Tectonics of the Mozambique Margin Through the Integration of Gravity and Magnetic Modelling: the Rovuma Basin Case Study.

Abstract

The Rovuma Basin is located along the eastern margin of northern Mozambique and southern Tanzania, forming one of a series of continental passive margin basins that stretch along the coast of East Africa. The basin covers onshore and offshore areas for approximately 64,000 Km2. The correct definition of the geological evolution of an area is of primary importance for a proper assessment of its petroleum potential; in the present work an integrated approach, based on seismic interpretation, structural analysis and 2D Gravimetric/Magnetic modelling, has been applied on three different interpreted seismic sections to provide more predictive and reliable geological models. The Gravimetric/Magnetic modelling has contributed to the definition of the Rovuma Basin architecture by testing two possible geological scenarios: one with a shallow top basement surface and another with a deep top basement surface, both interpreted on seismic data. Through the integrated potential methods study one of the above scenarios has been validated. The results of the integrated workflow could be summarized as:–proper basement surface depth scenario definition;–description of the main structural lineament geometries;–basaltic bodies geometry and location definition;–characterization of continental, transitional and oceanic crusts and definition of a possible Continental Ocean Boundary (COB) location. The mutual support between the structural studies and potential method teams has been the key to improve the geological knowledge in frontier exploration areas. Introduction The correct definition of the geological evolution of an area is of primary importance for a proper assessment of its petroleum potential. In the present work an integrated approach, based on seismic interpretation, structural analysis and 2D Gravimetric/Magnetic modelling, has been applied on three different interpreted seismic sections to provide more predictive and reliable geological models. 2D Gravimetric/Magnetic modelling are non-unique, many models may provide calculated gravity responses that will fit the observed profiles. However, with some geological control, sensible assumptions and knowledge of likely structural styles, the results can be constrained reasonably well. By combining geological and geophysical interpretations on three differently oriented interpreted seismic sections, the tectonic evolution of the Rovuma Basin has been investigated (Fig.1). The Gravimetric/Magnetic modeling has contributed to the definition of the Rovuma Basin architecture by testing two possible geological scenarios: one with a shallow top basement surface and another with a deep top basement surface, both interpreted on seismic data as possible basement. Through the integrated potential methods study one of the above scenarios has been validated.