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<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>Jorge Ledesma-Vazquez</dc:contributor>
  <dc:contributor>William Ussler III</dc:contributor>
  <dc:contributor>Justin T. Kulongoski</dc:contributor>
  <dc:contributor>David R. Hilton</dc:contributor>
  <dc:contributor>H. Gary Greene</dc:contributor>
  <dc:creator>Matthew J. Forrest</dc:creator>
  <dc:date>2005</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;We investigated hydrothermal gas venting associated with a coastal fault zone along the western margin of Bah&amp;iacute;a Concepci&amp;oacute;n, B.C.S., M&amp;eacute;xico. Copious discharge of geothermal liquid (&amp;asymp;&amp;nbsp;90 &amp;deg;C) and gas is occurring in the intertidal and shallow subtidal zones (to a depth of 13 m) through soft sediments and fractures in rocks along a &amp;sim;750 m linear trend generally sub-parallel to an onshore fault near Punta Santa Barbara. Hydrothermal activity shows negative correlation with tidal height; temperatures in the area of hydrothermal activity were up to 11.3 &amp;deg;C higher at low tide than at high tide (measured tidal range&amp;nbsp;&amp;asymp;&amp;nbsp;120 cm). Gas samples were collected using SCUBA and analyzed for chemical composition and stable isotope values. The main components of the gas are N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;(&amp;asymp;&amp;nbsp;53%; 534 mmol/mol), CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;(&amp;asymp;&amp;nbsp;43%; 435 mmol/mol), and CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;(&amp;asymp;&amp;nbsp;2.2%; 22 mmol/mol). The&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;13&lt;/sup&gt;&lt;span&gt;C values of the CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;(mean&amp;nbsp;=&amp;nbsp;&amp;minus;&amp;nbsp;34.3&amp;permil;), and the ratios of CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;to C&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;H&lt;/span&gt;&lt;sub&gt;6&lt;/sub&gt;&lt;span&gt;(mean&amp;nbsp;=&amp;nbsp;89), indicate that the gas is thermogenic in origin. The carbon stable isotopes and the&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N of the N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;in the gas (mean&amp;nbsp;=&amp;nbsp;1.7&amp;permil;) suggest it may be partially derived from the thermal alteration of algal material in immature sedimentary organic matter. The He isotope ratios (&lt;/span&gt;&lt;sup&gt;3&lt;/sup&gt;&lt;span&gt;He&amp;nbsp;/&amp;nbsp;&lt;/span&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;span&gt;He&amp;nbsp;=&amp;nbsp;1.32&amp;nbsp;&lt;/span&gt;&lt;i&gt;R&lt;/i&gt;&lt;sub&gt;A&lt;/sub&gt;&lt;span&gt;) indicate a significant mantle component (16.3%) in the gas. Here, we suggest the name El Reques&amp;oacute;n fault zone for the faults that likely formed as a result of extension in the region during the late Miocene, and are currently serving as conduits for the observed hydrothermal activity.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/j.chemgeo.2005.07.015</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Gas geochemistry of a shallow submarine hydrothermal vent associated with the El Requesón fault zone, Bahía Concepción, Baja California Sur, México</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>