<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>M. Sato</dc:contributor>
  <dc:creator>R. Brett</dc:creator>
  <dc:date>1984</dc:date>
  <dc:description>&lt;p&gt;Intrinsic oxygen-fugacity (&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;) measurements were made on five ordinary chondrites, a carbonaceous chondrite, an enstatite chondrite, a pallasite, and a tektite. Results are of the form of linear log&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-1-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mtext&gt;f&lt;/mtext&gt;&lt;mtext&gt;O&lt;/mtext&gt;&lt;msub&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mtext&gt;&amp;amp;#x2212;&lt;/mtext&gt;&lt;mtext&gt;1&lt;/mtext&gt;&lt;mtext&gt;T&lt;/mtext&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;fO&lt;sub&gt;2&lt;/sub&gt;−1T&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;plots. Except for the enstatite chondrite, measured results agree well with calculated estimates by others.&lt;/p&gt;&lt;p&gt;The tektite produced&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values well below the range measured for terrestrial and lunar rocks. The lowpressure atmospheric regime that is reported to follow large terrestrial explosions, coupled with a very high temperature, could produce glass with&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in the range measured.&lt;/p&gt;&lt;p&gt;The meteorite Salta (pallasite) has low&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and lies close to Hvittis (E6). Unlike the other samples, results for Salta do not parallel the iron-wüstite buffer, but are close to the fayalite-quartz-iron buffer in slope.&lt;/p&gt;&lt;p&gt;Minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites.&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;conditions. The samples equilibrated with respect to&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in relatively short time on heating. Equilibration with respect to&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in ordinary chondrites takes place between grades 3 and 4 of metamorphism. Application of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;P&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;−&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;T&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;−&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;O&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;relations in the system C-CO-CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;indicates that the ordinary chondrites were metamorphosed at pressures of 3–20 bars, as it appears that they lay on the graphite surface.&lt;/p&gt;&lt;p&gt;A steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior, an oxidized near-surface layer, and an interior that is increasingly reduced with depth; a shallow thermal gradient will produce the reverse. A body heated by accretion on the outside will have a reduced exterior and oxidized interior. Meteorites from the same parent body clearly are not required to have similar redox states.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0016-7037(84)90353-3</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Intrinsic oxygen fugacity measurements on seven chondrites, a pallasite, and a tektite and the redox state of meteorite parent bodies</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>