A estrutura do segmento oeste da Serra do Curral, Quadrilátero Ferrífero, e o controle tectônico das acumulações compactas de alto teor em Fe

Sanglard, Júlio Carlos Destro; Rosière, Carlos Alberto; Santos, João O.S.; McNaughton, Neil; Fletcher, Ian R.

doi:10.5327/z1519-874x201400010006

Cited by 16 publications

(5 citation statements)

References 15 publications

(27 reference statements)

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“…An upgrade in the Fe content of itabirite to form high-grade orebodies of massive, hard hematite has been attributed to the metamorphic overprint of the Transamazonian orogeny, an interpretation supported by a U–Pb age of 2034 ± 11 Ma for monazite that coexists with granoblastic hematite after magnetite 32 . The Fe upgrade involved leaching of gangue minerals by hydrothermal fluids 33 .…”

Section: Discussionmentioning

confidence: 99%

Karst-bauxite formation during the Great Oxidation Event indicated by dating of authigenic rutile and its thorium content

Cabral

Zeh

2023

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Aluminium (Al)-rich palaeosols—i.e., palaeobauxite deposits—should have formed in karst depressions in carbonate sequences as a result of acidic solutions from oxidative weathering of sulfide minerals during the Great Oxidation Event (GOE), but no GOE-related karst-palaeobauxite deposits have so far been recorded. Here, we report results of in situ uranium–lead (U–Pb) dating of detrital zircon and spatially associated rutile from a metamorphosed Al-rich rock within a dolomite sequence in the Quadrilátero Ferrífero (QF) of Minas Gerais, Brazil, known as the Gandarela Formation. Rutile grains are highly enriched in thorium (Th = 3–46 ppm; Th/U ratio = 0.3–3.7) and yielded an isochron, lower-intercept age of ca. 2.12 Ga, which coincides with the final phase of the GOE—i.e., the Lomagundi event. The rutile age represents either authigenic growth of TiO2 enriched in Th, U and Pb during bauxite formation, or subsequent rutile crystallisation during metamorphic overprint. Both cases require an authigenic origin for the rutile. Its high Th contents can be used as a palaeoenvironmental indicator for decreased soil pH during the GOE. Our results also have implications for iron (Fe)-ore genesis in the QF. This study demonstrates that in situ U–Th–Pb-isotope analyses of rutile can place tight constraints on the age and nature of palaeosols.

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Section: Discussionmentioning

confidence: 99%

Karst-bauxite formation during the Great Oxidation Event indicated by dating of authigenic rutile and its thorium content

Cabral

Zeh

2023

Sci Rep

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“…A wedge-shaped, near-vertical, massive high-grade ore body is hosted by dolomitic itabirite. The ore body trends NE-SW and cuts the layers of the Cauê Formation narrowing with depth (Sanglard 2013). The contact between the ore body and dolomitic itabirite is sharp.…”

Section: Esperança Depositmentioning

confidence: 92%

Chemical fingerprint of iron oxides related to iron enrichment of banded iron formation from the Cauê Formation - Esperança Deposit, Quadrilátero Ferrífero, Brazil: a laser ablation ICP-MS study

et al. 2015

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Chemical signatures of iron oxides from dolomitic itabirite and high-grade iron ore from the Esperança deposit, located in the Quadrilátero Ferrífero, indicate that polycyclic processes involving changing of chemical and redox conditions are responsible for the iron enrichment on Cauê Formation from Minas Supergroup. Variations of Mn, Mg and Sr content in different generations of iron oxides from dolomitic itabirite, high-grade iron ore and syn-mineralization quartz-carbonate-hematite veins denote the close relationship between high-grade iron ore formation and carbonate alteration. This indicates that dolomitic itabirite is the main precursor of the iron ore in that deposit. Long-lasting percolation of hydrothermal fluids and shifts in the redox conditions have contributed to changes in the Y/Ho ratio, light/heavy rare earth elements ratio and Ce anomaly with successive iron oxide generations (martite-granular hematite), as well as lower abundance of trace elements including rare earth elements in the younger specularite generations.KEYWORDS: high-grade iron ore; geochemistry; iron oxide; LA-ICP-MS analysis. RESUMO: As assinaturas químicas dos óxidos de ferro presentes no itabirito dolomítico e no minério de ferro de alto teor do Depósito de Esperança, localizado no Quadrilátero Ferrífero, indicam que processos policíclicos envolvendo mudanças nas condições químicas e de redox são res ponsáveis pelo enriquecimento em ferro na Formação Cauê do Supergrupo Minas. A variação nos conteúdos relativos de Mn, Mg e Sr nas diferentes gerações de óxidos de ferro encontradas no itabirito dolomítico, no minério de ferro de alto teor e nos veios de quartzo carbonato hematita associados à mineralização denotam uma estreita relação entre a formação do corpo de minério de ferro de alto teor e a alteração dos carbonatos. Isso indica que o itabirito dolomítico é o principal precursor do corpo de minério naquele depósito. Percolação de longa duração de fluidos hidrotermais e mudança nas condições de redox contribuíram para a alteração das razões Y/Ho, elementos terras raras leves/pesados e da anomalia de Ce com sucessivas gerações de óxido de ferro (martita hematita granular), bem como depleção dos conteúdos de elementos traço, incluindo os elementos terras raras das gerações mais recentes de especularita. PALAVRAS-CHAVE: minério de ferro de alto teor; geoquímica; óxido de ferro; análise por LA ICP MS.Chemical fingerprint of iron oxides related to iron enrichment of banded iron formation from the Cauê FormationEsperança Deposit, Quadrilátero Ferrífero, Brazil: a laser ablation ICP-MS study INTRODUCTIONThe genesis of high-grade iron ore bodies has been extensively discussed worldwide. Different processes such as hydrothermal syn-metamorphic (Guild 1953(Guild , 1957Dorr 1965Dorr , 1969, residual supergene (Dorr 1964; Eichler 1968;Melfi et al. 1976), or paleo-supergene enrichment (Morris 1980(Morris , 1987Harmsworth et al. 1990), and the juxtaposition of hypogene and supergene fluids (Hagemann et al. 1999(Hagemann et al....

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“…However, recent studies on the structural evolution of the western part of the Serra do Curral suggest a regional NE-SW-trending, refolded, inverted syncline (Sanglard et al, 2011(Sanglard et al, , 2014. Although the western part of the Serra do Curral was not significantly strained during thrusting, the eastern part has undergone higher internal deformation and is crosscut by several fold and shear zones (Chemale et al, 1994).…”

Section: Introductionmentioning

confidence: 94%

Hydrothermal and metamorphic fluid-rock interaction associated with hypogene “hard” iron ore mineralisation in the Quadrilátero Ferrífero, Brazil: Implications from in-situ laser ablation ICP-MS iron oxide chemistry

Hensler

Hagemann

Rosière

et al. 2015

Ore Geology Reviews

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A estrutura do segmento oeste da Serra do Curral, Quadrilátero Ferrífero, e o controle tectônico das acumulações compactas de alto teor em Fe

Cited by 16 publications

References 15 publications

Karst-bauxite formation during the Great Oxidation Event indicated by dating of authigenic rutile and its thorium content

Karst-bauxite formation during the Great Oxidation Event indicated by dating of authigenic rutile and its thorium content

Chemical fingerprint of iron oxides related to iron enrichment of banded iron formation from the Cauê Formation - Esperança Deposit, Quadrilátero Ferrífero, Brazil: a laser ablation ICP-MS study

Hydrothermal and metamorphic fluid-rock interaction associated with hypogene “hard” iron ore mineralisation in the Quadrilátero Ferrífero, Brazil: Implications from in-situ laser ablation ICP-MS iron oxide chemistry

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