Mapeamento geológico e aspectos tipológicos das ocorrências de cobre da porção Oeste da Bacia EoPaleozóica do Cococi-Ce

Abstract

The area of work is situated in the municipality of Parambu, southwest of the state of Ceara. In geological terms this area is inserted in Cococi Basin-and Paleozoic age, located in the northern pardon of the Borborema Province. The basin represents a watershed Cococi molássica Stage Transition (Brasiliano Cycle - 0.7 - 0.5 Ga) of the rift and / or pull-apart controlled by the activity of late transcurrent related to the collapse of the Brasiliano orogen. In recent decades, the basin has been the subject of research by mining companies, due to the varied number of occurrences of copper and barite present there. Aiming at a better characterization of these occurrences took place in the geological mapping on 1:25,000 scale an area of 100 square kilometers in the western Basin Cococi. For it was used satellite images Landsat 5 and Landsat 7, SRTM radar and gamaespectrométrica that were processed using ENVI and ArcGIS. The results show that the basin consists of a Cococi plutono-sedimentary sequence which sedimentary rocks are composed of polymictic conglomerates, sandstones, siltstones, mudstones and limestone interspersed representing about 80% of the units in the Basin. The sequence is represented by plutonic Brasiliano granitoids that are distributed mainly along the southern and northern edges of said bowl along the faults bounding the basin. These rocks are largely changed brecciated and hydrothermally. Among the changes include the propylitic, silicification and chloritization. The occurrences of copper, represented by malachite and chalcopyrite occur disseminated and in veins associated with grande syn-to late Brasiliano hidrotermalizados and locally brecciated mainly in the southern border. In addition to these occurrences are also found along veins of malachite green to gray siltstones of this basin. Whereas the copper mineralization shows a dose relationship with gravite rocks that are altered and hydrothermally brecciated can be said that the main control of this occurrence is litho-structural type, whose source is associated with the triggered plutonism along the zunes shear bordering the basin. This also reinforces the hypothesis that the edges of basins, particularly the rift, correspond to the most favorable concentrations of mineralizing fluids, which can be both source vulcanogênica and / or plutonic and derived sedimentary rocks (meteoric fluids and / or conatos) that show a preference for local and / or areas of lower pressure.