Sedimentology of hot spring systems

Abstract

Hot springs and geysers hold a special fascination for many people. To the casual visitor and tourist, they provide a powerful visual display of nature at work. If their temperature is tolerable, “taking the waters” can provide relaxation, comfort, and alleged health benefits. To the scientist, however, terrestrial hydrothermal systems are of major importance in many disciplines. They serve as models for understanding the processes in the shallowest part of the geothermal systems that produce epithermal mineral deposits. They are commonly the surface manifestation of large subsurface geothermal systems that may be tapped for geothermal energy. Their fascinating ecosystems are dominated by diverse arrays of microorganisms, many of which thrive in waters of extremely high temperatures and compositions that are toxic to all other organisms. Although the life of a geothermal system may be geologically brief, typically lasting only a few hundred to a few hundred thousand years, many hot springs leave a tangible record of former activity in the deposits that were precipitated in and around their vents. These hot spring deposits, which are composed mainly of calcium carbonate (travertine) and silica (siliceous sinter), are the topic of this Special Issue. Hot spring deposits have been studied seriously for more than a century. The pioneer of their detailed study was Walter Harvey Weed, who in the 1880s was one of the first to examine the deposits of siliceous sinter and travertine at Yellowstone National Park in Wyoming, U.S.A. More than a century ago, Weed (1889 a , 1889 b , 1889 c ) recognized that the abundant microorganisms that inhabit spring environments may play a role in the formation of travertine and sinter. The subsurface geothermal systems that feed hot springs were widely studied with a view to understanding and predicting epithermal mineralization. Interest in surface hot spring deposits, however, …