Absolute Age of Formation and Relative Age of Intrusion of the Kimberlites of Yakutia

Phlogopite from Kimberlite pipes of the Arbarastakhsky massif is 661 million years or Riphean. However, the age of intrusion is shown to be post-Jurassic, i.e. less than 140 million years, on basis of an Upper Jurassic belemnite found in a xenolith. Previous theories of kimberlite formation are reviewed. It is concluded that kimberlite is intruded as a cold solid acting as a fluid under gravitational and tectonic pressures at great depth.–M. Russell