I know that some labs still measure titanite fission tracks. Why is it not so popular? I assume there are several factors, but the main ones are presumably:

1) A comparatively high closure temperature which nearly overlaps with much more precise techniques such as Ar/Ar on biotite

2) Not so well constrained annealing kinetics, meaning that it is not straight forward to forward model thermal histories vs track length distributions

3) A general trend of stronger developments of the (U-Th)/He techniques and automated analyses of these, which may have partly replaced fission track counting as the "easiest" low temperature thermochronometer. Fission track method development in general is not going very fast nowadays; although combining methods is probably the best approach