The structure of western Serra do Curral, Quadrilátero Ferrífero, and tectonic control of the high-grade iron hard bodies

Abstract

The structure of western Serra do Curral, Quadrilátero Ferrífero, represents the partial exposure of a syncline that verges to NNW – Piedade Syncline. This regional structure has parasitic folds denominated as B1A which are refolded by folds B1B that also have vergence to NNW. Both of them have ENE-WSW direction, are non-cylindrical folds and configure an interference pattern that is similar to Type 3 from Ramsay. This refolding occur during progressive deformation. The occurrence of high-grade magnetitic-martitic accumulation (> 64% Fe) of medium size (~ 100 Mt) is controlled by the combination of these folds and high angle thrust fault, both with the same direction. Above these structures, there is a development of folds with NNW- SSE direction and WSW vergence (B2 folds). These folds are restricted to the B1 limbs and they configure an interference pattern named “abbuting fold”. The age obtained by U/Pb SHRIMP on monazite grains is 2034±11 Ma. The monazite grains occur on textural balance with the iron oxide from high-grade accumulations. This age corresponds to the formation timing of the high-grade bodies and suggests that the mineralization process is contemporary to the regional metamorphic peak of Quadrilátero Ferrífero.

Keywords

• Structural geology
• Serra do Curral
• Iron ore
• Quadrilátero Ferrífero