Geophysical imaging of the Luhoi geothermal field, Tanzania

• Main Authors: Egidio Armadillo, Daniele Rizzello, Claudio Pasqua, Taramaeli Mnjokava, Jonas Mwano, Makoye Didas, Lucas Tumbu
• Other Authors: Armadillo, Egidio, Rizzello, Daniele, Pasqua, Claudio, Mnjokava, Taramaeli, Mwano, Jona, Didas, Makoye, Tumbu, Lucas
• Format: Conference Object
• Language: English
• Published: 2018
• Subjects: Indian; Iceland
• Online Access: http://hdl.handle.net/11567/930811

The Luhoi prospect is a coastal basin located within Rufiji Trough along the passive continental margin of western Indian Ocean of Tanzania, a sector extending south of the termination of the eastern branch of the African Rift System. The structural pattern is dominated by tectonic features belonging to the WNW-ESE Tagalala Trend and to the NE-SW Selous Trend that have been active until recent times. The thermal manifestations are mostly located along a WNW-ESE direction flowingfollowing the Ruhoi River, in the south-western sector of the focal study area. The Wingoyongo Hill, located in the north-eastern sector of the focal area, forms a morphological high where emissions of H2S and bituminous staining were observed. Here, an old well intersected 800 m of quartz sandstone with minor intercalations of siltstone and claystone (Kipatimu Series, Lower Cretaceous). Magnetotelluric (MT), time-domain electromagnetic (TDEM) and gravimetric geophysical surveys were carried as part of a geoscientific study funded by the Ministry of Foreign Affairs of Iceland through Icelandic International Development Agency (ICEIDA) and the Nordic Development Fund (NDF). The goal of the survey was to advance the state of knowledge of the Luhoi geothermal prospect, in order to elaborate the conceptual model of the field. The survey area extends over a surface of approximately 75 km2, designed to include the Luhoi hot springs and the Wingoyongo fumaroles. The gravimetric data set is composed of 124 measurements collected on a regular grid at a nominal spatial sampling of 800 m, and 16 more to infer the regional field. The residual Bouguer anomaly map shows an elongated gravimetric high trending NE-SW with values up to 3 mGal, surrounded by gravimetric lows up to -2 mGal. Forward and inverse 2D/3D models image an asymmetrical horst like structure trending NE-SW. Both the thermal manifestations and the Wingoyongo Hill are aligned along the NW flank of the horst. Since the Wingoyongo well intersected sandstones for about 800 m, the horst ...