[en] The most important kaolin deposits from Campo Alegre region (S C) were formed by the conjunction of at least one hydrothermal phase followed by many others weathering, supergenic, phases. Possibly deposits formed by only one of these processes exist, but these deposits shall be small and smaller than those mined today. Besides kaolinization, illitization/muscovitization and silicification, hydrothermalism also generated pyritized and propilitized zones, with quartz + chlorite. Together, hipogenic alterations related to kaolin deposits are very similar to alterations of high sulfidation epigenetic volcanogenic gold deposits. Most part of the biggest kaolin mines from the southern part of Campo Alegre Basin are distributed along a 13 Km long and 0,5 Km width bent zone that is parallel to structural alignments that point out the eastern Basin border. This zone was originated by deformation that has inclined and broken rocks, generating a fault system alongside and parallel to structural lineaments. This fault system has made possible the ascent of hydrothermal hot aqueous fluids and of diqueform intrusions that caused hydrothermalism genetically related to kaolin deposits. Gamma spectrometry may indicate hydro thermalized zones. Although the potassium equivalent rock contents, derived from aerial gamma spectrometry of the mine regions, varies from a minimum of 2,07% to a maximum of 3,78%, 17 of the 20 mines are on high grade regions, with equivalent potassium contents grater than 3,04% and lower than 3,58%. The 'F factor' ((K.U)/Th) seems to indicate hydro thermalized zones better than potassium equivalent rock contents. Practically all the biggest mines on region are placed where 'F factor' is large, bigger than 10,05% and lower than 13,70%. The biggest mines are restricted to regions with altitudes between 950 and 1060 m. The average altitude of 23 mines is 1012,1+-13,8 m. This zone agrees with an ancient peneplane that makes possible the development of the intense weathering necessary to generates large kaolin deposits. (author)