Massive diamond cache may be hidden 100 miles below Earth’s surface

Rodiano Bonacci
Luglio 19, 2018

Diamond continues to lure the world for an endless search of it - a treasure hunt of a child's dream that continues to live on in the heart and minds of not only diamond merchants but also in the hearts of the hungry dreamer.

"The velocities that are measured are faster than what we think we can reproduce with reasonable assumptions about what is there..."

To estimate the total mass of diamonds in the Earth, the researchers assumed cratonic roots were 1-2% diamond and combined that with the total volume of cratonic roots distributed throughout the Earth. Scientists have discovered over a quadrillion tons of diamonds hidden deep inside the Earth.

"We can't get at them, but still, there is much more diamond there than we have ever thought before", said MIT's Ulrich Faul, who recently co-authored a paper on this new discovery, published in the journal Geochemistry, Geophysics, Geosystems.

The incredible discovery was made by scientists at MIT, Harvard and the University of California at Berkeley after they analyzed seismic records.

In studying how fast or slow these waves (triggered by earthquakes, tsunamis, explosions, and other ground-shaking sources) move through the Earth, geologists are able to figure out what type of rock the waves are passing through. Seismic data can also be used to effectively see inside Earth, similar to an ultrasound scan. Then came a fun experiment of building virtual rocks of different mineral compositions and calculating the velocity of sound waves in each separate case. This is atleast 1000 times more diamonds than they expected.

Faul said, 'Diamond in many ways is special.

"Only one type of rock produced the same velocities as what the seismologists measured: one that contains 1 to 2 percent diamond", the scientists explained in the study.

Faul and his colleagues calculated that the anomaly could be caused by 1%-2% of diamonds in the 'cratonic roots'. In addition, the small fraction of diamond would not affect the overall density of a craton, which has less density than the surrounding mantle. They're located between 90 and 150 miles below the Earth's surface, which is far deeper than any drills are capable of reaching.

'This is how they preserve the oldest rocks. Down there, diamonds may not be so rare after all - it's just hard for them to make it to the surface and onto the rings and earrings of human beings.

Our continents have "roots" - huge inverted mountains extending deep into our core. The reason why they are rare is that they only get close to the surface in specific eruptions that carve out geological pipes made of a rock called kimberlite.

Diamonds fetch their lofty price tags because they form over millions of years under high pressures and temperatures deep within the Earth's crust.

"It's circumstantial evidence, but we've pieced it all together", Faul says.

This research was supported, in part, by the National Science Foundation.

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