Journal of Petroleum Geology, Vol.7, No.4, pp.365-380, 1984

©Copyright 2000 Scientific Press, Ltd.

FISSION TRACK DATING OF AN APATITE CRYSTAL
FROM HORMUZ ISLAND, IRAN

A. J. Hurford*, H. R. Grunau** and J. Stöcklin***

*Abteilungfur Isotopengeologie der Universität Bern, Erlachstrasse 9a, 3012 Bern, Switzerland.

**Petroconsultants S.A., 8-10, Rue Muzy, 1211 Geneve 6, Switzerland.

***Erdbuhlstrasse 4, 8472 Seuzach, Switzerland.

Abstract

Geological evidence points to a Late PreCambrian origin for the Hormuz apatites associated with the red iron oxides, salt and other sedimentary and igneous rocks of the Hormuz Complex. Fission track dating of an apatite crystal from Hormuz Island gives an age of 55.4 ± 2.6 MM* years for a cooling temperature of approximately 100°C corresponding to the Paleocene-Eocene boundary. This result is interpreted in the light of the burial and temperature history of the apatite associated with the Hormuz salt. It is concluded that the apatite clock registers the time elapsed since the temperature decreased to 100°C at the Paleocene-Eocene boundary. Steady cooling took place thereafter due to the continuing upward movement of the salt plug until Quaternary times. The stratigraphic position which the salt diapir (with the associated apatite) had reached 55 MM years ago corresponds to a level somewhere within the Triassic sequence. This would have been the zone of oil generation in Paleocene-Eocene time, assuming that a source rock was present. Interpretational uncertainties are due to in sufficient knowledge of the paleotemperature regime and of the stratigraphy and sedimentary thicknesses of the complete sequence down to the PreCambrian. In addition, it is not possible to draw far-reaching conclusions based on the dating of only one sample.