Interesting link. Thank's Chris. I was unaware of pseudotachylite.

After sleeping on the idea I've realized a few things.

For one, my analogy to the soldering iron isn't so good. The reason the tip gets so hot is that there's 80 watts going in, but the only place it can go out is through conduction to the surrounding air, which is not very efficient. I bet if I stuck that soldering iron in a some rock/clay it wouldn't get so hot. The rock would act as a heat sink to draw the heat away.

So although there is significant power over the fault plane, I failed to realize the massive heat sinks on either side of plane, the crust itself.

On the other hand, I think there may have still been a sufficient heat impulse in the area of maximum slippage to overcome the thermal conductivity of the rock and possibly melt some of the material. I'm not sure I could estimate it accurately enough. Crunching the numbers wouldn't be so hard, just finding the accurate numbers.

You mentioned the subduction zone being loaded with fluids. As I understand it, it is these fluids which lower the melting point of the rock, which eventually leads to the volcanism seen further 'down range' in subduction zones.

Brian