Gold Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! ===Asteroid origin theories=== Because the Earth was molten [[History of Earth|when it was formed]], almost all of the gold present in the [[early Earth]] probably sank into the [[core (geology)|planetary core]]. Therefore, as hypothesized in one model, most of the gold in the Earth's [[crust (geology)|crust]] and [[mantle (geology)|mantle]] is thought to have been delivered to Earth by [[asteroid impact]]s during the [[Late Heavy Bombardment]], about 4 billion years ago.<ref name="Willbold 2011">{{cite journal |last2=Elliott |first2=Tim |last3=Moorbath |first3=Stephen |date=2011 |title=The tungsten isotopic composition of the Earth's mantle before the terminal bombardment |journal=Nature |volume=477 |issue=7363 |pages=195β8 |bibcode=2011Natur.477..195W |doi=10.1038/nature10399 |pmid=21901010 |last1=Willbold |first1=Matthias|s2cid=4419046 }}</ref><ref name="Battison-2011">{{cite news |url=https://www.bbc.co.uk/news/science-environment-14827624 |title=Meteorites delivered gold to Earth |last=Battison |first=Leila |date=8 September 2011 |work=[[BBC]] }}</ref> Gold which is reachable by humans has, in one case, been associated with a particular asteroid impact. The asteroid that formed [[Vredefort impact structure]] 2.020 billion years ago is often credited with seeding the [[Witwatersrand basin]] in [[South Africa]] with the richest gold deposits on earth.<ref>{{cite web |url=http://superiormining.com/properties/south_africa/mangalisa/geology/ |title=Mangalisa Project |publisher=Superior Mining International Corporation |access-date=29 December 2014}}</ref><ref>{{cite journal |last1=Therriault |first1=A. M. |first2=R. A. F. |last2=Grieve |first3=W. U. |last3=Reimold |title=Original size of the Vredefort Structure: Implications for the geological evolution of the Witwatersrand Basin |journal=Meteoritics |volume=32 |pages=71β77 |date=1997 |bibcode=1997M&PS...32...71T |name-list-style=amp |doi=10.1111/j.1945-5100.1997.tb01242.x|doi-access=free }}</ref><ref>[https://web.archive.org/web/20120327184158/http://www.cosmosmagazine.com/news/2101/meteor-craters-may-hold-untapped-wealth Meteor craters may hold untapped wealth]. Cosmos Magazine (28 July 2008). Retrieved on 12 September 2013.</ref><ref>{{Cite journal |last1=Corner |first1=B. |last2=Durrheim |first2=R. J. |last3=Nicolaysen |first3=L. O. |title=Relationships between the Vredefort structure and the Witwatersrand basin within the tectonic framework of the Kaapvaal craton as interpreted from regional gravity and aeromagnetic data |doi=10.1016/0040-1951(90)90089-Q |journal=Tectonophysics |volume=171 |issue=1 |pages=49β61 |year=1990 |bibcode=1990Tectp.171...49C}}</ref> However, this scenario is now questioned. The gold-bearing [[Witwatersrand]] rocks were laid down between 700 and 950 million years before the Vredefort impact.<ref name="McCarthy">McCarthy, T., Rubridge, B. (2005). ''The Story of Earth and Life''. Struik Publishers, Cape Town. pp. 89β90, 102β107, 134β136. {{ISBN|1 77007 148 2}}</ref><ref name="Norman">Norman, N., Whitfield, G. (2006) ''Geological Journeys''. Struik Publishers, Cape Town. pp. 38β49, 60β61. {{ISBN|9781770070622}}</ref> These gold-bearing rocks had furthermore been covered by a thick layer of Ventersdorp lavas and the [[Transvaal Basin|Transvaal Supergroup]] of rocks before the meteor struck, and thus the gold did not actually arrive in the asteroid/meteorite. What the Vredefort impact achieved, however, was to distort the [[Witwatersrand basin]] in such a way that the gold-bearing rocks were brought to the present [[erosion surface]] in [[Johannesburg]], on the [[Witwatersrand]], just inside the rim of the original {{cvt|300|km|adj=on}} diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the [[Witwatersrand Gold Rush]]. Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks.<ref name="Norman" /> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page