Surface Mercury Geochemistry As A Guide To Volcanic Vent Structure And Zones Of High Heat Flow In The Valley Of Ten Thousand Smokes, Katmai National Park, Alaska
Journal Article: Surface Mercury Geochemistry As A Guide To Volcanic Vent Structure And Zones Of High Heat Flow In The Valley Of Ten Thousand Smokes, Katmai National Park, Alaska
AbstractA reconnaissance survey of Hg° was designed to model the 1912 Novarupta vent structure and delineate zones of near-surface high heat flow. Statistical analysis of 294 regolith samples collected at 127 sites from fossil/active fumaroles and relatively unaltered ash-flow tuff and air-fall ejecta indicates two Hg° sample populations; one associated with fumarole deposits and the other corresponding to the relatively unaltered regolith. Measured Hg° concentrations range from 12 to 6913 ppb. Sample threshold (upper limit of background Hg° concentrations; fumarole deposits: 351 ppb, unaltered regolith: 110 ppb) and contrast (sample value/threshold) determinations enable differentiation between relict and actively accumulating Hg° contents. All significant Hg° anomalies (contrast values > 1.5) occur within Novarupta Basin. High-magnitude, active Hg2 enrichment was found on the Turtle, a dome-like feature northeast of the Novarupta extrusive dome. The Hg° data, coupled with available geologic and geophysical evidence, suggest a shallow intrusion beneath the Turtle. Results from two Novarupta Basin sample traverses do not support the presence of a near-surface magma feeder dike connecting the proposed intrusion beneath the Turtle with the Novarupta dome. Based on the Hg° data, the preferred vent model is one generated by collapse of supporting walls after the major eruptive phase into a cored-out explosive vent. Collapse of vent walls is initiated along a series of deep-extending faults which subsequently serve as migration pathways for Hg° to the surface. The overall vent morphology is funnel-like with subsidence concentrated in the narrow funnel center. Results of this study show that Hg° surveys can further constrain the morphology of the 1912 vent and aid in delineating zones of near-surface high heat flow in this region.
- Lawrence G. Kodosky
- Published Journal
- Journal of Volcanology and Geothermal Research, 1989
- Not Provided
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Lawrence G. Kodosky. 1989. Surface Mercury Geochemistry As A Guide To Volcanic Vent Structure And Zones Of High Heat Flow In The Valley Of Ten Thousand Smokes, Katmai National Park, Alaska. Journal of Volcanology and Geothermal Research. (!) .