Alpha-recoil track dating of Quaternary volcanics

Like fission-track dating, alpha-recoil track (ART) dating is based on the accumulation of nuclear particles that are released by natural radioactivit y and produce etchable tracks in solids. ARTs are formed during the alpha-d ecay of uranium and thorium as well as of Their daughter nuclei. When emitt ing an alpha-particle, the heavy remaining nucleus recoils 30-40 nm, leavin g behind a trail of radiation damage. Through etching the ART tracks become visible with interference phase-contrast microscopy. Under the presupposit ion that all tracks are preserved since the formation of a sample their tot al number is a measure for the sample's age. The technique has already been proposed more than three decades ago [Huang, W.H., Walker, R.M., 1967. Fos sil alpha-particle recoil tracks: a new method of age determination. Scienc e 155, 1103-1106.], but due to inherent difficulties, it was hardly applied or made any substantial progress since then. The present paper describes a methodology by which reliable ART ages of dark mica can be obtained. The t echnique is applicable to tiny (similar to 0.5 mm) single mica flakes in th e 10(2) to 10(6) years age-range. It is tested on Quaternary volcanics from the Eifel region, Germany. Alpha-recoil dating has a great potential for Q uaternary chronometry and tephrochronology. (C) 2000 Elsevier Science B.V. All rights reserved.