Alpha-recoil tracks in natural dark mica

Dating geological samples by optical and scanning force microscopy

U. A. Glasmacher*, M. Lang, S. Klemme, B. Moine, L. Barbero, R. Neumann, G. A. Wagner

*Corresponding author for this work

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Alpha-recoil tracks (ART) are lattice defects caused by the α-decay of 238U, 235U, 232Th, and daughter products. Visualization of etched ARTs in dark mica by phase-contrast microscopy allows dating of Quaternary geological as well as archaeological materials. Visualization of etched ARTs by Nomarski-differential-interference-contrast microscopy (NDICM) and scanning force microscopy (SFM) enables the access to areal densities (ρa) of ART etch pits beyond 104 mm-2 and thus the extension of the new ART-dating technique to an age range >1 Ma. The successful application of SFM as a new tool in geochronology could open the way to a field to be characterized as nanogeochronology. In order to visualize ARTs by NDICM and SFM, dark mica was etched with 4% HF at 21 °C for 5-107 min. A linear relationship between ρa and etching time (te) was observed for phlogopites from the Kerguelen Islands (French territory, Indian Ocean), and the Kovdor magmatic complex (Russia). The volume density (ρv) of ART is a function of etching speed (veff) and slope of the ρa-growth curve. The ART-age equation allows the calculation of an individual ρv-growth curve for the phlogopite analysed by us using the uranium and thorium content. The ART-ages were determined by combining the experimentally obtained volume density with the individual ρv-growth curve.

Original languageEnglish
Pages (from-to)351-356
Number of pages6
JournalNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Volume209
DOIs
Publication statusPublished - Aug 2003
Externally publishedYes

Keywords

  • Alpha-recoil track dating
  • Natural radiation damage
  • Nomarski-differential-interference-contrast microscopy
  • Scanning force microscopy

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