The area comprising by the cities of Monte Carmelo, Romaria and Estrela do Sul in the Southwest of Minas Gerais is one of the best known under the point of view of geology and geophysics. Gravity, aeromagnerics, aeroscintilometry, electrical soundings, and terrestrial magnetism are the methods used there. The Bouguer gravity map led to the determination of a sutural zone separating two different structural units: on one side, the mobile-belt of Alfenas, and on the orther side, the cratonic province of Paramirim. The area of our investigation lies on that cratonic province, 100km from the sutural zone. A spectacular zone of tension fissures, filled in part by magnetic material (basic rocks), 400km long in the NW - SE direction, passes along our area of investigation. The main cretaceous alcaline basic intrusions and may be the kimberlites have been placed along this zone. The gravity map indicates a predominance of NE - SW linements problably of Archean age. Would the basic and kimberlitic intrusions be related to those two main directions of tensional fractures? During the Mesozoic the investigated area was submitted to the transgression of the sediments and the basalt flows of the Paraná Basin. There occurs the Ubcraba's Formation, whose basal conglomerate is diamantiferous. West and southward occur Botucatu Sandstone and basalt.The area comprising by the cities of Monte Carmelo, Romaria and Estrela do Sul in the Southwest of Minas Gerais is one of the best known under the point of view of geology and geophysics. Gravity, aeromagnerics, aeroscintilometry, electrical soundings, and terrestrial magnetism are the methods used there. The Bouguer gravity map led to the determination of a sutural zone separating two different structural units: on one side, the mobile-belt of Alfenas, and on the orther side, the cratonic province of Paramirim. The area of our investigation lies on that cratonic province, 100km from the sutural zone. A spectacular zone of tension fissures, filled in part by magnetic material (basic rocks), 400km long in the NW - SE direction, passes along our area of investigation. The main cretaceous alcaline basic intrusions and may be the kimberlites have been placed along this zone. The gravity map indicates a predominance of NE - SW linements problably of Archean age. Would the basic and kimberlitic intrusions be related to those two main directions of tensional fractures? During the Mesozoic the investigated area was submitted to the transgression of the sediments and the basalt flows of the Paraná Basin. There occurs the Ubcraba's Formation, whose basal conglomerate is diamantiferous. West and southward occur Botucatu Sandstone and basalt.