Geologia de uma área a NW do município de Banabuiú — CE

Abstract

The present work is result of a geologic mapping in the scale of 1:25.000, in an area of approximately 24 km2, located in the municipality of Banabuiú, central hinterland of Ceará. The area is inserted in the Central Ceará Domain, inside the Borborema Province. The main lithostratigraphic units identified during the mapping, from base to top, are: gneissic basement (Acopiara Unit); Granites; pegmatites and colluvium coversAlluvial. The gneissic basement named of Acopiara Complex is located in the portion northwest and northeast of the area. Calcissilicáticas Rocks are presents in the lenses form. Granite is the most abundant lithology in the region and display a characteristic staining leucocratic. The pegmatites are found cutting basement and the granite intrusion. The cover colluvium-alluvium present, in the most case, white coloration, from granite region. During mapping measurements were taken structural joints throughout the area being possible to observe their preferential directions to NW-SE and NE-SW observed on chart stereogram. The petrography shows better definition of these rock types: Gneiss consisting of quartz, feldspar potassium, plagiocásio, biotite, muscovite, garnet and opaque, the calcissilicática, composed of plagioclase, diopisídio, quartz, epidote, titanite, and granite composed of quartz, K-feldspar, plagioclase, biotite, muscovite, garnet , zircon, apatite and opaque, it is possible to determine conditions of metamorphism of amphibolite facies in gneiss and in calcissilicáticas. Finally, with data acquired, beyond the existing bibliography, it was possible to make a possible geological evolution of the region where gneisses underwent partial melting giving rise to migmatites that evolved to form by anatexis, S-type granites, where ali these rock types are cut by pegmatite intrusion from late. This evolution can be represented in a schematic drawing.