Hydrous mantle transition zone indicated by ringwoodite included within diamond

For 50 years Earth scientists have predicted, from seismology and lab experiments, the presence of ultra-high pressure forms of the mineral olivine - “peridot”, deep in the Earth.  But no specimen has ever been recovered in its original form.  25 years ago scientists began to predict that such high-pressure olivines might contain vast amounts of water, locked deep in the Earth, but such a notion has remained highly controversial, with many scientists maintaining that the deep Earth is a desert in terms of water.  Our international team has settled both issues with one discovery - a tiny mineral called ringwoodite, the highest pressure form of olivine predicted to exist, found within a diamond from Brazil.  Using 3 different micro-beam analytical techniques we show that a special region of the Earth, between 400 and 700km, known as the "transition zone", is an oasis of water in an otherwise very dry deep interior.  This zone could contain a whole ocean mass of water, recycled from Earth’s surface.  Its presence may be responsible for many of the tectonic and volcanic features that make Earth such a unique planet.

Listen to Nature podcast (Secret Sea: starts at about 6:35)

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