Radiation Measurements 42 (2007) 190 – 197 www.elsevier.com/locate/radmeas Luminescence property of volcanic quartz and the use of red isothermal TL for dating tephras S. Tsukamoto a , b, ∗ , A.S. Murray b , S. Huot b , T. Watanuki c,  , P.M. Denby d , L. BZtter-Jensen d a Department of Geography, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan b Nordic Laboratory for Luminescence Dating, Department of Earth Sciences, Aarhus University, Ris National Laboratory, Roskilde DK-4000, Denmark c Department of Geosciences, National Taiwan University, Taipei 106, Taiwan, ROC d Radiation Research Department, Ris National Laboratory, Roskilde DK-4000, Denmark Received 12 April 2006; received in revised form 18 June 2006; accepted 27 July 2006 Abstract An optically stimulated luminescence (OSL) age obtained from a Japanese tephra using quartz phenocrysts severely underestimated the known age. The characteristics of the OSL signals were investigated in order to understand the cause of the underestimation; the main OSL component of volcanic quartz has a thermodynamic lifetime of about 1700 years at room temperature, and it also seems to fade anomalously (i.e. athermally). Measurement of conventional red thermoluminescence (RTL) using a Ga–As photomultiplier tube was difficult due to the presence of a strong thermal background, although RTL gave an age consistent with the independent age. Furthermore, red isothermal TL (RITL) at 380 ◦ C allowed the RTL signal to be separated from to the thermal background, and RITL ages of three volcanic quartz samples show good agreement with independent ages. © 2006 Elsevier Ltd. All rights reserved. Keywords: OSL; Red TL; Volcanic quartz; Fading 1. Introduction Volcanic quartz phenocrysts crystallize above the – tran- sition temperature (at 573 ◦ C) in the magma chamber, and cool very rapidly during volcanic eruption. They have more lattice defects and impurities than plutonic quartz due to the fast cool- ing rate (Hashimoto et al., 1993; Müller et al., 2003), and this makes the luminescence characteristics of volcanic quartz dif- ferent from plutonic quartz; the latter provides the majority of quartz found in terrestrial sedimentary deposits. Luminescence from volcanic quartz is characterized by a strong red thermo- luminescence (RTL; Hashimoto et al., 1986, 1987; Fattahi and Stokes, 2003; Rink et al., 1993), centered at around 620–625 nm (Hashimoto et al., 1987; Fattahi and Stokes, 2000). The RTL  Deceased. ∗ Corresponding author. Now at Institute of Geography and Earth Sciences, University of Wales, Aberystwyth SY23 3DB, UK. Tel.: +44 1970 622541; fax: +44 1970 622659. E-mail address: stt@aber.ac.uk (S. Tsukamoto). 1350-4487/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2006.07.008 of volcanic quartz is thermally stable, and has a reproducibility within around 10% and a high saturation dose (D o =∼ 6 kGy, Fattahi and Stokes, 2000), which makes it useful in the dat- ing of tephras (Pilleyre et al., 1992; Fattahi and Stokes, 2000; Ganzawa et al., 2005). However, there is a major difficulty in distinguishing the 380–390 ◦ C TL peak from black body ra- diation, and this has prevented RTL dating of volcanic quartz from becoming a routine method. Little is known about optically stimulated luminescence (OSL) from volcanic quartz. Bonde et al. (2001) reported an OSL age underestimation of more than a factor of 10 using quartz from a soil sample underlying the Capa Riva ignimbrite from Santorini, Greece. Tsukamoto et al. (2003) investigated the OSL components of volcanic quartz from Japan and found them to be different from sedimentary quartz; the main com- ponent, similar to Slow 1 (S1) of Jain et al. (2003), showed strong thermal transfer after heating. In this paper, we investigate the OSL characteristics of vol- canic quartz in more detail. These include: OSL components,