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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>Albert H. Hofstra</dc:contributor>
  <dc:creator>Jean S. Cline</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;Minerals and fluid-inclusion populations were examined using petrography, microthermometry, quadrupole mass-spectrometer gas analyses and stable-isotope studies to characterize fluids responsible for gold mineralization at the Getchell Carlin-type gold deposit. The gold-ore assemblage at Getchell is superimposed on quartz-pyrite vein mineralization associated with a Late-Cretaceous granodiorite stock that intruded Lower-Paleozoic sedimentary rocks. The ore assemblage, of mid-Tertiary age, consists of disseminated arsenian pyrite that contains submicrometer gold, jasperoid quartz, and later fluorite and orpiment that fill fractures and vugs. Late ore-stage realgar and calcite enclose ore-stage minerals.&lt;/p&gt;&lt;p&gt;Pre-ore quartz trapped fluids with a wide range of salinities (1 to 21 wt.% NaCl equivalent), gas compositions (H&lt;sub&gt;2&lt;/sub&gt;O, CO&lt;sub&gt;2&lt;/sub&gt;, and CH&lt;sub&gt;4&lt;/sub&gt;), and temperatures (120 to &amp;gt; 360°C). Oxygen- and hydrogen-isotope ratios indicate that pre-ore fluids likely had a magmatic source, and were associated with intrusion of the granodiorite stock and related dikes.&lt;/p&gt;&lt;p&gt;Ore-stage jasperoid contains moderate salinity, aqueous fluid inclusions trapped at 180 to 220°C. Ore fluids contain minor CO&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and trace H&lt;sub&gt;2&lt;/sub&gt;S that allowed the fluid to react with limestone host rocks and transport gold, respectively. Aqueous inclusions in fluorite indicate that fluid temperatures declined to ∼ 175°C by the end of ore-stage mineralization. As the hydrothermal system collapsed, fluid temperatures declined to 155 to 115°C and realgar and calcite precipitated.&lt;/p&gt;&lt;p&gt;Inclusion fluids in ore-stage minerals have high δD&lt;sub&gt;H2O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;and δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;H2O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values that indicate that the fluid had a deep source, and had a metamorphic or magmatic origin, or both. Late ore-stage fluids extend to lower δ&lt;sub&gt;H2O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values, and have a wider range of δ&lt;sup&gt;18&lt;/sup&gt;O&lt;sub&gt;H2O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;values suggesting dilution by variably exchanged meteoric waters.&lt;/p&gt;&lt;p&gt;Results show that deeply sourced ore fluids rose along the Getchell fault system, where they dissolved carbonate wall rocks and deposited gold-enriched pyrite and jasperoid quartz. Gold and pyrite precipitated together as H&lt;sub&gt;2&lt;/sub&gt;S in the ore fluids reacted with iron in the host rocks. As ore fluids mixed with local aquifer fluids, ore fluids became cooler and more dilute. Cooling caused precipitation of ore-stage fluorite and orpiment, and late ore-stage realgar. Phase separation and/or neutralization of the ore fluid during the waning stages of the hydrothermal ore system led to deposition of late ore-stage calcite.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1127/0935-1221/2000/0012-0195</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>E. Schweizerbart'sche Verldghuchhandlung</dc:publisher>
  <dc:title>Ore-fluid evolution at the Getchell Carlin-type gold deposit, Nevada, USA</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>