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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>Thomas W. Sisson</dc:contributor>
  <dc:contributor>W. Ben Hankins</dc:contributor>
  <dc:contributor>Nobumichi Shimizu</dc:contributor>
  <dc:contributor>Torsten W. Vennemann</dc:contributor>
  <dc:creator>Margaret Mangan</dc:creator>
  <dc:date>2021</dc:date>
  <dc:description>&lt;p&gt;The solubility of CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in hydrous basaltic andesite was examined in&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;&lt;sub&gt;O2&lt;/sub&gt;-controlled experiments at a temperature of 1125 °C and pressures between 310–1200 MPa. Concentrations of dissolved H&lt;sub&gt;2&lt;/sub&gt;O and CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in experimental glasses were determined by ion microprobe calibrated on a subset of run glasses analyzed by high-temperature vacuum manometry. Assuming that the solubility of H&lt;sub&gt;2&lt;/sub&gt;O in mafic melt is relatively well known, estimates of&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="inline-formula no-formula-id"&gt;𝑋H2Ofluid&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="inline-formula no-formula-id"&gt;𝑃H2Ofluid&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in the saturating fluid were modeled, and by difference, values for&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="inline-formula no-formula-id"&gt;𝑋CO2fluid&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="inline-formula no-formula-id"&gt;𝑃CO2fluid&lt;/span&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;were obtained (&lt;i&gt;X&lt;/i&gt;&lt;sub&gt;CO2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;~0.5–0.9);&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;&lt;sub&gt;CO2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;could be then calculated from the fluid composition, temperature, and pressure.&lt;/p&gt;&lt;p&gt;Dissolved H&lt;sub&gt;2&lt;/sub&gt;O over a range of 2.3–5.5 wt% had no unequivocal influence on the dissolution of CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;at the pressures and fluid compositions examined. For these H&lt;sub&gt;2&lt;/sub&gt;O concentrations, dissolved CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;increases with&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;&lt;sub&gt;CO2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;following an empirical power-law relation: dissolved CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;(ppmw) =&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;span class="inline-formula no-formula-id"&gt;14.9−3.5+4.5&lt;/span&gt;[&lt;i&gt;f&lt;/i&gt;&lt;sub&gt;CO2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;(MPa)]&lt;sup&gt;0.7±0.03&lt;/sup&gt;. The highest-pressure results plot farthest from this equation but are within its 1 standard-error uncertainty envelope.&lt;/p&gt;&lt;p&gt;We compare our experimental data with three recent CO&lt;sub&gt;2&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;O solubility models:&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B46"&gt;Papale et al. (2006)&lt;/a&gt;;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B26"&gt;Iacono-Marziano et al. (2012)&lt;/a&gt;; and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B21"&gt;Ghiorso and Gualda (2015)&lt;/a&gt;. The&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B46"&gt;Papale et al. (2006)&lt;/a&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B26"&gt;Iacono-Marizano et al. (2012)&lt;/a&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;models give similar results, both over-predicting the solubility of CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in a melt of the Pavlof basaltic andesite composition across the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;&lt;sub&gt;CO2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;range, whereas the&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;a class="link link-ref xref-bibr" data-modal-source-id="B21"&gt;Ghiorso and Gualda (2015)&lt;/a&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;model under-predicts CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;solubility. All three solubility models would indicate a strong enhancement of CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;solubility with increasing dissolved H&lt;sub&gt;2&lt;/sub&gt;O not apparent in our results. We also examine our results in the context of previous high-pressure CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;solubility experiments on basaltic melts. Dissolved CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;correlates positively with mole fraction (Na+K+Ca)/Al across a compositional spectrum of trachybasalt-alkali basalt-tholeiite-icelandite-basaltic andesite. Shortcomings of current solubility models for a widespread arc magma type indicate that our understanding of degassing in the deep crust and uppermost mantle remains semi-quantitative. Experimental studies systematically varying concentrations of melt components (Mg, Ca, Na, K, Al, Si) may be necessary to identify solubility reactions, quantify their equilibrium constants, and thereby build an accurate and generally applicable solubility model.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2138/am-2021-7531</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Mineralogical Society of America</dc:publisher>
  <dc:title>Constraints on deep, CO2-rich degassing at arc volcanoes from solubility experiments on hydrous basaltic andesite of Pavlof Volcano, Alaska Peninsula, at 300 to 1200 MPa</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>