Structural framework of rocks of the Lagoa D'anta mine area, iron-manganese Urandi-Caetité-Licínio de Almeida District, Bahia, Brasil

Abstract

ABSTRACT:The Urandi-Caetité-Licínio de Almeida Iron-Manganese District encompasses a total of 35 manganese mines, most of which are already exhausted, and 1 currently active iron mine. The host rocks of these ores are associated with the Paleoproterozoic Caetité-Licínio de Almeida Metavolcanossedimentary Sequence. These units have been deformed by the northern Serra do Espinhaço Thrust and Fold Belt, in the northern section of the Araçuaí Orogen. Interbeddings of itabirite, cummingtonite schist, calcite and manganese-dolomitic marbles, calc-silicate and carbonate-silicate rocks, and amphibolitic metabasalt were found at the Lagoa D'anta mine, in addition to quartz-jacobsite schist, residual manganese-rich soil and manganese lateritic breccia. The main structural framework presents a general NE-SW trend and it consists predominantly of compressional structures. This structural framework is associated with the evolution of two Ediacaran dextral transpressional shear zones, the Carrapato zone, in the western portion, and São Timóteo zone, in the eastern portion. The structural framework of the Lagoa D'anta mine reflects a higher degree of shortening in the southern sector of the northern Serra do Espinhaço Thrust and Fold Belt, in the northern area of the Araçuaí Orogen. The ductile structures related to these deformational phases were nucleated under conditions of progressive metamorphism with minimum temperature of 550°C. Stockwork structures of quartz, calcite, epidote, grunerite and magnetite truncate the mine's ductile structures. Fractures were the main circulation channels for meteoric water, which culminated in the formation of a high-content supergene ore in the mine. KEYWORDS: structural framework; aulacogen; shear zones; deformation. RESUMO: O Distrito Ferro-Manganesífero Urandi-Caetité-Licínio de Almeida congrega um total de 35 minas de manganês, a maioria exaurida, e 1 mina de ferro, em atividade, cujas rochas hospedeiras dos minérios estão associadas com a Sequência MetavulcanossedimentarCaetité-Licínio de Almeida, de idade paleoproterozoica. Essas unidades encontram-se deformadas pelo Cinturão de Dobramentos e Cavalgamentos Serra do Espinhaço setentrional, na porção norte do Orógeno

Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

“…This group of structures has been extensively described by Danderfer Filho (2000), Lagoeiro (1990), Cruz andAlkmim (2006, 2007a), Guimarães et al (2005Guimarães et al ( , 2012, Cruz et al (2007bCruz et al ( , c, 2012 and Borge et al (2015), among others. It reflects a regional stress field oriented WSW-ENE ).…”

“…6B). Folds with asymmetrical and symmetrical enveloping are associated with such deformation phase in the metavolcanossedimentary sequences of the basement (Borge et al 2015), as seen in Figures 6A and 6C. Moreover, a prominent mylonitic foliation was formed in Lagoa Real Intrusive Suite, parallel to a gneissic banding (Fig.…”

“…2, 3, 4A, 5A-B, 6A-B, 7, 8A-B), with NNW/ SSE orientation (Fig. 9A), and also pop-up structures (Cruz 2004, Borge et al 2015. The shear-sense indicators in these zones are S/C structures.…”

Unraveling sedimentary precursors and metal enrichment of high-grade metamorphosed manganese-rich rocks from the Borborema Province, northeastern Brazil

“…This orogeny was a promising candidate to trigger the high-grade metamorphism imprinted in these rock fragments. As a consequence of this process, other Paleoproterozoic manganese-rich rocks from South America and West Africa share some similar features to the Brazilian rocks in terms of mineral assemblage and metamorphic grade (e.g., Mücke et al, 1999;Chisonga et al, 2012;Borges et al, 2015;Cabral et al, 2019a;Rodrigues et al, 2019a, b;Salgado et al, 2019). In this setting, the best correlation maybe with the Serra do Navio manganese deposit in the Amazonian Craton (Chisonga et al, 2012) and the manganese ores at Morro da Mina, in the southern Quadrilátero Ferrífero (Cabral et al, 2019a).…”

Post‐Great Oxidation Event Orosirian–Statherian iron formations on the São Francisco craton: Geotectonic implications

“…The volcano‐sedimentary rocks are grouped into the Urandi, Licínio de Almeida, and Caetité sequences (Barbosa, Mascarenhas, Corrêa Gomes, Dominguez, & Souza Org., ; Figueiredo, Cruz, Ribeiro, & Fleck, ), that cover the metatexites and diatexites of the Rhyacian Santa Isabel Complex ((2095 ±8.6) Ma U–Pb LA–ICP–MS and SHRIMP zircon ages; Medeiros et al, ; Figures and ). The sequences are thick Orosirian successions with metamorphosed arkosic sandstones, metagraywackes, quartzites, mica and carbonaceous schists, marbles, carbonate–silicate rocks, and iron and manganese formations, hosting economic Fe and Mn ore deposits (Borges, Cruz, Barbosa, & Santos, ). Similarly to the southern cratonic domain, these sequences are covered by the post‐Statherian Espinhaço Supergroup, intruded by dykes and sills with the Statherian, Calymmian, and Tonian ages, and include dacite‐ and rhyolite‐bearing metavolcanic rocks similar to those in the southern Espinhaço Range (Guimarães, Alkmim, & Cruz, ).…”