A conceptual model for kimberlite emplacement by solitary interfacial mega-waves on the core mantle boundary |
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| Authors: | BL Sim FP Agterberg |
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| Institution: | aOttawa-Carleton Geoscience Centre and Department of Earth Sciences, University of Ottawa, 140 Louis Pasteur St, Ottawa, Ont., Canada K1N 6N5;bGeological Survey of Canada, 601 Booth St., Ottawa, Ont., Canada K1A 0E8 |
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| Abstract: | If convection in the Earth's liquid outer core is disrupted, degrades to turbulence and begins to behave in a chaotic manner, it will destabilize the Earth's magnetic field and provide the seeds for kimberlite melts via turbulent jets of silicate rich 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 differential behind the wave front then 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 turbulence transmission between layers is justified using a simple three-layer liquid model. The core derived melts eventually become frozen in place as localised topographic highs in the Mohorovicic discontinuity (Moho), or as deep rooted intrusive events. The intrusion's final composition is a function of melt contamination by two separate sources: the core contaminated mantle base and subducted Archean crust. The mega-wave hypothesis offers a plausible vehicle for early stage emplacement of kimberlite pipes and explains the age association of diamondiferous kimberlites with magnetic reversals and tectonic plate rearrangements. |
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| Keywords: | Core D″ layer Diamonds Kimberlite Rogue waves Ultra low velocity zone (ULVZ) |
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