A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

Abstract

Seventeen wall rock samples close to the contact and seven accidental inclusions have been collected from four South African kimberlite pipes. Magnetic measurements on these samples have been analysed to determine the viscous partial thermoremanence (VPTRM) acquired by them at the time of the emplacement of the kimberlite. Numerical integration of the heat flow equation for a thermal model including convection of the emplaced material has been performed to determine an upper limit for the emplacement temperatures required to cause the observed VPTRM. It is concluded that in these pipes the kimberlitic material, at least down to the levels studied, was almost certainly emplaced at a temperature of less than 350°C. The emplacement temperature cannot have been greatly overestimated and it is suggested that the emplacement temperature was about 300°C. Copyright © 1977, Wiley Blackwell. All rights reserved