Recent studies showing the decoupling of the lithosphere from the underlying asthenosphere hints that other, equally important, driving forces for plate tectonics are required. A very useful paper on this discussion is Riguzzi et al. 2009, tectonophysics. 

In addition, here are some new articles.

https://phys.org/news/2017-07-link-continental-breakup-volcanic-carbon.html

https://phys.org/news/2017-05-whole-mantle-convection-tectonic-plates-long-term.html

https://phys.org/news/2017-05-birth-death-tectonic-plate.html

https://phys.org/news/2017-01-earth-core-underlying-plate-tectonics.html

https://phys.org/news/2015-09-scientists-tectonic-plates-collide.html

https://phys.org/news/2015-02-dynamite-explosions-reveal-secrets-tectonic.html

https://www.eurekalert.org/pub_releases/2014-11/uonr-sst110414.php

https://phys.org/news/2014-10-air-earth-tectonicplates.html

https://phys.org/news/2014-04-plate-tectonics.html

http://physicstoday.scitation.org/do/10.1063/PT.5.027820/full/

https://www.eurekalert.org/pub_releases/2013-09/scp-scp091113.php

https://phys.org/news/2013-06-lubricant-reassessment-role-plate-tectonics.html

https://phys.org/news/2013-03-hidden-magma-layer-scientists-lubricant.html

https://phys.org/news/2013-03-congestion-earth-mantle-plate-tectonics.html

http://physicsworld.com/cws/article/news/2013/mar/20/deep-sea-imaging-reveals-how-tectonic-plates-slide

https://phys.org/news/2011-03-viscous-quartz-key-tectonics.html

Regards,

Joachim

Some great citations.

Convection currents in a solid are not such an acceptable idea from the point of view of physics. Such currents are inherent in more liquids.

Massive global hydrothermal water flows may act as a lubricant to allow movement of plates?

 Any lubricant can provide the conditions for movement. But for the most distant horizontal motion of the plates (even if lubricated) very powerful forces are needed. Perhaps the spreading of plumes can cause collisions, obduction, subduction (limited by the same spatial framework as the collision).

I do not know anything about global hydrothermal flows. Do you mean asthenosphere?

Gentlemens, it seems to me that we are looking for a mechanism for a phenomenon that has not yet been fully proved? The kinematics of the long-distance movement of plates do not get caught up globally. Perhaps it is more rational to retreat back to the time of the birth of platectonics and to assess its compliance with new facts about the structure of the crust and mantle?

Would very high radiogenic heat flow enable earth expansion and hydrothermal fluid flow, and so plate movement?

Yes, perhaps, but where do you see the source of this radiogenic heat? At what depth?

Accelerated radioactive decay?

Deuteronomy 32:22 Earth's foundations on fire!?