Ti site occupancy in zircon

Tailby, Nicholas D.; Walker, Andrew; Berry, Andrew J.; Hermann, Jörg; Evans, Katy; Mavrogenes, John; O’Neill, Hugh St. C.; Rodina, I. S.; Soldatov, A. V.; Rubatto, Daniela; Sutton, S.R.

doi:10.1016/j.gca.2010.11.004

Cited by 76 publications

(27 citation statements)

References 53 publications

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“…Fu et al (2008) found 90% of zircons to have Ti concentrations <20 ppm, far less than the Ti content of any magma, and Watson et al (2006) established D Ti to be $10 À2 . Our samples show minimal differential partitioning into the sector zones delimited by other elements, in contrast to the findings of Tailby et al (2011), possibly because of differences between the Na 2 WO 4 flux of that study and our silicate melt.…”

Section: Titaniumcontrasting

confidence: 86%

“…The scatter in the partition coefficients means that for the expected proportion of Ti 3+ present, the partition coefficient of Ti 3+ is constrained to be in the range from 0 to 3 times D Ti 4þ . Since conditions at which >25% Ti occurs as Ti 3+ are improbable for any differentiated planetary material, Ti partitioning is independent of fO 2 .Ti 4+ substitutes for Si 4+ (Ferry and Watson, 2007;Tailby et al, 2011), whereas Ti 3+ might be expected, like the REE, to substitute for Zr 4+ and thus a SiO 2 would affect the partitioning, and hence temperature estimates, very differently. The temperature-dependence of Ti 3+ partitioning is also unknown, so there is potential for Ti 3+ to have an effect on thermometric calculations of natural samples under extremely reducing conditions.…”

Section: Titaniummentioning

confidence: 99%

See 1 more Smart Citation

An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity

Burnham

Berry

2012

Geochimica et Cosmochimica Acta

272

111

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Section: Titaniumcontrasting

confidence: 86%

Section: Titaniummentioning

confidence: 99%

An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity

Burnham

Berry

2012

Geochimica et Cosmochimica Acta

272

111

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“…Temperatures calculated by the Ti-in-zircon thermometer are much higher (~1200-1400 °C) than the local metamorphic temperature. This is due to the very low aSiO2 (~0.1) in the rocks, reflected by the absence of quartz, which is known to enhance uptake of Ti in zircon [46]. Concentrations of selected trace elements, such as Hf, Y, and U, are compared with the compositional fields of zircon associated with different rock types (Figure 10), as proposed by [19].…”

Section: Zirconmentioning

confidence: 99%

The Cedrolina Chromitite, Goiás State, Brazil: A Metamorphic Puzzle

et al. 2016

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Abstract:The Cedrolina chromitite body (Goiás-Brazil) is concordantly emplaced within talc-chlorite schists that correspond to the poly-metamorphic product of ultramafic rocks inserted in the Pilar de Goiás Greenstone Belt (Central Brazil). The chromite ore displays a nodular structure consisting of rounded and ellipsoidal orbs (up to 1.5 cm in size), often strongly deformed and fractured, immersed in a matrix of silicates (mainly chlorite and talc). Chromite is characterized by high Cr# (0.80-0.86), high Fe 2+ # (0.70-0.94), and low TiO 2 (av. = 0.18 wt %) consistent with variation trends of spinels from metamorphic rocks. The chromitite contains a large suite of accessory phases, but only irarsite and laurite are believed to be relicts of the original igneous assemblage, whereas most accessory minerals are thought to be related to hydrothermal fluids that emanated from a nearby felsic intrusion, metamorphism and weathering. Rutile is one of the most abundant accessory minerals described, showing an unusually high Cr 2 O 3 content (up to 39,200 ppm of Cr) and commonly forming large anhedral grains (>100 µm) that fill fractures (within chromite nodules and in the matrix) or contain micro-inclusions of chromite. Using a trace element geothermometer, the rutile crystallization temperature is estimated at 550-600 • C (at 0.4-0.6 GPa), which is in agreement with P and T conditions proposed for the regional greenschist to low amphibolite facies metamorphic peak of the area. Textural, morphological, and compositional evidence confirm that rutile did not crystallize at high temperatures simultaneously with the host chromitite, but as a secondary metamorphic mineral. Rutile may have been formed as a metamorphic overgrowth product following deformation and regional metamorphic events, filling fractures and incorporating chromite fragments. High Cr contents in rutile very likely are due to Cr remobilization from Cr-spinel during metamorphism and suggest that Ti was remobilized to form rutile. This would imply that the magmatic composition of chromite had originally higher Ti content, pointing to a stratiform origin. Another possible interpretation is that the Ti-enrichment was caused by external metasomatic fluids which lead to crystallization of rutile. If this was the case, the Cedrolina chromitites could be classified as podiform, possibly representing a sliver of tectonically dismembered Paleoproterozoic upper mantle. However, the strong metamorphic overprint that affected the studied chromitites makes it extremely difficult to establish which of the above processes were active, if not both (and to what extent), and, therefore, the chromitite's original geodynamic setting.

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“…Ca occupies a 12-coordinated polyhedron and Al occupies five M sites. The cation site multiplicity and their coordination numbers can be described as [12] Ca [6] M1 [5] M2 [4] M3 2 [6] M4 2 [6] M5 6 O 19 [6]. Here the multiplicity of the site is subscripted and the coordination numbers are superscripted in brackets.…”

Section: Experiments and Methods Of Calculationmentioning

confidence: 99%

“…without long-range order) [3]. Recently, XANES spectroscopy was used successfully to investigate the local environment of Ti at defect sites in minerals [4][5]. But the method of extracting information from experimental XANES spectra is not direct and requires computer modelling.…”

Section: Introductionmentioning

confidence: 99%

The Ti environment in natural hibonite: XANES spectroscopy and computer modelling

Kravtsova

Soldatov

Walker

et al. 2016

J. Phys.: Conf. Ser.

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Abstract. The local atomic structure around Ti in Ti-bearing hibonite (CaAl 12 O 19 ) was studied using X-ray absorption near-edge structure (XANES) spectroscopy and computer modelling. Structural models of the direct substitution of Al by Ti 3+ , Al by Ti 4+ charge balanced by the coupled substitution of Mg 2+ for Al, and small Ti clusters were considered. The Ti K-XANES spectra of natural hibonite with different Ti concentration were recorded. Theoretical Ti K-XANES spectra for structural models of hibonite were calculated. It was shown that the theoretical Ti K-XANES spectra for a model with Ti at the five-coordinated M2 site are in agreement with the experimental XANES spectra of hibonite with low concentrations of Ti, while the theoretical spectra for a structural model of clustered Ti are in agreement with the experimental spectra of hibonite with higher Ti contents.

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Ti site occupancy in zircon

Cited by 76 publications

References 53 publications

An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity

An experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity

The Cedrolina Chromitite, Goiás State, Brazil: A Metamorphic Puzzle

The Ti environment in natural hibonite: XANES spectroscopy and computer modelling

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