Re: [meteorite-list] Meteorites Delivered Earth's Gold
There was a story going around the turn of the last century that some placer miners (oldtimers) used to leave some small gold nuggets in situ in a fast moving stream so the nuggets would grow larger. Chris. Spratt Victoria, BC __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites Delivered Earth's Gold
There was a story going around the turn of the last century that some placer miners (oldtimers) used to leave some small gold nuggets in situ in a fast moving stream so the nuggets would grow larger. There must have been some mighty dumb miners where you lived. The one's I hung out with were a lot smarter than this. :O) GeoZay __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites delivered Earth's gold
Quartz formed in the Earth's crust, and stayed there. It is light (compared with gold) and doesn't have an affinity for iron. Indeed, it continues to form, given the abundance of silicon and oxygen in the crust and mantle. In bulk, there is no more gold in meteorites than in the Earth. The Earth is simply more differentiated, and most of its original gold is now in the core. What this paper proposes is that meteorites were the source of gold (and possibly other elements) that we find in surface material, since these elements were introduced after the Earth differentiated. Nothing changed meteorites (in the sense I think you mean), and we don't find solid gold meteorites because gold is a trace element, and there was no mechanism to concentrate it. Chris *** Chris L Peterson Cloudbait Observatory http://www.cloudbait.com On 9/10/2011 3:36 PM, cdtuc...@cox.net wrote: Paul, List, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Thanks. Carl __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites delivered Earth's gold
Quartz forms on Earth. On 9/10/2011 2:36 PM, cdtuc...@cox.net wrote: Paul, List, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Thanks. Carl -- Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote. Paul H.oxytropidoce...@cox.net wrote: Young Earth was sprinkled with precious metals physicsworld.com, Sept. 7, 2011 http://physicsworld.com/cws/article/news/47116 Where does all the gold come from? University of Bristol, Sept 7, 2011 http://www.bristol.ac.uk/news/2011/7885.html Meteorites delivered Earth's gold, by Leila Battison BBC News, Sept 8, 2011 http://www.bbc.co.uk/news/science-environment-14827624 The paper is: Willbold, M., T. Elliott, and S. Moorbath, 2011, The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature. vol. 477, no. 7363, pp. 195-198. DOI: 10.1038/nature10399 http://www.nature.com/nature/journal/v477/n7363/full/nature10399.html A related paper is: Marty, B., and A. Meibom, 2007, Noble gas signature of the Late Heavy Bombardment in the Earth’s atmosphere. eEarth. vol. 2, pp. 43–49. PDF file at: http://hal.archives-ouvertes.fr/docs/00/33/07/83/PDF/ee-2-43-2007.pdf Yours, Paul H. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites delivered Earth's gold
Carl all, From what I understand gold is deposited with quartz because gold rarely occurs as a mineral. Mineral deposits are formed by mineralized waters and magma. As these solutions move along faults, joints and form veins, different elements mate together to produce minerals as pressure/temp conditions change. The remaining solution will consist of the elements that didn't precipitate our or combine with the other elements to form a specific mineral. This is usually excess silica, which comes out as quartz (because there are few things left to combine with and produce silicate minerals) and gold (if it was there to begin with). I suppose this is how most deposits of native metals/elements occur. It's a basic prospector's understanding, but that is what I have come to learn. Gold and quartz don't have to be together, but they often are. But that's not because quartz is necessary in the formation of gold. All elements on earth come from space, both gold and silica. I've never looked into why quartz doesn't occur in meteorites, but I suspect that conditions existed where all the silica was used up to form silicate minerals (that we do find in meteorites) and no excess silica remained to form quartz. Gold occurs in meteorites in traces because it isn't abundant in the solar system. Gold occurs in commercial deposits on earth because it can be concentrated by weathering processes found on earth. That doesn't occur in space so it remain as a trace element. I hope the others out there who have a better understanding will chime in and correct me and fill in the gaps of my limited understanding :) Clear skies, Mark B Vail, AZ From: cdtuc...@cox.net cdtuc...@cox.net To: meteorite-list@meteoritecentral.com meteorite-list@meteoritecentral.com; Paul H. oxytropidoce...@cox.net Sent: Saturday, September 10, 2011 2:36 PM Subject: Re: [meteorite-list] Meteorites delivered Earth's gold Paul, List, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Thanks. Carl -- Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote. Paul H. oxytropidoce...@cox.net wrote: Young Earth was sprinkled with precious metals physicsworld.com, Sept. 7, 2011 http://physicsworld.com/cws/article/news/47116 Where does all the gold come from? University of Bristol, Sept 7, 2011 http://www.bristol.ac.uk/news/2011/7885.html Meteorites delivered Earth's gold, by Leila Battison BBC News, Sept 8, 2011 http://www.bbc.co.uk/news/science-environment-14827624 The paper is: Willbold, M., T. Elliott, and S. Moorbath, 2011, The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature. vol. 477, no. 7363, pp. 195-198. DOI: 10.1038/nature10399 http://www.nature.com/nature/journal/v477/n7363/full/nature10399.html A related paper is: Marty, B., and A. Meibom, 2007, Noble gas signature of the Late Heavy Bombardment in the Earth’s atmosphere. eEarth. vol. 2, pp. 43–49. PDF file at: http://hal.archives-ouvertes.fr/docs/00/33/07/83/PDF/ee-2-43-2007.pdf Yours, Paul H. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Meteorites delivered Earth's gold - Then plate tectonics concnetrated it
In [meteorite-list] Meteorites delivered Earth's gold at: http://six.pairlist.net/pipermail/meteorite-list/2011-September/079706.html Carl Asked, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Nothing has changed in the composition of meteorites. The quartz came from a combination of primary differentiation, by the crystallization and preferential settling of mafic minerals, of the magma that intruded into the Earth's crust and by melting and recycling of older sedimentary rock to form silica-rich magmas. This happened long after the gold was theoretically was delivered to the Earth by meteorites and asteroids. There was no quartz in the meteorites and asteroids, which were proposed to have brought the gold to Earth. During the last 3 or more billion years, the meteorites, asteroids, impactites, and gold in them were completely consumed by either erosion or plate tectonics and recycled by plate tectonics along with large parts of the Earth's crust. The crust included sediments in which quartz has been concentrated by weathering. In a subduction zone, some of these recycled materials were melted and turned into magma, of which some intruded back into the overlying crust. As these magma intrusions cooled, some of it differentiated to enrich the magma in silica. As these magmas cooled to form large bodies of plutonic rocks, i.e. granitic batholiths, various processes concentrated the gold and quartz from the magma together into gold-bearing veins. Thus, the gold and quartz came together only in the process of the gold-bearing deposits being created. Before that time, they were separate from each other. For a more detailed explanation, go see: Macdonald, E. H., 2007, Handbook of gold exploration and evaluation. Woodhead Publishing, Cambridge, England. 647 pp. ISBN 1845692543 http://www.worldcat.org/title/handbook-of-gold-exploration-and-evaluation/oclc/77257822?referer=diht=edition Yours, Paul H. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites delivered Earth's gold
Carl, The earth's crust is under a continuous process of differentiation by various processes. By differentiation I mean the separation and concentration of the various elements. There are probably a multitude of mechanisms that allow concentration of specific elements, and all three rock types (sedimentary, igneous, and metamorphic) are formed by processes that are capable of doing this. For instance.. Sedimentary processes (rivers, oceans, wind etc) can sort stuff out and deposit it in different places due to density. Gold notably is concentrated in this manner with placer deposits. Igneous rocks are derived from molten magmas at depth in the earth's crust. As the melt cools, depending on the pressure and temperature regimes various minerals will crystallise out. At any given stage in the cooling process the remaining melt will consist of the more volatile constituents that still remain fluid (silica, water, CO2 etc), along with the relatively unreactive or incompatible elements that don't easily combine in the minerals that are precipitating. If the melt has a chance to vent up a crack you get this siliceous solution migrating towards the surface carrying incompatible stuff with it. As it gets closer to the surface and cools the constituent elements are forced to precipitate at some stage giving rise eventually to ore bearing quartz veins. Gravity is also a big player in helping to physically differentiate a cooling melt Dunites (90% plus olivine) may be formed by olivine precipitating out of a basaltic magma and falling to the bottom of the magma chamber to form a thick deposit or 'cumulate'. Given a magma chamber that doesn't vent or have fresh basaltic magma injected before it cools, the very top layers of the cumulate body can get concentrated with all sorts of rare stuff. I believe the south african ore body called the Merensky Reef which is rich in the platinum group was formed along these lines. Indeed the differentiation of the earth's interior into an iron/(nickel?) core, outer dense mafic (silica poor) mantle, and felsic (silica rich) granitic continental crust is driven in part by gravity. Now on Earth, plate tectonics is a still active mechanism that is continually recycling crust, bringing it from deep to the surface, or melting and redifferentiating it. Some of the larger asteroids presumably were molten long enough to undergo a substantial degree of differentiation as evidenced by irons/pallasites as analogues to the earth's inner/outer core material, but the mechanism for exposing this material at the body's surface is probably catastrophic impact, whereas the closest we get on Earth to sampling even the moderately deep stuff is via ancient vulcanism like kimberlites. But back to the original question which is an interesting one, whether hydrothermal gold bearing quartz analogues exist on other bodies in the solar system. Don't know but it wouldn't surprise me if Mars for instance had them. It has patently had water and extensive volcanism. I think small quantities of free quartz exist in some eucrites and basaltic shergotites indicating sufficient differentiation to produce the mineral in some of the parent bodies out there. Whether it has become further concentrated in places with additional hydrothermal or magmatic processes is something I don't know if there is any direct evidence for. Maybe it's just very rare. Our planet has had a good 4 billion years of active geology to push deep rocks to the surface, and take surface rocks to the depths, and an active atmosphere to continually erode and expose and redistribute material. We're still not exactly tripping over gold bearing quartz, and you have to pick up an awful lot of random pebbles to find a nugget. Maybe our crust is gold poor relative to meteorites because we are relatively overdifferentiated - maybe the bulk of it migrated to the core; gold is dense and does alloy well with nickel. Is that a realistic hypothesis? Regards, John On 10/09/2011 16:36, cdtuc...@cox.net cdtuc...@cox.net wrote: Paul, List, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Thanks. Carl -- Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote. Paul H. oxytropidoce...@cox.net wrote: Young Earth was sprinkled with precious metals physicsworld.com, Sept. 7, 2011 http://physicsworld.com/cws/article/news/47116 Where does all
Re: [meteorite-list] Meteorites Delivered Earth's Gold
John Hendry gave us a good description of gold forming processes but there is another method. This is the direct deposition of gold that has been dissolved by biologic processes and not necessarily at higher than surface temperatures. Here's one article: http://www.asknature.org/strategy/c7372dfb952636b3557a79e175387755 and here is one of a somewhat unique example of gold crystallizing on a 1908 gold coin found in Alaska: http://www.springerlink.com/content/vnr200440355pm42/ So, has anyone come across a gold plated meteorite? Chauncey I drove by the Holiday Inn show in Denver yesterday and it looks like they are already cranking up. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
[meteorite-list] Meteorites delivered Earth's gold
Young Earth was sprinkled with precious metals physicsworld.com, Sept. 7, 2011 http://physicsworld.com/cws/article/news/47116 Where does all the gold come from? University of Bristol, Sept 7, 2011 http://www.bristol.ac.uk/news/2011/7885.html Meteorites delivered Earth's gold, by Leila Battison BBC News, Sept 8, 2011 http://www.bbc.co.uk/news/science-environment-14827624 The paper is: Willbold, M., T. Elliott, and S. Moorbath, 2011, The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature. vol. 477, no. 7363, pp. 195-198. DOI: 10.1038/nature10399 http://www.nature.com/nature/journal/v477/n7363/full/nature10399.html A related paper is: Marty, B., and A. Meibom, 2007, Noble gas signature of the Late Heavy Bombardment in the Earth’s atmosphere. eEarth. vol. 2, pp. 43–49. PDF file at: http://hal.archives-ouvertes.fr/docs/00/33/07/83/PDF/ee-2-43-2007.pdf Yours, Paul H. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
Re: [meteorite-list] Meteorites delivered Earth's gold
Paul, List, It seems to me that much of the Gold found on Earth is accompanied by Quartz. In fact most of the finest Non-nugget specimens are usually found in quartz. That said; If this gold came from space then where did the quartz come from and for that matter why is gold not found buried in chonditic rock instead of quartz. . Quartz does not seem to be terribly abundant in meteorites. Just curious why we don't find gold / quartz meteorites. What changed meteorites? Do we have any witnessed falls of Gold meteorites? Do these researchers consider the Quartz issue here? Thanks. Carl -- Democracy is two wolves and a lamb voting on what to have for dinner. Liberty is a well-armed lamb contesting the vote. Paul H. oxytropidoce...@cox.net wrote: Young Earth was sprinkled with precious metals physicsworld.com, Sept. 7, 2011 http://physicsworld.com/cws/article/news/47116 Where does all the gold come from? University of Bristol, Sept 7, 2011 http://www.bristol.ac.uk/news/2011/7885.html Meteorites delivered Earth's gold, by Leila Battison BBC News, Sept 8, 2011 http://www.bbc.co.uk/news/science-environment-14827624 The paper is: Willbold, M., T. Elliott, and S. Moorbath, 2011, The tungsten isotopic composition of the Earth’s mantle before the terminal bombardment. Nature. vol. 477, no. 7363, pp. 195-198. DOI: 10.1038/nature10399 http://www.nature.com/nature/journal/v477/n7363/full/nature10399.html A related paper is: Marty, B., and A. Meibom, 2007, Noble gas signature of the Late Heavy Bombardment in the Earth’s atmosphere. eEarth. vol. 2, pp. 43–49. PDF file at: http://hal.archives-ouvertes.fr/docs/00/33/07/83/PDF/ee-2-43-2007.pdf Yours, Paul H. __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list __ Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html Meteorite-list mailing list Meteorite-list@meteoritecentral.com http://six.pairlist.net/mailman/listinfo/meteorite-list
