[meteorite-list] Fwd: Re: Nickel free metal in Meteorites

From: cdtucson at cox.net <cdtucson_at_meteoritecentral.com>
Date: Fri, 26 Mar 2010 17:16:53 -0400
Message-ID: <20100326171653.YXHL6.48663.imail_at_fed1rmwml4201>

-
>
> Alan,
> Wow, you like Jeff and Laurence (off-list) must also be an excellent teacher. All are Certainly a credit to your profession. I must say though as convincing as you are there remains a tad bit of reasonable doubt. when you said.
>
> " Please note that
> volumetrically, the amount of low-Ni metallic Fe is trivial, far less than
> 0.1% of a typical chondrite."
>
> ,1% is a relative term. Earth may be only a fraction of the size of Artares but, it is still a pretty big rock.
>
> I'm also not sure an Iron has to have all those other things like troilite either. But again, just a smidgen of reasonable doubt.
>
> Thanks so much. You are Kind and that is a very good thing. Carl
> --
> Carl or Debbie Esparza
> Meteoritemax
>
>
> ---- Alan Rubin <aerubin at ucla.edu> wrote:
> >
> > ----- Original Message -----
> > From: <cdtucson at cox.net>
> > To: "Alan Rubin" <aerubin at ucla.edu>; "meteoritelist"
> > <meteorite-list at meteoritecentral.com>
> > Sent: Friday, March 26, 2010 12:23 PM
> > Subject: Re: [meteorite-list] Nickel free metal in Meteorites
> >
> >
> > > Alan,
> > > Wow, I appreciate that your points are put in terms I can follow but Would
> > > you be so kind as to explain a bit better for me to understand?
> > > Again, I respect you enough to hear what you are saying but, you lost me
> > > in some of your points. I will question below in all caps. No, I'm not
> > > yelling.
> > > Thanks.
> > > --
> > > Carl or Debbie Esparza
> > > Meteoritemax
> > >
> > >
> > > ---- Alan Rubin <aerubin at ucla.edu> wrote:
> > >> Low-Ni or Ni-free iron doesn't occur just in some chondrules. It is also
> > >> found in impact-melt-rock clasts in ordinary chondrites and at the edges
> > >> of
> > >> olivine grains in ureilites.
> > > SO, THIS MAY EXPLAIN THE KALAHARI FIND OF THIS NICKEL FREE IRON? AND YOUR
> > > INPUT IS HIGHLY APPRECIATED HERE.
> >
> > I'm afraid I don't know anything about
> > this.
> >
> >
> > > These rocks have experienced localized in situ
> > >> reduction of FeO to metallic Fe as Jeff has pointed out. But let's look
> > >> at
> > >> the context, these low-Ni metallic iron grains are situated within mafic
> > >> silicate grains that have lots of SiO2, MgO and (away from the reduced
> > >> metal) FeO. They are formed in the solid state. A large iron meteorite
> > >> isn't situated within a mass of mafic silicate. You could argue that it
> > >> broke off, but this also wouldn't work. Diffusion of oxygen out of the
> > >> iron
> > >> mass would probably take longer than the age of the solar system.
> > > ARE WE TALKING 13 BILLION YEARS HERE (BIG BANG) ? OR 4.6 BILLION?
> > > WHY COULD THIS NOT HAVE OCCURRED AT THE TIME OF BIG BANG .THIS WAS VERY
> > > HOT AND QUICK?
> >
> > I was talking about the age of the solar
> > system, circa 4.6 billion years. There was no iron at the time of the Big
> > Bang: only hydrogen, helium and a little lithium. The heavier elements (up
> > to iron) were forged later in stars by normal fusion processes and did not
> > enter the interstellar medium until these stars died. Iron and heavier
> > elements were made in supernova explosions of heavy stars and spewed into
> > the interstellar medium.
> >
> >
> >
> >
> > > In
> > >> addition, iron meteorite falls typically contain at least a few
> > >> inclusions
> > >> of troilite, schreibersite, cohenite, graphite, etc. that would not form
> > >> by
> > >> reduction of FeO.
> > > RESPECTFULLY, EXACTLY MY POINT. HOW WOULD WE EVER KNOW IF THESE THINGS ARE
> > > IN A ROCK THAT WE DISMISS BECAUSE IT HAS NO NICKEL? SEEMS TO ME THERE
> > > SHOULD BE A BETTER WAY.
> >
> > I have looked at a lot of iron meteorwrongs and
> > they do not include troilite, schreibersite, and cohenite.
> >
> >
> > > So, I'm afraid that I don't believe that we're missing
> > >> real meteorites by categorizing Ni-free iron masses as meteor-wrongs.
> > > JUST ASKING. I JUST DON'T GET HOW NICKEL IN AN IRON CAN BE 3 TO 60 PERCENT
> > > AND NOT ZERO PERCENT? ESPECIALLY NOW THAT WE KNOW ZERO PERCENT DOES EXIST
> > > IN SPACE. SOMETHING DIFFERENT MIGHT BE GOING ON?
> >
> > Metallic Fe can form in two ways. Cosmochemists
> > surmise that at the beginning of solar-system history there was a hot and
> > cooling gas of solar composition at low pressure. If we assume a certain
> > pressure, say 1/10,000 of an atmosphere, the we can calculate the
> > temperatures at which different elements condense as solids from the gas.
> > Metallic Ni condenses at 1354 K; metallic Fe condenses at a slightly lower
> > temperature, i.e., 1337 K. The iron is expected to condense on the Ni grains
> > to form a solid solution of metallic Fe-Ni. As temperatures drop, these
> > grains will coarsen. At much lower temperatures, some of the metallic Fe
> > will react with oxygen and form FeO. This component is generally
> > incorporated into silicate minerals. A chondrite will generally contain
> > grains of metallic Fe-Ni and silicates that contain FeO. Except in the most
> > oxidized chondrites, e.g., R and CK, there is little NiO in the olivine.
> > So, when we have localized in situ reduction, we can form low-Ni metallic Fe
> > from the silicates occurring inside the silicate grains. Please note that
> > volumetrically, the amount of low-Ni metallic Fe is trivial, far less than
> > 0.1% of a typical chondrite. The bulk of the metal grains outside these
> > silicates will be largely unaffected, except that they may have somewhat
> > enhanced Fe/Ni ratios at their margins. Bulk melting of these rocks will
> > merge all of the metal and it will have essentially the cosmic Fe/Ni ratio.
> > Igneous processes such as fractional crystallization in metallic magmas in
> > the cores of differentiated asteroids will change the Fe/Ni ratio of
> > different samples leading to the variety in the irons we see today.
> >
> >
> >
> > > THANK YOU AGAIN FOR YOUR HELP.
> > > CARL
> > >> Alan
> > >>
> > >>
> > >> ----- Original Message -----
> > >> From: <cdtucson at cox.net>
> > >> To: "Jeff Grossman" <jgrossman at usgs.gov>; "meteoritelist"
> > >> <meteorite-list at meteoritecentral.com>
> > >> Sent: Friday, March 26, 2010 11:06 AM
> > >> Subject: Re: [meteorite-list] Nickel free metal in Meteorites
> > >>
> > >>
> > >> > Jeff,
> > >> > Thank you for your well explained points.
> > >> > As I have said many times before, you would make an excellent teacher
> > >> > as
> > >> > your answers always stimulate more thoughts.
> > >> > On that note. you acknowledge that nickel free metal does exist but,
> > >> > from
> > >> > reduced metal and is very small. With all due respect.
> > >> > Isn't size a relative thing?
> > >> > I mean looking at things on our scale the size of Nickel free metal in
> > >> > chondrules is small. So, doesn't this means it could be bigger?
> > >> > Look no farther than our own planet. We are way different than other
> > >> > planets.
> > >> > I have been told by Scientists that the earth is so diverse that it
> > >> > makes
> > >> > identification of meteorites difficult. This because Earth can and does
> > >> > have so many different types of rocks. And this is just one planet.
> > >> > So, going back to scale. What if this Reducing of Fe O that turns it
> > >> > into
> > >> > nickel free iron happens to be really big? Say the scale more like
> > >> > Artares
> > >> > which makes Earth look like a grain of sand?
> > >> > Based on our current method of weeding out meteorwrongs we may never
> > >> > know
> > >> > if really big reduction occurs because as part of the weeding process
> > >> > we
> > >> > eliminate all metal objects that do not contain nickel. And this
> > >> > reduction
> > >> > process as you say is a known fact.
> > >> > I see more abstracts based on theory than on nickel free iron facts.
> > >> > Another size scale dilemma is also acknowledged in meteorites. They say
> > >> > ( tongue in cheek) this is either a very large inclusion and the rest
> > >> > of
> > >> > the meteorite is missing. Or this is the whole thing. This is the case
> > >> > with irons. Sometimes the iron is nearly pure and other times it is
> > >> > mixed
> > >> > with silicates as in meso's. But again the point is that these small
> > >> > bits
> > >> > of nickel free iron could be big but we will never know.
> > >> > It seems to me if we paid more attention to morphology and find
> > >> > location
> > >> > and less on nickel content (as a must) that we would discover an iron
> > >> > without nickel. Maybe not as big as Hoba but not as small as what was
> > >> > found in HAH 237 CBb either. I believe this nickel free iron was also
> > >> > found in one of the Kalahari Lunar's. Is that from a chondrule also?
> > >> > This particular meteorite HAH 237 is the one they used recently to
> > >> > reset
> > >> > the date of our solar system but not important enough to open our eyes
> > >> > to
> > >> > the lack of nickel in bigger meteorites.
> > >> > I don't get it?
> > >> > I understand there is always a story. "This thing fell through the
> > >> > roof"
> > >> > Okay, does it look man made? Does it have serial numbers on it? Is it
> > >> > identifiable as an object of any kind like a piece of a tree shredder
> > >> > blade? If these answers are no then maybe just maybe it did fall from
> > >> > the
> > >> > sky? (NJ meteorite).
> > >> > In this example it was determined to be possible space junk and yet
> > >> > nobody
> > >> > bothered to show which space object it could have come from. This
> > >> > object
> > >> > would have had a significant amount of not only monetary value but
> > >> > scientific as well. What was this stainless steel chunk of metal doing
> > >> > up
> > >> > in space?
> > >> > Why would NASA have misplaced such a strange piece of stainless steel?
> > >> > The
> > >> > science was dropped but, it came from somewhere. We may never know from
> > >> > where though. We dropped the ball on NJ and we may be dropping balls
> > >> > every
> > >> > day from a lack of nickel. Heaven forbid we find the first large nickel
> > >> > free iron! Obviously it would be rare but, there are known ungrouped
> > >> > irons
> > >> > that are equally rare.
> > >> > Just another question.
> > >> > Carl
> > >> >
> > >> >
> > >> > --
> > >> > Carl or Debbie Esparza
> > >> > Meteoritemax
> > >> >
> > >> >
> > >> > ---- Jeff Grossman <jgrossman at usgs.gov> wrote:
> > >> >> Ni-free metal occurs within chondrules that have experienced reduction
> > >> >> during melting. These chondrules were originally mostly free of metal
> > >> >> and therefore free of Ni, but contained oxidized iron (FeO) in the
> > >> >> silicate minerals. During reduction, the FeO was converted into Fe
> > >> >> metal (if the reducing agent was H2, then you'd also make H2O; if it
> > >> >> was
> > >> >> C then you'd make CO/CO2). The pure Fe metal that is made can
> > >> >> manifest
> > >> >> itself as "dusty metal" grains within olivine crystals, or sometimes
> > >> >> can
> > >> >> coalesce into larger Fe metal particles in the chondrule.
> > >> >>
> > >> >> The thing about this is, it is a local effect within a few chondrules.
> > >> >> Most of the metal in the chondrite is still Ni-bearing. There is no
> > >> >> easy way to make large masses of this pure Fe metal, such as would
> > >> >> form
> > >> >> iron meteorites, because any process that would segregate metal, would
> > >> >> segregate all of it, not just these strange particles.
> > >> >>
> > >> >> Jeff
> > >> >>
> > >> >> On 2010-03-25 5:59 PM, cdtucson at cox.net wrote:
> > >> >> > List,
> > >> >> > During recent research into CBb chondrites I stumbled upon an
> > >> >> > article
> > >> >> > from 2007 with references from Rubin that shows an image of a CC
> > >> >> > chondrite with nickel free metal.
> > >> >> > How is this possible?
> > >> >> > In past conversations with Scientists when I have asked why do iron
> > >> >> > meteorites always have to have nickel. The typical response is that
> > >> >> > they not only have to have nickel but, it has to have a few percent
> > >> >> > of
> > >> >> > nickel and not just PPM's of it. In explanation of this as I recall,
> > >> >> > I've always been told the reason that meteoritic iron always has to
> > >> >> > have Nickel is because in nature there is no way to separate the two
> > >> >> > elements.
> > >> >> > If that is true then how is it that in this case we do in fact have
> > >> >> > meteoritic metal without nickel? somehow they got separated.
> > >> >> > Unless this analysis is wrong does this not teach us that yes in
> > >> >> > fact
> > >> >> > there can and does exist meteoritic iron devoid of nickel. And
> > >> >> > therefore there not only could be Iron meteorites without nickel
> > >> >> > but,this ups the odds that there in fact are meteorites without
> > >> >> > nickel.
> > >> >> > Please see attached abstract. Back scattered images Figure 2 at the
> > >> >> > fifth page from the top of the article. It says;
> > >> >> > "D. Close up of a CC Chondrule texture. Radiating unidentified
> > >> >> > minerals
> > >> >> > and Nickel free metal (met) are set up in a silica-rich matrix."
> > >> >> >
> > >> >> > http://www2.mnhn.fr/hdt205/leme/doc/2007%20Gounelle%20et%20al.%20EPSL.pdf
> > >> >> >
> > >> >> > Thanks Carl
> > >> >> >
> > >> >> > --
> > >> >> > Carl or Debbie Esparza
> > >> >> > Meteoritemax
> > >> >> > ______________________________________________
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> > >> >> >
> > >> >> >
> > >> >>
> > >> >>
> > >> >> --
> > >> >> Dr. Jeffrey N. Grossman phone: (703) 648-6184
> > >> >> US Geological Survey fax: (703) 648-6383
> > >> >> 954 National Center
> > >> >> Reston, VA 20192, USA
> > >> >>
> > >> >>
> > >> >> ______________________________________________
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> >
Received on Fri 26 Mar 2010 05:16:53 PM PDT