Post by 1dave on Apr 21, 2021 13:36:39 GMT -5
Finally! I found someone who agrees with me!
Copyright David P. Howcroft South Africa 2020
In a Special Paper for the 29th De Beers Alex L. Du Toit Memorial Lecture, Wolf Uwe Reimold wrote, ‘This has proven, just like the debate about continental drift, and on a smaller scale, about the origin of the Vredefort Dome, that ideas and hypotheses that initially are widely regarded as absurd and consequently are subjected to negative critique, may well have merit’ (Reimold 2007). Reimold was discussing the new multidisciplinary research; bringing together scientists from the planetary, earth and life sciences. It would never have been possible for me to write about my hypotheses without them. ‘If I have seen further it is by standing on the shoulders of giants’ (Isaac Newton 1675, ‘coined by a 12th century cathedral school’, Seb Falk 2020).
In a Special Paper for the 29th De Beers Alex L. Du Toit Memorial Lecture, Wolf Uwe Reimold wrote, ‘This has proven, just like the debate about continental drift, and on a smaller scale, about the origin of the Vredefort Dome, that ideas and hypotheses that initially are widely regarded as absurd and consequently are subjected to negative critique, may well have merit’ (Reimold 2007). Reimold was discussing the new multidisciplinary research; bringing together scientists from the planetary, earth and life sciences. It would never have been possible for me to write about my hypotheses without them. ‘If I have seen further it is by standing on the shoulders of giants’ (Isaac Newton 1675, ‘coined by a 12th century cathedral school’, Seb Falk 2020).
1.0 Abstract
Since the 1900s when Geoscientists investigated the geochronological record of the Vredefort Impact Structure using many new sources of dating based on nuclear decay and zircon crystals, they assumed that the dark, almost black, pseudotachylyte breccia (PTB) between the cracked rocks was impact melt. Over the past 30 years they have improved their accuracies of measurement to arrive at a figure of 2023+ 4 Ma (Million years ago) for the impact. However, in the past 5 years it has been accepted that the PTB is powdered rock made from adjacent enclosing country rocks that were shaken violently by the earthquakes following the impact or compression/decompression shock waves. The age of the PTB has also been found to be the same as the surrounding rock and the Vredefort Granophyre. I suggest that the existing precise age measurements are for the target rock and not the meteorite impact.
It is also now accepted that the Witwatersrand Basin, the source of the largest deposit of gold in the world, is connected to this impact (although it is not traditionally accepted that gold and uranium came from the meteorite). This oval crater, with a subsurface entry south of Welkom (identified by major faults) is an indication of an oblique impact of less than 15o to the horizontal which has little, if any, impact melt. Despite many years of searching by geoscientists from Witwatersrand University and others, no signs of ejecta from Vredefort have been found. Hydrocode 3D computer simulations indicate that it is possible for these low angle impacts at hypervelocity to travel long distances through rock or magma. I have named this a penetrative meteorite crater.
The Bushveld Complex (BC), a Large Igneous Province (LIP), starts about 50 km north-east of the northern rim of Vredefort and is presently dated 2060-2054 Ma. This intrusion, the Rustenberg Layered Suite (RLS), contains 7% by weight (approximately 100,000 billion tonnes) of minerals including world leading deposits of chrome, vanadium and Platinum Group Metals (PGMs) and 93% local rock. The age given for the RLS is the same as the strata from the floor and the roof. I suggest that this age for the horizontal intrusion is based on 2060 Ma strata of sedimentary rock in the meteorite’s pathway from Vredefort. This had been subject to acoustic fluidization (shattered without melting, flows like liquid) which carried eroded projectile minerals with it into the BC. As there are no signs of shock impact, the BC is not regarded as of meteoritic origin. My contention is that all the shatter cones and other shock metamorphic effects are near the Vredefort Dome as this was where the greatest impact forces occurred with the tail end of the penetration not generating sufficient pressures and temperatures.
The Great Dyke (GD) is not a dyke, but, I suggest, an astrobleme. This lopolithic, Y-shaped, scar starts roughly 250 km north-east of the end of the BC and ploughs horizontally for 550 km across Zimbabwe. The structure has been dated as 2575 Ma, although the target rock is in this age bracket. From overhead it is exactly in line with the centre of the Bushveld
4
Complex and the Vredefort Dome. From the side it is 0o to the ground. The entry points of Vredefort and the GD are 800 km apart. At 111 km per degree, the result is an oblique impact for Vredefort of about 7.2o. This is what would be needed to penetrate 25 km deep under the present Dome and continue through the BC to Polokwane in the north-east. The geological connection between the Bushveld Complex and Great Dyke is in the same minerals, especially chrome and PGMs with both deposits the only known with more platinum than palladium.
Up until the late 1980s, before the zircon and radiometric 2023/2060/2575 Ma dates were arrived at, geoscientists of the time believed that the Vredefort Structure’s age was in the order of at least 250 Ma (Dietz 1961) or that it was comparatively young looking for the ages given to it. ‘Unless a crater is unusually large all traces of its presence will be eroded away in less than 600 million years’ (Wetherill 1979). ‘Old craters are less abundant simply because they have been destroyed by erosion, sedimentation and other geologic processes’ (Grieve 1990). ‘The Bushveld magmatic province is an unusual LIP. In spite of its Palaeoproterozoic age [2055 Ma] it is undeformed’ (Kinnaird 2005). I am inclined to agree with these authors.
To look at an alternative time, we need to go to many other branches of science. 298 Ma, after spending millions of years under the Antarctic Circle covered in 4 km thick ice, the melting glaciers scraped across Gondwana, leaving the Dwyka layer of round, roughly 20 cm rocks, as markers. If Vredefort, the BC and GD were really formed prior to this glaciation event all the rims, rings and outcrops surrounding these three structures would have been scraped flat and shock-formed caves north of Witwatersrand collapsed under the weight of ice. The Dwyka layer is buried deep in the dish of the Bushveld Complex and then covered with young Karoo sediments to ground level. Only if the BC was formed after the glaciation could this have happened. If much earlier than Dwyka, say 2060 Ma, then the dish would have already silted and the Dwyka layer would be at ground level. The Karoo Elliot Formation dated from 220-201 Ma is stained red and contains traces of uranium, the same element that shares the lining of Vredefort Impact crater with fine gold. These layers contain large numbers of fossils, over 30,000 so far including about 3000 species.
Since the 1900s when Geoscientists investigated the geochronological record of the Vredefort Impact Structure using many new sources of dating based on nuclear decay and zircon crystals, they assumed that the dark, almost black, pseudotachylyte breccia (PTB) between the cracked rocks was impact melt. Over the past 30 years they have improved their accuracies of measurement to arrive at a figure of 2023+ 4 Ma (Million years ago) for the impact. However, in the past 5 years it has been accepted that the PTB is powdered rock made from adjacent enclosing country rocks that were shaken violently by the earthquakes following the impact or compression/decompression shock waves. The age of the PTB has also been found to be the same as the surrounding rock and the Vredefort Granophyre. I suggest that the existing precise age measurements are for the target rock and not the meteorite impact.
It is also now accepted that the Witwatersrand Basin, the source of the largest deposit of gold in the world, is connected to this impact (although it is not traditionally accepted that gold and uranium came from the meteorite). This oval crater, with a subsurface entry south of Welkom (identified by major faults) is an indication of an oblique impact of less than 15o to the horizontal which has little, if any, impact melt. Despite many years of searching by geoscientists from Witwatersrand University and others, no signs of ejecta from Vredefort have been found. Hydrocode 3D computer simulations indicate that it is possible for these low angle impacts at hypervelocity to travel long distances through rock or magma. I have named this a penetrative meteorite crater.
The Bushveld Complex (BC), a Large Igneous Province (LIP), starts about 50 km north-east of the northern rim of Vredefort and is presently dated 2060-2054 Ma. This intrusion, the Rustenberg Layered Suite (RLS), contains 7% by weight (approximately 100,000 billion tonnes) of minerals including world leading deposits of chrome, vanadium and Platinum Group Metals (PGMs) and 93% local rock. The age given for the RLS is the same as the strata from the floor and the roof. I suggest that this age for the horizontal intrusion is based on 2060 Ma strata of sedimentary rock in the meteorite’s pathway from Vredefort. This had been subject to acoustic fluidization (shattered without melting, flows like liquid) which carried eroded projectile minerals with it into the BC. As there are no signs of shock impact, the BC is not regarded as of meteoritic origin. My contention is that all the shatter cones and other shock metamorphic effects are near the Vredefort Dome as this was where the greatest impact forces occurred with the tail end of the penetration not generating sufficient pressures and temperatures.
The Great Dyke (GD) is not a dyke, but, I suggest, an astrobleme. This lopolithic, Y-shaped, scar starts roughly 250 km north-east of the end of the BC and ploughs horizontally for 550 km across Zimbabwe. The structure has been dated as 2575 Ma, although the target rock is in this age bracket. From overhead it is exactly in line with the centre of the Bushveld
4
Complex and the Vredefort Dome. From the side it is 0o to the ground. The entry points of Vredefort and the GD are 800 km apart. At 111 km per degree, the result is an oblique impact for Vredefort of about 7.2o. This is what would be needed to penetrate 25 km deep under the present Dome and continue through the BC to Polokwane in the north-east. The geological connection between the Bushveld Complex and Great Dyke is in the same minerals, especially chrome and PGMs with both deposits the only known with more platinum than palladium.
Up until the late 1980s, before the zircon and radiometric 2023/2060/2575 Ma dates were arrived at, geoscientists of the time believed that the Vredefort Structure’s age was in the order of at least 250 Ma (Dietz 1961) or that it was comparatively young looking for the ages given to it. ‘Unless a crater is unusually large all traces of its presence will be eroded away in less than 600 million years’ (Wetherill 1979). ‘Old craters are less abundant simply because they have been destroyed by erosion, sedimentation and other geologic processes’ (Grieve 1990). ‘The Bushveld magmatic province is an unusual LIP. In spite of its Palaeoproterozoic age [2055 Ma] it is undeformed’ (Kinnaird 2005). I am inclined to agree with these authors.
To look at an alternative time, we need to go to many other branches of science. 298 Ma, after spending millions of years under the Antarctic Circle covered in 4 km thick ice, the melting glaciers scraped across Gondwana, leaving the Dwyka layer of round, roughly 20 cm rocks, as markers. If Vredefort, the BC and GD were really formed prior to this glaciation event all the rims, rings and outcrops surrounding these three structures would have been scraped flat and shock-formed caves north of Witwatersrand collapsed under the weight of ice. The Dwyka layer is buried deep in the dish of the Bushveld Complex and then covered with young Karoo sediments to ground level. Only if the BC was formed after the glaciation could this have happened. If much earlier than Dwyka, say 2060 Ma, then the dish would have already silted and the Dwyka layer would be at ground level. The Karoo Elliot Formation dated from 220-201 Ma is stained red and contains traces of uranium, the same element that shares the lining of Vredefort Impact crater with fine gold. These layers contain large numbers of fossils, over 30,000 so far including about 3000 species.
