MMM 20180414 SUMMARY-31
The Real Story of Vredefort
By David P. Howcroft
Vredefort, the World’s Largest Meteorite Crater
Impact Effects – the Power and Forces involved
Asteroid Belt, Metallic Meteorites and Multiple Impacts
Simple, Complex and ‘Penetrative’ Craters
Continental Drift, Pangaea, Glaciers, Coal and Sedimentation
Ripples’ of Upturned Crust, Magma Dykes and Caves
Witwatersrand Basin, Worlds’ Largest Gold Deposit
Bushveld Complex, Worlds’ Largest Deposits of Platinum, PGMs, Chrome, Vanadium, Manganese, Vermiculite & Andalusite
Great Dyke of Zimbabwe
Swathe of Minerals South-West to North-East
Triassic-Jurassic Mass Extinction
Karoo Mantle Plume
From Meteorite to Mantle Plume to Continental Drift
The Diamond Ring
Coal in Crater and Ripple Valleys (Grabens)
Dating - 2020/2055/2575 Ma or 214 Ma (Million years ago)
Dr. Hans Merensky. The Worlds greatest Geologist
David Parkinson Howcroft
Copyright 2018, ISBN 978-0-620-79365-0
At two hundred and eighty four kilometers in diameter Vredefort Meteorite Crater in South Africa is accepted as the largest known impact crater on Earth. (Therriault, Grieve, Reimold, 1996). Radiometric dating in the rebound core has been used to calculate the age at 2023 Ma. (Allsop et al 1991, Kamo et al 1994, Spray et al 1995). The nearby Bushveld Large Igneous Province, which is a world renowned treasure chest of valuable minerals, is dated at 2054 Ma (Walraven & Hattingh, 1993) and the chrome and platinum-rich Great Dyke in Zimbabwe is dated as 2575 Ma (Oberthuer, Davis, Blenkinsop & Hoehndorf, 2002). As a result of the multi-million year age differences the geological community does not consider that these three sub-crustal structures are connected, and, with +2000 Ma dates they certainly do not accept that Vredefort, Bushveld and Great Dyke could have had anything to do with the extreme events that started in that vicinity with worldwide effects approximately 214 Ma.
Examples of these are the Manicouagan cluster of five impacts in northern Pangaea, (Spray, Kelley & Rowley, 1998) the Karoo Mantle Plume (Courtillot, 1990) leading to the upliftment of South Africa creating the Drakensberg Mountain Range (Hancox & Goetz, 2014) and the breakup of Gondwana restarting continental drift. Other evidence of an extreme event at about 214 Ma is the Triassic-Jurassic Mass Extinction where 80% of all species on Earth were wiped out (Taylor, n.d.) and for which no cause has yet been found.
My main hypotheses contend that the Vredefort Meteorite Impact was directly linked to the 214 Ma Manicouagan Group of meteorite impacts, the Bushveld Complex, the Great Dyke, gold lining the Witwatersrand Basin, minerals of the Bushveld and Great Dyke, the end Triassic Mass Extinction, and the Karoo Mantle Plume. This plume then led to the Gondwana breakup and explosion of Kimberlite diamond pipes of southern Africa. I also hypothesise that the coalfields of the Free State, Highveld, Lephalale (Ellisras) and Limpopo were formed separately from the lower Vryheid coalfields. They were formed in the remnant crater and enclosed valleys to the north remaining after the impact.
I accept that the dating methods are accurate but contend that samples came from, or were contaminated by, the Vredefort crater rebound floor rocks and, in the case of the Bushveld Complex and Great Dyke, from the target layer of strata into which the minerals were infused horizontally. This would account for the three separate 2 Ga ages for the same event and totally overshadow the true age of 214 Ma.
Up until the early nineteen sixties it was believed that the 60 km diameter ring of hills surrounding the small Free State town of Vredefort, in South Africa, was the meteorite crater. (Daly, 1947). Geological and geophysical data then showed that the Vredefort Dome was only the remnant core of a far larger impact structure. This and further research into the planer deformation features (PDFs) and quartz converted to Stishovite at extreme pressure proved that the Vredefort crater was the result of an extremely large meteorite impact resulting in a crater with a complex structure. (Dietz, 1961; Hargreaves, 1961; Carter, 1965, 1968; Manton, 1965; Martini, 1978, 1991; Grieve et al, 1990; Leroux et al, 1994 & Kamo et al, 1995). ‘Thus the impact origin of the Vredefort structure has been reconfirmed with these recent findings and is now accepted as such by the majority of the geological community.’ (Therriault, ibid.)
Work in 1996 used the transient cavity diameter of 136–152 km and a central uplift of 29 km to arrive at an outer rim diameter of 284 km which would make it the largest known meteorite crater in the world. (Therriault, id). The present depth of the crater floor below the sedimentation, debris and melt is 15 km established using seismic technology (Friese et al, 1995). This depth would have been much deeper immediately after impact, in the order of 50 km, (Collins, Melosh & Marcus, 2017) before the center rebounded about 29 km above the crater floor before collapsing (Henkel & Reimold, 1996).
The final crater diameter above is based on the assumption that the original crater was round. However, if gold reef lining the impact crater is linked, as I propose, then it is possible to follow a map of the Witwatersrand Basin gold mines. (Map www.geoscience.org.za). The jelly bowl shaped crater is roughly oval in shape and 330 km long on its south-west to north-east axis and about half that width across.
The oval shape is due to a large, metallic, meteorite particle impacting with the Earth at a very shallow angle from the (current) south-west (Dietz 1961) and north-east trending (Kinnaird 2005) On this approach side the outer crater rim is not visible, the fractured reefs more than a kilometer below ground (Free State goldfields, Wikipedia; Lehmann, 1955) covered with sedimentation, whereas to the north-east the 300 meter high, upturned, old, sedimentary strata (Witwatersrand, Magaliesberg, Waterberg, etc.) are piled into 100 km wide ridges, or ‘ripples’. Further, the richest, 41,000 tons of gold mined (Pretorius 1991), Central Rand Group through Johannesburg, is robust, exposed and unbroken.
A large chunk of a fragmented meteorite that made this crater would have been soundless and barely visible on approach. It would have compressed and exploded the atmosphere in a brilliant flash of 50000C ahead of it before impacting with Earth at a shallow angle a few seconds later (Struve 1947). This cluster of metal-rich meteorites which left a legacy of the world’s greatest deposits of minerals could only have come from remnant core material of some long-ago shattered planet (Elkins-Tanton, 2016), the remains of which are now left over as the Asteroid Belt.
Purdue University has published an interesting Earth Impact Effects Program which is useful for calculating the size, speed and other effects of a meteorite strike. This is a good starting point because we have our estimated size of the impact crater from the chapter above www.purdue.edu/impactearth.
Using the final Outer Rim Diameter of 284 km and adjusting the parameters of Meteorite Diameter verse Speed to get to this figure.
Diameter: 28 km, (which is within the range estimated for this impact).
Speed: 25 km/sec (min 17 km/sec, max 70 km/sec) ‘Asteroids strike the earth at an average speed of about 25 km/second’ (Grieve, 1990).
Impact: Angle: 5o (which we allocate a shallow angle, for reasons in chapter above).
Composition: Iron, 8000 kg/m3 (vast iron deposits before and after of the crater, large amounts of iron, chrome, nickel, vanadium, manganese, platinum, PGMs impacted through to the Bushveld complex) and by formula, a rock meteorite could not create such a large crater).
Target Composition: Sedimentary (Transvaal Supergroup)
By inserting various estimated diameters and speeds for the meteorite it is possible to obtain the final impact diameter required. In this case when the meteorite was selected as 28 km in diameter and speed of 25 km/sec the final impact crater was 284 km which roughly averaged the diameter of the uneven oval area of the existing Vredefort outer crater.
During impact this meteorite would have dissipated energy equivalent of 6.86 billion Megatons of TNT. This is 180 billion times greater than the combined atomic bombs dropped on Hiroshima (16 kilo tons) and Nagasaki (22 kilo tons) and 137 million times greater than the largest man-made nuclear explosion on Earth (Russia’s Tsar Bomba 50 Megaton)!
The transient cavity would have been 48 km deep in a fraction of a minute before gravity caused the center to rebound starting a few seconds later. The remains of this core, which would have been as high as 29 kilometers above final floor level before collapsing, (Henkel & Reimold, 1996) can be seen now as a 60 km diameter ring of hills around the village of Vredefort in the Orange Free State. The impact would have vapourised 44 thousand cubic kilometers of the sedimentary rock and created a fireball 1068 km in diameter.
If you were standing 1000 km away, where Port Elizabeth is today, the Thermal Radiation, 1440 times more intense than the Sun, would have incinerated you, followed by a seismic shock wave that would have reached you in less than three and a half minutes with a force of 11.2 on the Richter scale which would damage or flatten every single structure. The air blast would arrive 50 minutes later at the speed of sound and a pressure of 50 atmospheres which would blast away any structures left standing as well as all trees.
‘Every day hundreds of thousands of meteors crash into the Earth’ (Parkes). Most are millimeters in size and burn high up in the atmosphere. About every 100 years one that is meters in diameter almost reaches the ground resulting in serious local damage such as that in Russia in1947 (Struve, 1950. Apollo objects average one km diameter impact about every 250,000 years leaving a 20 km diameter crater (Wetherill 1979) and about every 100 million years a meteorite of more than ten kilometers in size will cause worldwide damage that could cause mass extinction. The Vredefort Meteorite cluster that impacted earth should be a once in Earth’s lifetime event (Melosh, et al, 2017) and should theoretically only have occurred during planetary formation 4500 – 4000 Ma. (Elkins-Tanton, 2016).
‘Several thousand of these asteroids, the largest of which are a few miles in diameter and the smallest between 10 and 100 feet, have been discovered and accurately recorded. It is believed that they represent the debris left over from the explosion of what was originally a major planet revolving between the orbits of Mars and Jupiter’ (Struve 1950).
‘When the solar system began (4,567 billion years ago), dust particles banged together, clumping into planetesimals, some hundreds of kilometers across. Within a quick 500,000 years, many formed partly or completely differentiated interiors (cores) In this initial period of solar system formation, crowded planetesimals often slammed together to form larger bodies, yet some of these were splintered when hit again. After many collisions, some planetesimals grew big enough – many thousands of kilometers across – to form larger planetary embryos. When embryos got large enough, their gravity disturbed the orbits of surrounding material. At times this caused debris to hit them, and the giant impacts created large oceans of magma and released gases that formed the early atmosphere. At other times the increased gravity flung nearby bodies away. These large bodies with paths cleared of other material earn the label “planet” (Elkins-Tanton, 2016).
Planetary formation in the solar system was successful except for that stable area between Mars and Jupiter where today there are more than 400 000 objects of more than one kilometer in diameter (Wetherill, 1979). This is the Asteroid Belt which is left with a relatively small amount of material, the remnants of planetesimals or the remains of one or more successful planets that were smashed up later. Most of the remains are rocky in nature but some are rich in minerals which would have originated from a core. An example of this is the 226 km diameter nickel-iron asteroid known as Psyche which is expected to be visited by a NASA mission in 2021 (Elkins-Tanton, 2016).
Most of the meteors which burn up in the atmosphere or impact Earth as meteorites originate in this Asteroid Belt after being deflected by the gas giant, Jupiter or Apollo Objects (Asteroids or Comets whose orbits pass through the Asteroid Belt) (Wetherill 1979).
‘A large proportion, probably most, of the meteorites falling on earth are fragments of Apollo objects produced in collisions as the eccentric orbits of the objects carry them through the asteroid belt, which lies between the orbits of Mars and Jupiter’ (Wetherill 1979).
The relationship between meteorites and minerals is well established. For example, ‘Some impact melt rocks have unusual amounts of certain trace elements that could only have come from a meteorite. For example, the concentration of nickel in an impact melt rock can be 20 times greater than that in the local bedrock. It is improbable that the nickel originated from the bedrock or farther beneath the Earth’s surface. Nickel and other elements such as platinum, iridium and cobalt are more concentrated in the iron cores of planets than in their crusts, because they migrate to the core during planet formation. For this reason they are called siderophiles, which means ‘iron lovers.’ Siderophilic elements are therefore not abundant in volcanic rocks and other rocks of the earth’s crust. This is not the case, however, for old asteroids and comets that formed independently of the planets. Hence, a high concentration of Siderophilic elements in melt rock is a good indicator of meteorite impacts’ (Alvarez & Asaro, 1990). Most of the metallic elements in and around the Vredefort Crater, such as gold, platinum, PGMs, cobalt, manganese, vanadium, nickel and even the iron, are siderophilic.
It now appears that many of these asteroids are not always alone on their long journeys through space. The following extract is from The University of Chicago Chronicle ‘Geophysicist David Rowley, working with colleagues in Canada and UK has discovered that five craters in Europe and North America form a chain, indicating the breakup and subsequent impact of a comet or asteroid that collided with Earth approximately 214 million years ago. The impacts may have contributed to a mass extinction that occurred at the end of the Triassic period – one of the five greatest mass extinctions in history. This discovery was reported in the March 12 issue of the journal Nature.
When scientists observed the impacts of the pieces of Comet Shoemaker-Levy 9 on Jupiter in July 1994, they said that the impact of a fragmented comet could never happen here on Earth because the gravitational field is too weak to break a comet into pieces,” said Rowley, Associate Professor in Geophysical Sciences. “But our studies of these five craters provide compelling evidence that this happened at least once, and there is no reason it couldn’t have happened more than that.”
Rowley’s colleagues – John Spray and Simon Kelley – were interested in the relationship between craters of similar ages – Kelley had developed a technique to precisely date craters using laser argon/argon. Rowley’s help was needed in determining how the craters were aligned when the impacts occurred -- because of plate tectonics, the continents have moved extensively during the last 214 million years. Three of the five craters, Rochechouart in France and Manicouagan and St Martin in Canada were at the same latitude – 22.8 degrees—forming a nearly 5000 km chain. The other two, Obolon’ in Ukraine and Red Wing in Minnesota lay on identical declination paths with Rochechouart and Saint Martin’. (Steele, Diana-News Office 1998).
From the original article in Nature “We therefore suggest that the five impact structures were formed at the same time (within hours) during a multiple impact event caused by a fragmented comet or asteroid colliding with Earth” (Spray, 1998).
‘There are 150 known impact craters worldwide; the scientists are now studying others to see if there are other chains of co-latitudinal craters. Based on current estimates of age of the 150 craters, no other comparable chains have been found. (Steele, Diana).
Provided that the Vredefort Crater, Bushveld Complex and the great Dyke were the same age, and, at 214 Ma, Pangaea would have had North America and Eurasia joined together at the top of the continent and Gondwana (Southern Pangaea) lying on its side, rotated clockwise relative to now. (Veevers 2004 & Senckenberg Museum). This would be the perfect position and time frame to be impacted from exactly west to east by the same meteor cluster that impacted the northern hemisphere west to east at that time.
However if separate meteorites had collided with Vredefort 2020 Ma, Bushveld Complex in 2055 Ma and the Great Dyke in 2575 Ma then there would have been a 70% chance for each of them to have impacted in the ocean, the remains never to be seen again. It is also unlikely that southern Africa would have been in a location and rotation on Earth to create three separate once in a solar lifetime events, perfectly aligned west to east with each other and the planetary plane.
Another example of multiple impacts on Earth is: ‘TWIN CRATERS of Clearwater Lakes in Canada show that multiple impacts on the Earth are not as unlikely as they might seem’. (Alvarez & Asaro, 1990).
Simple Meteorite Crater
If the meteorite is less than about one hundred meters across, it forms a simple crater when it collides with Earth. This impact makes a crater in the form of a dish when the explosive shock waves compress, melt, vapourise, and blasts out ejecta; molten rock as well as debris from the meteorite itself. On Earth these craters can reach a maximum diameter of about 5 km and depth of about 1 km (Grieve 1990). The immediate or transient diameter of the crater is smaller than the final size as the steep walls slide into the cavity but the transient depth is greater as the cavity is filled with debris and melt.
Shock waves from the impact followed by a release wave shatter the bedrock which is compressed, melted, vapourised and blasted out of the crater. A well-known example of a large simple crater is the Meteor Crater (formally Barringer) in the Arizona desert in the USA. The iron meteorite was estimated to be about 60 meters in diameter, weighed a million tons and left a crater 1.2 km in diameter and 170 meters deep. Age 25 – 50 ka, Energy, 5 Mega ton TNT.
Complex Meteorite Crater
When meteorites are larger than about 100 meters in diameter and travelling in excess of 20 km/sec (Grieve 1990) the impact energy excavates a transient cavity deep enough for the shattered and melted rock above a fluid floor which allows gravity to rebound the center like a stone dropped in water. With large complex craters the transient depth is deep enough to penetrate the brittle crust to an area which is plastic. The hydraulic and gravitational effects can raise the central rebound core to great heights before they collapse.
After the ejecta is blasted out the crater the walls collapse and molten rock slides down into the newly formed jelly-bowl shaped crater. Examples of complex craters on Earth are Sudbury, 250 km, 1849 Ma (Ontario, Canada) and Manicouagan, 75 km, 214 Ma (Quebec) (Spray, Kelly & Rowley 1998).
Penetrative Meteorite Crater
My hypothesis is that there is a third category that should be considered. This type of crater would result from a meteorite impacting Earth at a very shallow angle, less than 10o. If we look at the cross-section of Meteor Crater, it is seen that the borings beneath its floor and rim have reached a deep pocket of shattered rock on one side containing meteorite fragments (Beals 1958). From the cross-section it would appear that the angle of impact was about 30o. The crater rim on the hollowed out side is higher than the entry side. This profile is similar to that which we have from the Vredefort Crater with the rim 1.2 km below ground level where an asteroid plunged into the earth from the south-west (Dietz 1961) near Welkom and a relatively large rim in the north-east, Johannesburg, where the crustal strata has tipped southward at 600 (Whiteside, et al, 1976) back into the crater.
For impact penetration, think about modern anti-tank weapons (Wiki/M829). High density depleted uranium darts, 800mm long x 27mm diameter, weighing about 10 kg, are propelled at relatively high speed, about 1.5 km/s, to penetrate up to 765mm hardened steel with only kinetic energy. This is 30 times the projectiles’ diameter. The uranium remains intact whereas other metal projectiles become molten but still penetrate with extreme pressure.
Now, compare this to the Vredefort Meteorite. After a shallow trajectory impact from the south-west the vapourised target rock was ejected and metals from the meteorite continued at high speed into the side of the existing strata lifting it upwards off the floor and penetrating at very high speed and pressure. (Think fracking where explosives are used to create fractures in the rock which are then filled with a water/sand mixture under high pressure). Even when the chrome-rich projectile became liquid (above 3 km/sec), (Charters 1960) due to the energy dissipation it’s momentum carried it on for almost a hundred kilometers before the highly viscous melt fanned out between layers of existing strata to form the Bushveld Large Igneous Complex.
Of the initial 28 km diameter Vredefort Meteorite particles weighing about 90 trillion tons, at least 5.5 billion tons of chrome (Vorster, 2001) with other high density, high temperature minerals continued to lift and intruded the lighter sedimentary crust for a considerable horizontal distance, in the order of three hundred and twenty kilometers from Johannesburg to Polokwane.
My examples of these are Vredefort Meteorite Crater, 284 km diameter which is Complex, with rebound, as well as penetrative to the Bushveld Complex and the Great Dyke in Zimbabwe, 550 km long which is purely penetrative.
From 650 Ma to 500 Ma separate old continents on the Earths’ crust, floating over the heavier mantle, were moving together to eventually amalgamate by 320 Ma (Veevers, 2004). This supercontinent, Pangaea, with northern America, Europe and Asia to the north and Gondwana (southern Pangaea) comprising southern Africa, South America, India, Australia and Antarctica in the south. The whole supercontinent of Pangea floated southwards positioning Gondwana over the South Pole for fourteen million years from about 302 Ma to 288 Ma (Bangert et, al., 1999). During this time buildup of snow and ice up to 4 km thick (Horton et al, 2010, 2012; Montanez et al, 2013) followed by melting from below causing glaciers to gouge out a huge area which included present day South Africa (Karoo Supergroup), South America (Parana, Argentina), Antarctica (Beacon) and Eastern Australia (Victoria to Queensland).
After drifting away from the South Polar Region this left a mix of stony, sandy, muddy glacial debris up to seven hundred metres deep, known in South Africa as the Dwyka Group. ‘It is now widely accepted to be the product of glacio-marine sedimentation, and part of the Late Palaeozoic Ice Age (LPIA) that affected most southern Gondwanan basins’ (Dineen et al, 2013). This left a huge inland lake covering Gondwana, about three thousand kilometers in diameter.
As the lake silted up from rivers (fluvial) and windswept dust (aeolian) it eventually became a huge swamp with dense forests of the famous Glossopteris flora from 298 Ma to 252 Ma. (From Etheridge, 1901 to Prevec, 2008). This was a water loving tree with tongue shaped leaves that grew up to thirty meters high. For roughly fifty million years these swampy jungles laid down the organic debris that became the future Natal Vryheid formation coalfields in South Africa as well as those in South America and Eastern Australia. The protected Antarctic fields are buried under thick ice once again. In South Africa these deposits became the Pietermaritzburg shale, and Vryheid Formations coal.
By 252 Ma the giant lake with its’ swampy jungle had silted and become dryer as Gondwana drifted northwards towards hotter climates and all the vast forests of Glossopteris died out. Intermittent floods and windborne dust buried the Natal coal under kilometers of Ecca Group sediments; this is where the situation had stabilized by 214 Ma.
It was at this time that a large part of the core of the Vredefort meteorite impacted with Earth creating the 330 km by 165 km crater with a cavity to the (present) north-east into which the sedimentary Ecca layers tilted and tipped into the crater. The exposed upper surface of this 56 km wide slab of sediments and the rest of the crater walls then melted into quartz with the superheated aerial fireball. Separate pieces of the original meteor would account for an initial chrome-rich meteorite including iron, platinum and other minerals, penetrating the crust to form the Bushveld Complex whilst leaving the vapourised gold to follow minutes later, precipitating to impregnate the molten quartz of the crater bowl and shower gold particles down onto the surface to the north and north-east.
After the dust had settled, meters thick, the Free State-Highveld area was left with a large, 15 kilometers deep crater filled with debris as well as newly formed valleys in the ripples to the north and Limpopo, all of which had no immediate drainage. These became large freshwater lakes accumulating sediment from wind and runoff over millions of years until they became wide enough to balance incoming water with evaporation. At this time they again became swamps. Pollen samples show that other swamp vegetation proliferated as the Glossopteris flora had since become extinct. This new flora later became covered with sediment to form new, rich coalfields in these areas.
We know that this glaciation event took place about 288 Ma which would have scraped off the center cone and outer rims of the Vredefort crater including the ‘ripples’ if they had been there. This would also prove that the Vredefort impact and Bushveld Complex took place after glaciation about 214 Ma and not 2020/2054 M.
‘Dwyka aged glacial scouring and the induced basement palaeotopography is by far the greatest factor impacting on the distribution of the coal seams in the Witbank Coalfield. The northern margin of the MKB in the Witbank Coalfield displays vast valleys and ridges left after the scouring ice-sheets migrated across this part of Gondwana. The basal Pietermaritzburg Formation of the Ecca Group is not present in the Witbank Coalfield and rocks of the Dwyka Group are directly overlain by the coal bearing Vryheid Formation of the Ecca Group. (Hancox loc cit).
The Free State Coalfield is located in the north-western Free State Province and covers an area of about 1 500,000 ha (Gilligan, 1986). It stretches from the Vaal River in the north to Theunissen in the south, overlying nearly all of the Free State goldfields. The northern and western limits are subcrops against basement. The southern boundary is taken as the limit of coal deposition and is believed to be south of the town of Theunissen. The eastern boundary is a common boundary with the adjoining Vereeniging-Sasolburg Coalfield. (Hancox loc cit).
The chrome and other minerals in the meteorite did not disintegrate on impact but, because of their size, metallic content and the shallow angle, they penetrated the Earths’ crust and travelled hundreds of kilometers underground in minutes, flattening out and spreading as they went. This high speed penetration would have converted some of its’ immense kinetic energy into heat, melting itself and the target sedimentary rocks in seconds as pressure was converted to heat. The metal-rich fluid then ploughed on through the sub-surface strata creating wide waves of uplifted crust, hundreds of meters high, in the form of ripples, alternating with east-west dykes of newly formed doleritic magma (molten rock) as it went. Eventually the molten meteorite remains lost energy, slowing down to hydraulically intrude horizontally between layers of sedimentary rock to form the Bushveld Large Igneous Province (Kinnaird 2005).
However, the ripples did not stop there as the tsunami-like waves below the hard crust radiated outwards to the north thrusting up more mountain ranges as it went.
The first ripple is the north-eastern outer rim of the meteorite crater. This is the Witwatersrand Ridge, stretching from Klerksdorp in the west through Johannesburg (Northcliff) to Ermelo in the east with sedimentary slabs, jagged on edge, facing north and sloping steeply back. The additional ripples that spread outwards through the crust to the north left us with the Magaliesberg, Waterberg, Strydpoortberge, Soutpansberg and Lebombo mountain ranges. The distance from Vredefort to Witwatersrand is roughly 120km, then 65km on to Magaliesberg, 105km on to Waterberg, 120km on to Strydpoortberg, 175km to Soutpansberg and 350km to Lebombo Mountains.
Rising Magma Dolerite Dykes
Midway from Johannesburg to Pretoria, between the Witwatersrand and Magaliesberg ranges is a twenty kilometer wide west-east seam of hard, blue, igneous, dolerite rock which is mined in huge quarries at Diepsloot and Midrand for crusher stone to make concrete or surface roads.
Beyond Pretoria turn west on the N4 along the valley floor north of the Magaliesberg Range. Here you will follow a 100 km long string of pyramid shaped hills stretching all the way past Rustenburg. These pointed hills contain the sought after Pyramid Gabbronorite; a dark-coloured inverted pigeonite bearing gabbronorite. (Commonly known as black marble; the Reserve Bank building in Pretoria is clad with this product). In the village of Pyramid on the R101 you can see a hundred meter high cross-section in a rock quarry showing slabs of sedimentary rock that were lifted up by the magma. The pigeonite indicates that the magma could not have been too hot, about 9000C and that it had to have cooled fast. (Wiki Pigeonite 2017) This pigeonite is part of the pyroxene layer that caps the minerals of the Bushveld Complex where the intrusion stopped abruptly. It is also found in meteorites. (Handbook of Mineralogy)
The shock wave from the meteorite impact radiates outward first compressing the sedimentary crust into ridges followed by a rebound that can tear underground strata apart to form massive cave systems. Signs of these remain in long valleys alongside the Witwatersrand ridge, most of them now flooded. ‘This aquifer covers a vast area, extending from Springs and Brakpan east of Johannesburg to Lenasia south of the city, Zuurbekom, Carltonville and Magaliesberg on the West Rand, Kuruman in the Northern Cape and even as far as parts of Botswana. To give you an idea of size, the Witwatersrand mining basin’s aquifer storage capacity is about the size of Lake Kariba.’ (Turton 2012).
Until 1938 when the Vaal Dam was built, Rand Water pumped its supply for Johannesburg out of this aquifer at Zuurbekom, near Lenasia. Mines to the west of Johannesburg could only sink shafts after the development of cementation in 1925 to get through these flooded caves and others have had to pump hundreds of thousands of tons of a cement-minedump-sand mix into the caves to stop flooding. To the west sinkholes are a huge problem, even swallowing an entire mine crusher plant in 1962 at West Driefontein with the loss of 29 lives and a house with the entire Oosthuizen family at Blyvooruitzig in 1964. (www.geoscience.org.za/images/geohazard/sinkholes.pdf).
A team from the University of Johannesburg is now examining one recently discovered giant cave in the West Rand area that has not flooded. Researchers have linked it to the Vredefort Meteorite impact and are trying to determine its’ age. They have named this cave Armageddon due to its huge size, 4km long, 50m wide and 350m deep. “We think it happened this way. When the meteorite struck the ground about 2 billion years ago in the Vredefort area, rocks over a huge area were suddenly compressed by the impact. What also happened is that some rock layers sort of ‘slipped’ across each other creating new structures. We call these structures low angle slip faults where the rocks have ‘torn’” (Armageddon 2015).
The problem with this statement is that the underground photos clearly show that the torn sides are sedimentary and these layers were deposited after the period of glaciation about 302-288 Ma (Bangert op cit. 1999). These Caves would certainly not have been able to withstand the forces of up to 4 km thick ice followed by the scraping glaciers. If the meteorite struck the ground 214 Ma after the glaciers when the Ecca strata had been formed then the statement would make sense.
The almost 300 km diameter Vredefort Crater rim is surrounded on all sides except the south-east by the world’s largest accumulation of gold mines as can be seen on the Geoscience/Gold map (Vorster, 2000). One hundred and thirty years of mining around the Witwatersrand Basin has produced over 56,000 tons of gold (Chamber of Mines 2015) and they still have the largest reserves in the world although current levels of newly mined gold accounts for only 5% of worldwide production. Currently the deepest mines are now down below four kilometers, only costs of mining limit the depth of extraction
Looking within the Vredefort impact crater, gold, mainly as fine particles less than 0.5mm, imbedded with 25mm round translucent pebbles in a matrix of quartz (Whiteside 1976) is associated with the entire meteorite crater excluding the interior of the rebound at Vredefort itself. The gold reef lies on the inside of the Witwatersrand Basin, sloping at about 600 to the south at the surface of the Main Reef in the vicinity of Johannesburg decreasing to about 150 at a depth of three kilometers (Whiteside, 1976. The walls of the entire original ‘jelly bowl’ from Welkom to Klerksdorp to Johannesburg and Evander are lined with fine gold and it is possible that the original floor at 15 km deep is also lined with gold as that also occurs on the outside layer of the remnant rebound core.
Imagine less than a minute after the impact crater is formed, the steep sides glowing with molten quartz and a delayed precipitation of vaporised gold from a meteorite core fragment. The fine gold particles stick to the molten crater walls forming the enriched gold reef. Quartz debris from ejecta tumbling down the steep sides also imbed themselves in the molten lining as 25mm, round translucent pebbles. Some of the vapourised gold is deflected to the north and north-east by the remains of the surge wave from the initial explosion causing fine particles and condensed gold nuggets to rain down in the Mpumalanga and Limpopo provinces as well as north into Zimbabwe.
It is well known historically that this area was a great source of surface and alluvial gold that was exported via the Mozambique coast by Arab and then Portuguese traders. Great Zimbabwe was known as a gold trading center from 700 to 1100 AD (Gayre 1972). To this day you can still find Zimbabweans panning for gold in the streams.
The geological community still write about the gold was placed in reefs on the walls of the Witwatersrand Basin by age old river deltas (paleoplacer deposits) or welled up out the earth (hydrothermal deposits) (Therriault, et al, 1996). I believe that the reason for overlooking an extra-terrestrial source of gold was that until about 1960 the Vredefort Dome of 60 km diameter was considered to be the full size of the meteorite crater. Such a simple crater did not align with the Witwatersrand Gold Reef and therefore could not be considered. No one has returned to the enlarged complex crater to examine why the gold lines the walls of the rim as well as the outer walls of the rebound.
I propose that the gold came from a core particle of the Vredefort Meteorite cluster which arrived behind the main chrome-platinum-mineral rich main meteorite that had penetrated under the Witwatersrand and Magaliesberg to form the Bushveld complex. The kilometers thick Pretoria Group strata tipped into the crater at 600, forming a new wall, the surface of which melted in the extreme heat from the fireball. Some of the quartz ejecta tumbled down the steep side, being rounded smoothly in the process and became imbedded in the molten walls with minute particles of vapourised gold.
(Flying above the flat hilltops of Mpumalanga, you can see old fields where rocks have been cleared into hundreds of circles possibly by people searching for the gold particles that rained down eons ago).
The Bushveld Large Igneous Province (LIP) is located from about 200 km north-east of Vredefort and is the largest layered igneous intrusion in the world. It is more than 60,000 square kilometers in size, crescent-shaped with the open end facing Vredefort, was formed horizontally and is not volcanic. (Kinnaird, 2005). This complex contains the largest deposits of chrome, platinum, platinum group minerals (PGMs), vanadium, andalusite and vermiculite in the world as well as iron, gold, nickel, silver, titanium, tin, copper, manganese and asbestos.
Our equivalent 28 km diameter, metallic meteorite cluster, weighing 90 trillion tons and travelling 13 times faster than an anti-tank dart would have had a de-acceleration force of about 40g (40 times its’ own weight) for a few minutes before it eventually ran out of kinetic energy about five hundred and fifty kilometers further on. After causing the huge explosion forming the Vredefort Crater the dense, chrome-rich material from the meteorite penetrated the strata horizontally deep below the now-forming Witwatersrand Ridge at Johannesburg. Below Midrand this meteoritic bullet had spread out to about 20 km wide lifting a wave of shattered, molten rock before fanning out and lifting the strata to form the Magaliesberg Range. Beyond this range another wave of magma broke through the existing strata to form a string of 100 m high ‘Black Marble’ pyramids stretching from Pretoria to Rustenburg and beyond.
Now the molten meteorite and surrounding magma had spread out into a 300 km crescent from Rustenburg in the west to Polokwane in the north and Lydenburg in the east. The dense, molten chrome-rich (up to 43.5%) front hydraulically forced existing layers of 2055 Ma sedimentary rock apart, lifting the roof off the floor and intruding in between.
Secondary intrusions from other multi-million ton chunks of chrome-rich meteorite, now liquid magma, found it easier to force the roof upwards than continue pushing kilometers of dense melt forward. This magma found the next weak joint in a layer above and intruded, pushing the roof further upwards. Minutes later another wave of magma, this mix including platinum, gold, vanadium and other minerals intruded into a layer above to form the famous Merensky Reef, the richest source of platinum and PGMs on Earth.
‘Large Igneous Provinces (LIPs) are defined as massive crustal emplacements of predominantly mafic Mg (magnesium) and Fe (iron) rich extrusive and intrusive rock which originate via processes other than normal seafloor spreading’ (Coffin & Eldholm, 1994 from Kinnaird 2005).
‘Magnetic foliations and lineations are horizontal reflecting vertical host-rock compression and horizontal magma flow during emplacement with space created for the granites by roof uplift and floor depression’ (Wilson et al 2000 from Kinnaird Loc cit).
‘This intruded within the Transvaal metasedimentary sequence as sills. As further pulses followed, some metasedimentary material became detached from the floor and later magma flowed under or over these layers’ (Kinnaird Loc cit).
‘The fact that the Rustenburg Layered Suite components intrude into the Rooiberg Group and yet RLS-derived detritus is found within sediments of the overlying Loskop Formation argues that the Rooiberg-Bushveld magmatism must have occurred over a short period of geological time’ Harmer & Armstrong (2000) (Kinnaird Loc cit).
‘In the case of the Eastern and Western limbs of the BC it is argued here that they represent a single intrusion and that the magma spread remarkably uniformly throughout the intrusion.’ (Cawthorn & Walraven 1998).
‘The BC is the crystallization product of numerous injections of magma. The absence of intraplutonic quenching, and of significant changes in mineral composition within cycles and short vertical sequences, suggest that such injections are not widely separated in time’ (Cawthorn & Walraven 1998).
‘The evidence presented above suggests that magma addition within the Eastern and Western limbs of the BC terminated abrupt’ (Cawthorn & Walraven 1998).
What the above three quotations mean is that the magma all came from the same source, it was fast and ended abruptly. This is not typical of volcanoes but would apply to the penetrative meteorite impact I have described.
‘No consensus of opinion as to tectonic setting for the magmatism or whether it was plume related’ (Kinnaird 2005). This indicates that the cause of the Bushveld Complex is not settled.
‘In spite of its Palaeoproterozoic age it is undeformed’ (Kinnaird, loc cit). This means that it in spite of being 2055 Ma it has not eroded much. However this lack of deformation or erosion would be in line with a much younger age, say 214 Ma.
‘…and it comprises in part voluminous volcanics that were predominantly felsic rather than basaltic in composition’ (Kinnaird, loc cit). The pale felsic rocks are in the middle of the Bushveld LIP surrounded by dark basaltic ones. This is the opposite to conventional volcanoes and is probably caused by the initial high temperature and pressure in the middle from the meteoritic intrusion that can transform mafic rocks into felsic. (Tackley, P., 2017)
‘Despite intensive study, determining the precise crystallization age of the Bushveld Complex has proven to be difficult’.
‘Integration of the Merensky reef crystallization age with existing U-Pb age determinations for intrusions that pre- and postdate emplacement and crystallization of the layered rocks of the Bushveld Complex indicate that magmatism occurred at ca. 2054 Ma’ (Scoates, Friedman, 2008.
The above paragraph shows that scientists could not date the minerals so they dated the rocks below and above the Merensky Reef at 2054 Ma. If, however the Merensky Reef was intruded from the side horizontally (Wilson, et al Loc cit) at a depth that matched a layer of 2054 million year old, existing rocks in the strata then Scoates & Friedman were measuring the age of the local rock in the layers of the strata that existed before the meteorite strike. There is no reason that the minerals in the Merensky Reef could not have been intruded there 214 Ma or any time from 2054 Ma until now. It is too much of a co-incidence that the physical position of the Bushveld Complex matches the age of the existing strata at that depth.
2000-1800 Ma: Rooiberg Group
2230-2000 Ma: Pretoria Group
2054 Ma Strata age <<<<<<<<<<<< 214 Ma: Bushveld Complex
2500-2100 Ma: Transvaal Supergroup
2700-2500 Ma: Kaapvaal Craton
3000-2700 Ma: Swazian
I contend that 214 Ma large pulses of magma from fragments of ferrochrome and chrome-rich core material from the Vredefort Meteorite particles travelled hundreds of kilometers just below the surface came to rest in the Transvaal Supergroup (Pretoria Group) at a depth that corresponded to an age of 2054 Ma. Incorrectly the layer of strata is being dated and not the projectile that penetrated the strata from the side 214 Ma.
If, today, you shot a bullet into a wall that was known to be 50 years old you would not say that the bullet was 50 years old.
The Great Dyke is not a dyke but a straight, 550km long astrobleme, ‘This newly coined word refers to ancient scars left in the earth's crust by huge meteorites’ (Dietz 1961). Its’ lopolithic, Y-shaped cross section gouge scars the top of the old Zimbabwe Craton from SW to NE. It can be seen from the satellite pictures and contour maps of the Great Dyke that the direction was from the south-west as the scar left on the surface rock of the Zimbabwe Craton starts in a straight line from the SW and ends in a swirly question mark at the higher north-eastern end as it ran out of directional speed. The Y-shaped cross-section is from the fast moving subterranean explosion that ‘zipped’ through the existing rock strata horizontally as it ploughed through.
This 3 – 12km wide gouge is unusual in that most ultramafic layered intrusions display near horizontal sill or sheet forms. The Great Dyke is a strategic economic resource with significant quantities of chrome and platinum. Chromite occurs to the base of the Ultramafic Sequence and is mined throughout the Dyke. Below this are economic concentrations of nickel, copper, cobalt, gold, and platinum group metals (PGMs) (Great Dyke – Wikipedia).
The similarity with the Bushveld Igneous Complex is striking. Firstly, the horizontal intrusive layering of the sills is indicative of a formation that was not volcanic. Then, the minerals contained in the magma are the same as the Merensky Reef which would indicate that they were derived from the same source.
The third interesting observation is that the straight–line scar of the Great Dyke is in the same direction and path as the SW–NE trending impact of Vredefort. In fact, on a map you can draw a straight line back from the Great Dyke which will pass over the South African border at Pontdrif, through the center-line of the Bushveld Complex, over the highest part of the Witwatersrand Ridge (Northcliff) and end up in direct line with the Vredefort Dome!
If you cannot imagine that a high density core meteorite, rich in chrome and platinum can penetrate through 550 km of crustal sedimentary rock then look back at the Bushveld Complex where the same mixture of high density elements penetrated the same distance from first entering the ground at Welkom, passed under Johannesburg and came to a stop fanned out in the bushveld Complex. The longest distance chrome travelled through sedimentary rock was to the Polokwane (Pietersburg) area, about 550 km where the worlds’ largest chrome deposits are found.
If you are wondering why the meteorite could travel such a long distance and maintain the same level below ground, consider that the sedimentary target layers were relatively undisturbed since their formation and lying horizontal. The meteorite entering almost parallel to the ground would follow the weaker joints between the layers of strata, pushing up the roof and shedding mineral layers, staying at that level until eventually coming to a stop.
Now, let us look at the age estimation of the Great Dyke. The dyke lies within the Zimbabwe craton and has been dated at 2.575 billion years old (Oberthuer, Davis, Blenkinsop, Hoehndorf, 2002). However the target rock of Zimbabwe Craton is aged from 2.8 to 2.5 Ga (Jelsma, Dirks, 2002). This means that the age given for the dyke is the same as 25% down into the craton. If the core material of a metallic meteorite consists of elements that cannot be aged then the age measurement will come from material in the magma derived from the target rock. It is presumed that the age measurement will be reset to zero during the melting or solidifying process. This does not always happen as a result of meteorite strikes.
‘Graham Ryder of the Lunar and Planetary Institute in Houston vigorously revived the idea in 1990. Ryder makes three points. One is that ages of rocks are not so easily reset. Recent work on the effects of impacts on ages demonstrates that the only materials whose ages are affected are those that melt during the impact and perhaps, a small percentage of other rocks in the target. Most rocks are crushed up and tossed around but not heated substantially’ (Taylor 1994).
Not only do we have Vredefort Meteorite Crater with its gold lining, the Bushveld Complex and Great Dyke in an exact line to the north-east with chrome, platinum, PGMs, gold, nickel, vanadium and asbestos, but there are large mineral deposits from 1000 km to the south-west and 1000 km to the north-east of Vredefort. This 400 km wide swathe of economically viable minerals stretches from O’Okiep Copper District in the Northern Cape to the Copperbelt in Zambia.
The Council for Geoscience (Vorster 2005) has produced downloadable maps of all the minerals of South Africa showing where they are mined. The 25 minerals that fall into the swathe above are, in alphabetical order: Andalusite, Antimony, Asbestos, Barytes, Chromite, Cobalt, Copper, Fluorspar, Gold, Iron, Lead, Manganese, Molybdenum, Nickel, Phosphate, Platinum, PGMs, Rare Earths, Silver, Tin, Titanium, Uranium, Vanadium, Vermiculite, Zinc and Zirconium.
This vast array of minerals, many of which are the largest deposits in the world, could not have seeped up through the Earths’ crust from the mantle as they have a higher density. Most of them are siderophiles that would have sunk to the Earths’ core if they had been there during the formation of this planet. After the crust was formed they could only have come from space.
These were all minerals that would typically have been separated out with density and temperature in the molten core of some long past planetary formation. After cooling down over thousands of millions of years and solidifying, with different materials in neat layers, like the segments of an onion, a serious smashup occurred throwing off the crust and leaving the shattered core to be held together by its’ own reduced gravity. It is clear that this disintegrated core had mostly separated into the various minerals before colliding with Earth.
As the shattered core approached Pangaea at a very shallow angle the dense gold, platinum, PGMs as well as a large amount of chrome gathered in the center surrounded by iron and manganese, then copper and lastly rocky remnants of the mantle spread out over thousands of kilometers.
Looking at the swathe of mineral deposits, the bottom of the outer core rich in copper collided with Earth first in the O’Okiep Copper Region of the Western Cape followed by chunks of iron and manganese in the area of Manganore, Hotazel and Sishen. The center of the core containing the densest, high temperature minerals then impacted into the ground from Welkom, through Vredefort and under Johannesburg/Pretoria to the Bushveld Complex. Most of the high density gold, vapourising first due to its lower melting point and the long horizontal distance through the atmosphere, remained behind, lining the crater.
Past the Witwatersrand Basin the order of impact was reversed with iron and manganese impacting in a semi-circle from Thabazimbi to Swaziland and copper to the east at Phalaborwa and north from Musina on the Zimbabwe border to the Copperbelt in Zambia.
Some of the far out, shattered, rock, mantle debris surrounding the core impacted with the northern parts of Pangaea colliding with Canada, Ontario, France and Ukraine as the Manicouagan cluster of meteorites 214 Ma. The direction of approach and shallow angle matched the Vredefort/Bushveld/Great Dyke cluster as close as can be estimated for that period.
(Dr LG Boardman, a Geologist, who was our scoutmaster in the 1950s, discovered the manganese deposits at Manganore and Hotazel and named the two towns).
With an impact such as Vredefort you will have worldwide devastation with immediate effects from the blast wave, base surge, earth quakes, tsunamis and vaporization of water and rock. The dust and ejecta would be 4.1 meters thick one thousand kilometers away from the impact (www.purdue.edu/impactearth) and the dust encircling the world would be so thick that you would not be able to see your hand in front of your face for weeks. (Alvarez & Asaro, 1990)
Longer term effects would be global distribution of ejecta, wildfires and darkness, acid rain and greenhouse effect. With all this we would expect a mass extinction, and, here is the one that I propose, at 214 Ma, at the end of the Triassic Period, in which 80% of all species of that period vanished. It is only that the date of Vredefort is believed to be 2020 Ma that this event was not considered as a candidate. I propose that the Triassic–Jurassic Mass Extinction was as a direct result of the Vredefort Impact caused by all the worldwide effects of such a catastrophic event.
‘An impact event comparable to that suggested for the Cretaceous-Tertiary event is estimated to occur approximately every 100 million years. For this reason, some investigators have advanced that other mass extinctions were also caused by the impact of meteorites’. (Grieve, 1990).
‘End Triassic, 200 million years ago, 80% of species lost. Of all the great extinctions, the one that ended the Triassic is the most enigmatic. No clear cause has been found’.
(Taylor Paul, n.d.)
A mantle plume is an upwelling of very hot magma, a few hundred kilometers in diameter, originating from the core-mantle boundary 2900 km below the surface. There are only about twenty of these plumes around the world, mostly welling up as mid-ocean ridges (Wyllie 1975). The Karoo Mantle Plume only came into existence about 200 Ma. As there was no reason for this plume to begin rising under Gondwana, which had been part of a stable Pangaea for the previous 100 million years I would propose that the Vredefort meteorite impact of 214 Ma was the cause of it.
We all know of those steel balls hanging from strings, lift the end one and let it drop against a few others and the shock wave is transmitted through the ball to send the other end one flying. Imagine a similar effect happening here. The impact shock wave travelled downwards until it reached the core-mantle boundary, about half way to the center of the Earth. It then rebounded back up off the denser metallic core leaving a disrupted path through the mantle.
The second effect of the meteorite impact would be to dissipate energy into the mantle in the form of heat directly below the crater. This additional heat would cause the thick, molten magma in the mantle to become lighter than its surroundings resulting in a slow upward movement.
Mantle plumes, because of their sheer size and weight are very slow moving, a mere five centimeters per year (Wyllie, 1975). This would account for the time delay of about 10 million of years between the Vredefort impact and the uplift of southern Africa by a few kilometers, creating the flood basalt of the Karoo system roughly 200 Ma followed with the Drakensberg (185–180 Ma) created by some 1.4 km of basaltic lavas. (Veevers 1994, Johnson 1996).
Later, as the African plate moved west over the mantle this volcanic plume left a trail to Madagascar and close to Reunion, where the west side of India was at about 65 Ma. It is therefore possible that the Deccan Traps were formed by the same mantle plume. As the crust carrying India moved northwards the undersea trail to the south, left by the plume, is now at a related hotspot under Marion Island. (Courtillot 1990).
As described above the Pangaea supercontinent was stable from 320 Ma until about 185 Ma at which time it started to break up and began its slow drift apart. The center of this expansion was southern Africa with South America heading west, Australia east, India north and Antarctica south to where they are today. It would take an impact of such a magnitude as Vredefort to have caused shock waves and heat that could result in a volcanic plume which was then capable of moving continents apart.
‘Another model for the plate-driving mechanism involves ‘thermal plumes’ in the mantle. According to the argument, all upward movement of mantle material is confined to about 20 plumes, each plume a few hundred kilometers in diameter, rising from the corresponding boundary. The return flow is accomplished by a slow downward movement of the rest of the mantle’. (Wyllie, 1975).
‘Movements of the mantle also cause volcanic eruptions, earthquakes and continental drift.’ (Wyllie, loc sit)
‘…capped by some 1.4 km of basaltic lavas of the Drakensberg Group’ (Veevers et al, 1994; Johnson et al, 1996, ‘the extrusion of which is related to break-up of Gondwana’ (Cox 1992).
‘There is no doubt that these provinces [Karoo, Ferrar and Chon Aike] are linked in some way to the Gondwana breakup…’ ‘-that formed prior to the initial breakup of Gondwana. Although the Karoo province has been most clearly linked to a mantle plume, …’ (Storey, Leat & Ferris 2001)
DIAMONDS from kimberlite pipes
It cannot be a coincidence that about 80 comparatively young, 100 Ma, Kimberlite diamond pipes encircle the Vredefort crater? The largest of these are located from Jagersfontein in the south-east, to Kimberley in the south, Jwaneng and Orapa in the west, Cullinan in the north and Venetia in the far north. Most of these are 200 – 300 km from Vredefort except Orapa and Venetia which are about 600 km (Vorster 2000).
There is only one way in which the rich quantity and size of diamonds could have formed in this specific area. A source of carbon is required to be converted into diamonds, this being from carbohydrates in gas, oil or coal. A large area of carbon needs to be deep underground, contained, and subjected to pressures of 100 -150 Giga Pa, which is 1 to 1.5 million Bar. It also needs to be raised in temperature to over a thousand degrees Celsius.
I propose that the Vredefort meteorite impact drove large amounts of carbon down under the Earths’ crust from the Glossopteris coalfields that were laid down below the Ecca formation from 298 to 252 Ma. This source of carbon then mixed with the mantle material.
Over millions of years as the mantle plume rose slowly the carbon-rich magma sank down the sides of the plume until they reached about 160 km deep below the surface where the pressures and temperatures are ideal for the formation of diamonds. The increased heat in this area from the impact created the conditions 100 Ma for the diamond-rich Kimberlite to expand, rise up and explode upwards through a ring of weakened crust surrounding the Vredefort Crater. This theory is supported by the composition of minerals in mantle peridotite which confirm the depth and temperature from where the Kimberlite came.
Later many diamonds would be eroded out of the Karoo strata from where they were washed away down the Orange River to the newly created Atlantic sea channel and then north by ocean currents.
An alternative theory is that the immediate heat and pressure from the impact shock wave through the kilometers thick Ecca sediments could supply enough energy to create diamonds from underground Vryheid Formation coal driving the diamonds and molten Kimberlite down about 40km then out from under the crater to the sides below the crust. The volcanic plume that followed millions of years later could then force the Kimberlite to explode out of the crust, mainly in a ring of weakened crust around the crater.
‘Shock can also produce various high-pressure materials such as diamond from carbon or Stishovite from quartz. Stishovite is an exceptionally good indicator of shock metamorphism at 16 Giga Pascal pressure’ (Grieve 1990).
‘The pressure exerted on the meteorite and the target rocks can exceed 100 Giga pascal (one million times atmospheric pressure), temperatures can reach several thousand degrees Celsius’ (Grieve, op cit).
Diamonds can form at pressures of 100-150 Giga Pa (1–1.5 million atmospheres) and several 1000 Degrees Centigrade (Hart, 1992).
After the Vredefort Meteorite had left a huge, oval crater, three hundred and thirty by one hundred and sixty five kilometers in size and about fifteen kilometers deep with the rebound cone in the middle, it became a deep lake. In the now isolated valleys between the ‘Ripples’ lakes also formed. As they all silted up with inflowing rivers and streams, as well as air borne dust, (grass only evolved 60 million years ago), their area became larger until they too reached a point where they became swamps with thick water loving plants. Not Glossopteris, as they had died out after creating the Natal coalfields. These world class coalfields of the Free State, Transvaal and Witbank cover all the area where the crater had been and more, equally large, coalfields of Limpopo Province (Springbok Flats, Waterberg, Mopane) occur in the west-east valleys between the mountain ranges, the ‘Ripples’ north of Vredefort.
Vredefort - Dating on the rebound
The Vredefort Dome is the remnant rebound core and comprises target rock thrown up from the transient crater floor. This floor is part of the deeply buried Transvaal Supergroup which has an age in the range of 2558 Ma at the bottom of the Chuniespoort Group, to 2000 Ma for the top of the Rooiberg Group. Depending on which layer of the floor strata is now being dated at the present dome ground level, an age determination dating of 2020 Ma would be from crystals in the rock even though the actual impact date could be anything from 100 Ma to 2500 Ma. My proposal of 214 Ma would fit in to this time period.
Referring to complex craters: As the transient cavity begins to grow, however, some of the rocks in the center rebound upward. The rebound effect lifts the floor of the transient cavity to form a central feature. The uplift in the center of a complex crater amounts to about one tenth of the craters’ final diameter (Grieve, 1990).
Referring to age reset by meteors: Graham Ryder of the Lunar and Planetary Institute in Houston vigorously revived the idea in 1990. Ryder makes three points - One is that ages of rocks are not so easily reset. Recent work on the effects of impacts on ages demonstrates that the only materials whose ages are affected are those that melt during the impact and perhaps, a small percentage of other rocks in the target. Most rocks are crushed up and tossed around but not heated substantially (Taylor, 1994).
With reference to the Vredefort Dome: “No evidence for shock melting (ie, compression/decompression melting early in the cratering process) could be observed”; “The respective geological settings do not favour significant impact shock related melting”; “Evidence for frictional melting has not been forthcoming”; “The proposal that the massive occurrences of PTB on the Vredefort Dome are products of frictional melting on alleged superfaults (Spray, 1997) has, to date, not been supported by field evidence.” "These results clearly support . melting of locally available country rocks with to date no evidence of support of impact melt plus assimilation of local material”. (Reimold, Hoffmann, Hauser, et al, 2016).
If the rocks within the Vredefort Dome were not heated sufficiently to reset their age at the time of impact then the nuclear dating would show the age of the rocks and not the age of impact. These target rocks from the Transvaal Supergroup are aged between 2558 Ma and 2000 Ma. This would fit in with the date of 2020 Ma but would be the age of the rocks and not the impact which could be 214 Ma.
Bushveld Complex - dating between strata layers
Scientists cannot date fossils themselves but they can accurately date the strata above and below to get precise dates of when the fossils were laid down. In 1980, Luis and Walter Alvarez, Frank Asaro and Helen Michels could also date the mass extinction that was caused by a meteorite by measuring the age of the strata above and below iridium that rained down worldwide after a great meteorite impact which caused the Cretaceous-Paleogene (K-Pg) mass extinction 65.5 Ma. . Fern spores below but not above the iridium confirmed the mass extinction marker.
These examples are possible because the fossils and iridium were laid down on top of strata of measurable age and then covered by another layer of measurable age. One can then assume that the fossil or iridium is of an age between the two.
However, if you have many kilometers of sediment laid down between 2558 and 2000 Ma and can measure how old every layer is from bottom to top, you cannot know the age of some un-age-able minerals that were intruded later somewhere in between any of those layers more than a thousand million years later.
In our case, the meteorites’ minerals and magma in the Bushveld Complex were intruded horizontally, forcing the floor down and the roof up, between layers of rock in the Transvaal Supergroup that happen to be the same age as claimed for the formation of the Bushveld Complex.
By this reasoning there is nothing to prevent the Bushveld Large Igneous Complex from being formed in 214 Ma.
The Great Dyke in Zimbabwe
This straight, 550km long, mineral rich, penetrative crater across Zimbabwe is obviously directly connected with the Vredefort Crater. As described in Chapter 09 above, it matches the Bushveld Complex in minerals and Vredefort in direction and approach angle. Accepting that the three sites are from the same event then there is a problem with the ages being 2020 Ma (Vredefort), 2055 Ma (Bushveld) and 2575 Ma (Great Dyke), a spread of 555 million years. If, however you look at the age of target rock you will see that, in each case, this can match the age measurement that is currently given.
We need to consider that if Vredefort Crater and the Bushveld Complex were formed in 2020 and 2060 Ma, their remains, such as Northcliff on the crater rim, the Witwatersrand Ridge and the ripples of the other ranges such as the Magaliesberg and Waterberg, would all have been scraped away by the immense glaciation event that took place during the Dwyka period (302–288 Ma) when Gondwana was emerging from the South Pole.
This event scraped out an inland sea leaving a pile of glacial debris between 100 and 700 meters thick covering most of Gondwana including southern Africa. This was followed later by sediments forming the Ecca Group (286-253 Ma) and the Beaufort Group (250-215 Ma). At 215 Ma the Beaufort Group stopped laying down sediment, possibly because the source of the fluvial sedimentation was disrupted. This disruption was quite likely to have been caused by the huge crater left by the Vredefort impact which would then have changed the landscape and become a receptacle for all runoff in the area.
Following this, the Karoo Volcanic Plume slowly began to erupt lifting southern Africa and covering it with a 1.4 km thick layer of lava to form the Drakensberg Group.
In 1961, before the Radiometric 2020/2060 Ma dates were arrived at, Planetary Geologists of the time believed that Vredefort was in the order of 250 Ma.
(See Tektites by Virgil E Barnes SciAm 1961 Pg 64 referring to Dietz) Virgil Barnes wrote in Scientific American about tektites: Such an impact would dig a crater of the same order of magnitude as the so-called Vredefort Ring in South Africa. This formation, with an inside diameter of 30 miles and an outside diameter of 130 miles, has been identified by Dietz as an astrobleme. It was formed so long ago (250 million years) that its associated tektites have disappeared.
SciAm 1979 Pg 60 Apollo Objects by George W Wetherill says: Most of the well- studied craters are geologically young, being no more than a few hundred million years old. Only two Precambrian craters are known (one near Sudbury in Ontario and the other near Vredefort in South Africa), even though Precambrian time encompasses more than 80% of the Earth’s history. Unless a crater is unusually large all traces of its presence will be eroded away in less than 600 million years.
SciAm 1990 Pg 67 Impact Cratering on Earth by Richard Grieve says: Impact craters on earth range in age from a few thousand to almost two billion years, even though the evidence from the moon suggests the cratering rate has been roughly constant during the past three billion years. Old craters are less abundant simply because they have been destroyed by erosion, sedimentation and other geologic processes.
In The Bushveld Large Igneous Province, University of Witwatersrand: The Bushveld magmatic province is an unusual LIP. In spite of its Palaeoproterozoic age (2050 Ma) it is undeformed. Kinnaird (2005).
Multiple Meteorite Impacts at 214 Ma.
Assume that a planet or planetoid in the Asteroid belt which had been large enough to form a metallic core had been involved in a major collision, broken up, knocked out of orbit and then collided with Planet Earth 214 Ma. This would be a once in a solar lifetime event.
It is known that five large particles had created meteorite craters, the largest at Manicouagan in Canada and another in France, at the same latitude, with the three others in Ontario and Ukraine. Bear in mind that North America and Europe were joined together 214 Ma and, importantly, were on the same longitude in those days as South Africa. Furthermore, todays SW to NE axis of the Vredefort Crater in 214 Ma would have been more like west to east as southern Africa was rotated clockwise relative to todays’ position.(Veevers 2010, 2012; Senckenberg Museum). This combination of locations, directions of approach and timing is unlikely to have ever happened before or likely to happen again. The Planetary Scientists expected to find more impacts connected with the Manicouagan event but were only looking at impacts with the date of 214 Ma. As Vredefort is dated 2020 Ma the Manicouagan research team never thought of looking at it.
If Vredefort, Bushveld and the Great Dyke had been three separate events, vastly separated in time as the current dating of 2020/2055/2575 Ma indicates, they could not have had any relation to each other. The chances of these three separate unique events happening in the same vicinity, from the same direction and angle and leaving similar mineral signatures, is incomprehensible. During these three periods of time southern Africa would have been in a different location and rotation where there was very little chance of an impact from the planetary plane and a seventy percent chance of landing in the ocean leaving no record for us to find.
The Vredefort Meteorite Impact being dated 214 Ma would lead to its’ connection with minerals of South Africa, the Triassic-Jurassic mass extinction, the Karoo volcanic plume, the Drakensberg, diamonds of South Africa and continental drift restarted.
2000-1800 Ma: Rooiberg Group
2230-2000 Ma: Pretoria Group (Into which Vredefort Crater lies)
2054 Ma: <<<<<<<Bushveld Complex (Into which the minerals were intruded)
2500-2100 Ma: Transvaal Supergroup (Chuniespoort, Pretoria and Rooiberg)
2700-2500 Ma: Kaapvaal Craton
3000-2700 Ma: Swazian.
If the Vredefort Impact Crater, the Bushveld Complex and the Great Dyke are all from the same event then they should all be the same age. Not 2020, 2054 and 2575 Ma. All three of these ages match the age of the target rocks or strata.
Bushveld Complex can be penetrative impact as Great Dyke is the same distance underground.
Vredefort, Bushveld and Great Dyke were all on the same latitude, west to east, 214 Ma but highly unlikely 2020, 2054 or 2575 Ma.
(Look Beyond the Wind by Olga Lehmann)
When Dr Hans Merensky returned to South Africa after studying geology in Germany he went for a holiday in South West Africa. Whilst there, railway workers discovered a diamond in a new cutting near Swakopmund. Merensky went to look and found a seam of 200 Ma fossilized oyster shells which Witwatersrand University identified as warm water oysters. This led him to propose that there were undersea volcanoes that warmed the water and spewed up the diamonds. He was right about volcanoes as the mid-Atlantic Ridge was close by then! After he became rich and famous for his platinum reef discovery he returned to SWA to look for the Oyster Line near the Orange River. Here, about a kilometer in from the sea he found it with rich deposits of diamonds. The Earths’ crust had split along that coastline about 200 Ma leaving a warm sea as it was shielded by the new continent of South America and there was volcanic activity as the continents started to spread and the mid-Atlantic ridge began life in this narrow channel. However Merensky was wrong about the source of the diamonds as these had come from the interior of Southern Africa, washed down the Orange River and up the channel, to be deposited along the coastline where the oysters lived. As the channel widened the cold water entered from the South, the oysters died out, the diamond laden beaches silted and widened for kilometers and additional diamonds were deposited out to sea where they are now mined with dredgers.
Copyright David Howcroft 2018
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David Howcroft is a Fellow and Past Chairman of the Society for Automation, Instrumentation, Measurement and Control in South Africa. (SAIMC)
Past Chairman of the Industrial Instrumentation Group (IIG)
Born in Cape Town during 1942 and grew up in Johannesburg, serendipitously in the lee of Northcliff, the highest outcrop of the uplifted Witwatersrand, the White Waters Ridge. After matriculating at Roosevelt High School I went to Cambridge and studied electronics at the Pye Radio and Television training college. 1960 was the age of the first commercial transistors and my final project was to build a 9-transistor portable radio. Each separate transistor was the size of a fingernail. Today, in a memory stick, billions of transistors fit in the same space! After two years of practical experience in Rhodesia (now Zimbabwe), I returned to Johannesburg to study further at Witwatersrand Technical College and use my knowledge of electronics to work in industry on instrumentation and automation.
Over the next 47 years I:
Designed, installed and commissioned systems for just about every industry in South Africa.
Installed the measuring instruments for the first synthetic diamond press in South Africa at de Beers Diamond Research Labs as well as steelmaking at Iscor, continuous casting at Highveld Steel, arc furnaces at Middleburg, Impala Platinum at Springs, vanadium at Steelpoort and gold refining in Germiston.
Was in charge of supply and installation of electrical data logging transducers for Escom and SA Railways.
In 1980, started my own business that designed and installed equipment for automation of factories at Unilever, SA Breweries, Nestle and many more.
(Presentations) to final year students at Wits Uni at invitation of Prof Roy Marcus
Designed a 32 channel computer based FFT sound analyser for large power station boilers to identify and locate high pressure leaks before they could cause serious consequential damage. When I sold my businesses and retired in 2010 over 260 of these systems had been fitted to boilers on power stations in South Africa and around the world.
During 2008 I was invited to consult on measuring instrumentation for the Nuclear Pebble Bed Reactor which should have made South Africa the world leader in this technology. Unfortunately, as the prototype was being built, the funding was suddenly diverted to the more immediate needs of the FIFA 2010 soccer World Cup with its’ required stadiums, roads, trains and airport infrastructures.
In order to control anything, whether compressing carbon into diamonds, continuous casting steel or ensuring the quality of beer, one needs to understand the process and then imagine the dynamics of how the system will operate and what you want it to do. You then select sensors to measure force, level, temperature, pressure, flow, speed, frequency, time, distance, position, composition and anything else that may be required. For this one needs a thorough understanding of science as modern instrumentation uses almost every technology known. Level alone can be measured using optical, mechanical, electrical (resistive, capacitive inductive), pressure, force, acoustic, radar, laser, and nuclear technology. I have always maintained that ‘instrumentation is the practical application of science’. Luckily I was always seriously interested in science and an avid reader of Scientific American for more than 50 years. During a lifetime in Process Automation I knew instinctively which processes would work and how to automate them. I have approached my thirty five year interest in the Vredefort Meteorite Impact in the same way. Even though the forces, pressures and temperatures are almost beyond imagination, the philosophy remains the same. I am not looking at the geology in a conventional way, but rather from what feels right to me both physically and dynamically.
From 1964 onwards my work took me to lots of mines, going down cramped, wet, crowded, high speed lifts into the bowels of the Earth. It became obvious to me that the gold in the Witwatersrand Complex was related to the Vredefort Meteorite crater. I was always told that this was not the accepted geological explanation, because the dates were wrong although everyone always thought it was a good story. In the early 1990s I produced my first PowerPoint on this subject which I called ‘Meteorites, Minerals and Merensky’. This, and updated versions, have entertained and intrigued many groups of people ever since.
In order to understand what I feel you have to really open your mind to the immensity of the variables involved. Most of them are millions, if not billions of times greater than what we are used to in the world around us.
Provided I am right about what happened regarding the impact effects and the minerals and that it happened 214 Ma. If I am correct on both counts then this will change the way we look at our World and the geology of southern Africa
The Sudwala Cave, in one of these ‘ripples’, was originally an underground river that was sheared up out of the ground and tilted about 30 degrees. I spoke to the original farm owner, Mr Owen in about 1970, he told me that the University of Witwatersrand had taken cores through the largest pillar that indicated an age of about 200m years. Also the upheaval was geologically instantaneous as the initial stalactite left the roof at the same angle as it is now. (I have not found the original reference)
Copyright (c) 2018
dave (at) howcroft.co.za