EAGE Student Webinar
Student Webinar by Siraj Beyan Mohamed
This talk involves the Western Ethiopia represents a critical segment of the southern Arabian–Nubian Shield, where prolonged Neoproterozoic mantle–crust interaction, arc accretion, ophiolite emplacement,
granitoid intrusion, and subsequent transpressional deformation collectively established
favorable physicochemical and structural conditions for gold mineralization, particularly within
regionally developed shear zone systems hosted by low-grade metavolcanic–metasedimentary
sequences and spatially associated ultramafic complexes.
The geodynamic evolution of the region is characterized by episodic mantle-derived magma
injection, crustal reworking, and progressive strain localization along first- and second-order
shear zones that acted as long-lived fluid conduits, enabling efficient transport of gold-bearing
metamorphic and magmatic-hydrothermal fluids. Variations in redox state, sulfur fugacity, and
fluid composition, driven by interaction between oxidized crustal lithologies and reduced mantle-
derived ultramafic rocks, played a fundamental role in controlling gold solubility, transport as
sulfur-complexed species, and eventual precipitation during pressure–temperature fluctuations
associated with deformation.
Two genetically distinct ultramafic suites, namely ophiolitic mantle fragments and Alaskan-type
arc-related intrusions, reflect contrasting mantle sources, magma evolution histories, and
tectonic settings, which in turn influenced their metallogenic fertility and styles of gold
mineralization.
Major gold occurrences, including those at Tulu Kapi, Kurmuk, Yubdo, Akobo, Segele, and Joru,
demonstrate strong spatial and genetic links to shear-controlled fluid flow, ultramafic–felsic
lithological contacts, and rheological contrasts that enhanced permeability during
transpressional deformation.
This synthesis highlights Western Ethiopia as a coherent geodynamic and metallogenic
province in which the integration of mantle processes, crustal architecture, and structural
evolution fundamentally governed the localization, grade, and style of gold mineralization.