[meteorite-list] Re: Geological History of terrestrial "Olivine Bomb"?

[Gerald Flaherty]

Paul, my most heartfelt thanks for your informative reply. All of the sites 
are added to my Geology favorites.
Most interesting that Glass plays such a significant role in volcanic and 
subterranean processes as it does in meteorite impacts.
Now to try to understand some of the relationships ie. pressures and heat 
and chemical processes as they relate??!...
Jerry Flaherty
----- Original Message ----- 
From: "Paul" <bristolia at yahoo.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, September 04, 2006 7:39 PM
Subject: [meteorite-list] Re: Geological History of terrestrial "Olivine 
Bomb"?


> Gerald Flaherty wrote:
>
> "I picked up an Olivine Bomb from Norbert and
> Helke Kammel of "Rocks On Fire" a couple of
> years ago when I knew less than I know now of
> meteorites. It's Location is listed as Mt.
> Shadwell, Victoria, Australia. At the time the
> very word "olivine" immediately brought pallasite
> to mind. I think I'd just invested in my frist
> Imilac. This piece is tantalizing in every way,
> from is thick jet black volcanic crust, to its
> beautifully polished green interior. Is this
> terrestrial mantle tossed up in a violent
> volcanic blast? Are these common?"
>
> Techincally speaking, they are not volcanic bombs, which are
> thrown out of volcanoes during eruptions. Rather, they are
> exotic chunks of rocks, called xenoliths, carried upward by
> magma as it ascended through the crust. The best preserved
> xenoliths are those carried up rapidly from deep in the
> mantle by the formation of diatremes.
>
> Mount Shadwell is the highest of a cluster of basaltic scoria
> cones. It is well known as a source of olivine and augite
> ultramafic xenoliths and clinopryoxene and orthoclase
> megacrysts contained in basalts and scoria. My understanding
> that although such xenoliths can be found in many basaltic
> lavas, the ones found at Mount Shadwell are uncommon for
> their size and preservation. The xenoliths found at Mt.
> Shadwell are inferred to have come from both the lower
> crust and upper mantle.
>
> Some web pages:
>
> 1. Mount Shadwell - Victorian Resources Online
> http://www.nre.vic.gov.au/dpi/vro/coranregn.nsf/pages/eruption_points_shadwell
>
> 2. Coexisting Andesitic and Carbonate Melts in a
> Lherzolite Xenolith from Mt. Shadwell, Victoria
>
> http://www.es.mq.edu.au/geology/MNAGC98.html
> http://www.es.mq.edu.au/geology/MNHP.html
>
> 3. Melting and Metasomatism in the Lithospheric Mantle Beneath
> SE Australia: Trace Element Studies by Laser Microprobe by
> Marc Norman and Suzanne O'Reilly
>
> http://www.es.mq.edu.au/GEMOC/annrep97/abs96/Norm396.htm
>
> 4. Roach, I. C., 2004, Mineralogy, Textures and P-T
> Relationships of a Suite of Xenoliths from the Monaro
> Volcanic Province, New South Wales, Australia. Journal of
> Petrology. vol. 45, no. 4, pp. 739-758.
>
> http://petrology.oxfordjournals.org/cgi/content/abstract/45/4/739
>
> 5. Ellis. D. J., 1976, High pressure cognate inclusions
> in the Newer Volcanics of Victoria. Contributions to
> Mineralogy and Petrology. vol. 58, no. 2, pp. 149-180.
>
> http://www.springerlink.com/content/r02x704tlm23w415/
>
> 6. Xenolith
>
> http://en.wikipedia.org/wiki/Xenolith
>
> Yours,
>
> Paul H.
>
>
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