No abstract available

[en] Published in summary form only

[en] Etchable length reduction of thermal-neutron induced fission tracks is observed in four apatites that experienced temperatures no greater than approximately 23⁰C subsequent to track formation. In each apatite, the mean etchable fission track lengths parallel (l_c) and perpendicular (l_a) to the crystallographic c-axis as well as the arithmetic (conventional) mean (1_m) decrease by approximately 0.5 μm during the time interval ∼10 min-∼3 weeks after irradiation. Two crystallographic orientation dependencies of mean etchable fission track length at room temperature are identified: (a) 1_c>1_a in all cases (tracks etched for 25 s at 23⁰C in 5 M HNO₃) and (b) l_a decreases approximately twice as fast as l_c. These measurements strongly support previous suggestions that natural charged-particle tracks in crystalline materials, including fission tracks, undergo slow annealing at low ambient temperatures. The observed sensitivity of induced fission tracks in apatite to low-temperature annealing requires that care be taken to avoid heating apatites before and during track etching for so-called ''initial'' mean track length measurements. (author)

[en] The chief advantage of the fission track (F.T.) technique is that it can be used for dating young volcanic glasses (obsidians) where most other well-established techniques fail. Lipari obsidians from three different lava flows have been dated to check the hypothesis of their historic origin. F.T. dating of Australasian tektites provides evidence in support of different falls in this vast strewn field, as reported elsewhere. (author)

[en] The age of fission tracks and the thermal history are closely related. In addition, fission tracks have different sensitivities on different minerals (apatite, zirconium, titanite), and slight thermal alterations of the minerals can be detected by this method. The technique of fission track dating (Rb/Sr and K/Ar dating) is described and applied to the folding of the Alpine region and the heat-up of the Noerdlinger Ries region as a result of a meteorite impact. Fission track dating is a valuable aid in hydrocarbon prospecting. (DG)

[en] Empirical calculations for estimating dates by the fission track (external detector) method are presented and discussed. It is concluded that estimating the effective ratio of spontaneous to induced tracks from the respective totals of tracks counted is to be preferred in all cases. This can be supplemented, but not replaced, by other methods to provide insight into the quality or special characteristics of the sample under study. Plotting a probability density diagram as described here is recommended for the latter purpose. (author)

[en] A multidisciplinary study of the Uquia Formation has been performed. The results of the paleontologic, paleomagnetic, radiometric and stratigraphic analyses suggest that the superior levels of the formation are equivalent to the 'Marplatense Superior', while the basic ones should be considered older. Radiometric ages have been determined by fission tracks in zircons

[en] By means of the fission track method age determinations were performed on five natural rhyodacitic glasses (volcanic glasses). Although there are relatively great differences between fission track ages and hitherto existing geological classification, a rough correspondence could be found at least for three samples. K/Ar-ages which were determined with the same material are in a higher contradiction to the geological assumptions than the fission track ages. (author)

[en] Recently Miller et al. (1990) published the results of the third interlaboratory comparison of fission-track ages for the 1988 Fission-Track Dating Workshop held at Besancon. The samples distributed to the Fission Track community were a zircon (88-1), two apatites (88-2 and 88-3) and a glass (88-4). The above authors discussed the results and concluded that, whereas zircon 88-1, apatite 88-3 and glass 88-4 seemed to be adequate for interlaboratory comparison, apatite 88-2 needed further investigation because of the wide range in measured age, especially in comparison with apatite 88-3, analysed by the same workers. One of the sample characteristics which could produce a large scatter of age is the large inter-grain track-content variation shown by apatite 88-2. The results of an extensive analysis of apatites 88-2 and 88-3 is presented to support this view. (author)

[en] Published in summary form only