Proterozoic rifting and closure, SE border of the Sمo Francisco Craton, Brazil

This article presents an overview of the present knowledge of the tectonic evolution of the transition zone between the São Francisco Craton and the Araçuaı́Fold Belt in Minas Gerais State. Two extensional events with rift formation and sedimentation and one compressional orogenic event were identified. rst extensional event, dated at 1750–1700 Ma, is represented by the N–S Espinhaço basin formation along a continental rift. The lower part of the sedimentary infill (Lower Sequence of the Espinhaço Supergroup) is made up of acid to intermediate metavolcanics and fluvial metasediments, with strong fault-block activity related to the initial rift phase (with mechanical subsidence). The Middle Sequence is composed of quartzite with large-scale cross-bedding and the Upper Sequence consists of an alternation of quartzite and metapelitic rocks deposited in a shallow marine setting related to a subsequent flexural phase (with thermal subsidence). cond extensional phase corresponds to the Araçuaı́rift formation (1000–900 Ma), accompanied by a mafic dike swarm intruded into the Espinhaço Supergroup. On the highest uplifted blocks, continental glaciogenic facies and a glacio-marine sequence (Jequitaı́Formation) were deposited. To the east, in the Araçuaı́basin, they grade into marine deposits with gravitational sedimentation (debris-flows and turbidites) organized in a probably prism of passive continental margins. To the West on the craton, the younger Bambuı́Group was deposited directly on the basement. No equivalents of this group were identified in the Araçuaı́basin, so either they were not deposited or they were eroded. mpressional orogenic event (650–550 Ma) is characterized by zones with asymmetric folds showing westward vergence separated by thin belts of ductile shearing (Dp phase). An east dipping Sp cleavage with down-dip stretching lineation is consistent with a relative westward tectonic transport, towards the São Francisco Craton. Regional Barrovian metamorphism is associated with Dp, increasing from anchizone to amphibolite facies. During this orogenic event the São Francisco Craton and the Araçuaı́and Paramirim Fold Belts were formed as individual geotectonic units.