Estudo e caracterização tipológica do minério de ferro situado a sudoeste do Arco Magmático de Santa Quitéria nos municípios de Ararendá e Ipaporanga/Ce

Abstract

The geological mapping made in scale 1: 20,000, in an area southwest of the Santa Quitéria Magmatic Arc between the cities of Ararendá and Ipaporanga/CE, allowed to characterize six lithostratigraphic units, three of which are Precambrian and the others Phanerozoic, distributed the bottom to the top:: Ceará Complex,Metavolcanic Estreito Unit, Tamboril Santa QuitériaComplex, Serra GrandeGroup, Ceará Mirim Magmatism and Cenozoic covers. The Ceará Complex is represented by supracrustal rocks dominated by pelitic gneisses and calcsilicate rocks, deformed and metamorphosed in anphibolite facies average to high. The Tamboril Santa QuitériaComplex is characterized by a set of granite-migmatitic rocks, on which stand the anatetics phases (diatexits and leucogranitoids) of granodiorite to monzogranitic composition associated with biotite-gneisses migmatizated (metatexits). The Metavolcanic Estreito Unit is composed specially by bimodal metavolcanic rocks, represented by metabasalt-andesitics and metarhyolites, which constitute the main host rocks of the occurrences of Fe-Cu-P in the region. It is important to emphasize that this is a new lithostratigraphic unit within the Precambrian dominion of Central Ceará, which was identified during this study and although there is still no precise geochronological and geochemical data on these associations, their tectonic-metamorphic aspects, presence of bimodal magmatism, characteristic of extensional environment and its proximity to the Magmatic Arc of Santa Quiteria, suggest that was developed in the context of the Arc, probably in a back arc basin.These metavolcanic rocks exhibit fracture patterns well marked and also stockwork structures and magmatic breccias type. The Serra Grande Group, here represented by the Tianguá Formation is predominantly composed of sandstones and conglomerates with diverse textures and structures that lie in erosive disagreement about the Precambrian Units in the region, probably having a major role in the preservation of sulfide mineralization, on the occasion of their formation. Ceará Mirim Magmatism is represented by basic dykes presenting preferred direction NE / SW and is well dispersed throughout the area. The Cenozoic covers are presented throughout the study area, and are represented mostly by sandstones blocks of Serra Grande Group.In terms of mineral resources, the main products were the occurrences of Fe-Cu-P that are associated with Metavolcanic Estreito Unit.They present two types of mineralization: i) Mineral stratabound magnetite phosphate; and ii) hematite ore with relicts of magnetite. The origin of these occurrences is still under discussion, but considering the different typologies, it can be said that there is more of a formation mechanismfor these different ores or a complex history of mineralization, which are common in mineralization system IOCG type or more precisely the type Kiruna.