Detection of alteration zones using ASTER imagery and geological field observations: Al Wajh area, Northwestern Arabian
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ORIGINAL PAPER
Detection of alteration zones using ASTER imagery and geological field observations: Al Wajh area, Northwestern Arabian Shield, Saudi Arabia Wadee A. AlKashghari 1 & Mohamed Matsah 2 & Haitham M. Baggazi 2 Abdelhamid Elfakharani 2,4 & Mohamed K. El-Shafei 5
&
El-Sawy K. EL-Sawy 2,3 &
Received: 30 April 2020 / Accepted: 30 July 2020 # Saudi Society for Geosciences 2020
Abstract Neoproterozoic rocks are exposed in the southwestern Midyan terrane, which is located in the northwestern Arabian Shield. This terrane contains ophiolitic and metavolcanic rocks and arc-related intrusions. A NW-trending sinistral fault system (Najd Fault System, NFS) affected these Neoproterozoic rocks. The integration of remote sensing techniques, such as band combinations and band ratios of ASTER images, with field observations, helped to discriminate sulfiderich rocks and to delineate alteration zones, gossans, and quartz veins, which commonly host ore mineralization. The band ratios used were the Al-OH minerals/advanced argillic alteration and the silica and Fe2+ band ratios. ASTER images were used to discriminate different rock units and construct an alteration map of the study area. Additionally, principal component analysis and frequency filtering techniques for ASTER images were used to extract linear faults and shear zone structures. Remote sensing ASTER images helped in the discovery of ancient mines that had not been previously recorded in the study area. Keywords Midyan terrane . Najd Fault System . Alteration zones . ASTER imagery . Gossan . Sulfide-rich rocks . Band combinations
Introduction The authors would like to mention that this article is a part of AlKashghari, W. A. (2017) Ph.D dissertation at King Abdulaziz University. Responsible Editor: François Roure * Haitham M. Baggazi [email protected] 1
Geological Survey Department, Saudi Geological Survey, Jeddah, Saudi Arabia
2
Faculty of Earth Sciences, Structural Geology and Remote Sensing Department, King Abdulaziz University, P.O. Box 80206, Jeddah 21589, Saudi Arabia
3
Geology Department, Faculty of Sciences, Al-Azhar University (Assiut Branch), Assiut, Egypt
4
Geology Department, Faculty of Science, Aswan University, Aswan, Egypt
5
Geology Department, Faculty of Sciences, Suez Canal University, Ismailia, Egypt
The tectonic history of Precambrian rocks of the region has started with Neoproterozoic rifting and fragmentation of Rodinia Supercontinent in the early Cryogenian (Meert and Torsvik 2003; Stern 1994; Collins and Pisarevsky 2005). The Arabian–Nubian Shield (ANS) developed mainly of Neoproterozoic basement rocks exposed on the Red Sea banks. The shield is represented by Nubian Shield (NS) in the northeastern Africa and Arabian Shield (AS) in the western Arabian Peninsula (Kröner 1984; Stern 1994; Johnson 2006). The exposed Neoproterozoic rocks in the Al Wajh area of northwestern Saudi Arabia are considered part of the Arabian Shield (AS). The shield evolved during several tectonic phases, including (1) rifting of Rodinia (> 950 Ma) fol
