Wednesday, 20 February 2013

14 - Geo team at the Beebe Hydrothermal Vent Field

Beebe black smoker image from previous HYBIS expedition
Looking over the side of the ship into the deep blue of the Caribbean Sea, it is hard to believe that directly below us, almost 5 km (3 miles) down, lies the Beebe Hydrothermal Vent Field, the deepest of its kind yet discovered, and by a team from the National Oceanography Centre. The site is named after William Beebe, the first ecologist to observe deep-sea animals in their natural habitat. Today, we will be diving at the site for the geo team’s first sampling on JC82 with the Isis  ROV.

The extraordinarily high pressure (of 500 x atmospheres) at the Beebe site, situated at nearly double the normal depth of most known hydrothermal systems, is important due to the physical changes that seawater undergoes at extremely high pressures and temperatures. Instead of being a liquid or vapour, the vent fluid becomes supercritical. These supercritical fluids are very reactive, dissolve metals at depth in the Earth’s crust, and transport them to the seafloor where they form spectacular hydrothermal vents and mineral deposits.

The Beebe site is also fascinating because it contains a history of hydrothermal activity represented by a series of older mounds. Sampling them will give us an idea of how the deposit has changed through time. The mineral deposits oxidise (like rusting) to a bright red colour, a process that greatly increases the concentration of valuable metals: a process known as ‘supergene enrichment’.

We are studying the Beebe site because it is a natural laboratory in which to study the effects of temperature and pressure on the composition of hydrothermal mineral deposits. Studying modern day hydrothermal systems like the Beebe Field allows us better to understand the formation of land-based ore deposits from which humankind gets all its essential metals.

By Matt Hodgkinson

Verity teaches Matt a lesson

5 comments:

  1. This is brilliant; every school child should be following this!

    ReplyDelete
  2. And university student!

    ReplyDelete
  3. Thanks Claire Murphy. The Beebe Geo-team dive yesterday was a great success; we sampled the whole Beebe vent field for rocks of different types and are now busy describing and curating them for later analysis in the laboratory.

    ReplyDelete
  4. As the minerals precipitate/crystallize out of the vent fluid, do they emit fluorescence in a process like crystalloluminescence?

    ReplyDelete
  5. Hi Justin. Most of the minerals in the samples that the geo team have collected at the site had already precipitated on the seafloor before we got there. We have sampled actively forming minerals but unfortunately we do not know whether they emit fluorescence as the ROV is not set up do detect this. Thank you for your comment.

    ReplyDelete