Chapter 15
Submarine hydrothermal vents
Studies in the early 1970s by J. (Jack) B. Corliss (1973) suggested that basalt dredged
from crustal spreading centers along mid-ocean ridges had been strongly modified by
percolation of very hot seawater next to them. He assembled an impressive array of
circumstantial evidence to that effect, much of it derived from isotopic comparisons of
rocks from various sites. Without having seen a submarine geyser, he drew a diagram
of water moving down through sediments and basalt in the vicinity of a subsurface
magma intrusion then entrained upward into a convectively driven spring above it, a
submarine geyser. Nearly identical diagrams are used to describe the sub-seafloor
circulation around vents now that they are found and well studied. Corliss argued that
many terrestrial sulfide-rich ore bodies were in fact precipitated along submarine
spreading axes, eventually buried in sediment, subducted with their tectonic plate,
and, finally, uplifted with continental mountain ranges. His model for the
concentration process was simply stated (Box 15.1).
Box 15.1 From “The sea as alchemist” (Corliss
1973)
(^) “Most of the metals of economic interest are the last metals to crystallize in the slowly cooling lavas.
These minerals occupy grain boundaries in the rocks and thus are accessible to leaching by the
circulating, heated seawater through the formation of soluble chloride complexes ... Interaction of
seawater and basalt leads, at shallow depth, to simple leaching of rocks with little apparent
alteration of the major mineral phases. At somewhat greater depths and higher temperatures, the
interaction leads to alteration of major mineral phases and conversion of basaltic rocks to
greenschists. During such alteration, considerable iron is leached from the rocks along with lesser
amounts of manganese, copper, nickel, lead, cobalt, and other metals. The remaining iron is
extensively oxidized from its initial reduced state in the magma. This oxidation is coupled with
reduction of the sulfate in seawater which initiates the precipitation of the metals from solution as
sulfides. The solutions rise and are vented into seawater as submarine hot springs. A reddish-brown
precipitate of iron hydroxide then forms, incorporating other metals in the hydrothermal solutions
and scavenging elements from the overlying seawater. Most of the precipitate settles, forming a layer
of metalliferous sediment around the vent. Some fraction may be more widely dispersed into the
seawater ...”
Corliss and a group of marine geologists and chemists, mostly from Oregon State
University, advanced arguments that a submersible should be sent to examine these
submarine “geysers”, if in fact they existed. Considerable work went into getting the
expedition approved, but finally in 1977 the group set sail aboard the Woods Hole