Kimberlite CraterThis photograph captures a remarkable spot, a single volcanic crater from the Igwis

Kimberlite CraterThis photograph captures a remarkable spot, a single volcanic crater from the Igwisi Hills in Tanzania. This and the surrounding craters are the youngest known example of a kimberlite eruption on Earth.Kimberlites are themselves unique geologic systems. They’re well known as the major source of diamonds to the surface and therefore they are mined around the world in sites like this one in Russia, one of the world’s deepest mine pits http://tmblr.co/Zyv2Js1VUXqS4. They also have been used as guides for what is happening inside the Earth; hints at certain types of plume activity within the mantle.No one has ever seen a Kimberlite eruption. These volcanoes are about 2 million years old and the most recent known kimberlite eruption before this site is about 40 million years old. However, because of their link to diamond mining, we know a lot about their eruptive processes.When found at the surface, Kimberlites form extremely vertical paths with brecciated (broken) rocks at the top. They appear to produce explosive eruptions that break through the crust and toss out a mixture of magma and chunks of the surrounding rock.The evidence from sites like this one suggest that the eruptions are explosive and violent, but not extremely so. You wouldn’t want to be near this site during the eruption of a kimberlite, there would be lots of rocks and debris thrown out near the site of the eruption but it wouldn’t necessarily be obviously more threatening on a regional scale than a standard volcanic eruption.That the surface expression of a this kimberlite can be described as a weak explosive eruption stands in sharp contrast to the processes that bring them to the surface. A kimberlite eruption is able to sample diamonds because it starts at extreme depths. Most magma chambers in the crust sit only a few kilometers below the surface, but a kimberlite eruption starts several hundred kilometers deep, sometimes even in the lower mantle (over 700 kilometers deep). The vertical path represented by kimberlite mines testifies to this deep origin; by the time they reach the surface they are traveling through an enormous vertical pipe.Kimberlite eruptions are thought to start from a unique chemical process. They start from carbon-rich fluids within the mantle, the same sort of fluids that might produce diamonds under the right conditions. Those carbon-rich fluids can begin interacting with some of the minerals of the mantle and pick up silica. As they absorb silica, the carbon dioxide is pushed out of the fluid, causing it to separate into a buoyant gas phase. As the kimberlite starts moving up, it interacts with more mantle minerals and picks up more silica, driving even more CO2 into the gas phase. The more it moves, the more CO2 goes into the gas phase, causing the magma to bubble and basically foam. The CO2 gas foam builds up enough stress on the mantle that it actually breaks its way through the entire planet.As that fluid fractures its way upward it picks up chunks of anything it passes through, including possibly diamonds. Sometimes it drops those rocks, sometimes they interact with the fluid, and sometimes they’re lost in the crust. By the time it reaches the surface, it will have created a pipe hundreds of kilometers deep. The CO2 then rushes out at the surface, creating a weak explosive eruption and throwing debris out into cones like these.Not every kimberlite eruption carries diamonds with it and some may have slightly different chemical origins. The eruptions on this site probably continued over a period of weeks, creating several craters fed by the same pipe at depth. Despite being presented as some of the most violent events on Earth, fracturing the planet for hundreds of kilometers, the surface expression of kimberlite eruptions can be surprisingly subdued.-JBBImage credit: Dr. Richard Brown (With permission)http://link.springer.com/article/10.1007/s00445-012-0619-8Read more:http://www.livescience.com/10727-discovering-earth-hidden-diamonds-easier.htmlhttp://www.sciencedaily.com/releases/2012/01/120123094523.htmhttps://lithics.wordpress.com/2012/06/18/diamond-geyser-anatomy-of-a-kimberlite-eruption/http://www.britannica.com/science/kimberlite-eruption -- source link

More pics about