Aeromagnetometria na Caracterização do rifte intracontinental na Faixa Paraguai

Abstract

Studies based on magnetic airborne geophysical data for determining the boundaries between mobile belts and tracks cratonic blocks, usually marked by great physical discontinuities represented by faults or shear zones. In the case of the boundaries are masked by recent coverage, the interpretation could be done by geophysical signatures responses. Its is the case of the Amazon Craton and surrounding Paraguay and Araguaia folded belts in the Tocantins Province, Central Brazil, that are developed along their limits during the end of Precambrian times. We interpret the geophysical features as formed relate to a continental rift environments during different stages of basin evolution. The most striking features are large zones of transcurrent shear character. Representing the highest expression is the EW Campinapolis shear zone delimiting (discriminates) the contact between the Cuiaba Group rocks, in the central portion, and Alto Paraguay Group rocks to the north. Also, the the General Carneiro shear zone, developed along a central corridor, where we identified occurrences of volcanic rocks, near the city of Nova Xavantina, in the state of Mato Grosso. These volcanic rocks are well represented by high magnetic signals in all products. The variation of the magnetic anomaly is interpreted as characteristic of rifts, attributed to thinning and formation of oceanic crust during the evolution of the Paraguay basin. The distinction of these old normal faults its possible because they developed in the limits of an expressive discontinuities along the rift boundaries. They control the deposition of different sediments unities in depth. Our results help in seeking new guidelines for understanding evolutionary Paraguay Belt and identification of magmatic sources related to the opening of the basin and the tectonic framework, as well to understand the structural behavior of the basement under the Parana Basin in the study area. Introducao