blt
Cartographer
Reged: 01/25/03
Posts: 637
Loc: Santa Cruz, Ca
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I read a nice article today in Scientific American on the Jack Hills' zircons. These small crystals are the oldest bits of Earth known and have been dated to 4.4 Ga (Ga=Giga Annum=1 Billion Years). The discovery of the zircons was made by a team lead by John W Valley at the UW Madison Geology department. Read the complete story at the website: "The Earliest Piece of Earth"
The attached placemark will take you to the place of it's discovery, and contains two geologic overlays extracted from the 2005 paper by Cavosie and others.
Jack Hills Australia
Outcrop of the oldest known sample of the Earth, a 4.4 Ga detrital zircon (sample W74) in the Jack Hills metaconglomerate, Eranondoo Hill, Jack Hills, Western Australia. From l to r: John Valley, University of Wisconsin-Madison; Aaron Cavosie, University of Wisconsin-Madison; Simon Wilde, Curtin University.
Outcrop of the oldest known sample of the Earth
The oldest mineral yet discovered is a spec of zircon (tagged W74/2-36) found near this placemark. The U-Pb age of 4.4 billion years was determined by ion microprobe from the spot shown below.
4.4 Ga detrital zircon (sample W74)
This small (notice the scale bar) zircon apparently eroded out of the initial crust of the Earth and was transported here much later. Oxygen isotope analysis indicates that it may be have formed from wet oceanic sediments.
Here is a nice timeline from the UW showing the relative age of 4.4 Ga.
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Jumble
Master Guide
Reged: 04/20/03
Posts: 4096
Loc: Philadelphia, PA
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Sandwichman, you missed the "fun".. Click Here!!
Maybe a dedicated "Geology Forum" would help keep us rock docs coordinated!!
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There are none so blind......
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beno
Master Guide
Reged: 07/02/05
Posts: 1308
Loc: Dunchurch, Warwickshire, UK
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Someone else with an interest in GAFA country?
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blt
Cartographer
Reged: 01/25/03
Posts: 637
Loc: Santa Cruz, Ca
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drat..., I've been caught double posting again - Although It would have been a bit more obvious if the thread you point had not been written in code  . Easy to miss things in the GAFA
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beno
Master Guide
Reged: 07/02/05
Posts: 1308
Loc: Dunchurch, Warwickshire, UK
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Quote:
drat..., I've been caught double posting again - Although It would have been a bit more obvious if the thread you point had not been written in code . Easy to miss things in the GAFA
Maybe, but your post has much better graphics!
Beno
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beno
Master Guide
Reged: 07/02/05
Posts: 1308
Loc: Dunchurch, Warwickshire, UK
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I spent hours trying to find out about this place to answer Jumble's challenge and never came across this paper - Internal zoning and U–Th–Pb chemistry of Jack Hills detrital zircons: a mineral record of early Archean to Mesoproterozoic (4348–1576 Ma) magmatism - Aaron J. Cavosie, Simon A. Wilde, Dunyi Liu, Paul W. Weiblen, John W. Valley which has the great maps you've posted.
Personally, I would worry about a double post here it's not Alcatraz, http://bbs.keyhole.com/ubb/showthreaded.php?Cat=&Board=EarthTravel&Number=350 !
Beno.
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X_fighter_plane
Tourist
Reged: 09/25/05
Posts: 8
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hi im new to google earth and this is the most interesting post so far its nice to see a little bit of geog once in a while nice touch 
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beno
Master Guide
Reged: 07/02/05
Posts: 1308
Loc: Dunchurch, Warwickshire, UK
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Hi X_fighter_plane
You're spot on - this is a brilliant placemark - I wish all of mine were at this standard.
Beno
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