“…upflow of fluids transporting heat from depth to shallower reservoirs (or the surface)…”
The majority of current operating Geothermal power plants are utilising convection-dominated play systems to successfully access heat resources.
For the plays shown, there are not necessarily always surface manifestations (“Blind Geothermal”)
Ref. Inga S. Moeck, Graeme Beardsmore, Colin C. Harvey “Cataloging Worldwide Developed Geothermal Systems by Geothermal Play Type”, Proceedings World Geothermal Congress 2015, Melbourne, Australia, 19-25 April 2015