[meteorite-list] Volcanic Rocks in Minnesota / Eastern US

From: Mr EMan <mstreman53_at_meteoritecentral.com>
Date: Sun Aug 20 04:16:49 2006
Message-ID: <20060820064247.4170.qmail_at_web51006.mail.yahoo.com>

A few years back there was a question on the list as
to the possible presence of volcanic rocks in
Midwestern (US) glacial moraines. I presume that this
was to help scope out potential sources of igneous
rocks which might be identified as meteorwrongs.

I asserted then, that there were no naturally occuring
volcanic rocks in the Midwest which were later than
the Cambrian -- East of the Rockies, I likely said,
(except for BBQ grills and fancy landscape
settings)--noting there were the Triassic flows and
diabase dikes of the Northeastern US down into North
Carolina.

So essentially I said,NO,...noway... nohow.. no
basalts would be found. Seems there are basalts--even
pristine pillow lavas left over from some distant
pre-Cambrian failed rift event in the Lake Superior
District of Minnesota.

We know that icecap glaciering from the last 2 million
years did carry all manner of rocks southward. So to
revise and extend my remarks, it is very possible to
encounter basaltic rocks through out the region. In
addition to unaltered lavas there are "greenstone
belts" of altered basalt or meta-basalts which also
would be found which may superficially resemble
achondrites.

A document on the classic outcrops of Minnesota is
here
<http://www.tc.umn.edu/~smith213/CLASSICSTEXTwfigs.pdf>

amd a small geological map the state is here:
<http://www.tc.umn.edu/~smith213/index.htm>

Seems Minnesota has an abundance of very old, yet
largely unaltered rock types.

To whomever asked the question, I apologize if you
were mislead or just mearly confounded. My conscience
is now clear..

Elton

PS: I have also since learned that there are
meta-basalts in the folds of the Southern Appalachains
of pre-Cambrian age for whomever is keeping tabs.
Received on Sun 20 Aug 2006 02:42:46 AM PDT