[meteorite-list] shock help?

From: mafer_at_domafer.com <mafer_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:18 2004
Message-ID: <004701c295dc$2b6cf5a0$6401a8c0_at_vs.shawcable.net>

Hi Tom and list

Well, we have a problem then, since basalts are basalts, here or there, and
they do come in varieties within varieties (a well traveled and studied
volcanologist can almost tell you which volcano a basalt came from from
close detailed inspection). So, what do you do, well, if theres a university
close by (community and junior colleges most likely won't have what you
need), you can check and see if they have a volcanologist on staff. Or find
a university close enough that you wouldn't mind sending it to them, and
insure yourself by cutting a slice of say 10-20 grams (maybe some of the
more practiced people on the list could help here) to send and donate to
them for study with the understanding that if it is a meteorite, you get
credit for finding it and they get it classified ect.
Lets revisit basalts a little to help you understand what they can or cannot
do. Most if not all basalts are lower in silica than rhyolites and
andesites, and are also lower in volatiles in composition as well. This
means that they almost never are "blown" out of the volcano/vent with any
great force, so they typically flow out (Hawaii and Iceland are like this,
little fountains, lots of lava flows, Hawaii is on a "hot spot" and Iceland
is on a spreading center). Rhyolites are inbetween basalts and andesites,
not as passive (if I may use that term loosely) as basalts and not as
explosive as andesites. They are rich in silica and are usually much lighter
in color than basalts and should be less dense too. Andesites are also rich
in silicates and volatiles and are they scenes of explosive and dramatic
eruptions (Mt Pinatubo, Mt St Helens ect). The only way a basalt can be
thrown a large distance (really, just about any distance beyond the crater)
is when it is "old" magma, ie it was from a earlier basaltic eruption and
happened to be caught up in a more recent rhyolitic or andesitic eruption
and then thrown far from the crater. When these "old" magma chunks are
caught up in such an eruption, they can be partially remelted (sometime they
aren't at all and you find these old magma chunks as clasts within a newer
lava), plasticized as it were, which allows for a little remolding of shape
and can be thrown miles away from a crater. But this isn't common, the
remelting as usually, the old material is up vent from much of the hot stuff
and is broken free on the erupting magmas journey up the vent and carried
out with it. This can leave a crusty appearance to it. It may have a
coating, as it were, of the newer material on it. But this would be lighter
in color, I should think, than the older basalt. It should also flake off if
it isn't "welded" to the old. You won't find free metal or chondrules in a
basalt from here on earth and I don't think that will change coming from the
moon or mars. Just too much differentation on all three bodies for that.
And, it will take a isotope measurment to distinguish it from a earthly
basalt if it doesn't resemble basalts from the region in which you found it.
Hope this helps, but I fear it just compounds the problem.
Mark
----- Original Message -----
From: Tom / james Knudson <peregrineflier_at_hotmail.com>
To: <mafer_at_domafer.com>
Sent: Tuesday, November 26, 2002 9:35 PM
Subject: Re: [meteorite-list] shock help?


> Hello Mark, let me tell you a story. I was out meteorite hunting, when I
> spied a nice dark rock.The closer I got the happier I got. I thougt I
found
> my self a meteorite. This rock looks more like a meteorite than most of
the
> meteorites in my collection! I picked it up and it was kinda heavy. I took
> out my magnet and checked it. Nothing, not even a little. Oh well another
> meteorwrong! Or wait a Achondrite????? Well I took it home and made me a
> window. Darn does not look like any thing I have seen! Well I took out my
> nicest crusted meteorites and compared the two, It sure looks like a crust
> to me!!!! Then A few days later, I was looking at Nortons new book and on
> page 181 there is a pic of a mare basalt NWA 032 (fig 8.41)Well, I can't
say
> I have not seen a rock like mine before! Not exact but very close! and
like
> I discribed before, the small fratures all through the rock. Now What?
>
>
> Thanks, Tom
> The proudest member of the I.M.C.A. #6168
>
>
>
>
> From: <mafer_at_domafer.com>
> To: "Tom / james Knudson" <peregrineflier_at_hotmail.com>
> CC: <meteorite-list_at_meteoritecentral.com>
> Subject: Re: [meteorite-list] shock help?
> Date: Tue, 26 Nov 2002 20:44:10 -0800
>
> Hi Tom
>
> Well, I did learn a little in school (and am looking for work) and try to
> pass it on as I can. There are the other more fundamental checks you can
do
> like magnetism and metal detector testing (of course, these will only work
> with some metal present). If you have a rock saw (you can almost always
find
> a rock or mineral club in any town larger than one stop light and they are
> always willing to help determine a rocks identity), you can slice it and
> look for more tell-tale signs like chondrules and metal flecks and
> breciation.
>
> Mark
>
>
> ----- Original Message -----
> From: Tom / james Knudson <peregrineflier_at_hotmail.com>
> To: <mafer_at_domafer.com>
> Sent: Tuesday, November 26, 2002 8:36 PM
> Subject: Re: [meteorite-list] shock help?
>
>
> > Wow, That was quite an explaination! I am going to keep that one. I
don't
> > know if it will help me figure out if this rock is a meteorite or not,
it
> is
> > so confusing to try to know if it is a meteorite or not!
> >
> >
> > Thanks, Tom
> > The proudest member of the I.M.C.A. #6168
> >
> >
> >
> >
> > From: <mafer_at_domafer.com>
> > To: "Tom / james Knudson" <peregrineflier_at_hotmail.com>
> > CC: <meteorite-list_at_meteoritecentral.com>
> > Subject: Re: [meteorite-list] shock help?
> > Date: Tue, 26 Nov 2002 19:21:50 -0800
> >
> > Hi Tom and list
> >
> > Well, your sure digging correctly. Actually, terrestrial rock can show
> > minute "fractures" and crack from a variety of things such as, but not
> > limited to: earthquake, volcanic eruption and weathering. Now whats
> > interesting about weathering is that it take a wide variety of forms.
> Quite
> > often, "shocked" quartz grains are found in volcanicly derived "green"
> sand
> > layers and are a result of the eruption itself. The simplest forms we
see
> > are the wind scoured rocks like sandstone or water worn pebbles (which
is
> > actually a tumbling grinding effect and not so much to do with water
> doing
> > the grinding away, but the tumbling on rocks against themselves). Less
> > realized are the freeze-thaw effects which can most easily be seen on
> > exposed plutonic rock such as seen in Yosemite in Ca. or Stone Mountain
> in
> > Ga. which causes the rock to break apart and almost looks like orange
> peels
> > till it slides down into a talus slope of rubble. Freeze-thaw also
causes
> > most of the falling rock around the continent for which the dot puts up
> the
> > "watch for falling rock" signs. And basicly, what happens here is that
> > moisture gets into minute crevices of the rock and when it freezes, it
> > expands, then it thaws in the spring and is repeted till the chunk of
> rock
> > gives way to gravity and heads toward the road. Now, about these minute
> > crevices. They can be from a few things, one of which is acid rain. Not
> > something only invented by 20th century man, it has been around as long
> as
> > rain has and happens every time there is any volcanic activity which
> places
> > acids into the atmosphere. This acid rain accounts for a lot of long
term
> > weathering and will attack the carbonates first which is often the
> cementing
> > agent in sedimentary rock. It also attacks the silica cements in many
> types
> > of rock, just not seds, but metamorphic and volcanic rock too. Water
too
> can
> > disolve as its a polar solvent. So, to finally answer your initial
> question,
> > fractures are found in terrestrial rock all the time and in order to
> > determine if its from shock or weathering, one needs to look at the
> frains
> > of the rock itself, not the cracks, for a shock fracture of any kind,
be
> it
> > terrestrial or extra-terrestrial, will not just go around the grains
> > (crystals ), but will go through them if thats the easiest path to
> relieving
> > the stress of shock.
> >
> > Mark
> >
> >
> >
> > ----- Original Message -----
> > From: Tom / james Knudson <peregrineflier_at_hotmail.com>
> > To: <meteorite-list_at_meteoritecentral.com>
> > Sent: Tuesday, November 26, 2002 6:55 PM
> > Subject: [meteorite-list] shock help?
> >
> >
> > > Hello List, pardon me for picking your brains! I have a meteorite
> > hopefull
> > > that if you look at it with a loop at an angle in good light you can
> see
> > > that the stuff that makes up the mass of the rock has small cracks
> only
> > > visible with a loop) all through it. Every thing looks like it has
> been
> > > shattered. Now then, Is this shock? Do or can terrestrial rocks have
> > these
> > > tiny cracks all through them?
> > >
> > >
> > > Thanks, Tom
> > > The proudest member of the I.M.C.A. #6168
> > >
> > >
> > >
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Received on Wed 27 Nov 2002 01:13:55 AM PST