Supergenic alteration and tropical morphogenesis in the Barro Alto stratiform mafic-ultramafic complex, GO.

Este trabalho objetivou caracterizar as f?cies de altera??o desenvolvidas quando do processo de bauxitiza??o dos corpos anortositicos do Complexo M?fico-Ultram?fico Acamadado de Barro Alto (GO), enfatizando suas implica??es geomorfol?gicas. Tratamentos de imagens multiespectrais Landsat TM 7, associados aos trabalhos de campo, revelaram a exist?ncia de tr?s dom?nios de forma??es superficiais: i) dom?nio de coura?a baux?tica, ii) dom?nio de pedimentos aluminosos e iii) dom?nio de lateritas ferruginosas. O primeiro dom?nio ? o mais expressivo (55,6%) e constitui o foco deste trabalho. Nele foram definidas 10 f?cies de altera??o a partir da descri??o de 17 perfis distribu?dos em tr?s topossequ?ncias e em diferentes posi??es no maci?o. Foi constatada uma correla??o m?tua entre as diferentes f?cies e o relevo, evidenciando que tanto o relevo teve uma participa??o fundamental na g?nese dessas f?cies quanto estas influenciaram na evolu??o do modelado. Assim, nas ?reas mais altas e planas, testemunhos de antigas superf?cies aplainadas, prevalecem os perfis essencialmente baux?ticos e isalter?ticos, produtos do processo de alitiza??o. J? nos topos de menor altitude, encostas e ?reas rebaixadas predominam perfis que alternam f?cies baux?ticas e f?cies argilosas, originadas da degrada??o geoqu?mica da f?cies baux?tica isalter?tica ou da forma??o progressiva por bissialitiza??o e monossialitiza??o sobre os corpos anortos?ticos.This study aims to characterize the facies of alteration developed from the mechanism of bauxitization of the anortosite bodies from the Barro Alto Stratiform Mafic-Ultramafic Complex emphasizing their geomorphological implication. Treated Landsat Images from the field work showed the presence of three domains of superficial formations: i) the domain of bauxitic duricrust, ii) the domain of aluminous colluvial and, iii) the domain of ferruginous laterite. The first domain is the more expressive (55,6%) and constitutes the focus of this study. For the purpose of this study, ten facies were identified from the macromorphological, mineralogical and chemical analysis of 17 profiles distributed through three toposequences and in different positions within the bauxitic domain. An interdependent correlation was observed between the different facies and their position within the slope showing that not only did the relief have a fundamental participation in the genesis of the facies but the facies also influenced the evolution of the landscape. Therefore, there is a prevalence of bauxitic profiles, predominantly isalteritic and macive, originated from alitization mechanisms. These bauxitic profiles preserve old planned surfaces due to their resistance to mechanic erosion. In the lower altitude summits and in the medium and low slopes of the bauxitic domain, there is a predominance of profiles with bauxitic friable facies intercalated with argilous facies originated from geochemical degradation of the isalteritic bauxitic or from anortosite derived from bissialitization and monossialitization process