Abstract
AbstractThis paper reviews four hypotheses for the origin of the continental crust–mantle boundary and discusses seismic parameters with which these hypotheses might be tested. The relict Moho hypothesis posits that the oceanic Moho is preserved during continental assembly; the magmatic underplating hypothesis posits formation of a new Moho by episodic emplacement of sill‐like intrusive bodies; the metamorphic (or metasomatic) front hypothesis posits that the Moho is overprinted by a phase transformation; and the regional décollement hypothesis posits that the Moho behaves as a structural detachment. These hypotheses are not mutually exclusive, and examples from the Canadian Lithoprobe program suggest that all four may be applicable in different regions of North America. Comparison of seismic images from a fossil subduction zone with modern subduction at Cascadia suggests that serpentinization of the forearc mantle, a previously unrecognized mechanism for overprinting and erasing the reflection Moho, may have occurred in the Proterozoic.
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