Fission track dating of zeolites

The fission track method has become acceptable in geochronology, not only in straightforward dating of igneous and metamorphic events but also in stratigraphic studies by the dating of ash layers(1,2), the elucidation of crustal uplift history(3-7), and in archaeology(8). Such studies have mostly used accessory minerals such as apatite, sphene and zircon, whose track-retentive properties are well documented. However, fission tracks can be developed and observed under the optical microscope in most minerals(9-11). We report here on reconnaissance studies of fission track dating of zeolites, a complex group of tectosilicates, which is, for example, widely developed in basaltic rocks after their emplacement by later stage processes. We describe the etching conditions for some zeolites, in particular the minerals chabazite, stilbite and heulandite(12) and detail the track recording and retention characteristics for chabazite, with particular reference to fossil hydrothermal systems in the Faeroe Islands.