Diffusion of Zr, Hf, Nb and Ta in rutile: effects of temperature, oxygen fugacity, and doping level, and relation to rutile point defect chemistry

Dohmen, Ralf; Marschall, Horst R.; Ludwig, Thomas; Polednia, Joana

doi:10.1007/s00269-018-1005-7

Cited by 30 publications

(12 citation statements)

References 64 publications

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“…6). Oxygen vacancies, on the other hand, are present at levels two orders of magnitude less than Al even under dry conditions (Bak et al 2006;Dohmen et al 2019). Changes in the extent to which the reactions controlling the formation of oxygen vacancies proceed (by varying f O 2 ) would have a negligible effect on Al solubility in equilibrium with corundum (i.e., under this model n V,A ≅ n Al,M through the range of f O 2 explored in this study).…”

Section: Comparison With Previous Workmentioning

confidence: 99%

“…These defects, such as oxygen vacancies, titanium interstitials, hydroxyl groups, or other cation substituents, and the variables that control their solubility can exert a tremendous influence on the solubility of aliovalent impurities like Al. Although some attention has been paid to the effect of defects on trace element partitioning and kinetics (e.g., Harrison and Wood 1980;Dohmen et al 2019), the limited availability of data on high-pressure point defect formation reactions has made the characterization of aliovalent cation solubility in silicates and oxides difficult.…”

Section: Introductionmentioning

confidence: 99%

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Aluminum solubility in rutile (TiO2)

Hoff

Watson

2021

Phys Chem Minerals

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The solubility of aluminum in rutile has been studied in the systems Al 2 O 3 -TiO 2 -H 2 O and Al 2 O 3 -SiO 2 -TiO 2 -H 2 O at 700-1200 °C and 0.075-3.3 GPa. Electron probe microanalysis (EPMA) measurements of rutile crystals grown in equilibrium with corundum show that the concentration of Al increases with increasing temperature, pressure, and oxygen fugacity. Solubility is enhanced by the addition of Nb and reduced by the addition of trivalent cations. These results are consistent with the substitution of Al 3+ for Ti 4+ on normal cation sites and the simultaneous incorporation of positively charged hydrous defects for charge compensation. Parameters for a thermodynamic model of Al substitution in rutile are calculated and the merits of using the model as a geochemical tool are discussed.

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Section: Comparison With Previous Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aluminum solubility in rutile (TiO2)

Hoff

Watson

2021

Phys Chem Minerals

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“…For rutile, a range of values have been proposed for the Pb closure temperature, the minimum temperature at which Pb is mobile via volume diffusion and can decouple from U, affecting the geochronometer (Cherniak, 2000;Dohmen et al, 2019). U, Pb and Zr profiles were also demonstrated to yield different closure temperatures and cooling histories in the same rock (Kohn et al, 2016;Kooijman et al, 2010;Smye and Stockli, 2014) and the spread of 206 Pb/ 238 U ages (Romer and Rötzler, 2001) resulting from initial isotope heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

The geochemical and geochronological implications of nanoscale trace-element clusters in rutile

Verberne

Reddy

Saxey

et al. 2020

Geology

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The geochemical analysis of trace elements in rutile (e.g., Pb, U, and Zr) is routinely used to extract information on the nature and timing of geological events. However, the mobility of trace elements can affect age and temperature determinations, with the controlling mechanisms for mobility still debated. To further this debate, we use laser-ablation–inductively coupled plasma–mass spectrometry and atom probe tomography to characterize the micro- to nanoscale distribution of trace elements in rutile sourced from the Capricorn orogen, Western Australia. At the >20 μm scale, there is no significant trace-element variation in single grains, and a concordant U-Pb crystallization age of 1872 ± 6 Ma (2σ) shows no evidence of isotopic disturbance. At the nanoscale, clusters as much as 20 nm in size and enriched in trace elements (Al, Cr, Pb, and V) are observed. The 207Pb/206Pb ratio of 0.176 ± 0.040 (2σ) obtained from clusters indicates that they formed after crystallization, potentially during regional metamorphism. We interpret the clusters to have formed by the entrapment of mobile trace elements in transient sites of radiation damage during upper amphibolite facies metamorphism. The entrapment would affect the activation energy for volume diffusion of elements present in the cluster. The low number and density of clusters provides constraints on the time over which clusters formed, indicating that peak metamorphic temperatures are short-lived, <10 m.y. events. Our results indicate that the use of trace elements to estimate volume diffusion in rutile is more complex than assuming a homogeneous medium.

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“…Even though rutile is a stable phase at high grade metamorphic conditions, the diffusion rates of trace elements, such as Zr, Pb, Nb, Hf, Nb, and Ta, differ significantly at high P‐T conditions (e.g., Cherniak, 2000; Cherniak et al, 2007; Dohmen et al, 2019; Marschall et al, 2013). According to Cherniak (2000), the effective closure temperature of Pb in rutile is ~ 600°C for a 100 μm rutile grain, depending also on cooling rate.…”

Section: Discussionmentioning

confidence: 99%

Petrochronology of high‐pressure granulite facies rocks from Southern Brasília Orogen, SE Brazil: Combining quantitative compositional mapping, single‐element thermometry and geochronology

Fumes

Luvizotto

Moraes

et al. 2021

Journal Metamorphic Geology

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We use a combination of several in situ techniques to assess the P‐T‐t path of high‐pressure granulites from the Passos Nappe in the Southern Brasília Orogen (SE Brazil). Quantitative element mapping and single‐element thermometers (Zr‐in‐rutile and Ti‐in‐quartz) are coupled with P‐T pseudosections and monazite and rutile dating. Compositional and temperature maps, based on cathodoluminescence mapping and in situ analyses of Ti‐in‐quartz, are presented as a novel approach to evaluate crystallization temperature. The studied rocks have a pelitic protolith and record a peak pressure assemblage of garnet + kyanite + rutile + K‐feldspar + quartz + melt ± plagioclase that formed at ~830°C and 1.2 GPa. Retrograde conditions of ~560°C and 0.6 GPa are determined based on the grossular content of garnet and the crystallization of biotite and ilmenite. Metamorphic peak conditions occurred ca. 635 Ma, according to monazite dating, with a younger date of ca. 615 Ma associated with later kyanite crystallization. Rutile ages of ca. 590 Ma are linked to the late retrograde stage (at ~600°C). Results show that the distribution of Ti‐in‐quartz is heterogeneous, decreasing in abundance towards the rim of crystals, though the higher temperatures constrained with Ti‐in‐quartz thermometry are broadly consistent with peak conditions. The peak pressure conditions are consistent with continental collision setting in the Southern Brasília Orogen and were followed by an early cooling/decompression stage and then by a slow cooling during exhumation and transport to shallower crustal levels.

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Diffusion of Zr, Hf, Nb and Ta in rutile: effects of temperature, oxygen fugacity, and doping level, and relation to rutile point defect chemistry

Cited by 30 publications

References 64 publications

Aluminum solubility in rutile (TiO2)

Aluminum solubility in rutile (TiO2)

The geochemical and geochronological implications of nanoscale trace-element clusters in rutile

Petrochronology of high‐pressure granulite facies rocks from Southern Brasília Orogen, SE Brazil: Combining quantitative compositional mapping, single‐element thermometry and geochronology

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