JC007: Drilling the Mid-Atlantic Ridge


Cruise diary

Day 21: Sunday 25 March
Sampling area: TOBI survey


Sam writes:

Michelle, Chris, Kay and I all have different objectives to meet during our voyage, because our PhDs focus on different topics. Chris processes the TOBI data using specialist software, Kay works on the fabric of rocks (the structures and alignments that develop due to the different forces the rock has experienced as it formed, and as it is uplifted and faulted), and Michelle and I are geochemists.

Geochemists are interested in the chemistry of the rocks, and the minerals that they contain.

When at sea, the geochemists concentrate on describing and labelling the rock samples that they collect. When a dredge or a rock drill is brought to the surface, we clean the samples to get rid of seafloor sediment, then dry, label, and photograph the samples so that we know exactly where they were found. Describing the rocks is the next task. We do this by examining the rocks under a magnifying hand-lens to check which minerals are present. Some of the samples have been highly altered because they have been infiltrated by seawater and serpentinised, whilst others keep more of their original composition. It is important that we collect some fresh, less altered rocks, because these are the samples that we will be able to analyse in our chemistry labs when we get back to our universities.

The chemical data we collect from these rocks will give us a ‘fingerprint’ signature of the mantle they formed from, and help us to build up a better picture of why there is so little melt at the ridge, which will help us to understand why the crust is so thin and why the mantle rocks are exposed here.

Check tomorrow’s diary to learn more about Chris’s work!



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February 2007