Kimberlite Emplacement: Solitary Mega-Waves on the Core-Mantle Boundary

Bradley L. Sim
University of Ottawa

Frederik P. Agterberg
Geological Survey of Canada

If convection in the earth’s liquid outer core is disrupted by turbulence and begins to behave in a chaotic manner, it may destabilize the Earth’s magnetic field and provide the seeds for kimberlite melts via turbulent jets of core material which invade the lower mantle. These (proto-) melts may then be captured by extreme amplitude solitary nonlinear waves generated through interaction of the outer core surface with the base of the mantle. A pressure differational behind the wave front provides a mechanism for the captured melt to ascend to the upper mantle and crust so quickly that emplacement may indirectly promote a type of impact fracture cone within the relatively brittle crust. These waves are very rare but of finite probability. The assumption of turbulent effects transmission between layers is justified using a simple three-layer liquid model. The core derived melts eventually become frozen in place as localized topographic highs in the Mohorovicic discontinuity, or as deep rooted intrusive events. The intrusions final state composition is a function of melt contamination by two separate sources, the core contaminated mantle base and subducted Archean crust. The mega-wave hypothesis may offer a plausible vehicle for early stage emplacement of kimberlite pipes, carbonates, or orangeite melts and explain the age association of diamondiferous kimberlites with magnetic inversions.  

Created by Mathematica  (April 20, 2004)