A gravity and magnetic traverse from Port Sudan to Abu Hamad, NE Sudan

Abstract

Gravity and magnetic measurements were recorded while making a geotraverse from the Red Sea at Port Sudan to the River Nile at Abu Hamad. Much of the region is poorly known geologically and the geophysical interpretations have been constrained by new observations along and near to the traverse line. There are close correlations between gravity, magnetics and many of the major geological features of the region. Western, central and eastern blocks can be distinguished on the basis of combined geology and geophysics. The largely metasedimentary western block shows flat geophysical profiles, whereas the batholith which composes most of the central block shows minor anomalities related to its inhomogenous primary composition and to zones of later N-S shearing. The eastern block is composed largely of low-grade metavolcanic rocks but has a local basement of higher grade rocks, and there are numerous intrusions of granite and gabbro, with ophiolitic lenses within the NE-trending Nakasib shear zone. The strong geophysical anomalies over the Nakasib zone are in keeping with interpretation of this zone as a reworked oceanic suture. Other strong anomalies relate to the presence of basic intrusions and the distribution of basic basement rocks. The regional gravity profile is similar to those measured elsewhere on the flanks of the Red Sea and reflects thinning of the lithosppheric units as the Red Sea axis is approached.