Research Article Fluid Circulations at Structural Intersections through the Toro-Bunyoro Fault System (Albertine Rift, Uganda): A Multidisciplinary Study of a Composite Hydrogeological System Bastien Walter , 1 Yves Géraud, 1 Yann Hautevelle, 1 Marc Diraison, 1 and François Raisson 2 1 GeoRessources, UMR 7359, Université de Lorraine, CNRS, CREGU, ENSG Campus Brabois, 2 Rue du Doyen Roubault, BP10162, F-54505 Vandoeuvre les Nancy, France 2 Total CSTJF, Avenue Larribau, F-64016 Pau Cedex, France Correspondence should be addressed to Bastien Walter; bastien.walter@univ-lorraine.fr Received 8 May 2018; Revised 22 September 2018; Accepted 28 October 2018; Published 27 February 2019 Academic Editor: Domenico Montanari Copyright © 2019 Bastien Walter et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Regional fault structures along rift basins play a crucial role in focusing fluid circulation in the upper crust. The major Toro-Bunyoro fault system, bounding to the east of the Albertine Rift in western Uganda, hosts local fluid outflow zones within the faulted basement rocks, one of which is the Kibiro geothermal prospect. This major fault system represents a reliable example to investigate the hydrogeological properties of such regional faults, including the local structural setting of the fluid outflow zones. This study investigated five sites, where current (i.e., geothermal springs, hydrocarbon seeps) and fossil (i.e., carbonate veins) fluid circulation is recognized. This work used a multidisciplinary approach (structural interpretation of remote sensing images, field work, and geochemistry) to determine the role of the different macroscale structural features that may control each studied fluid outflow zones, as well as the nature and the source of the different fluids. The local macroscale structural setting of each of these sites systematically corresponds to the intersection between the main Toro-Bunyoro fault system and subsidiary oblique structures. Inputs from three types of fluid reservoirs are recognized within this fault-hosted hydrogeological system, with “external basin fluids” (i.e., meteoric waters), “internal basin fluids” (i.e., hydrocarbons and sediment formation waters), and deep-seated crustal fluids. This study therefore documents the complexity of a composite hydrogeological system hosted by a major rift-bounding fault system. Structural intersections act as local relative permeable areas, in which significant economic amounts of fluids preferentially converge and show surface manifestations. The rift-bounding Toro-Bunyoro fault system represents a discontinuous barrier for fluids where intersections with subsidiary oblique structures control preferential outflow zones and channel fluid transfers from the rift shoulder to the basin, and vice versa. Finally, this work contributes to the recognition of structural intersections as prime targets for exploration of fault-controlled geothermal systems. 1. Introduction Large varieties of potentially geothermal systems are nowa- days recognized, depending on their geological, hydrogeologi- cal, and heat source and transfer characteristics (e.g. [1–7]). Current technology development thus broadens the geo- thermal play types that can be operated, especially in intra- cratonic area [8]. In order to catalog the geological controls on geothermal resources, Moeck [9] proposed a new geo- logically based classification, involving both magmatic vs. nonmagmatic and convective vs. conductive dominated geo- thermal systems. Classification of the different geothermal play types can therefore significantly help in the choice of exploration methods and heat and power production tech- niques subsequently. Among the different geothermal play types defined by Moeck [9], geothermal systems are broadly prospected especially in “extensional domain play type (CV3).” This geothermal play type consists in nonmagmatic convection- dominated domains, where active faulting represents Hindawi Geofluids Volume 2019, Article ID 8161469, 20 pages https://doi.org/10.1155/2019/8161469