The world’s largest source of natural diamonds — and of more than 90 percent of all natural pink diamonds found so far — may have formed due to the breakup of Earth’s first supercontinent, researchers report September 19 in Nature Communications.
On Earth’s surface, carbon atoms tend to form soft, dull graphite. But down in the forge that is the upper mantle, extreme conditions mold the element into hard, dense gemstones (SN: 9/14/20). These diamonds can escape their chthonic womb by hitching a ride in rapidly ascending magmas (SN: 1/18/12). Near the surface, the molten material solidifies as vertical tubes of volcanic rock, known as kimberlite pipes. Most diamonds are found in these formations.
But this classic story does not explain the Argyle formation, nor its pink diamonds. To make a diamond blush, something more powerful than mere mantle conditions must contort its sturdy crystal structure, altering how it absorbs and transmits light.
Another wrinkle lies in Argyle’s diamondiferous pipes. They are not kimberlite, but rather lamproite pipes, which are generally thought to form at shallower depths, says geologist Maya Kopylova of the University of British Columbia in Vancouver, who was not involved in the new study.
2023-09-19 10:00:00
Article from www.sciencenews.org