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As old as the seas

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23.04.2003

Leeds scientists are to investigate the birthplace of life – sea water billions of years old – with new high-tech laser equipment, the first of its kind in the UK.

The ancient sea water is found trapped in tiny pockets – called fluid inclusions – within crystals such as emerald and quartz. The oldest known examples are found in the rock 3.8 billion years old – the oldest land on the planet. Although liquid water is believed to have existed on earth over 4 billion years ago, obtaining samples from that time is impossible.

The Leeds scientists are using quartz formed from lava flow under the sea, which hasn’t been affected by geological processes, ensuring the pockets of water remain exactly as they were when the rock was formed. They are analysing rock from 3.8 to 3.2 billion years ago, to see how the sea changed during that time and how that might have affected the first life forms.

Dr David Banks said: “The sea was the birth place of life as we know it, where the first biological molecules and microbes formed. It was a major factor in limiting the levels of oxygen in the earth’s early atmosphere at concentrations much lower than we have today. Understanding its composition at the time the first life on Earth emerged will help us learn more about how the process began and how the first forms of life came about.”

Traditional methods of analysis involve crushing small pieces of the crystal to open the inclusions and dissolving the salts with water before using conventional methods to determine the composition. "The crystals we are analysing contain very few inclusions," said Dr Banks. " These methods couldn’’t be used in our case, as thousands of inclusions need to be tested at once to get a result, and you can mix up different ages of sea water. We needed to look for another way."

The scientists gained funding for specialised equipment – the first in the UK – which uses a laser to ‘drill’ into a single inclusion (normally between one hundredth and one thousandth of a millimeter in diameter). The high temperature then vapourises the sea water, allowing its chemical composition to be analysed in a mass spectrometer. The equipment is called a laser ablation inductively coupled plasma mass spectrometer (ICPMS).

The ICPMS is part of two new £900K laboratories, which also include state-of-the-art equipment for dating geological samples, through their isotopic composition.

Abigail Chard | Source: alphagalileo
Further information: www.leeds.ac.uk/media/current/seawater.htm

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