Laser depth profiling studies of helium diffusion in Durango fluorapatite

Matthijs Van Soest, Brian D. Monteleone, Kip Hodges, Jeremy W. Boyce

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Ultraviolet lasers coupled with sensitive mass spectrometers provide a useful way to measure laboratory-induced noble gas diffusion profiles in minerals, thus enabling the calculation of diffusion parameters. We illustrate this laser ablation depth profiling (LADP) technique for a previously well-studied mineral-isotopic system: 4He in Durango fluorapatite. LADP studies were conducted on oriented, polished slabs from a single crystal that were heated under vacuum to a variety of temperatures between 300 and 450°C for variable times. The resolved 4He profiles exhibited error-function loss as predicted by previous bulk 4He diffusion studies. All of the slabs, regardless of crystallographic orientation, yielded modeled diffusivities that are statistically co-linear on an Arrhenius diagram, suggesting no diffusional anisotropy of 4He in this material. The data indicate an activation energy of 142.2±5.0 (2σ)kJ/mol and diffusivity at infinite temperature - reported as ln(D0) - of -4.71±0.94 (2σ)m2/s. These values imply a bulk closure temperature for 4He in Durango fluorapatite of 74°C for a 50μm radius grain, infinite cylinder geometry, and a cooling rate of 10°C/Myr.

Original languageEnglish (US)
Pages (from-to)2409-2419
Number of pages11
JournalGeochimica et Cosmochimica Acta
Volume75
Issue number9
DOIs
StatePublished - May 1 2011

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fluorapatite
Helium
Depth profiling
helium
laser
ablation
diffusivity
Lasers
slab
Laser ablation
Minerals
closure temperature
noble gas
mineral
Noble Gases
Ultraviolet lasers
activation energy
Diffusion in gases
anisotropy
Mass spectrometers

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Laser depth profiling studies of helium diffusion in Durango fluorapatite. / Van Soest, Matthijs; Monteleone, Brian D.; Hodges, Kip; Boyce, Jeremy W.

In: Geochimica et Cosmochimica Acta, Vol. 75, No. 9, 01.05.2011, p. 2409-2419.

Research output: Contribution to journalArticle

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