Effect of alpha-damage annealing on apatite (U–Th)/He thermochronology

Gautheron, Cécile; Tassan‐Got, L.; Barbarand, Jocelyn; Pagel, Maurice

doi:10.1016/j.chemgeo.2009.06.001

Cited by 329 publications

(412 citation statements)

References 36 publications

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“…While both models discussed in this paper are justified by laboratory data (e.g., Shuster et al 2006; Shuster and) , implementing either model, or other models for the (UTh)/He system in apatite (e.g., Gautheron et al 2009) , requires the assumption that what has been determined in the lab can be accurately extrapolated to geologic timescales and temperatures. Because laboratory experiments are limited to durations orders of magnitude shorter than geologic timescales, we commonly increase experimental temperatures to achieve a similar net effect.…”

Section: Extrapolating From Laboratory Conditions To Geologic Timescalesmentioning

confidence: 99%

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Willett

Fox

Shuster

2017

Earth and Planetary Science Letters

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Widely used to study surface processes and the development of topography through geologic time, (UTh)/He thermochronometry in apatite depends on a quantitative description of the kinetics of 4He diffusion across a range of temperatures, timescales, and geologic scenarios. Empirical observations demonstrate that He diffusivity in apatite is not solely a function of temperature, but also depends on damage to the crystal structure from radioactive decay processes. Commonlyused models accounting for the influence of thermal annealing of radiation damage on He diffusivity assume the net effects evolve in proportion to the rate of fission track annealing, although the majority of radiation damage results from recoil. While existing models adequately quantify the net effects of damage annealing in many geologic scenarios, experimental work suggests different annealing rates for the two damage types. Here, we introduce an alphadamage annealing model (ADAM) that is independent of fission track annealing kinetics, and directly quantifies the influence of thermal annealing on He diffusivity in apatite. We present an empirical fit to diffusion kinetics data and incorporate this fit into a model that tracks the competing effects of radiation damage accumulation and annealing on He diffusivity in apatite through geologic time. Using timetemperature paths to illustrate differences between models, we highlight the influence of damage annealing on data interpretation. In certain, but not all, geologic scenarios, the interpretation of lowtemperature thermochronometric data can be strongly influenced by which model of radiation damage annealing is assumed. In particular, geologic scenarios involving 12 km of sedimentary burial are especially sensitive to the assumed rate of annealing and its influence on He diffusivity. In cases such as basement rocks in Grand Canyon and the Canadian Shield, (UTh)/He ages predicted from the ADAM can differ by hundreds of Ma from those predicted by other models for a given thermal path involving extended residence between ~40 80 ºC.

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Section: Extrapolating From Laboratory Conditions To Geologic Timescalesmentioning

confidence: 99%

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Willett

Fox

Shuster

2017

Earth and Planetary Science Letters

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“…Higher eU in apatite leads to more radiation damage, higher He retentivity, and hence a higher effective closure temperature and a greater accumulation of He for a given cooling history [Flowers et al, 2007]. Alternatively, variations in the effective diffusion domain size could influence the closure temperature of the crystal [Gautheron et al, 2009]. To explore these possibilities, we plotted AHe age versus eU and versus grain size.…”

Section: Apatite (U-th-sm)/he Resultsmentioning

confidence: 99%

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

et al. 2015

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Key points: Data and modeling show Paleogene and middle Miocene cooling episodes  Cooling episodes separated by stable conditions, slow exhumation or subsidence  Extension pattern is compatible with random rift initiation above a plume This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2015TC003949 ©2015 American Geophysical Union. All rights reserved. AbstractThe cooling history of rift shoulders and the subsidence history of rift basins are cornerstones for reconstructing the morphotectonic evolution of extensional geodynamic provinces, assessing their role in paleoenvironmental changes, and evaluating the resource potential of their basin fills. Our apatite fission-track and zircon (U-Th)/He data from the Samburu Hills and the Elgeyo Escarpment in the northern and central sectors of the Kenya Rift indicate a broadly consistent thermal evolution of both regions. Results of thermal modeling support a three-phased thermal history since the early Paleocene. The first phase (~65-50 Ma) was characterized by rapid cooling of the rift shoulders and may be coeval with faulting and sedimentation in the Anza Rift basin, now located in the subsurface of the Turkana depression and areas to the east in northern Kenya. In the second phase, very slow cooling or slight reheating occurred between ~45 and 15 Ma as a result of either stable surface conditions, very slow exhumation, or subsidence. The third phase comprised renewed rapid cooling starting at ~15 Ma. This final cooling represents the most recent stage of rifting, which followed widespread flood-phonolite emplacement and has shaped the present-day landscape through rift shoulder uplift, faulting, basin filling, protracted volcanism, and erosion. When compared with thermochronologic and geologic data from other sectors of the East African Rift System, extension appears to be diachronous, spatially disparate, and partly overlapping, likely driven by interactions between mantle-driven processes and crustal heterogeneities, rather than the previously suggested north-south migrating influence of a mantle plume.

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“…For many others, we have no good understanding of the effects of natural compositional variability or deformational history on diffusivity. This may be particularly problematic for (U-Th)/He thermochronometers; at least in apatite, 4 He diffusivity appears to be affected by radiation damage that increases with age and uranium content (Gautheron et al, 2009;Shuster et al, 2006). The experiments necessary to improve our understanding of such phenomena are difficult and time-consuming, but they are of tremendous importance.…”

Section: Directions For Future Researchmentioning

confidence: 97%

Thermochronology in Orogenic Systems

Hodges

2014

Treatise on Geochemistry

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Effect of alpha-damage annealing on apatite (U–Th)/He thermochronology

Cited by 329 publications

References 36 publications

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

A helium-based model for the effects of radiation damage annealing on helium diffusion kinetics in apatite

Cenozoic extension in the Kenya Rift from low‐temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa

Thermochronology in Orogenic Systems

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