hy·dro·ther·mal 
(hī′drə-thûrməl)
(hī′drə-thûrməl)adj.
1. Of or relating to hot water.
2. Geology
a. Of or relating to hot magmatic emanations rich in water.
b. Of or relating to the rocks, ore deposits, and springs produced by such emanations.
hy′dro·thermal·ly adv.