Compreensão da dinâmica intempérica nas rochas metamórficas do núcleo urbano de Marabá

Abstract

Considering that it is necessary to understand the geotechnical properties of the soil is fundamental for the Building industries, and that the different types and degrees of weathering affect the state of the soil, this research focuses on the intemperic dynamics of the metamorphic rocks of the urban nucleus of Marabá city, in order to explain how the intemperic process of such rocks occurred in this city. In order to do it was necessary to locate the occurrence of metamorphic rocks in the study site and in the regional geological context, to recognize the lithotypes, to analyze the degree of wearing of the formations and to relate the results to tectonics and metamorphism. A bibliographical and field research was accomplished, with a basic strategic purpose, using deductive hypothetical method, qualitative approach and explanatory objective. Therefore, it is verified that drainage pattern and drainage alignment are strongly structured and indicate the presence of large faults in the study site, especially where the main rivers flow, it is observed the existence of three types of rocks , meta-argillites, metassyltites and phyllites, and they have distinct metamorphic grades, being classified in the facies zeolite, prehnita-pumpellyita and green shale, respectively, it is also seen that the rocks have different intemperic degrees, which vary from slightly to very weathered, and that occurs evidence of shear zones in phyllites found on the banks of the rivers Tocantins and Tauarizinho, such as S-C structures and milonitic foliation. This imposes evidences that the studied site is within a splinter of the Araguaia Belt, which is limited by zones of shearings to the west, east and north, where the Itacaiunas, Tauarizinho and Tocantins rivers are located, in this order, and this action of the tectonic caused different metamorphic degrees in their rocks, directly influencing the rheology of them, so that the lithologies with lower metamorphic degrees were more susceptible to weathering, thus generating different intemperic degrees.