Parente, Clóvis Vaz, Veríssimo, César Ulisses Vieira, Botelho, Nilson Francisquini, Xavier, Roberto Perez, Menez, Jacqueline, Oliveira Lino, Ramon de, Araújo da Silva, Cristian Dickson, and Santos, Ticiano José Saraiva dos
The main style of IOA mineralization of the Santa Quiteria magmatic arc is cut by dikes and/or apophysis of granitic rocks. This mineralization presents a lightly banded structure marked by the alternation of magnetite (Mt) and apatite (Ap) (A, B and C). When in contact with post-Brazilian granite displays, apatite and magnetite aggregates with a polygonal granoblastic texture as a result of contact metamorphism (D, E and F). • The first IOA type occurrences identified in Brazil were at the Santa Quiteria magmatic arc, Ceará. • They are hosted by metadiorite, felsic-mafic metavolcanics and paragneiss. • Five iron oxide-apatite occurrences types are recognized. • The main types are stratabound, massive, disseminated magnetites, and rhombohedral hematite. • Mineral chemicals in apatite and magnetite indicate igneous and hydrothermal origin. Iron oxide-apatite (IOA) occurrences have recently been identified in the western sector of the Neoproterozoic Santa Quitéria magmatic arc (Ceará state, northeast Brazil), close to the boundary with the Paleozoic Parnaíba Basin. The IOA mineralization is hosted by albitized metadiorites and metavolcano-sedimentary rocks, which are crosscut by a late- to post-Brasiliano/Pan-African biotite granite intrusion with a U-Pb age approximately 548 ± 4 Ma. Within the metavolcano-sedimentary sequence, metavolcanic rocks are bimodal and consist of albitized metabasalt-andesite and metarhyolites with a U-Pb age of 554 ± 6 Ma, whereas the metasedimentary units are represented by calc-silicate, marble, and pelitic gneisses. The iron oxide-apatite mineralization occurs as (i) banded–stratabound lenses/layers composed of magnetite (50–70%), with or without ilmenite exsolution; apatite (≤8%); monazite; and locally subordinate copper sulfides (~2%); (ii) massive magnetite-(specular hematite)-apatite bodies; (iii) disseminated and vein magnetite-apatite within albitized metadiorite; (iv) massive rhombohedral hematite bodies; and (v) garnet-magnetite type. The host rocks also display marialite, diopside, albite, and epidote (sodic-calcic alteration), biotite and K feldspar (potassic alteration), chlorite and epidote in lower-T hydrothermal alteration assemblages. Mineral chemistry data reveal that (i) except for vein types, apatite in all the other occurrences is F rich (2.4 ≤ F ≤ 4.4%) and low in Cl (<0.5%), and (ii) magnetite contains variable concentrations of Ti, V, Cr and Ni attributed to both igneous and hydrothermal environments. In addition, the magnetite of the stratabound occurrence is low in TiO 2 (≤1.6%); however, its oxy-exsolutions are rich in TiO 2 (14–52%), indicating a titanium-rich original iron oxide. The low sulfide content and high concentration of apatite indicate that the investigated Fe-P occurrences are of the IOA type, similar to those of IOA provinces elsewhere, such as Kiruna, El Laco, Gushan, Pea Ridge, Pilot Knob, and Bafq. Hence, the discovery of these occurrences in the Neoproterozoic Santa Quitéria magmatic arc has a twofold metallogenic significance: (i) these are the first records of IOA-type deposits in Brazil; and (ii) open a favorability potential for the exploration of IOCG-type deposits in this tectonic domain. [ABSTRACT FROM AUTHOR]