The effects of radiation damage accumulation and annealing on fission-track dating of titanite Eva Enkelmann * , Raymond Jonckheere, Lothar Ratschbacher Institut fu ¨ r Geowissenschaften, Technische Universita ¨ t Bergakademie Freiberg, Bernhard-von-Cottastraße 2, D-09599 Freiberg, Germany Received 6 July 2004 Abstract Fission-track dating of titanite is hindered by the fact that track etching is anisotropic in fresh titanites and becomes isotropic with increasing radiation damage. Independent age determinations with the population method are problem- atic due to different track counting efficiencies (Q) for q s in unannealed and q i in annealed titanite. Independent age determinations with the external detector method depend on correction factors for the track registration geometries (G = 0.5), counting efficiencies (Q) and range deficit (R = 1.38); however, Q is unaffected by annealing. It was attempted to determine GQR through calculation, direct experiment and on the basis of age standards. The direct experiment involves measurements of the ratio of the induced-track densities in titanite and a co-irradiated exter- nal detector. The track densities in the internal titanite surfaces could not be measured but the results for the external surfaces confirm that this approach leads to a significant overestimation of GQR, due to prior annealing. The GQR-val- ues determined on the basis of age standards are consistent with that obtained by calculation assuming that Q  1, although there is no experimental confirmation for this fact apart from their isotropic etching characteristics. The fact that identical GQR-factors were obtained on standards of different age and uranium content suggests that a single GQR-value is appropriate for dating titanites within a broad range of radiation damage. In terms of the f-calibration this implies that a single f-factor is also suitable for dating different titanites. These findings suggest that other factors besides the accumulation of alpha-recoil damage, such as a phase transition, could be co-responsible for the different etching characteristics of annealed and unannealed titanites. Ó 2004 Elsevier B.V. All rights reserved. PACS: 34.50.s; 91.70.c; 23.60.+e Keywords: Fission-track dating; Titanite; Radiation-damage; Annealing 0168-583X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2004.10.084 * Corresponding author. Tel.: +49 3731 393813; fax: +49 3731 393599. E-mail address: eva.enkelmann@geo.tu-freiberg.de (E. Enkelmann). Nuclear Instruments and Methods in Physics Research B 227 (2005) 567–576 www.elsevier.com/locate/nimb