Geologia e arcabouço estrutural da Sequência Metavulcanossedimentar Urandi, Bahia Geology and structural framework of the Urandi Metavolcanosedimentary Sequence, Bahia

The Urandi Metavolcanosedimentary Sequence (UMS) is located in the northern portion of the Aracuai Orogen. Its basement consists of rocks from the Santa Isabel Complex. This unit represents one of the metavolcanosedimentary sequences of the south- ern portion of the Gaviao Block. The geological mapping, performed on a scale of 1:2,000, allowed the identification of amphibolitic me- tabasalts, itabirites, metapelites, queluzites, marbles, calcic-silicate rocks and quartzites. The structural survey allowed the identification of three deformational and compressional stages: D n ; D n+1 (divided into D n+1' and D n+1'' ), which were nucleated under an E-W to NE-SE orientated stress field; and D n+2 , whose structures reflect a WSW-ENE orientated stress field. The two most ancient stages are possibly related to the deformations of Rhyacian-Orosirian age, while the last defor- mational stage reflects the interactions between the substrate from the Paramirim Aulacogen and the Aracuai Orogen. The mineral para- genesis that was observed suggests amphibolite facies condition for the first two stages and greenschist for the last one.