A nifty idea, but there are countermeasures a miner might take that are easy to implement.

a solution of solvent and typical mine explosive, either sprayed over the entire field of installed mines, sprayed over un-mined areas that you'd like to slow them down, or better yet, spray patches randomly over an installed mine field so that there are many false positives, indistinguishable from the tell of a real mine. Do all of these randomly so that a detection will require a thourough seach no matter what. Thats the whole point of a mine field anyway...

Edge a real mine field with 50 meters of false spots. Regions of false spots bordering regions of mines, randomly shaped and sized.

Encapsulate mines with impermeable skin... ziplok?

Saturate the ground with a persistent anti-microbial =)

Saturate only some of the field with anti-microbial =D