Liddicoatite Tourmaline From Anjanabonoina, Madagascar

Dirlam, Dona M.; Laurs, Brendan M.; Pezzotta, Federico; Simmons, William B.

doi:10.5741/gems.38.1.28

Cited by 21 publications

(21 citation statements)

References 22 publications

(24 reference statements)

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“…Large areas of the Anjanabonoina pegmatite are severely kaolinized by the activity of late-stage hydrothermal fluids. The rocks are also deeply weathered to depths exceeding 20 m, particularly in the southern portion of the mining area where extensive eluvial deposits were worked (Dirlam et al 2002). The Anajanabonoina pegmatite shows a geochemical "mixed" lithium, caesium, tantalum (LCT) and niobium, yttrium, fluorine (NYF) signature, following Černý and Ercit's (2005) classification, where high-geochemically evolved core zones are enriched with LCT minerals (e.g., elbaite-liddicoatite, Li-rich micas, spodumene, hambergite, pink-beryl) and other portions where NYF minerals are abundant (like microcline, pyrochlore, monazite, and allanite) (De Vito et al 2006).…”

Section: Sample Description and Mineralogymentioning

confidence: 99%

A single-crystal neutron diffraction study of hambergite, Be2BO3(OH,F)

Gatta

McIntyre

Bromiley

et al. 2012

American Mineralogist

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The crystal chemistry and crystal structure of hambergite from the Anjanabonoina mine, Madagascar [Be 2 BO 3 (OH) 0.96 F 0.04 , Z = 8, a = 9.762(2), b = 12.201(2), c = 4.430(1) Å, V = 527.6(2) Å 3 , space group Pbca], were reinvestigated by means of electron microprobe analysis in wavelength-dispersive mode, secondary-ion mass spectrometry, single-crystal X-ray and neutron Laue diffraction. Chemical analyses show only a small amount of F (0.7-0.8 wt%, approximately 0.04 atoms per formula unit) substituting OH and no other substituent at a significant level. An anisotropic neutron structural refinement has been performed with final agreement index R 1 = 0.0504 for 76 refined parameters and 1430 unique reflections with F o > 4σ(F o ). The geometry of the hydroxyl group and hydrogen bonding in hambergite is now well defined: (1) only one independent H site was located and the O4-H distance, corrected for "riding motion," is ∼0.9929 Å;(2) only one hydrogen bond appears to be energetically favorable, with a symmetry-related O4 as acceptor and with O4⋅⋅⋅O4 = 2.904(1) Å, H⋅⋅⋅O4 = 1.983(1) Å, and O4-H⋅⋅⋅O4 = 157.5(1)°. In other words, O4 sites act both as donor and as acceptor of the hydrogen bond, with a zigzag chain of H-bonds along [001]. The hydrogen-bonding scheme in hambergite found in this study is consistent with the pleochroic scheme of the infrared spectra previously reported, with two intensive modes ascribable to stretching vibrations of the hydroxyl group, at 3415 and 3520 cm -1 , respectively. The two modes suggest at least two distinct hydrogen-bonding environments, ascribable to the presence of oxygen and fluorine at the acceptor site.

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Section: Sample Description and Mineralogymentioning

confidence: 99%

A single-crystal neutron diffraction study of hambergite, Be2BO3(OH,F)

Gatta

McIntyre

Bromiley

et al. 2012

American Mineralogist

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“…Excavations of tunnels and pits in 1995-1996 by a private mining company led to intersections of a series of tourmaline-rich veins, as recounted by Dirlam et al (2002). At that time, the second author (F.P.)…”

Section: Background Informationmentioning

confidence: 93%

“…Anjanabonoina represents a significant example of a granitic pegmatite with "mixed" geochemical features. As described by Dirlam et al (2002), the pegmatite outcropping at Sarodivotra displays a typical NYF geochemical signature. In that part of the pegmatitic system, significant concentrations of pyrochlore-group minerals, and in particular uranoan pyrochlore and uranoan betafite, associated with fersmite and zircon, are present together with vivid green amazonitic microcline.…”

Section: Columbite-group Mineral: Fersmitementioning

confidence: 95%

Nb-Ti-Ta OXIDES IN THE GEM-MINERALIZED AND "HYBRID" ANJANABONOINA GRANITIC PEGMATITE, CENTRAL MADAGASCAR: A RECORD OF MAGMATIC AND POSTMAGMATIC EVENTS

Vito¹,

Pezzotta²,

Ferrini³

et al. 2006

The Canadian Mineralogist

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The Anjanabonoina rare-element-enriched granitic pegmatite dikes, located about 40 km southwest of Betafo, in central Madagascar, are emplaced in a complex environment characterized by paragneiss, marble and orthogneiss of the Neoproterozoic Itremo Group, of medium metamorphic grade. The subhorizontal bodies of pegmatite are strongly zoned and, in the mineralized area called Sarodivotra, they show a rich paragenetic assemblage in which Ti-Nb-Ta-bearing minerals occur. We recognize two generations of pyrochlore-group and columbite-group minerals. They have a high Nb:Ta ratio, with predominance of Nb-and Ti-dominant phases, and a rare late development of Ta-bearing minerals in fractures. Crystals of the first generation, Nb-dominant (1.20-1.23 apfu), are pyrochlore, whereas those of the second generation, mainly Ti-dominant, are U-rich betafite (0.29-0.57 apfu U) and locally pyrochlore. The primary minerals are typical of an NYF-type pegmatite, and contrast with the LCT-type mineralogy (which includes abundant elbaite-liddicoatite, a pink variety of beryl, spodumene, and hambergite) typical of much of the Anjanabonoina dike. Large crystals of pyrochlore of the first generation are affected by a primary alteration, at high temperature, due to circulation of hydrothermal fluids, represented by the substitution A Ca Y O ! A M Y M at the core, and by a secondary alteration (at low temperature) along fractures and at the rim, during which the vacancies increased in the A and Y sites. Crystals of the second generation are even more intensely altered. The columbite-group mineral, also formed in two generations and by exsolution in pyrochlore, is fersmite. Rarely, fersmite replaces pyrochlore in the second-generation crystals. We use pyrochlore-and columbite-group minerals to monitor magmatic evolution and postmagmatic events related to circulation of the hydrothermal fluids and weathering-type reactions.

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“…The High Grade Dyke is a member of the Cat Lake -Winnipeg River pegmatite field, belonging to the Maskwa Lake pegmatite series, and outcrops mainly in the Bird River Greenstone Belt, close to the English River Subprovince. data of J.B. Selway), Nigeria, Tanzania and Vietnam (Dirlam et al 2002) and Minas Gerais, Brazil (Bastos 2002, Dirlam et al 2002. The only other examples of liddicoatite reported worldwide are from Mozambique (Sahama et al 1979), Malkhan, Russia (Zagorskyi et al 1989), the Czech Republic (Novák & Povondra, 1995, Novák & Selway 1997.…”

Section: Introductionmentioning

confidence: 99%

“…Liddicoatite has only been found in abundance at the type locality and its analogues in Madagascar (Dunn et al 1977, Aurisicchio et al 1999, Akizuki et al 2001, Dirlam et al 2002. So unusual is it that Teertstra et al (1999a) referred to it as the "stranger in paradise" in describing its occurrence in the High Grade Dyke, a spodumene-subtype pegmatite in southeastern Manitoba, Canada.…”

Section: Introductionmentioning

confidence: 99%

Liddicoatite and Associated Species From the McCombe Spodumene-Subtype Rare-Element Granitic Pegmatite, Northwestern Ontario, Canada

Tindle¹,

Selway²,

Breaks³

2005

The Canadian Mineralogist

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Liddicoatite, a rare species of tourmaline, has been found in the McCombe pegmatite, of complex type and spodumene subtype, an example of the LCT (lithium, cesium, tantalum) family. It is one of a group of beryl-and complex-type pegmatites exposed along the Uchi -English River subprovincial boundary-zone, Ontario, in the Superior Province of the Canadian Shield. The mineral assemblage containing zoned "fluor-elbaite"-liddicoatite crystals was the last product of primary, near-solidus crystallization of the pegmatite and is unique not only to this subprovincial boundary, but also throughout the vast number of rareelement pegmatites distributed across Ontario. The most calcic composition of liddicoatite analyzed here corresponds to fluorapatite. Evidence from progressively evolved units of the pegmatite and mineral zonation shows that contamination of the pegmatite-forming melt occurred, and that fluids from the pegmatite migrated out into the mafic metavolcanic host-rocks, creating a Li-, Cs-, and B-enriched metasomatic aureole. The evolution of the pegmatite-forming melt resulted in increased activity of fluorine, and the essentially in situ fractionation of the contaminated melt led to the crystallization of the rare-element-enriched minerals. Patterns of zonation seen in back-scattered-electron images show that primary crystallization of columbite-tantalite, garnet and tourmaline species involved multiple episodes of growth and dissolution in a dynamic system. Liddicoatite was able to form, not because of any one of these processes, but because they all acted together to concentrate both Li and Ca, a sequence of events that is apparently very rare in nature.

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Liddicoatite Tourmaline From Anjanabonoina, Madagascar

Cited by 21 publications

References 22 publications

A single-crystal neutron diffraction study of hambergite, Be2BO3(OH,F)

A single-crystal neutron diffraction study of hambergite, Be2BO3(OH,F)

Nb-Ti-Ta OXIDES IN THE GEM-MINERALIZED AND "HYBRID" ANJANABONOINA GRANITIC PEGMATITE, CENTRAL MADAGASCAR: A RECORD OF MAGMATIC AND POSTMAGMATIC EVENTS

Liddicoatite and Associated Species From the McCombe Spodumene-Subtype Rare-Element Granitic Pegmatite, Northwestern Ontario, Canada

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