New Historian

Wits Diamonds Are a Geoscientist's Best Friend

A cluster of witwatersand diamonds

<![CDATA[Three diamonds, formed billions of years ago and unearthed from an ancient rock formation sometime between 1890 and 1930, have revealed some of the planet's closely held secrets regarding what the Earth was like billions of years ago. The goal of the research was to determine when modern plate tectonics began occurring on the planet, a question that doesn’t naturally lead most people to look around for diamonds. However, the green Witwatersrand (Wits) diamonds (named after the region where they were discovered) are ancient – the sedimentary rock they were extracted from is approximately 3 billion years old and the diamonds themselves are even older. Because diamonds are one of the hardest materials on Earth, they can act as perfect time capsules. The chemical composition of a diamond can indicate what was happening during the very early days of Earth’s history, at least as far back as the diamond's formation. The path from the Wits diamonds to plate tectonic activity goes like this: diamond formation occurs much deeper than where the Wits diamonds were discovered – between 7 km and 2800 km below Earth's surface, within the Earth’s mantle. Then consider that the composition of the nitrogen isotopes trapped within the Wits diamonds are associated with sedimentary sources – meaning the nitrogen incorporated into the diamonds at the time of their formation came from the Earth’s surface rather than from the Earth’s mantle. Plate tectonics as we know it today is the planet’s mechanism for moving material from its surface to its middle, therefore, researchers have concluded that plate tectonics was occurring at the time the Wits diamonds were formed. Additionally, the analysis has also determined that the diamonds were formed around 3.5 billion years ago. Since diamonds themselves can’t be dated directly researchers often use radiogenic isotopes to date the mineral deposits (called inclusions) found within them on the assumption the diamond and the inclusion were formed simultaneously. Planet Earth is around 4.5 billion years old, and there are records of rocks that existed about four billion years ago. It is the complexities involved in the preservation history of a majority of ancient rocks and their exposure to natural and human elements that have led to an ongoing (some even describe it as heated) debate among geoscientists as to when plate tectonics started on the planet. Many experts believe plate tectonics started sometime within the Archean eon (approximately 4 to 2.5 billion years ago). As a planet, Earth is unique due to the plate tectonics process which constantly moves material from its surface to its mantle, a process that’s key to the shaping of Earth landscapes as they are today as a result of the earthquakes, eruptions, etc., plate tectonics causes. The Witwatersrand diamonds were provided to the research group, which was comprised of researchers from Wits University, the University of Johannesburg and the University of Alberta (Canada), by the Museum Africa, in Johannesburg. Image courtesy of Wits University]]>

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