[meteorite-list] Blueberries - are they miniature Moqui Marbles

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:51 2004
Message-ID: <20040318215814.38379.qmail_at_web60309.mail.yahoo.com>

Hey Ron,

We could use some help here. Several of us are having
a discussion about these new reports and the use of
the words "concretion" and "precipitation". A lot of
people that I have talked to think that these
"blueberries" are oolitic in nature, meaning that they
are formed under standing bodies of water.
My impression is that these "spherules" are
concretionary (see definiton, below).

Maybe you could exert some influence, and get some
clarification on these terms that are being used in
these reports. Let me know who is more correct -
oncolites or Moqui Marble-like concretions?


Concretions - form in rock after it has consolidated:
deposited if it is a sediment, hardened if it is
volcanic. So the concretions replace or enclose
material already present.

Moqui marbles - contain sand in the middle, indicating
that they formed within the sandstone after it had
been deposited. Because they have an outer layer of
iron oxide, the iron compounds moved through the sand
to precipitate on the edge of the nodule.
Precipitation of the iron compounds is a localized
chemical reaction, controlled by the changes in the pH
of flowing groundwater, such as when encountering
organic matter (i.e. bacteria, plant fossils, etc.).

 Oncolite - A small, often spheroidal, concentrically
laminated, calcium-carbonate sedimentary structure
formed by the buildup of layered masses of gelatinous
sheaths of blue-green algae; generally not more than
10 centimeters in diameter.

 Oolitic - Pertaining to oolite, a sedimentary rock
made up of round to oval accretionary bodies with
diameters ranging from 0.25 to 2 millimeters and
usually formed of calcium carbonate.

So the question is: Are the "blueberries" actually
miniature "Moqui Marbles", or are they more like
oolitic or oncolitic structures?

Bob V.

------------ Original Message --------------
[meteorite-list] Mystery Spheres on Mars Finally
Ron Baalke baalke_at_zagami.jpl.nasa.gov
Thu, 18 Mar 2004 08:41:22 -0800 (PST)


Mystery Spheres on Mars Finally Identified
By Leonard David
17 March 2004

Formation via precipitation

"Hematite as a major compositional phase in the
spherules supports their formation via precipitation,
rather than as impact-related fallout," Garvin said.

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Received on Thu 18 Mar 2004 04:58:14 PM PST

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