Mapeamento de uma Área a Leste do arco magmático de Santa Quitéria, Região de Umirim-Ce

Abstract

The geologic mapping realized in county of Umirim-CE at 1:25,000 scale in an area of 50km2 inboard Central Ceará Domain (DCC), centric portion of the Borborema Province northern. This DCC is limited to the NW shear zone Sobral-Pedro II, the SE by the Senador Pompeu shear zone and SW-W gets covered by the sediments of Parnaíba basin. The main lithostratigraphic units in the area are the base to the top: i) gneisses; ii) quartzite iii) biotite granite e iv) granite, being the foundation of the Ceará Group (Tonian 750 Ma) and granites of the Magmatic Arc of Santa Quitéria (Neoproterozoic 1000-540 Ma) and Cenozoic cover. Structurally, the studied area reflects a tectonic of influence of the cycle Brasiliano / Pan-African Neoproterozoic, determining a gneissic foliation with NNE-SSW marking major transcurrent bordering the east Magmatic Arc, in and phase of this cycle in character tardi-tectonic occurred deformation in a weak regime marked by mineral lineation subparallel to foliation and fracturing in several directions. The Neoproterozoic began with the deposition of the hedges between 900 and 750 Ma (Tonian), under the influence of an extensional regime that would be terminated with the onset of Brasiliano Cycle. The stage of the Brasiliano Cycle, understood, 600-540 Ma, was marked by metamorphism in amphibolite facies conditions marking the crustal levei of at least 10Km depth or mesozonal and intense magmatism. Brasiliano granites developed by anatexis of metapelites and basement rocks between 620-580 Ma (NOGUEIRA, 2004).