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 radioactivity and produce etchable tracks in solids. ARTs are formed during the alpha-decay of uranium and thorium as well as of their daughter nuclei. When emitting an alpha-particle, the heavy remaining nucleus recoils 30–40 nm, leaving behind a trail of radiation damage. Through etching the ART tracks become visible with interference phase-contrast microscopy. Under the presupposition that all tracks are preserved since the formation of a sample their total number is a measure for the sampleʹs age. The technique has already been proposed more than three decades ago [Huang, W.H., Walker, R.M., 1967. Fossil alpha-particle recoil tracks: a new method of age determination. Science 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 technique is applicable to tiny (∼0.5 mm) single mica flakes in the 102 to 106 years age-range. It is tested on Quaternary volcanics from the Eifel region, Germany. Alpha-recoil dating has a great potential for Quaternary chronometry and tephrochronology.