Quantifying the diffusion kinetics and spatial distributions of radiogenic 4He in minerals containing proton-induced 3He

Shuster, David L.; Farley, K. A.; Sisterson, J. M.; Burnett, D. S.

doi:10.1016/s0012-821x(03)00594-6

Cited by 132 publications

(150 citation statements)

References 24 publications

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“…In contrast, we find that zonation of a factor of 3 in parent nuclide concentration produces 4 He/ 3 He spectra that deviate substantially from the homogeneous model. When parent nuclides are highly concentrated near the grain rim and/or cooling is fast, the resulting 4 He/ 3 He spectra will be readily identified as aberrant. However, more subtle zonation, higher concentrations in the grain interior, or samples that have cooled slowly regardless of zonation style can yield 4 He/ 3 He spectra that look acceptable but will lead to inaccurate thermochronometric interpretation if parent homogeneity is assumed.…”

contrasting

confidence: 76%

“…Existing data argue against anisotropy of this magnitude. We find that analysis of apatites with broken terminations will also bias 4 He/ 3 He spectra, but not greatly so. In contrast, we find that zonation of a factor of 3 in parent nuclide concentration produces 4 He/ 3 He spectra that deviate substantially from the homogeneous model.…”

mentioning

confidence: 73%

“…We find that analysis of apatites with broken terminations will also bias 4 He/ 3 He spectra, but not greatly so. In contrast, we find that zonation of a factor of 3 in parent nuclide concentration produces 4 He/ 3 He spectra that deviate substantially from the homogeneous model. When parent nuclides are highly concentrated near the grain rim and/or cooling is fast, the resulting 4 He/ 3 He spectra will be readily identified as aberrant.…”

mentioning

confidence: 73%

“…Under similar conditions anisotropic diffusion from the cylinder can greatly bias 4 He/ 3 He spectra, but only if diffusion is >10 times faster in the axial than the radial direction. Existing data argue against anisotropy of this magnitude.…”

mentioning

confidence: 99%

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Numerical investigations of apatite ⁴He/³He thermochronometry

Farley

Shuster

Watson

et al. 2010

Geochem Geophys Geosyst

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Apatite 4He/3He thermochronometry has the potential to constrain cooling histories for individual samples provided that several presently untested assumptions are valid. Here we simulate the sensitivity of 4He/3He spectra to assumptions regarding geometric model, crystallographic anisotropy, broken grain terminations, parent nuclide zonation, and the accuracy of results obtained from analyses of aggregates of multiple crystals. We find that 4He/3He spectra obtained from a cylinder with isotropic diffusion are almost indistinguishable from those obtained from an equivalent sphere with an equivalent initial 4He distribution. Under similar conditions anisotropic diffusion from the cylinder can greatly bias 4He/3He spectra, but only if diffusion is >10 times faster in the axial than the radial direction. Existing data argue against anisotropy of this magnitude. We find that analysis of apatites with broken terminations will also bias 4He/3He spectra, but not greatly so. In contrast, we find that zonation of a factor of 3 in parent nuclide concentration produces 4He/3He spectra that deviate substantially from the homogeneous model. When parent nuclides are highly concentrated near the grain rim and/or cooling is fast, the resulting 4He/3He spectra will be readily identified as aberrant. However, more subtle zonation, higher concentrations in the grain interior, or samples that have cooled slowly regardless of zonation style can yield 4He/3He spectra that look acceptable but will lead to inaccurate thermochronometric interpretation if parent homogeneity is assumed. Finally, we find that analysis of an aggregate of crystals with identical 4He distributions can yield 4He/3He spectra (and diffusion Arrhenius arrays) that are very different from those that would be obtained on the individual crystals if even small variations in He diffusion exist among the grains. Overall, our observations suggest that modeling tools that assume spherical geometry and isotropic diffusion are appropriate for interpreting apatite 4He/3He spectra. However, it is essential to analyze only individual crystals and to assess the degree of parent nuclide zonation in those crystals.

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confidence: 76%

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confidence: 73%

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confidence: 73%

mentioning

confidence: 99%

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Numerical investigations of apatite ⁴He/³He thermochronometry

Farley

Shuster

Watson

et al. 2010

Geochem Geophys Geosyst

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“…However, if its size is not large, it seems difficult to explain why relatively large hot spots such as Hawaii and Iceland which show the high 3 He/ 4 He, are systematically derived from such limited portions. In the case of He, diffusion coefficients of olivine crystals at 1400°C are in the order of 10 -6 cm 2 /sec (Shuster et al, 2003). Under these conditions, He moves more than several km through the Earth's history by diffusion alone.…”

Section: Evaluation Of Geochemical Models Based On Noble Gas Signaturesmentioning

confidence: 99%

On the degassing state and the chemical structure of the Earth's interior inferred from noble gas isotopes-Past and recent views

Kaneoka

2008

Geochem. J.

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The degassing state of the Earth's interior is one of the main issues in relation to the evolution of the Earth and has been discussed by many investigators over several decades. I outline some trials to reveal the state of degassing based on noble gas isotopes. Then, based on noble gas isotope signatures so far obtained, I discuss models of the chemical structure of the Earth's interior which are inevitably related to the degassing state of the Earth. I propose a preferred model which suggests the possibility for the occurrence of relatively undegassed and possibly less fractionated reservoir(s) in the Earth's deep interior, which might be located in a relatively non-convective mantle.

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Incorporating 3‐D parent nuclide zonation for apatite ⁴He/³He thermochronometry: An example from the Appalachian Mountains

Fox

McKeon

Shuster

2014

Geochem Geophys Geosyst

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The ability to constrain km-scale exhumation with apatite 4 He/ 3 He thermochronometry is well established and the technique has been applied to a range of tectonic and geomorphic problems. However, multiple sources of uncertainty in specific crystal characteristics limit the applicability of the method, especially when geologic problems require identifying small perturbations in a cooling path. Here we present new 4 He/ 3He thermochronometric data from the Appalachian Mountains, which indicate significant parent nuclide zonation in an apatite crystal. Using LA-ICPMS measurements of U and Th in the same crystal, we design a 3-D model of the crystal to explore the effects of intracrystal variability in radiation damage accumulation. We describe a numerical approach to solve the 3-D production-diffusion equation. Using our numerical model and a previously determined time temperature path for this part of the Appalachians, we find excellent agreement between predicted and observed 4 He/ 3 He spectra. Our results confirm this timetemperature path and highlight that for complex U and Th zonation patterns, 3-D numerical models are required to infer an accurate time-temperature history. In addition, our results provide independent and novel evidence for a radiation damage control on diffusivity. The ability to exploit intracrystal differences in 4 He diffusivity [i.e., temperature sensitivity) greatly increases the potential to infer complex thermal histories.

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Quantifying the diffusion kinetics and spatial distributions of radiogenic 4He in minerals containing proton-induced 3He

Cited by 132 publications

References 24 publications

Numerical investigations of apatite ⁴He/³He thermochronometry

Numerical investigations of apatite ⁴He/³He thermochronometry

On the degassing state and the chemical structure of the Earth's interior inferred from noble gas isotopes-Past and recent views

Incorporating 3‐D parent nuclide zonation for apatite ⁴He/³He thermochronometry: An example from the Appalachian Mountains

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Quantifying the diffusion kinetics and spatial distributions of radiogenic 4He in minerals containing proton-induced 3He

Cited by 132 publications

References 24 publications

Numerical investigations of apatite 4He/3He thermochronometry

Numerical investigations of apatite 4He/3He thermochronometry

On the degassing state and the chemical structure of the Earth's interior inferred from noble gas isotopes-Past and recent views

Incorporating 3‐D parent nuclide zonation for apatite 4He/3He thermochronometry: An example from the Appalachian Mountains

Contact Info

Product

Resources

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Numerical investigations of apatite ⁴He/³He thermochronometry

Numerical investigations of apatite ⁴He/³He thermochronometry

Incorporating 3‐D parent nuclide zonation for apatite ⁴He/³He thermochronometry: An example from the Appalachian Mountains