Iridium emissions from Kilauea Volcano

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Abstract
During May 1983, gas and particulate samples were collected at the cooling vents of Kilauea volcano in Hawaii. Three vents on the southeast rift zone were sampled using base‐treated filter packs to absorb acidic gases and Teflon filters for particles. The samples were analyzed for 40 elements by nondestructive neutron activation analysis. As with other volcanoes, the chalcophilic and volatile elements were enriched by up to seven orders of magnitude relative to the erupted basalt. Unlike the case of other volcanoes, iridium was observed to be highly enriched (105 fold) at the two higher temperature vents, and the degree of enrichment appears to be related to both high temperatures and high fluorine content of the gases. Estimates of the emission rates of Ir during eruptions of Kilauea based on the measurements reported here and those of the Hawaiian Volcano Observatory yield an emission rate of about 3 g Ir per 106 m3 of magma. This rate amounts to only about 0.3% of the Ir present in the magma that is being released by the volcano. This previously unidentified Ir source to the atmosphere and ocean may have a significant influence on the geochemical cycle of Ir on the earth. The uniqueness of Kilauea in its emissions of Ir is probably related to the deep source of magma, which contains significant levels of Ir (0.32 ppb) and high levels of the halogens F and Cl.