The examination of hot springs (hydrothermal systems) along volcanically active areas of the seabed leads to the understanding of the processes that shape the surface of the earth and globally influence the chemistry of seawater. The formation of these hot springs is based on the convection of seawater through the oceanic crust. During this convection process the seawater gets transported deep into the crust and is thereby heated and chemically altered. When it is reemitted at the seafloor into the ocean the water has a high temperature (ca. 400 °C) and the reaction with the normal (unaltered) seawater causes the formation of metal-sulfide deposits. Because the shapes of this deposits look like factory chimneys these objects are called “black smokers”. In some cases these sulfide deposits contain a substantial amount of copper and zinc as well as precious metals like gold and silver and may therefore be interesting as a reservoir for the raw material supply in the future.
The understanding of these hydrothermal systems is complicated by the lack of information from the interior of these systems. Only few deposits were examined by drilling ships in the course of the Ocean Drilling Program (former ODP, now IODP). We therefore increasingly use portable drilling platforms which enable us to gain more information on the bedrock (5-15 m) with considerable less effort.
The goal of the research project PALINDRILL was to gain information about the third dimension of an active hydrothermal system that was formed at shallow water depth and in an island arc by using a mobile shallow drilling methods (<5 m using the ROCKDRILL 1 of the British Geological Survey). Such deposits are commonly enriched in precious metals and yet sparsely examined worldwide. They represent a modern analogue to terrestrial deposits which are an important source for metals such as copper, zinc, gold, silver and even high-tech metals such as Indium, Bismuth, or Germanium. The examination of deposits originated from such a geotectonic setting plays an important role in understanding the formation processes of these deposits (in general).
There are three deposits of this kind in the Tyrrhenian Sea in a water depth of < 100 to 1000 metres. They are characterized by boiling processes of the ascending hydrothermal fluids and a substantial amount of magmatic volatiles (CO2 and other gases).
With this project we want to examine to what extent the formation of sulfide deposits is determined by the composition of the surrounding rock. On the basis of the rock alteration processes in the drill core samples the origin, nature and evolution of the sulfide-forming hydrothermal fluids was to be reconstructed. We also wanted to investigate whether the input of magmatic volatiles into the shallow (< 1000 m) hydrothermal systems of the Tyrrhenian Sea is a pre-condition for the high precious metal and trace metal element amounts in this system or if the anomalous high element amounts can be explained by the boiling of the hydrothermal fluids in a shallow water setting.
Furthermore, the nature and adaptation mechanisms of the microorganisms present in the hydrothermal systems of the Tyrrhenian Sea was investigated with respect to the highly gas-rich nature of the fluids and the toxidity of some of the trace elements that are enriched in these deposits.