Geophysical Models for the Cu-Dominated VHMS Mineralization in Katta District, Western Ethiopia

Abstract

Volcanic hosted massive sulfides (VHMS) have been recognized for many years within the Arabian–Nubian Shield of western Ethiopia. The Shield is a collision belt formed when East and West Gondwana collided during the Neoproterozoic time. It covers NE Africa and the Middle East and is known to have hosted several economic mineral deposits. Situated within the Shield, the Katta VHMS mineralization is primarily made up of chalcopyrite, sphalerite, pyrite, pyrrhotite, and magnetite. These minerals are known to have contrasting values in resistivity, chargeability, and magnetic susceptibility with the enclosing host rocks. These physical attributes make resistivity, IP, and magnetic methods ideal to study and detect the mineralization and possibly delineate the ore body. Dipole–dipole DC resistivity and induced polarization data collected along parallel profiles are inverted to generate both 2D and 3D models of resistivity and chargeability. The chargeability model successfully delineates the zone of sulfide mineralization and the resistivity model gives information on the stratigraphic horizons and the structures. Magnetic data collected along more closely spaced profiles were also inverted to recover the 3D magnetic susceptibility model. The recovered model shows a linear magnetic anomaly that could be associated with the sulfides. This anomaly shows good spatial continuity and is in good agreement with the result obtained in the chargeability model. The geophysical inversion results indicate a NNW oriented mineralized zone of considerable strike length and extending to a depth of about 380 m. This study suggests the presence of exploitable VHMS presence in Katta district and that the inversion methodology is an important interpretation tool in guiding the exploration and exploitation of sulfide mineralization.