The Geology and Structural Evolution of the Area Around the River Nile Between /lthara and Ahidiya, Nile State, Sudan; Remote Sensing, Structural and Geochemical Approaches.

Abstract

ABSTRACT The study area covers 8100 Kmz in north central Sudan bounded by Latitudes 17° 50‘- 18° 30‘ N and Longitudes 33° 40‘ and 34° 30‘ E. Different digital image processing techniques applied to enhance the geological and structural details of the study area, using Landsat Thematic Mapper (TM) and Enhance Thematic Mapper (ETM 7). The (ETM+) images show that the southeast trending structural lineaments of the Nakasib Suture Zone (N SZ) continue to the southeastern part of the Bayuda Desert north of Atbara. Geologically, the area is underlain by highly sheared mafic-ultramafic rocks, volcanosedimentary sequences and supracrustal metasediments. All of the units are invaded by calc-alkaline and post to anorogenic intrusions. The mafic-ultramafic masses have all the features characteristic of ophiolite suits including layered cumulate, sheeted dolerite dykes, pillow lavas section and associated deep marine sediments, but are dismembered and recrystallized. The pillow lava sections have typical mid-oceanic ridge basalt geochemical signature as indicated by discriminate diagrams. The ophiolitic massifs identified in this work have been grouped into three complexes, namely Sotrebab, Qurun and El-Fadlab complexes forming discontinues NE-SW trending belt that merges with the ophiolitic fragments along the Nakasib Suture Zone. Therefore, these complexes may represent the southwestern continuation of the Nakasib Suture Zone. The volcanosedimentary sequence is comprised of turbidities besides massive volcanic flows which have been recrystallized in the condition of the greenschist facies of regional metamorphism. They have predominantly tholeiitic to mild calc- alkaline geochemical affinity, thus suggesting subduction related geotectonic setting. XIII