Zinc- and Y-group-bearing senaite from St Peters Dome, and new data on senaite from Dattas, Minas Gerais, Brazil

Foord, Eugene E.; Sharp, William N.; Adams, John W.

doi:10.1180/minmag.1984.048.346.13

Cited by 16 publications

(17 citation statements)

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“…3) mimics the chondrite-normalized pattern for the REE distribution in natural loveringite and davidite and clearly confirms the suggestion (Gatehouse et al, 1978;Campbell and Kelly, 1978;Foord et al, 1984) that the REE substitute into two distinctly different sites in the crystal lattice of crichtonite group minerals. Thus the light REE enter the A site, along with Ca, while the heavy REE enter the M site.…”

Section: Discussionsupporting

confidence: 83%

“…Gatehouse et al, 1978;Campbell and Kelly, 1978). However, Foord et al (1984) note the uncertainty surrounding the FeO/ Fe20 3 ratio in loveringite-davidite, and the consequent uncertainty in the sum of the cations in structural formulae determinations. The effect of increasing FeO at the expense of Fe20 3 would be to increase the number of cations placed in the M position, thus giving cation totals closer to the general formula AM2tOss than recorded in Table 2.…”

Section: Resultsmentioning

confidence: 99%

“…These data are then compared with selected chondritic normalized REE patterns published for natural crichtonite group minerals Haggetty, 1983;Foord et al, 1984, andreferences Mineralooical Maoazine, March 1987, Vol. 51, pp.…”

Section: Introductionmentioning

confidence: 99%

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High-pressure, synthetic loveringite-davidite and its rare earth element geochemistry

Green

Pearson

1987

Mineral. mag.

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Loveringite-davidite members of the crichtonite group were synthesized at high pressure and temperature (7.5 kbar, 1000-1050 ~ from a melt of TiO2 and rare earth element (REE) enriched basaltic andesite composition. Four sets of partition coefficients for La, Sin, Ho, Lu and Sr (analogue for Eu 2+) were obtained. These show that light and heavy REE are readily accommodated, but the intermediate REE are discriminated against in the loveringite-davidite structure. This confirms the previously proposed two sites (A and M) for REE substitution in the crichtonite group. Additional experiments verified the stability of REE-rich crichtonite group minerals to 20 kbar, 1300 ~ and 30 kbar, 1000 ~ and indicate that this phase may be an important accessory repository for the light and heavy REE in the upper mantle.

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Section: Discussionsupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

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High-pressure, synthetic loveringite-davidite and its rare earth element geochemistry

Green

Pearson

1987

Mineral. mag.

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“…As Foord et al (1984) reestudaram essas mesmas amostras (embora não tenham feito nenhuma menção ao trabalho anterior). Juntamente com o estudo de Grey et al (1976), esses dois últimos artigos encerram os dados mais completos sobre a química mineral da senaíta aluvionar da Serra do Espinhaço (Tabela 2).…”

Section: Descrição Dos Minerais E Seus Depósitosunclassified

“…Os primeiros dados químicos fornecidos por Cassedanne (1986), quando ainda se considerava tal material como "senaíta", limitaram-se a uma análise semiquantitativa por A redefinição da senaíta de Presidente Kubitschek como crichtonita e a suspeição sobre a senaíta rica em Zn de Datas (conforme Foord et al, 1984) levaram os autores a realizarem novas análises geoquímicas com microssonda eletrônica sobre outras amostras de aspecto semelhante da região serrana do Espinhaço. Tais análises, conforme anteriormente visto, conduziram à descoberta do primeiro depósito de senaíta in situ, mas outras amostras coletadas na Bahia, quando analisadas, revelaram-se ainda mais surpreendentes.…”

Section: Descrição Dos Minerais E Seus Depósitosunclassified

Minerais do grupo da crichtonita em veios de quartzo da Serra do Espinhaço (Minas Gerais e Bahia)

Chaves

Filho²

2017

Geol. USP. Sér. Cient.

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ResumoO trabalho descreve quatro minerais do grupo da crichtonita encontrados em veios hidrotermais de quartzo, que cortam diversas formações geológicas da Serra do Espinhaço (Supergrupo Espinhaço). Esses minerais -senaíta, crichtonita, almeidaíta e gramaccioliíta-(Y) -foram coletados em duas regiões: Presidente Kubitschek, ao sul de Diamantina (MG), e Novo Horizonte, na Chapada Diamantina Ocidental (BA). A idade de tais veios é relacionada ao final do Ciclo Brasiliano, em ca. 490 Ma. A senaíta é um mineral descoberto no Brasil e classicamente identificado nos aluviões diamantíferos da região de Diamantina; sua primeira ocorrência primária é aqui descrita. A crichtonita, apesar de conhecida desde longa data, teve seu primeiro depósito no país reportado nessa mesma região. A almeidaíta é o 61º e um dos mais recentes dos "minerais brasileiros", sendo encontrada na região de Novo Horizonte. A gramaccioliíta-(Y), uma espécie descoberta na última década (Itália), tem sua primeira ocorrência brasileira descrita também nessa região. Os depósitos e as composições químicas desses minerais são caracterizados, bem como as problemáticas envolvidas até suas definições finais. Palavras-chave:Grupo da crichtonita; Veios de quartzo; Serra do Espinhaço. AbstractFour minerals of the crichtonite group found in hydrothermal quartz veins that cross several units of the Espinhaço Supergroup in the Espinhaço Mountain Range are described in this paper. These minerals, senaite, crichtonite, almeidaite and gramaccioliite-(Y), were collected in two regions: Presidente Kubitschek, south from Diamantina (State of Minas Gerais), and Novo Horizonte, in the Western Diamantina Tableland (State of Bahia). The age of these veins are related with the end of Brasiliano Cycle, at ca. 490 Ma. Senaite is a mineral discovered in Brazil and is usually recognized in diamond-bearing alluvial deposits of the Diamantina region. Its occurrence as a primary mineral in situ is for the first time described here. Although crichtonite has been known for quite a long time, its first occurrence in Brazil has been reported in the same region in Minas Gerais. Almeidaite is the 61 th "newest Brazilian mineral" and has been found in the region of Novo Horizonte. Gramaccioliite-(Y), a species discovered in the last decade in Italy, has also been described for the first time in Novo Horizonte, Bahia. The deposits and the chemical compositions of these rare minerals are characterized in this paper, as well as the problems involved until their final recognition.

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Mineralogy of Niobium and Tantalum: Crystal Chemical Relationships, Paragenetic Aspects and Their Economic Implications

Černý

Ercit

1989

Lanthanides, Tantalum and Niobium

116

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A systematic review of the oxide minerals of niobium and tantalum is presented, including varietal names, crystal chemistry, structural features, relationships to other phases and paragenesis of each mineral group, series or species. A separate section deals with oxide minerals that occur exclusively as secondary, low-temperature phases of largely metasomatic origin. Oxide minerals of Sn, Ti and W that carry substantial Nb and Ta are discussed as well. A new crystal chemical classification ofthe oxide minerals ofNb and Ta is presented.Abriefreview is presented of the crystal chemistry ofthe silicates ofNb and Ta, and ofthe silicates ofTi and Zr that exhibit Substitution ofthese elements by Nb and Ta. Paragenetic affiliation of these silicates is reviewed. Miscellaneous minerals of Nb and Ta (borates, phosphates, borosilicates) arealso mentioned.Most of the oxide minerals of Nb and Ta typically occur in granitic rocks of orogenic affiliation, particularly in rare-element granitic pegmatites. However, some ofthese arealso found in, and a few are characteristic of, anorogenic alkaline igneous sequences from carbonatites and gabbros to nepheline syenites and alkaline granites. In contrast, all silicates ofNb (±Ta)-and (Nb,Ta)-bearing titanosilicates and zirconosilicates are related to the anorogenic parageneses.At present, the oxide minerals are the only important sources of Nb and Ta. Niobosilicates, and mainly some of the titanosilicates and zirconosilicates with significant Nb substitution, represent potential ore minerals forthe future. However, no alternate ore minerals seem to be available for extraction of tantalum.Note added in press: Continuing examination ofTa-rich wodginites has revealed the presence of significant quantities of Li, suggestive of a Li4 Ta120 32 component known as a synthetic wodginite-type phase (Gatehouse BM, Leverett P 1972, Lithium triniobate (V), LiNb30 8 ; Cryst Struct Comm 1 :83-86). This development will require modification ofthe wodginite systematics presented here.

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Zinc- and Y-group-bearing senaite from St Peters Dome, and new data on senaite from Dattas, Minas Gerais, Brazil

Cited by 16 publications

References 14 publications

High-pressure, synthetic loveringite-davidite and its rare earth element geochemistry

High-pressure, synthetic loveringite-davidite and its rare earth element geochemistry

Minerais do grupo da crichtonita em veios de quartzo da Serra do Espinhaço (Minas Gerais e Bahia)

Mineralogy of Niobium and Tantalum: Crystal Chemical Relationships, Paragenetic Aspects and Their Economic Implications

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