[meteorite-list] Platinum is from outer space

From: Galactic Stone & Ironworks <meteoritemike_at_meteoritecentral.com>
Date: Fri, 31 Jul 2009 18:37:20 -0400
Message-ID: <e51421550907311537g2e2bd3dek5ad6af4e71962d60_at_mail.gmail.com>

Hi David,

Thanks for sharing this. It's very cool to think that the platinum
around us is meteoritic. :)

Best regards,

MikeG


On 7/31/09, David R. Vann <drvann at sas.upenn.edu> wrote:
> Of general interest, perhaps - I was researching Komatiites, and ran across
> this-
> Apparently all crustal platinum is from meteoritic deposits. So, your
> platinum
> wedding band is made of meteorites...
>
> Contact me off-list if you are interested in a copy of this article.
>
> Nature Vol 460|30 July 2009
> Progressive mixing of meteoritic veneer into the early
> Earth?s deep mantle
>
>
> Wolfgang D. Maier1, Stephen J. Barnes, Ian H. Campbell, Marco L. Fiorentini,
> Petri Peltonen,
> Sarah-Jane Barnes & R. Hugh Smithies
>
> synopsis from R&D daily
>
> A research program aimed at using platinum as an exploration guide for
> nickel
> has for the first time been able to put a time scale on the planet's
> large-scale convection processes.
>
> The research is reported in a Nature paper titled "Progressive mixing of
> meteoritic veneer into the early Earth's deep mantle".
>
> Report author CSIRO Minerals Down Under Flagship researcher Dr Stephen
> Barnes
> said the study group collected a large body of data on the platinum content
> of
> lava flows called komatiites, which host some of the world's major nickel
> deposits.
>
> "We found that the oldest komatiites have the lowest platinum content," Dr
> Barnes said. "The platinum content gradually increases from about 3.5
> billion
> years to 2.9 billion years ago. "This tells us that the deep source where
> the
> komatiite came from, down near the boundary between the Earth's core and
> mantle, was gradually gaining platinum over time".
>
> The paper's authors now think they know why.
>
> "When the Earth's core formed, it took all the available platinum with it,
> leaving the mantle and crust with none," Dr Barnes said.
>
> "Following that, a steady rain of meteorites created the so-called Late
> Veneer?a
> thin surface layer of meteorite debris rich in platinum."
>
> With time through large-scale convection processes, which now cause plate
> tectonics, this material was stirred down into the interior of the Earth.
>
> We are seeing the signal of that stirring, which took about 1.5 billion
> years to
> occur. This is the first time a time scale has been put on the stirring,
> which
> has important implications for the people who study the dynamics of mantle
> processes and the mechanisms that cause plate tectonics, earthquakes and
> volcanoes.
>
> Combined with some other work by the researchers on sister elements to
> platinum,
> iridium and osmium, we also now have a new framework for understanding the
> variations in isotopic ratios of osmium with time.
>
> Osmium isotopes are widely used as tracers of mantle processes, but there
> has
> been a mismatch between signals from osmium and from other important
> isotopic
> tracer systems which has eluded explanation until now.
>
> Co-authors Dr Marco Fiorentini and Dr Wolfgang Maier from the University of
> Western Australia are delighted that this is a completely academic outcome
> which came out of an industry-funded project.
>
> "It is a nice example of an unexpected fundamental discovery arising from a
> practical applied science study and demonstrates the very positive
> collaborations that exist between CSIRO and the University of Western
> Australia," Dr Fiorentini said.
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Received on Fri 31 Jul 2009 06:37:20 PM PDT