Aspectos geológicos-estruturais de uma área na região de Banabuiú-Quixeramobim/CE com auxílio de dados aerogeofísicos: relações entre zonas de cisalhamento e intrusões graníticas

Abstract

Granitic intrusions resulting from late-orogenic, synkinematic magmatism have widespread occurrence throughout the Borborema Province. However, these should not be treated in a generalized way because of a series of distinct petrogenetic processes involved in their formation. In this context, the Nenelândia Batholith, located along sinistral transcurrent shear zones of NE-SW and ESE-WSW, is inserted, possibly related to Senador Pompeu's Shear Zone as branches of the same. In the mapped area, the batholith is composed mainly of syenogranites, monzogranites, and granodiorites of fine to medium granulation, sometimes porphyritic, and gray to pink in color, intruded into Neoproterozoic supracrustals rocks, mainly migmatites. The texture variations exhibited by these leucogranitoids are related to aspects such as magma composition, oxygen fugacity and assimilation of material of a more crustal nature, which are related to the order of intrusion of the magmatic pulses in the batholith. The use of aerogeophysical data, associated to the geological mapping, allowed to perform a faciological zoning for the intrusion along the studied area, besides determining of linear structures, interpreted as zones of shear. Structural aspects presented in the field, such as the intensity of fracturing imposed on the rocks and the existence of riedel-antiriedel conjugate pairs suggest that the intrusion of the batholith occurred under extension conditions; and the concordance of magmatic structures, similar to stratification, oriented along the foliation corroborate the synchronous character between emplacement and transcurrency. The importance of the structural conditioning of the region is not only limited to the intrusion of the batholith, but also because it is associated with mineral occurrences, such as mineral oxides, located along shear zones, and intrafolial graphite located near a fault zone.