A stable isotope study of vein-hosted gold mineralization in the Livengood deposit, central Alaska
Susina, Dana Leigh
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The Livengood deposit is an Intrusion Related Gold System (IRGS) in Central Alaska with abundant vein-hosted Au mineralization. There are multiple sets of veins, and although petrography suggests that each vein was deposited from a single mineralizing hydrothermal fluid, disequilibrium between coexisting sulfides indicates a change in temperature and/or δ34SH2S during emplacement. Stable isotope analyses of these mineralized vein sets show no difference in the isotopic ratios of arsenopyrite, stibnite, or quartz. Calculated fluid compositions of mineralized veins are δ34SH2S=-2.7‰ to -1.6‰ and δ18OH2O=8.1‰ to 11.7‰, which indicate a magmatic source. At Livengood, biotite, albite, and sericite alteration facies are associated with mineralization. Calculated temperatures from biotite-quartz and sericite-quartz pairs are, 490° C and 284° C, respectively, and are consistent with crosscutting relationships. Calculated fluid compositions of these alteration facies are 10.1‰ to 13.8‰, which indicate a magmatic source. Mineralization and alteration calculated fluid compositions are consistent with other IRGS’s.