#vredefort

[unbfacts]

[keepingitneutral]

Witklipfontein Eco Lodge, 

Schoemansdrift Road, Vredefort District, Free State, South Africa,

Xavier Huyberechts Architect &. Damien Huyberechts (Builder)

[geologyjohnson]

The weird black and pink rock I'm stood next to its called Pseudo-tachylite and it formed in a spectacular and cataclysmic event. Around 2 billion years ago, a 15km wide chunk of rock face planted into what would become south africa at a velocity of around 200,000km+ an hour. It created a crater 60 km deep and 300 km wide with a central uplift region around 17 km high. This was one of the biggest impacts in Earth's history, including being larger than the one that caused the K-Pg. Luckily the microbes that inhabited earth at this time were pretty tough critters so life continued in the aftermath. Today most of the structure has been eroded away, a ring hills 90 km across is all that survives on the surface near the towns of Parys and Vredefort South Africa. These hills represent rock that was tilted upwards by the blast during the impact. The underlying rock made of hard granitic gneiss was shattered and blasted outwards as huge blocks carried in a slurry of melted rock. The melted rock quickly cooled to glass as water poured into the new crater. This rock is the pseudo-tachylite I'm stupid next to in the photo. It was injected into the bedrock in these wonderfully messy veins by the force of the impact. I've wanted to see this place in person for a long time and it did not disappoint! If you are in the area, contact Karen or Graeme at Otters Haunt for a tour of the quarry and the geological details! #geologyjohnson #geology #meteor #crater #pseudotachylite #vredefort #parys #archean #precambrian #paleoproterozoic #SouthAfrica #granite #gneiss https://www.instagram.com/p/Ccc_th8twwv/?igshid=NGJjMDIxMWI=

[earthstory]

Vredefort Granophyre You did not want to be around on the day this rock formed. The Vredefort Granophyre is an igneous rock found in certain parts of an area of South Africa called the Vredefort dome (http://tmblr.co/Zyv2Js1gYAvFm). The Vredefort structure is part of the remnant of an ancient impact crater – a gigantic hole in the ground formed from an asteroid impact just over 2 billion years ago.

The impact of the asteroid delivered a huge amount of energy to the target rocks – so much energy that some of them actually melted. The target rocks were a mixture of metamorphic gneisses and basaltic lava, with minor components of shale, carbonates, and metamorphosed quartz-rich sandstone. A granophyre is a fine-grained igneous rock with quartz and feldspar as the main minerals. That mineralogy actually makes sense – add up the ingredients that melted to make the rock and the end result is something like this molten rock. The granophyre is found filling a series of large cracks called dikes that form a swarm around the center of the crater. The large chunks in it were pieces of shattered rock broken by the impact that were picked up by the melt as it was injected. Although the impact super-heated the rocks that melted, by the time it picked up these chunks it had cooled enough that there wasn’t enough heat left to melt them. As the melt migrated through the cracks and cooled, it picked up and partially melted different components, leading to some variation in the chemistry of the rocks from one side of a dike to the other. The extremely violent processes recorded in this rock – shattering and melting of target rocks – are typical of high-energy, giant impacts on Earth and elsewhere. -JBB Image credit: https://flic.kr/p/oxjhQj Read more: http://bit.ly/1Bm3MnS http://bit.ly/1dtuMNb http://sajg.geoscienceworld.org/content/100/2/115.short http://www.hou.usra.edu/meetings/sudbury2013/pdf/3031.pdf http://adsabs.harvard.edu/abs/2012Icar..219..168L

[earthstory]

Vredefort Granophyre

You did not want to be around on the day this rock formed. The Vredefort Granophyre is an igneous rock found in certain parts of an area of South Africa called the Vredefort dome (http://tmblr.co/Zyv2Js1gYAvFm). The Vredefort structure is part of the remnant of an ancient impact crater – a gigantic hole in the ground formed from an asteroid impact just over 2 billion years ago.

The impact of the asteroid delivered a huge amount of energy to the target rocks – so much energy that some of them actually melted. The target rocks were a mixture of metamorphic gneisses and basaltic lava, with minor components of shale, carbonates, and metamorphosed quartz-rich sandstone.

A granophyre is a fine-grained igneous rock with quartz and feldspar as the main minerals. That mineralogy actually makes sense – add up the ingredients that melted to make the rock and the end result is something like this molten rock.

The granophyre is found filling a series of large cracks called dikes that form a swarm around the center of the crater. The large chunks in it were pieces of shattered rock broken by the impact that were picked up by the melt as it was injected. Although the impact super-heated the rocks that melted, by the time it picked up these chunks it had cooled enough that there wasn’t enough heat left to melt them. As the melt migrated through the cracks and cooled, it picked up and partially melted different components, leading to some variation in the chemistry of the rocks from one side of a dike to the other.

The extremely violent processes recorded in this rock – shattering and melting of target rocks – are typical of high-energy, giant impacts on Earth and elsewhere.

-JBB

Image credit: https://flic.kr/p/oxjhQj

Read more: http://bit.ly/1Bm3MnS http://bit.ly/1dtuMNb http://sajg.geoscienceworld.org/content/100/2/115.short http://www.hou.usra.edu/meetings/sudbury2013/pdf/3031.pdf http://adsabs.harvard.edu/abs/2012Icar..219..168L

[thomarse]

The Vredefort Crater in South Africa. Created by a 15km-wide impact bolide that struck the earth 2 billion years ago. Read more here.

[earthstory]

Ancient Impact

Over 2 billion years ago, a piece of space debris slammed into what today we know as South Africa. That impact created the Vredefort structure, a 250 to 300 kilometer wide crater that dominates the geology of that area. Much of the Vredefort structure has been destroyed by tectonic processes since that impact, but about 1/3 the rim and part of the interior remains.

Today that impact structure is drained by the Vaal River, but the area still bears the scars of that impact right down to the smallest scale. During an impact, a shock wave propagates through the target minerals and can alter or deform their structure. In the mineral quartz, one of the most common minerals in continental crust, offset planes called “planar deformation features” are developed: finding this structure can be diagnostic for finding an ancient impact structure.

Planar Deformation Features show up in these microscope images of quartz; the planar offset patterns are highlighted by arrows. The interesting thing about these grains is they’re not found in the crater itself, they’re found in the Vaal River. These scientists went far downstream of the crater and took scoops of the sediment to see if shock features survive sedimentary transport, even if they’re 2 billion years old, and found that quartz and other minerals do in fact preserve evidence of the ancient impact even when transported downstream. Finding similar shocked grains in other river basins around the world could therefore be used as evidence of ancient impacts somewhere in the river basin being sampled.

-JBB

Image credit: Cavosie et al. (2010) http://gsabulletin.gsapubs.org/content/122/11-12/1968.abstract All scale bars are 250 μm

[earthstory]

Vredefort Granophyre

You did not want to be around on the day this rock formed. The Vredefort Granophyre is an igneous rock found in certain parts of an area of South Africa called the Vredefort dome (http://tmblr.co/Zyv2Js1gYAvFm). The Vredefort structure is part of the remnant of an ancient impact crater – a gigantic hole in the ground formed from an asteroid impact just over 2 billion years ago.

The impact of the asteroid delivered a huge amount of energy to the target rocks – so much energy that some of them actually melted. The target rocks were a mixture of metamorphic gneisses and basaltic lava, with minor components of shale, carbonates, and metamorphosed quartz-rich sandstone.

A granophyre is a fine-grained igneous rock with quartz and feldspar as the main minerals. That mineralogy actually makes sense – add up the ingredients that melted to make the rock and the end result is something like this molten rock.

The granophyre is found filling a series of large cracks called dikes that form a swarm around the center of the crater. The large chunks in it were pieces of shattered rock broken by the impact that were picked up by the melt as it was injected. Although the impact super-heated the rocks that melted, by the time it picked up these chunks it had cooled enough that there wasn’t enough heat left to melt them. As the melt migrated through the cracks and cooled, it picked up and partially melted different components, leading to some variation in the chemistry of the rocks from one side of a dike to the other.

The extremely violent processes recorded in this rock – shattering and melting of target rocks – are typical of high-energy, giant impacts on Earth and elsewhere.

-JBB

Image credit: https://flic.kr/p/oxjhQj

Read more: http://bit.ly/1Bm3MnS http://bit.ly/1dtuMNb http://sajg.geoscienceworld.org/content/100/2/115.short http://www.hou.usra.edu/meetings/sudbury2013/pdf/3031.pdf http://adsabs.harvard.edu/abs/2012Icar..219..168L