On growth and form of etched fission tracks in apatite: A kinetic approach

Jonckheere, Raymond; Wauschkuhn, Bastian; Ratschbacher, Lothar

doi:10.2138/am-2019-6762

Cited by 17 publications

(26 citation statements)

References 47 publications

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“…The latter (vL < vR) implies that the confined tracks length increase at a lower rate than the apatite etch rate. This apparent paradox is nevertheless consistent with the proposed etch model (Jonckheere et al 2019). The endpoints of the track channels are concave and, according to the model, bounded by the slowestetching planes, i.e., the prism and basal planes, with vR ≈ 0.5 µm/min ( Figure 7a).…”

Section: Resultssupporting

confidence: 83%

“…We observed that the present track-etch model is not consistent with mainstream theories of crystal growth and dissolution, and proposed a model that is (Jonckheere et al 2019). The main difference is that the bulk etch rate vB, the etch rate of a point on a surface, is replaced by the radial etch rate vR of a lattice plane as a whole, i.e., its rate of displacement parallel to itself.…”

Section: Introductioncontrasting

confidence: 66%

“…These advantageous properties for practical fission-track dating are however not supported by evidence. Jonckheere et al (2019) argued that the existing etch model cannot account for the dual structure of etched surface tracks, consisting of an etch pit and a track channel, e.g., in an apatite basal face, nor for the variable track shapes in different apatite faces. Measured counting efficiencies are much lower than predicted, and different for an internal surface, external surface, and external detector (Jonckheere 2003;Enkelmann et al 2005;Jonckheere et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…This concept is copied from the theories of Burton et al (1951), Frank (1958) and, among others, Irving (1959), Frank and Ives, (1960) and Jaccodine (1962), which are the basis of modern applications of crystal etching (Woensdrecht 1993;Rakovan 2002;Chernov 2004;Woodruff 2015). On the assumption that the orientations of the apatite basal and prism faces correspond to cusp-like minima in a polar etch rate plot, the proposed model accounts for the default dual structure of etched tracks and for the variation of track shapes with the orientation of the etched surface (Jonckheere et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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A quantitative description of fission-track etching in apatite

Aslanian

Jonckheere

Wauschkuhn

et al. 2021

American Mineralogist

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We measured the apatite etch rate vR in 5.5 M HNO3 at 21 °C as a function of orientation. Results for Durango apatite evidence that vR varies by a factor >5 with angle to the c-axis. Our measurements also provided track etch rates vT and surface etch rates vS. However, these cannot be combined for calculating track etching or counting efficiencies. By inserting the measured etch rates in a recent model, we calculate the geometries and dimensions of surface tracks in different apatite faces. The proposed model must be recalibrated for different etching protocols and adapted for other minerals. We submit that the new model justifies reviewing track counting efficiencies based on the existing (vB-vT) etch model. We anticipate that this will have an effect on practical aspects of fission track dating. Single-track step-etch data show that the confined track lengths increase with etch time at a decreasing average rate vL that differs from the track etch rate vT and the apatite etch rate vR. Both vT and vL exhibit large track-to-track differences that produce irreducible length variation related to the latent-track structure resulting from formation and annealing. Step etching and track width measurements are effective for reducing or eliminating procedure-related artifacts from track length data, and so for accessing more fundamental track properties.

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Section: Resultssupporting

confidence: 83%

Section: Introductioncontrasting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A quantitative description of fission-track etching in apatite

Aslanian

Jonckheere

Wauschkuhn

et al. 2021

American Mineralogist

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“…The probability of a semi-track encountering a confined track at a given depth is proportional to the radius of this etched zone at that depth, increasing as the track widens. Revelation is actually anisotropic based on the shape of the etch figures (Galbraith et al, 1990;Ketcham, 2003) or internal crystallographic planes (Jonckheere et al, 2019), but we omit this consideration for our simplified initial model. Figure 3 shows examples of penetration and revelation rate.…”

Section: Semi-track Penetration and Confined Track Revelationmentioning

confidence: 99%

Confined fission track revelation in apatite: how it works and why it matters

Ketcham¹,

Tamer²

2020

Preprint

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Abstract. We present a new model for the etching and revelation of confined fission tracks in apatite, based on step etching measurements that demonstrate variable along-track etching velocity, vT(x). We define two end-member model forms: Constant-core, with a central zone of constant etching rate that then falls off toward track tips; and Linear, in which etching rates fall linearly from the midpoint to the tips. Based on these, we construct a characterization of confined track revelation that encompasses all of the relevant processes, including penetration and thickening of semi-tracks from the polished grain surface, intersection of confined tracks, and analyst selection of which tracks to measure and which to bypass. Both model forms are able to fit step-etching data from five sets of paired experiments of fossil tracks and unannealed and annealed induced tracks, supporting the correctness of our approach and providing a series of insights into the theory and practice of fission-track thermochronology. Etching rates for annealed induced tracks are much faster than those for unannealed induced and spontaneous tracks, impacting the relative efficiency of both confined track length and density measurements, and suggesting that high-temperature laboratory annealing may induce a transformation in track cores that does not occur at geological conditions of partial annealing. The model quantifies how variation in analyst selection criteria, summarized as the ratio of along-track to bulk etching velocity at the track tip (vT/vB), likely plays a first-order role in the reproducibility of confined length measurements. It also shows that a large proportion of tracks that are intersected are not measured, indicating that length biasing is an insufficient statistical model for predicting the relative probability of detection of different track populations. The vT(x) model provides an approach to both optimizing etching conditions and linking track length measurements across etching protocols.

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Fission Track Dating

Enkelmann

Jonckheere

2021

Encyclopedia of Geology

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On growth and form of etched fission tracks in apatite: A kinetic approach

Cited by 17 publications

References 47 publications

A quantitative description of fission-track etching in apatite

A quantitative description of fission-track etching in apatite

Confined fission track revelation in apatite: how it works and why it matters

Fission Track Dating

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