Multi-methodical study of the Ti, Fe2+ and Fe3+ distribution in chevkinite-subgroup minerals: X-ray diffraction, neutron diffraction, 57Fe Mössbauer spectroscopy and electron-microprobe analyses

Nagashima, Mariko; Armbruster, Thomas; Akasaka, Masahide; Sano‐Furukawa, Asami; Nishio–Hamane, Daisuke; Malsy, Anna; Imaoka, Teruyoshi; Nakashima, Keisuke

doi:10.1007/s00269-020-01096-5

Cited by 5 publications

(6 citation statements)

References 42 publications

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“…In terms of chemical composition, the three crystal fragments are bordering on perrierite-(La), but Ce is still the /Fe 2+ ratio of 1.84/1.0 or 65% Fe 3+ in a particularly Nbrich chevkinite-(Ce) by X-ray photoelectron spectroscopy. Nagashima et al (2020) report Fe 3+ contents of 34, 59 and 61% for three chevkinite-(Ce) samples studied by Mössbauer spectroscopy. The reported Fe 3+ content for perrierite-(La), which also originates from the LSV, is 60% (Chukanov et al 2012b).…”

Section: Chemical Composition Fe Oxidation State and Module Chargementioning

confidence: 99%

“…Calculating the module charge ideally requires knowledge of the chemical composition, the site occupancies and also of the oxidation state of the cations. While Sokolova et al (2004) assumed for chevkinite-(Ce) that ferrous iron can only occupy the B position (or M1), even though they did not entirely rule out that mixed occupancy occurs also at the C-and D-sites, Nagashima et al (2020) showed that ferrous and ferric iron can occupy the B-site (M1) and that ferrous iron is also present at the D-sites (M3, M4). If Fe 3+ is present, we have, therefore, equally distributed it over all Fecontaining sites.…”

Section: Comparison With Other Cgmmentioning

confidence: 99%

“…This difference in module height can be almost entirely attributed to the C-O bond that is normal to the (001) plane. This bond length ranges between 2.02 and 2.05 Å (Sokolova et al 2004;Nagashima et al 2020) in most chevkinite-type structures. Taking the LSV perrierite-(Ce) of this work as a representative of the perrierite-type structures, the equivalent C-O distance is just 1.966 Å.…”

Section: Comparison With Other Cgmmentioning

confidence: 99%

“…Hence, well crystallized, non-metamict natural samples and synthetic samples are needed to obtain reliable information about structural properties of well-equilibrated CGM. A detailed study of cation distribution in three non-metamict chevkinite-(Ce) samples has been published very recently (Nagashima et al 2020). One aim of the present work is to identify possible mechanisms that could help to explain the empirically known compositional controls (Macdonald et al 2019) over the formation of either the chevkinite-or perrierite-type structure in CGM.…”

Section: Introductionmentioning

confidence: 99%

“…While the A-sites are at least seven-coordinated by oxygen atoms, the remaining B-, C-and D-sites all have distorted octahedral coordination, hosting smaller cations with radii significantly below 1 Å. The site nomenclature of the CGM varies across publications by different authors (see Macdonald et al (2019) and Nagashima et al (2020) for summaries). We follow the site nomenclature of Macdonald et al (2019) here, but emphasize that the site occupancies of the B-, Cand D-sites are extremely variable.…”

Section: Introductionmentioning

confidence: 99%

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Perrierite-(Ce) from the Laacher See tephra, Eifel, Germany, and the modular character of the chevkinite group of minerals

Malcherek

Schlüter

Schäfer³

2021

Phys Chem Minerals

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Perrierite-(Ce) crystals from ejecta of the Laacher See volcano, Eifel, in Germany were studied by X-ray single-crystal diffraction and electron microprobe analysis. The composition and crystal structure of this sample is discussed in relation to the known properties of the chevkinite group minerals and related synthetic compounds. Taking into account the modular character of the chevkinite minerals, based on a rutile and a silicate module, the preferred formation of either the perrierite or the chevkinite structure type is correlated with the formal charge of the rutile and silicate modules. The rutile module is expected to carry a negative charge, compensated by a positive charge of the silicate module. On average, the charge modulus is observed to be larger for the chevkinite-type module stacking. It can drop to zero in perrierite-type structures rich in Sr or Ca. In such cases, it is generally not expected to rise above two. The perrierite-(Ce) described in this study crystallizes in space group C2/m. The anisotropic oxygen and rare-earth element displacements observed in this crystal indicate a local domain structure of $$P2_1/a$$ P 2 1 / a symmetry, when compared to the $$P2_1/a$$ P 2 1 / a symmetry of the synthetic perrierite $$\hbox {La}_4\hbox {Mg}_2\hbox {Ti}_3\hbox {O}_8(\hbox {Si}_2\hbox {O}_7)_2$$ La 4 Mg 2 Ti 3 O 8 ( Si 2 O 7 ) 2 .

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Section: Chemical Composition Fe Oxidation State and Module Chargementioning

confidence: 99%

Section: Comparison With Other Cgmmentioning

confidence: 99%

Section: Comparison With Other Cgmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Perrierite-(Ce) from the Laacher See tephra, Eifel, Germany, and the modular character of the chevkinite group of minerals

Malcherek

Schlüter

Schäfer³

2021

Phys Chem Minerals

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Chevkinite-group minerals in selected intrusions of the Mazury Complex, North-Eastern Poland: insights into the formation of a titanite-like phase by hydrothermal alteration

et al. 2022

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Chevkinite-group minerals forming large and common (up to 0.03 vol%) accessory phases in monzodiorites and granodiorites from the Mesoproterozoic anorthosite-mangerite-charnockite-granite (AMCG) suite intrusions, Mazury Complex, north-eastern Poland, range from pristine magmatic types to hydrothermally altered varieties. The unaltered phase is perrierite-(Ce), with the uncommon feature of having Al dominant in the C site. Hydrothermal alteration of the perrierite-(Ce) followed two main trends: one shows depletion in Ca, Fe, Si, Al and Mg, and increasing Ti contents; the other shows increases in Si, Ti and Ca and decreases in light rare-earth elements (LREE), Y and Mg, at about constant Fe content. The second trend resulted in the formation of a phase compositionally similar to titanite. Result of chemical analyses show that the transition from perrierite-(Ce) to the titanite-like phase is sharp; an electron back-scatter diffraction (EBSD) study shows the titanite- like material to be amorphous. The hydrothermal alteration of a chevkinite-group mineral to titanite has commonly been reported in natural sequences but this is the first record of the identification of a titanite-like phase made on the basis of a structural analysis.

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New Data on the Crystal-Chemistry of Metamict Minerals From the Velyka Vyska Syenite Massif (Ukrainian Shield)

Grechanovskaya¹,

Lunova²,

Kurylo³

et al. 2022

Mìneral. ž.

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The structural properties and composition of metamict minerals, namely allanite, chevkinite, and britholite, occurring as inclusions in allanite from feldspar syenites of the Velyka Vyska massif (Korsun-Novomyrgorod pluton, Ukrainian Shield) were investigated by X-ray diffraction and electron probe microanalysis (EPMA). The age of the syenites is 1.7-1.8 Ga, which corresponds to their formation ages within the Ukrainian Shield. X-ray analysis shows that of the original samples of chevkinite and allanite give a broad diffraction peak between 16—28° 2Θ as well as Bragg reflections in the region of the most intense reflections of semimetamict allanite and britholite, indicating the metamict state of chevkinite and the semimetamict state of allanite. The content of radioactive Th found in the chevkinite (0.25-0.33 apfu) is higher compared to its amount in allanite (0.024-0.033 apfu). Calculated unit-cell parameters of the chevkinite and allanite samples showed that their structures underwent significant changes after annealing. There is a slight distortion of the chevkinite unit cell related to a decrease in the a and an increase in b and c edges. A decrease in b and the increase in c in the allanite is caused by a redistribution of cations in the structure and an oxidation of iron, Fe2+ → Fe3+, during heating. Thereby the stability of the allanite structure decreases and it ultimately breaks down. The structural sites A and A2 in chevkinite and allanite are mainly occupied by REEs of the cerium group. The amount of Y is minor. The substitution mechanism А2(REE)3+ + М3М2+ → А2Са2+ + М3М3+(allanite) and M2Fe3+ + M3,4Ti4+↔ M2Fe2+ + M3,4Nb5+ (chevkinite) occur. The M2 site in the structure of chevkinite and M3 in allanite contain more Fe2+ than Fe3+. This leads to a weakening of the bonds in their structures, and a stepwise breakdown and partial or total metamictization of their structures. The britholite inclusions in allanite belong to the Y variety. They were probably formed much later than allanite and chevkinite in the Velyka Vyska massif. According to the EPMA results, namely BSE-images and REE content determinations, allanite and chevkinite formed almost simultaneously.

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Multi-methodical study of the Ti, Fe2+ and Fe3+ distribution in chevkinite-subgroup minerals: X-ray diffraction, neutron diffraction, 57Fe Mössbauer spectroscopy and electron-microprobe analyses

Cited by 5 publications

References 42 publications

Perrierite-(Ce) from the Laacher See tephra, Eifel, Germany, and the modular character of the chevkinite group of minerals

Perrierite-(Ce) from the Laacher See tephra, Eifel, Germany, and the modular character of the chevkinite group of minerals

Chevkinite-group minerals in selected intrusions of the Mazury Complex, North-Eastern Poland: insights into the formation of a titanite-like phase by hydrothermal alteration

New Data on the Crystal-Chemistry of Metamict Minerals From the Velyka Vyska Syenite Massif (Ukrainian Shield)

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