Petrogênese da sequência metassedimentar em Canindé, complexo Ceará, Província Borborema

Abstract

The metasedimentary sequence in Caninde region, north of the State of Ceará, is inserted in Ceará Complex, Ceará Central Domain in northern Borborema Province. Geological mapping techniques, thin and polished sections petrography, mineral chemistry, and geochronology have been useful in the distinction of the plataformal sedimentation sequence of quartzitic-peliticcarbonate type, metamorphosed in medium to high grade. Petrographically, the sequence consists of lithologies derived from quartz sediments and pelitic carbonate, generating a association of meta-arkose, schists, migmatites, amphibolite, calc-silicatic rocks and marbles, all parallel and gradual contacts with each other. Also, they are found albite granites and diorites, interpreted as a product of partial melting of amphibolites associated with restites rich in tremolite / actinolite. Structurally, the area is marked by ductile features (foliation, megadobras, shear zone and thrust tectonics) and fragile (faults and fractures). Metamorphic grade reached the high amphibolite facies to granulite, the metamorphic peak in granulite facies is evidenced by the association diopside + graphite in metacarbonates. The pressures calculated by the calibration Al amphibole, gave results between 2 and 7Kbar, this difference was related to the expansion sites generated scaled fractures. The decrease in pressure provided the melting of lithologies with the generation of migmatites and granites. The composition of granite is related to lithotype that situ melting. To identify the stratigraphic column plataformal sequence analyzes were performed in U-Pb isotopes in schists, amphibolites, and diatexito calcissilicático gneiss, whose sedimentation basin is recorded in maximum age at Riaciano and metamorphism during the Brasiliano event.