Geochemical and tectonic constraints on the genesis of iron formation-hosted magnetite-hematite deposits at the Guanhães Block (Brazil) by contact metasomatism with pegmatite intrusions

Braga, Flávia Cristina Silveira; Rosière, Carlos Alberto; Santos, João Orestes Schneider; Hagemann, Steffen; Danyushevsky, Leonid V.; Salles, Pedro Valle

doi:10.1016/j.oregeorev.2020.103931

Cited by 10 publications

(7 citation statements)

References 55 publications

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“…The Southern Espinhaço Mountain Range (SE) of southeastern Brazil contains commercially important, high-grade iron ore hosted by the Serra da Serpentina Group, a stratigraphic unit which includes the iron-rich Serra do Sapo Formation (Auler et al, 2019). These sedimentary units were formed by the precipitation of Fe(III) and Si phases from solution during the Proterozoic Eon (Weber et al, 2006;Rosière et al, 2019;Silveira Braga et al, 2021). Iron ores can include magnetite (Fe 3 O 4 ), hematite (α-Fe 2 O 3 ), or a ferric oxyhydroxide like goethite (α-FeOOH) or limonite (FeO(OH)•n(H 2 O), and highgrade ore averages between 60 and 67% Fe (Dorr, 1964;Beukes et al, 2003;Rolim et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

et al. 2021

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Previous work demonstrated that microbial Fe(III)-reduction contributes to void formation, and potentially cave formation within Fe(III)-rich rocks, such as banded iron formation (BIF), iron ore and canga (a surficial duricrust), based on field observations and static batch cultures. Microbiological Fe(III) reduction is often limited when biogenic Fe(II) passivates further Fe(III) reduction, although subsurface groundwater flow and the export of biogenic Fe(II) could alleviate this passivation process, and thus accelerate cave formation. Given that static batch cultures are unlikely to reflect the dynamics of groundwater flow conditions in situ, we carried out comparative batch and column experiments to extend our understanding of the mass transport of iron and other solutes under flow conditions, and its effect on community structure dynamics and Fe(III)-reduction. A solution with chemistry approximating cave-associated porewater was amended with 5.0 mM lactate as a carbon source and added to columns packed with canga and inoculated with an assemblage of microorganisms associated with the interior of cave walls. Under anaerobic conditions, microbial Fe(III) reduction was enhanced in flow-through column incubations, compared to static batch incubations. During incubation, the microbial community profile in both batch culture and columns shifted from a Proteobacterial dominance to the Firmicutes, including Clostridiaceae, Peptococcaceae, and Veillonellaceae, the latter of which has not previously been shown to reduce Fe(III). The bacterial Fe(III) reduction altered the advective properties of canga-packed columns and enhanced permeability. Our results demonstrate that removing inhibitory Fe(II) via mimicking hydrologic flow of groundwater increases reduction rates and overall Fe-oxide dissolution, which in turn alters the hydrology of the Fe(III)-rich rocks. Our results also suggest that reductive weathering of Fe(III)-rich rocks such as canga, BIF, and iron ores may be more substantial than previously understood.

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Section: Introductionmentioning

confidence: 99%

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

et al. 2021

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“…7), but are higher than the values obtained from the least altered samples collected in the Horto-Baratinha deposit (δ 18 O mineral +1.7 to +3.3‰ and δ 18 O fluid +9.8 to +11.4‰). The bulk-rock minor and trace element concentrations of the iron formations from these deposits are nevertheless chemically indistinguishable from other occurrences from the GB-ES belt (Silveira Braga et al, 2021) leading to the conclusion that the lower δ 18 O mineral of hematite from Horto-Baratinha is probably related to local variations in the characteristics of the syn-orogenic regional metamorphic fluids and unassociated with the mineralization.…”

Section: Fluid Sources and Oxygen Isotope Signature For Iron Depositsmentioning

confidence: 82%

“…Similar to the iron formations, the platy hematite-rich, high-grade orebodies bordering the Southern Espinhaço fold-thrust belt (ES) exhibit a schistose fabric comprised mostly of hematite and have undergone a syn-tectonic mineralization by selective removal of quartz by hydrothermal fluids (Silveira Braga et al, 2021). In the Guanhães Tectonic Block (GB), high-grade, elongated schistose bodies occurs in discrete zones, comprised by thick platy, lamellar and granular-textured hematite.…”

Section: Iron Ore Depositsmentioning

confidence: 99%

“…The mineralizing fluids generated from the Araçuaí Orogen during the Brasiliano orogeny (Gomes et al, 2018) were the primary conveyors of the mineralization system. They were forced upwards by pressure gradients along thrust planes in the eastern border of the São Francisco Craton (Rosière et al, 2021;Silveira Braga et al, 2021).…”

Section: From Iron Formation To Ore -The Evolution Of the δ 18 O Sign...mentioning

confidence: 99%

“…% Fe). The mineralization took place during the syn-to post-collisional phases of the Ediacaran to Cambrian Brasiliano orogeny with the consolidation of the São Francisco craton (Gomes et al, 2018;Rosière et al, 2021;Silveira Braga et al, 2020) and developed at distinct depths and stages of the evolution of the orogen, accounting for the different morphologic and genetic types described in the area (Silveira Braga et al, 2021). In the upper greenschist metamorphic distal foreland domains of the Araçuaí-West Congo Orogen specularitic orebodies are concentrated along thrust planes, whereas, the eastern Guanhães Tectonic Block is dominated by coarse-grained magnetite-hematite bodies hosted by coeval iron formations of amphibolite facies tectonically enclosed by gneissic rocks (Barrote et al, 2017;Gomes et al, 2018;Silveira Braga, Rosière, Santos, Hagemann, Mc-Naughton, et al, 2019;Silveira Braga et al, 2020.…”

Section: Introductionmentioning

confidence: 99%

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Oxygen Isotopes of Iron Oxides as a Diagnostic Tool for Iron Formation-Hosted High-Grade Magnetite-Hematite Deposits

Silveira Braga,

Rosière,

Pack

et al. 2023

American Journal of Science

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Coarse-grained granoblastic magnetite-hematite and sheared platy hematite iron orebodies comprise several small deposits (5 to 30 Mt each) on the eastern margin of the São Francisco Craton, bordering the Ediacaran–Cambrian Brasiliano Orogenic belt. Three main mineralization stages are associated with the Brasiliano Orogeny: (1) syn- to the late-collisional stage (ca. 580–560 Ma) with development of lens-shaped schistose orebodies along thrust planes. (2) late- to the post-collisional stage (ca. 560–530 Ma) with the formation of massive magnetite bodies by contact metamorphic-metasomatism with pegmatite. (3) Post-tectonic stage with crystallization of granular hematite associated with late pegmatite (ca. 530–490 Ma). In order to better evaluate the fluid oxygen signature of each mineralization stage, new oxygen isotopes measurements were performed on ore bodies associated with the three stages. These stages are followed by changes in the oxygen isotope signature, with a progressive decrease of the δ18O from the iron formation (1.7 to 8.1‰) to high-grade ore (-1.6 to 2.6‰) that appears to be a common aspect of the mineralization of iron formations. In the present cases, magmatic fluids (δ18O from 4.6 to 13.1‰) have imprinted a relatively “heavier” signature than the most hypogene iron formation high-grade ores worldwide that was progressively modified by meteoric water percolated along extensional fractures. The iron oxides from the contact zones of pegmatitic yielded intermediate δ18O values (1.8 to 5.0‰), indicating a higher magmatic fluid/rock ratio.

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Insight into the Origin of Iron Ore Based on Elemental Contents of Magnetite and Whole-Rock Geochemistry: A Case of the Bipindi Banded Iron Formations, Nyong Complex, SW Cameroon

Tamehe,

Li,

Ganno

et al. 2024

J. Earth Sci.

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Geochemical and tectonic constraints on the genesis of iron formation-hosted magnetite-hematite deposits at the Guanhães Block (Brazil) by contact metasomatism with pegmatite intrusions

Cited by 10 publications

References 55 publications

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

Oxygen Isotopes of Iron Oxides as a Diagnostic Tool for Iron Formation-Hosted High-Grade Magnetite-Hematite Deposits

Insight into the Origin of Iron Ore Based on Elemental Contents of Magnetite and Whole-Rock Geochemistry: A Case of the Bipindi Banded Iron Formations, Nyong Complex, SW Cameroon

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