[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? Definitions: 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? Thanks, Bob V. ------------ Original Message -------------- [meteorite-list] Mystery Spheres on Mars Finally Identified Ron Baalke baalke_at_zagami.jpl.nasa.gov Thu, 18 Mar 2004 08:41:22 -0800 (PST) http://space.com/missionlaunches/mars_blueberries_040317.html Mystery Spheres on Mars Finally Identified By Leonard David space.com 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. ---------------------------------------------------- __________________________________ Do you Yahoo!? Yahoo! Mail - More reliable, more storage, less spam http://mail.yahoo.com Received on Thu 18 Mar 2004 04:58:14 PM PST |
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