<?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>W.D. Gross</dc:contributor>
  <dc:contributor>L. F. Rader Jr.</dc:contributor>
  <dc:creator>R.R. Coats</dc:creator>
  <dc:date>1963</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;An investigation of more than 170 samples of glass-rich&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;volcanic&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;rocks&lt;/span&gt;&lt;span&gt;&amp;nbsp;of rhyolitic or rhyodacitic composition shows marked regional variations&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;in&lt;/span&gt;&lt;span&gt;&amp;nbsp;the&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;fluorine&lt;/span&gt;&lt;span&gt;&amp;nbsp;content. The uniformity of the class of&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;rocks&lt;/span&gt;&lt;span&gt;&amp;nbsp;was controlled by index of refraction determinations on fused beads and by chemical analyses of about one-seventh of the total number. The&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;fluorine&lt;/span&gt;&lt;span&gt;&amp;nbsp;content ranges from 20 to 4,900 ppm. The frequency&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;distribution&lt;/span&gt;&lt;span&gt;&amp;nbsp;closely approaches a log-normal one; the median value is 520 ppm, the 90 percentile 1,820 ppm. The mean for 167 samples is 820 ppm. These correspond fairly well with earlier averages for similar types of&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;rocks&lt;/span&gt;&lt;span&gt;. The highest values are predominantly from a belt&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;in&lt;/span&gt;&lt;span&gt;&amp;nbsp;central Colorado and west-central New Mexico, from the Big Bend region of Texas, and from southeastern Idaho and&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;western&lt;/span&gt;&lt;span&gt;&amp;nbsp;Utah and northeastern Nevada. The&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;distribution&lt;/span&gt;&lt;span&gt;&amp;nbsp;of the&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;fluorine&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;in&lt;/span&gt;&lt;span&gt;&amp;nbsp;these&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;rocks&lt;/span&gt;&lt;span&gt;&amp;nbsp;correlates well with the&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;distribution&lt;/span&gt;&lt;span&gt;&amp;nbsp;of significant fluorspar deposits and somewhat less well with areas where&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;volcanic&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;rocks&lt;/span&gt;&lt;span&gt;&amp;nbsp;are prevalent and ground waters carry large amounts of&amp;nbsp;&lt;/span&gt;&lt;span class="ScopusTermHighlight"&gt;fluorine&lt;/span&gt;&lt;span&gt;.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2113/gsecongeo.58.6.941</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Society of Economic Geologists</dc:publisher>
  <dc:title>Distribution of fluorine in unaltered silicic volcanic rocks of the western conterminous United States</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>