Évolution géochimique du pyrochlore au cours de l'altération météorique du gisement de Catalão II (Goiás, Brésil)

Rocha, Eronaldo Bonfim; Nasraoui, Mohamed; Soubiès, François; Parseval, Pierre de

doi:10.1016/s1251-8050(00)01504-4

Cited by 4 publications

(2 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the Nb-deposit of Catalão I, the pyrochlore is secondary and, with increasing weathering, it presents Ba enrichment and increasing in vacancy due to Ca and Na losses (Cordeiro et al 2011). In the Catalão II Nb-deposit, the pyrochlore alteration is marked by Ba and REE enrichment (Rocha et al, 2001). Secondary Ba-pyrochlore is the Nb ore mineral exploited at Araxá (Silva, 1986).…”

Section: Discussionmentioning

confidence: 99%

Mineralogy and geochemistry of laterites from the Morro dos Seis Lagos Nb (Ti, REE) deposit (Amazonas, Brazil)

Giovannini

Neto

Porto

et al. 2017

Ore Geology Reviews

View full text Add to dashboard Cite

The Morro dos Seis Lagos niobium deposit (2897.9 Mt at 2.81 wt.% Nb 2 O 5) is associated with laterites formed by the weathering of siderite carbonatite. This iron-rich lateritic profile (>100 m in thickness) is divided into six textural and compositional types, which from the top to the base of the sequence is: (1) pisolitic laterite, (2) fragmented laterite, (3) mottled laterite, (4) purple laterite, (5) manganiferous laterite, and (6) brown laterite. All the laterites are composed mainly of goethite (predominant in the lower and upper varieties) and hematite (predominant in the intermediate types, formed from goethite dehydroxylation). The upper laterites were reworked, resulting in goethite formation. In the manganiferous laterite (10 m thick), the manganese oxides (mainly hollandite, with associated cerianite) occur as veins or irregular masses, formed in a late event during the development of the lateritic profile, precipitated from a solution with higher oxidation potential than that for Fe oxides, closer to the water table. Siderite is the source for the Mn. The main Nb ore mineral is Nb-rich rutile (with 11.26-22.23 wt.% Nb 2 O 5), which occurs in all of the laterites and formed at expense of a former secondary pyrochlore, together with Ce-pyrochlore (last pyrochore before final breakdown), Nb-rich goethite and minor cerianite. The paragenesis results of lateralization have been extremely intense. Minor Nb-rich brookite formed from Nb-rich rutile occurs as broken spherules with an "oolitic" (or Liesegang ring structure). Nbrich rutile and Nb-rich brookite incorporate Nb following the [Fe 3+ + (Nb, Ta) for 2Ti] substitution and both contain up to 2 wt.% WO 3. The laterites have an average Nb 2 O 5 content of 2.91 wt.% and average TiO 2 5.00 wt.% in the upper parts of the sequence. Average CeO 2 concentration increases with increasing depth, from 0.12 wt.% in the pisolitic type to 3.50 wt.% in the brown laterite. HREE concentration is very low.

show abstract

Section: Discussionmentioning

confidence: 99%

Mineralogy and geochemistry of laterites from the Morro dos Seis Lagos Nb (Ti, REE) deposit (Amazonas, Brazil)

Giovannini

Neto

Porto

et al. 2017

Ore Geology Reviews

View full text Add to dashboard Cite

show abstract

“…Some authors argue that these are hydrothermal processes (Chakhmouradian and Williams, 2004) whereas others believe they are weathering process (i.e., Lottermoser and England, 1988;Nasraoui and Bilal, 2000;Rocha et al, 2001;Van Wambeke, 1971;Williams et al, 1997). In Tchivira the petrographic evidence indicate that Sr-rich, Ba-rich and Pb-rich pyrochlores correlate with the areas affected by dolomitization, ankeritization and fluoritization respectively.…”

Section: Discussionmentioning

confidence: 99%

Subsolidus processes as a key factor on the distribution of Nb species in plutonic carbonatites: The Tchivira case, Angola

Melgarejo

Costanzo

Bambi

et al. 2012

Lithos

View full text Add to dashboard Cite

Environmental challenges and identification of the knowledge gaps associated with REE mine wastes management

Edahbi

Plante

Benzaazoua

2019

Journal of Cleaner Production

View full text Add to dashboard Cite

Évolution géochimique du pyrochlore au cours de l'altération météorique du gisement de Catalão II (Goiás, Brésil)

Cited by 4 publications

References 10 publications

Mineralogy and geochemistry of laterites from the Morro dos Seis Lagos Nb (Ti, REE) deposit (Amazonas, Brazil)

Mineralogy and geochemistry of laterites from the Morro dos Seis Lagos Nb (Ti, REE) deposit (Amazonas, Brazil)

Subsolidus processes as a key factor on the distribution of Nb species in plutonic carbonatites: The Tchivira case, Angola

Environmental challenges and identification of the knowledge gaps associated with REE mine wastes management

Contact Info

Product

Resources

About