Controle estrutural no maciço Mestre Álvaro (Serra, Espírito Santo, Sudeste do Brasil)

Abstract

The main objective of this study is to understand how the structural elements may have influenced the relief formation of the Mestre Álvaro Massif, which is one of the most prominent geological features of the state of Espírito Santo, mainly because of the contrast of altitude that it presents in relation to its surroundings. The massif origin is directly related to the events related to the Araçuaí Orogen, with mainly in its final phase, when numerous post-tectonic granitic intrusions were generated. It is also necessary to emphasize the presence of the Belt of Lineaments Colatina (BLC), another important structural feature of the state, with associated lineaments varying between the NNW and NW directions. The methodological basis used for the development of this dissertation came from cabinet and field activities, highlighting the extraction of lineaments from Digital Elevation Models (MDEs), aerial photos and aeromagnetometric map, accompanied by the creation of rosettes for the respective analyzes. In the fieldwork, geological analyzes were performed: structural measurements of faults, fractures and mineralogical orientation, beyond the identification of the massif constituent rocks, as well as verification of their mineralogical, textural and structural characteristics; and geomorphological: identification of the main relief features. The analysis of the rosettes generated with the lineaments extracted from the different sources mentioned indicates that there is a clear predominance of features with orientations ranging from NNW-SSE and NW-SE, with secondary participation of NE-SW oriented lineaments. In the fieldwork, orientation measurements of porphyritic feldspar crystals were carried out, present in various points of the massif. Is was observed that most of these measurements indicate NNW-SSE to NW-SE orientation, corresponding to the observation made for the lineaments. Fractures and failed veins were also found, whose orientations also correspond to those indicated for oriented lineaments and crystals. These guidelines are aligned with the neotectonic studies developed by Bricalli (2011), which presents features with evidence of compressive stress NNW-SSE, with consequent distensive component in the ENE-SSW direction, at a point located within the so-called Colatina Compartment, where it`s located also the study area. So, the results indicate that the Belt of Colatina Lineaments is the most important geological structure conditioning the relief of the Mestre Álvaro Massif, influencing the orientation of most of its valleys and ridges, as well as the intrusion orientation of the granitic massif itself.