Kimberlite: Diamond-Bearing Rock Discovered in Antarctica

Dec 23, 2013 by Sci-News.com

For the first time, researchers have found kimberlite – a type of volcanic rock that often bears diamonds – in Antarctica.

This map shows the location of Prince Charles Mountains in Antarctica. Image credit: Alexrk2 / CC BY-SA 3.0 / Sci-News.com.

This map shows the location of Prince Charles Mountains in Antarctica. Image credit: Alexrk2 / CC BY-SA 3.0 / Sci-News.com.

Kimberlite is named after the town of Kimberley in South Africa, where the discovery of an 83.5-carat diamond in 1871 spawned a diamond rush.

The rock has been known on all continents except the southernmost one, until now. German and Australian scientists led by Dr Marc Norman from the Australian National University have discovered the eruption of kimberlites in the northern Prince Charles Mountains of Antarctica.

“Kimberlites are of great scientific and commercial importance, as the most deeply derived, direct samples of the Earth’s deep interior, and as the major hosts of diamond,” said Dr Greg Yaxley, also of the Australian National University, who is the first author of the paper published in the journal Nature Communications.

“However, until now, they have been completely unknown from Antarctica presumably reflecting the extensive ice cover, remoteness and harsh climatic conditions for geological mapping,” added co-author Prof Vadim Kamenetsky from the University of Tasmania.

This is a plain light photomicrograph of the Antarctic kimberlites showing porphyritic texture and olivine alignment: olivine (ol) crystals are set in a fine- to coarse-grained groundmass, consisting of phlogopite (phl), calcite (cc), perovskite (pr), apatite and magnetite. Scale bar is 20 μm. Image credit: Gregory M. Yaxley et al.

This is a plain light photomicrograph of the Antarctic kimberlites showing porphyritic texture and olivine alignment: olivine (ol) crystals are set in a fine- to coarse-grained groundmass, consisting of phlogopite (phl), calcite (cc), perovskite (pr), apatite and magnetite. Scale bar is 20 μm. Image credit: Gregory M. Yaxley et al.

“Robust dating of the samples demonstrates that they are part of an approximately 120 million-year-old episode of kimberlite volcanism that occurred over a vast area.”

The discovery is of outstanding scientific importance for an additional reason. The kimberlites are located at the margin of a major Antarctic transcontinental rift, the Lambert Graben, which was reactivated during separation of the Indian and Australia-Antarctica plates during the Cretaceous period.

“The kimberlites are a direct magmatic expression of this reactivation and therefore a direct manifestation of continental-scale tectonic processes,” Dr Yaxley said.

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Gregory M. Yaxley et al. 2013. The discovery of kimberlites in Antarctica extends the vast Gondwanan Cretaceous province. Nature Communications 4, article number: 2921; doi: 10.1038/ncomms3921