[Rockhounds] Ultra Rare Diamond Suggests Earth’s Mantle Has an Ocean’s Worth of Water

[Kreigh Tomaszewski]

A beautiful blue flaw in a gem-quality diamond from Botswana is actually a
tiny fragment of Earth’s deep interior—and it suggests our planet’s mantle
<https://www.scientificamerican.com/article/earths-mantle-is-hotter-than-scientists-thought/>
contains
oceans’ worth of water.

The flaw, technically called an inclusion, looks like a fish eye: a deep
blue center surrounded by a white haze. But it’s really a pocket of the
mineral ringwoodite from 660 kilometers down, at the boundary between the
upper and lower mantle. This is just the second time scientists have found
this mineral in a chunk of crystal from this zone, and the sample is the
only one of its kind currently known to science. The last example was
destroyed during an attempt to analyze its chemistry.

“It is incredibly rare to even have a super deep diamond
<https://www.scientificamerican.com/article/new-mineral-discovered-in-deep-earth-diamond/>,
and then to have inclusions is even rarer,” says Suzette Timmerman, a
mantle geochemist and postdoctoral fellow at the University of Alberta, who
was not involved in the new discovery. Finding a ringwoodite inclusion is
even more mind-boggling, she says.

The discovery indicates that this very deep zone of Earth is soggy, with
vast amounts of water locked up tight within the minerals there. Though
this water is chemically bound to the minerals’ structure and doesn’t flow
around like an actual ocean, it does likely play an important role in how
the mantle melts. This in turn affects big-picture geology, such as plate
tectonics and volcanic activity. For example, water could contribute to the
development of areas of mantle upwelling known as plumes
<https://www.nature.com/articles/s41598-019-43103-y>, which are hotspots
for volcanoes.

https://www.scientificamerican.com/article/oceans-worth-of-water-hidden-deep-in-earth-ultra-rare-diamond-suggests/