Emplacement time of the Loe-Shilman carbonatite from NW PakSUtan: Constraints from fSUsion-track dating

摘要

The Loc-Shilman carbonatite complex SU situated in the extreme west of the Peshawar Plain Alkaline Igneous Province (PAIP), near the PakSUtan-AfghanSUtan border. It comprSUes sill-form bodies emplaced along an E-W trending and N dipping fault zone in Paleozoic to Precambrian metasedimentary rocks of Khyber Agency. FSUsion-track dating studies on the apatite crystals using the external detector method and age standard approach (the method) yielded an age of 30.0 +/- 1.5 Ma 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 fSUsion-track apatite age of thSU study indicates that the Loe-Shilman carbonatite was emplaced at relatively shallow crustal level and quickly cooled to low temperatures (< 60 degrees C) required for the complete retention of fSUsion tracks in apatite and that the fSUsion-track age of thSU study SU the emplacement age of the Loe-Shilman carbonatite.