Emplacement time of the Loe–Shilman carbonatite from NW Pakistan: Constraints from fission-track dating

The Loe–Shilman carbonatite complex is situated in the extreme west of the Peshawar Plain Alkaline Igneous Province (PAIP), near the Pakistan–Afghanistan border. It comprises sill-form bodies emplaced along an E–W trending and N dipping fault zone in Paleozoic to Precambrian metasedimentary rocks of Khyber Agency.Fission-track dating studies on the apatite crystals using the external detector method and age standard approach (the ζζ method) yielded an age of 30.0±1.5Ma for the Loe–Shilman carbonatite. Close agreement between the previously determined radiometric ages from the same as well as the neighboring carbonatite complexes of the PAIP and the fission-track apatite age of this study indicates that the Loe–Shilman carbonatite was emplaced at relatively shallow crustal level and quickly cooled to low temperatures (<60∘C) required for the complete retention of fission tracks in apatite and that the fission-track age of this study is the emplacement age of the Loe–Shilman carbonatite.