Connection between the neutrino seesaw mechanism and properties of the Majorana neutrino mass matrix

If it can be ascertained experimentally that the $3\times 3$ Majorana neutrino mass matrix ${\mathcal{M}}_{\nu }$ has vanishing determinants for one or more of its $2\times 2$ submatrices, it may be interpreted as supporting evidence for the theoretically well-known canonical seesaw mechanism. I show how these two things are connected and offer a realistic ${\mathcal{M}}_{\nu }$ with two zero subdeterminants as an example.