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Minerals Report - International Seabed Authority

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4.7.2 How marine gas hydrate deposits are formed<br />

Gas hydrates form and accumulate where marine sediments contain<br />

suitable and sufficient dissolved gas and where the geothermal (sub-surface<br />

temperature gradient) conditions are within the stability field of the hydrate.<br />

The source of the dissolved gas is from the breakdown of organic matter<br />

trapped within the sediment. Therefore, the un-oxidsed organic carbon<br />

content of the sediment is a significant factor in determining the potential for<br />

gas generation.<br />

The methane hydrate pressure (depth) - temperature stability field<br />

(Figure 26) shows that these conditions may be met at water depths greater<br />

than about 500m on the continental slope (dependant on bottom water<br />

temperature) reaching some depth beneath the deep seafloor (determined by<br />

the geothermal gradient).<br />

IINTERNATIONAL SEABED AUTHORITY 728

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