The crystal-chemistry of high-aluminium titanites

Oberti, Roberta; Smith, David; Rossi, Giuseppe; Caucia, Franca

doi:10.1127/ejm/3/5/0777

Cited by 110 publications

(78 citation statements)

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“…Smith, 1988;Oberti et al, 1991;Perseil and Smith, 1995). However a preliminary microinfrared spectroscopic study of all of the Sb-rich rutile crystals described here did not reveal any OH bands.…”

Section: Ion Substitutions In the Rutile Structurementioning

confidence: 61%

Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry

Smith

Perseil

1997

Mineral. mag.

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The petrographical, crystal-chemical and petrogenetical aspects of rutile rich in antimony (up to 33.75 wt.% Sb205; equal to 0.2 Sb 5 § per O = 2) from St. Marcel-Praborna in the Aosta Valley, Italy, were re-examined. These compositions occur in two different petrographical environments (within the rock matrix or as microinclusions within Sb-rich titanite) in the manganese concentrations at this locality. The new data confirm our earlier hypothesis that two distinct petrogenetical/crystal-chemical processes both occurred: 1. Sbmetasomatism of pre-existing Sb-free rutile inclusions; and 2. creation of neoblastic Sb-rich futile by the expulsion of Ti from pre-existing Sb-free titanite being metasomatized by Sb to form Sb-rich titanite. In the literature, Sb in minerals is variably considered as being trivalent and/or pentavalent. This work demonstrates that within rutile it is entirely Sb 5+, substituting for Ti 4 § by the following heterovalent cation exchange mechanism which is also the dominant one in the host Sb-rich titanite: 2 viR4+ = viR3+ + viR5+, where viR3+ = (A1,Cr,Mn,Fe) 3 § A near-perfect correlation of Y.R 5 § vs. ER 3 § (r > 0.98) is perturbed only by the presence of trace amounts of Ca 2+, Sr 2+ and Ba 2+. Traces of Mn 4+, Si n+ and/or (OH)-might also be present. These alkaline earth cations are the largest cations ever recorded in the rutile structure and are seemingly too large to occupy normal octahedral sites. The cation exchange mechanism involved might be that found in the 'trirutile' mineral group: 3 viR4+ = viR2+ + 2 ViR5+. Alternatively these large divalent cations may be situated in the lozenge-shaped tunnels of the rutile structure, by analogy with other large cations occupying the wider subrectangular tunnels in the analogous cryptomelane/hollandite/priderite, romandchite and todorokite mineral groups. This leads to a possible new cation exchange mechanism for the rutile structure: 2 ViR4+ + tunnelvacant = 2 viR3+ + tunnelR2+.

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Section: Ion Substitutions In the Rutile Structurementioning

confidence: 61%

Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry

Smith

Perseil

1997

Mineral. mag.

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“…ivsi4+ = ivTi4+ (10) are somewhat doubtful at St. Marcel-Praborna since these large cations require relatively low-P-high-T conditions in titanite (e.g. Oberti et al, 1991) and in many other aluminosilicate minerals, notably amphiboles and pyroxenes (e.g. Smith, 1988).…”

Section: Crystal-chemistry:mentioning

confidence: 99%

“…Mottana and Griffin, 1979;Paul et al, 1981;Deer et al, 1982); Q') sum (vi + iv) = 2.0 (cf. Paul etal., 1981;Oberti et al, 1991); and (g) sum (vii + vi + iv) = 3.0 (cf. Groat et al, 1985;Bernau and Franz, 1987).…”

Section: 0);mentioning

confidence: 99%

“…Table 1 lists all of the known chemical elements which can substitute into the t i t a n i t e structure, ideally CaTiOSiO4 (Zachariasen, 1930), as mentioned in the reviews by Sahama (1946), Ribbe (1980), Deer et al (1982), Smith (1988) and Oberti et al (1991), and now adds antimony to the list.…”

Section: Introductionmentioning

confidence: 99%

“…59, pp. 9 Copyright the Mineralogical Society Notes: --Chemical elements from the lists in the reviews published by Sahama (1946), Ribbe (1980), Deer et al (1982) and Oberti et al (1991), with Sb 3+ and Sb 5 § added here, as well as several valencies which are unusual for geologists but not for chemists.…”

Section: Introductionmentioning

confidence: 99%

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Sb-rich titanite in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrography and crystal-chemistry

Smith

Perseil

1995

Mineral. mag.

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Titanitcs rich in antimony (up to 12.59 wt.% Sb205; equal to 0.165 Sb 5+ per Si 4+ = ] .000) arc described for the first time. They coexist with various grcenschist-facies minerals in three different petrographical environments in the manganese concentrations at St. Marcel-Praborna in the Aosta Valley, Italy. These titanites arc chemically zoned, the Sb-richest parts generally occurring alongside grain boundaries, microfractures, pores or inclusions. The data indicate a very late stage penetration of pre-existing titanites by mobilized Sb, A1, Cr, Mn, Fe, F and presumably also (OH) at this locality, whereas Sr and Ba were mobile at an earlier stage. Manganese, which existed in the sedimentary protoliths, did not enter the titanite structure in very significant quantities.

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Analysis of temperature‐dependent Raman spectra of minerals: Statistical approaches

Pankrushina

Kobuzov

Shchapova

et al. 2020

J Raman Spectroscopy

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The application of statistical methods to Raman spectroscopy is due to the need to analyse arrays of poorly resolved mineral spectra having low symmetry, large unit cells, and so forth. For the diagnosis of spectral changes under the influence of an external factor, as well as for the determination of critical values, statistical methods for the treatment of the spectrum profile provide more accuracy than a peak‐fitting procedure. The following algorithms for calculating statistical ξ parameters are used to parameterise I(ν,T) arrays of temperature‐dependent Raman spectra: Pearson correlation coefficient characterising the similarity/difference of signals; autocorrelation function, proposed earlier for estimating the weighted average width of spectral lines; and skewness and kurtosis, the parameters of the distribution of signal intensity. The ξ(T) relations were analysed for the synthetic and experimental spectra of natural zircon, titanite, and synthetic quartz in the range of T = 80–870 K. For zircon, the differences in the anharmonic behaviour of modes having various properties and symmetry are shown through the use of ξ(T). For quartz, at the temperatures preceding the displacive α–β phase transition, statistical analysis reveals the spectral region of soft modes, allowing their T‐behaviour to be analysed. For titanite, the critical temperature range corresponding to the displacive α–βγ phase transition is determined by differentiating ξ(T). The results show the potential of using a statistical approach for the rapid detection of spectral and temperature regions responding differently to an external effect, as well as for evaluating the critical values of an external parameter.

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The crystal-chemistry of high-aluminium titanites

Cited by 110 publications

References 0 publications

Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry

Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry

Sb-rich titanite in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrography and crystal-chemistry

Analysis of temperature‐dependent Raman spectra of minerals: Statistical approaches

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