<?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.E. Seyfried Jr.</dc:contributor>
  <dc:contributor>Wayne C. Shanks III</dc:contributor>
  <dc:creator>Jeffrey S. Seewald</dc:creator>
  <dc:date>1994</dc:date>
  <dc:description>&lt;p&gt;Organic-rich diatomaceous ooze was reacted with seawater and a Na-Ca-K-Cl fluid of seawater chlorinity at 325–400°C, 400–500 bars, and fluid/sediment mass ratios of 1.56–2.35 to constrain factors regulating the abundance and stable isotope composition of C and S species during hydrothermal alteration of sediment from Guaymas Basin, Gulf of California. Alteration of inorganic and organic sedimentary components resulted in extensive exchange reactions, the release of abundant H&lt;sub&gt;2&lt;/sub&gt;S, CO&lt;sub&gt;2&lt;/sub&gt;, CH&lt;sub&gt;4&lt;/sub&gt;, and C&lt;sub&gt;organic&lt;/sub&gt;, to solution, and recrystallization of the sediment to an assemblage containing albitic plagioclase, quartz, pyrrhotite, and calcite.&lt;/p&gt;&lt;p&gt;The&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;&amp;amp;#x3B4;&lt;/mtext&gt;&lt;msup&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;34&lt;/mn&gt;&lt;/msup&gt;&lt;mtext&gt;S&lt;/mtext&gt;&lt;msub&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;&lt;mtext&gt;cdt&lt;/mtext&gt;&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;δ&lt;sup&gt;34&lt;/sup&gt;S&lt;sub&gt;cdt&lt;/sub&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;/sub&gt;values of dissolved H&lt;sub&gt;2&lt;/sub&gt;S varied from −10.9 to +4.3‰ during seawater-sediment interaction at 325 and 400°C and from −16.5 to −9.0‰ during Na-Ca-K-Cl fluid-sediment interaction at 325 and 375°C. In the absence of seawater SO&lt;sub&gt;4&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;S is derived from both the transformation of pyrite to pyrrhotite and S released during the degradation of organic matter. In the presence of seawater SO&lt;sub&gt;4&lt;/sub&gt;, reduction of SO&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;contributes directly to H&lt;sub&gt;2&lt;/sub&gt;S production. Sedimentary organic matter acts as the reducing agent during pyrite and SO&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;reduction. Requisite acidity for the reduction of SO&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;is provided by Mg fixation during early-stage sediment alteration and by albite and calcite formation in Mg-free solutions.&lt;/p&gt;&lt;p&gt;Organically derived CH&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;was characterized by&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-2-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mtext&gt;&amp;amp;#x3B4;&lt;/mtext&gt;&lt;msup&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;13&lt;/mn&gt;&lt;/msup&gt;&lt;mtext&gt;C&lt;/mtext&gt;&lt;msub&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;&lt;mtext&gt;pdb&lt;/mtext&gt;&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;δ13Cpdb&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values ranging between −20.8 and −23.1‰, whereas&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="math"&gt;&lt;span id="MathJax-Element-3-Frame" class="MathJax_SVG" data-mathml="&lt;math xmlns=&amp;quot;http://www.w3.org/1998/Math/MathML&amp;quot;&gt;&lt;mtext&gt;&amp;amp;#x3B4;&lt;/mtext&gt;&lt;msup&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;13&lt;/mn&gt;&lt;/msup&gt;&lt;mtext&gt;C&lt;/mtext&gt;&lt;msub&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mn&gt;&lt;mtext&gt;pdb&lt;/mtext&gt;&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;"&gt;&lt;span class="MJX_Assistive_MathML"&gt;δ&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;pdb&lt;/sub&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values for dissolved C&lt;sub&gt;organic&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;ranged between −14.8 and −17.7%. Mass balance calculations indicate that&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;13&lt;/sup&gt;&lt;i&gt;C&lt;/i&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values for organically derived CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;were ≥ − 14.8%. Residual solid sedimentary organic C showed small (≤ 0.7‰) depletions in&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;13&lt;/sup&gt;C relative to the starting sediment.&lt;/p&gt;&lt;p&gt;The experimental results are consistent with the isotopic and chemical composition of natural hydrothermal fluids and minerals at Guaymas Basin and permit us to better constrain sources and sinks for C and S species in subseafloor hydrothermal systems at sediment-covered spreading centers. Our data show that the sulfur isotope composition of hydrothermal Sulfide minerals in Guaymas Basin can be explained by derivation of S from diagenetic sulfide and seawater sulfate. Basaltic S may also contribute to hydrothermal sulfide precipitates but is not required to explain their isotopic composition. Estimates of seawater/ sediment mass ratios based on sulfur isotopic composition of sulfide minerals and the abundance of dissolved NH&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in vent fluids range from 3–29 during hydrothermal circulation. Sources of C in Guaymas Basin hydrothermal fluids include thermal degradation of organic matter, bacteriogenic methane production, and dissolution of diagenetic carbonate.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0016-7037(94)90232-1</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Variations in the chemical and stable isotope composition of carbon and sulfur species during organic-rich sediment alteration: An experimental and theoretical study of hydrothermal activity at Guaymas Basin, Gulf of California</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>