially composed of metavolcanics and metasedimentary rocks, and it is intruded by different plutonic rocks of primarily diorite, syenite and porphyritic granite. The second belt is located northwest of Al-Aqiq, and it is composed of metavolcanics and metasedimentary rocks and is intruded by granite bodies. The current study aimed to distinguish the lithological units, detect and map the alteration zones, and extract the major fault lineaments around the Al-Hajar gold prospect. Digital satellite imageries, including Landsat 7 ETM + multispectral and panchromatic and SPOT-5 were used in addition to field verification. Areas with similar spectral signatures to the prospect were identified in the nearby metamorphic belt; it was considered as a target area and was inspected in the field. The relationships between the alteration zones, the mineral deposits and the structural elements were used to locate the ore-bearing zones in the subsurface. The metasedimentary units of the target area showed a dextral-ductile shearing top-to-the-north and the presence of dominant mineralized quartz vein-system. The area to the north of the Al-Hajar prospect showed also sub-parallel shear zones along which different types of alterations were detected. Field-based criteria such as hydrothermal breccia, jasper, iron gossans and porphyritic granite strongly indicate the presence of porphyry-type ore deposits in Al-Hajar metamorphic belt that may proof promising for subsurface mining.