info:eu-repo/semantics/article
CONTROLE ESTRATIGRÁFICO DAS MINERALIZAÇÕES DE CHUMBO, ZINCO, FLÚOR E BÁRIO NO GRUPO BAMBUÍ - PARTE LESTE DA CHAPADA DE IRECÊ: (BAHIA)
CONTROLE ESTRATIGRÁFICO DAS MINERALIZAÇÕES DE CHUMBO, ZINCO, FLÚOR E BÁRIO NO GRUPO BAMBUÍ - PARTE LESTE DA CHAPADA DE IRECÊ: (BAHIA)
Autor
MISI, AROLDO
SOUTO, PAULO
Institución
Resumen
Carbonate rocks of the Bambuí Group, in the State of Bahia, contain many small lead-zinc mineralizations associated with fluorite and barite. Detailed geological studies in the north-central part of the State (eastern part of the Chapada de Irecê) showed that the Bambuí Group, unconformably overlying the Chapada Diamantina Group (Guariba Formation), can be divided in the following stratigraphic units. Bebedouro Formation, at the base, with terrigenous meta sediments, chiefly slates, meta siltstones and quartzite. Sete Lagoas Formation, formed by three members: red dolomites with clayey material (C member); finely laminated light-grey limestones (B member) and massive dark limestones, with a narrow zone bearing interbedded dolomite near the base (A member). All of the mineralizations in this area are related to the dolomitic horizon, which is about 20 m thick. Most of them appear to be of epigenetic origin, occurring in small fissures (N30W to N50W) associated with calcitic or silicic gangue. These mineralized fissures occur either in the dolomite beds or in the nearby dark limestones. Only one mineralization, occurring in a dolomitic infraformational breccia, seems to be syn-diagenetically formed. Therefore, all of them indicate the same stratigraphic control, occurring in the transition between a weakly and a strongly-reducing facies. Carbonate rocks of the Bambuí Group, in the State of Bahia, contain many small lead-zinc mineralizations associated with fluorite and barite. Detailed geological studies in the north-central part of the State (eastern part of the Chapada de Irecê) showed that the Bambuí Group, unconformably overlying the Chapada Diamantina Group (Guariba Formation), can be divided in the following stratigraphic units. Bebedouro Formation, at the base, with terrigenous meta sediments, chiefly slates, meta siltstones and quartzite. Sete Lagoas Formation, formed by three members: red dolomites with clayey material (C member); finely laminated light-grey limestones (B member) and massive dark limestones, with a narrow zone bearing interbedded dolomite near the base (A member). All of the mineralizations in this area are related to the dolomitic horizon, which is about 20 m thick. Most of them appear to be of epigenetic origin, occurring in small fissures (N30W to N50W) associated with calcitic or silicic gangue. These mineralized fissures occur either in the dolomite beds or in the nearby dark limestones. Only one mineralization, occurring in a dolomitic infraformational breccia, seems to be syn-diagenetically formed. Therefore, all of them indicate the same stratigraphic control, occurring in the transition between a weakly and a strongly-reducing facies.