HR: 0800h
AN: OS51A-1297    [Abstracts]
TI: Ice core indicates explosive volcanic debris not a potent source of trace metals to environments of deposition
AU: Matsumoto, A
EM: aki.matsumoto@aist.go.jp
AF: Geological Survey of Japan, AIST, Central 7, 1-1-1 Higashi, Japan aki.matsumoto@aist.go.jp, Tsukuba, Ibaraki, Iba 305-8567 Japan
AU: * Hinkley, T
EM: thinkley@usgs.gov
AF: National Ice Core Laboratory, US Geological Survey, Box 25046 Federal Center, Denver, CO 80225 United States
AB: The products of explosive volcanic eruptions (tephra) represent massive additions of earth materials to the ocean and land environments on which they fall. There is a widespread assumption that tephra has high trace element content, and that it can be a potent source of excess trace metals. The source of this assumption may be that the plumes of quiescently degassing volcanoes have in fact been shown to be rich in trace elements. However, we show here by analysis of tephra in old Antarctic ice, reliably preserved and free of any anthropogenic influence, that explosive volcanic ejecta are not a source of enhanced trace elements to the lands or oceans on which they fall. This lack of enrichment of trace elements in products of explosive volcanism is consistent with what is observed in nearly all energetic, disordered, high-entropy processes in nature, in which fractionation is minimal. Volcanic tephra is probably a minor source of iron to the oceans, because iron content is low in the rock types of volcanoes that most commonly explode. Furthermore, tephra is probably only a minor source of soluble silica, because the massive nature of many falls leads to effective burial and sequestration, with the solubility limit of silica in seawater being quickly reached in the region of a fall.
DE: 8404 Ash deposits
DE: 4875 Trace elements
DE: 1615 Biogeochemical processes (4805)
DE: 0330 Geochemical cycles
DE: 0370 Volcanic effects (8409)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting