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Geochemical evidence for a magmatic CO2 degassing event at Mammoth Mountain, California, September-December 1997

Journal of Geophysical Research B: Solid Earth

By:
, , , and
DOI: 10.1029/2000JB900009

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Abstract

Recent time series soil CO2 concentration data from monitoring stations in the vicinity of Mammoth Mountain, California, reveal strong evidence for a magmatic degassing event during the fall of 1997 lasting more than 2 months. Two sensors at Horseshoe Lake first recorded the episode on September 23, 1997, followed 10 days later by a sensor on the north flank of Mammoth Mountain. Direct degassing from shallow intruding magma seems an implausible cause of the degassing event, since the gas released at Horseshoe Lake continued to be cold and barren of other magmatic gases, except for He. We suggest that an increase in compressional strain on the area south of Mammoth Mountain driven by movement of major fault blocks in Long Valley caldera may have triggered an episode of increased degassing by squeezing additional accumulated CO2 from a shallow gas reservoir to the surface along faults and other structures where it could be detected by the CO2 monitoring network. Recharge of the gas reservoir by CO2 emanating from the deep intrusions that probably triggered deep long-period earthquakes may also have contributed to the degassing event. The nature of CO2 discharge at the soil-air interface is influenced by the porous character of High Sierra soils and by meteorological processes. Solar insolation is the primary source of energy for the Earth atmosphere and plays a significant role in most diurnal processes at the Earth surface. Data from this study suggest that external forcing due largely to local orographic winds influences the fine structure of the recorded CO2 signals.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geochemical evidence for a magmatic CO2 degassing event at Mammoth Mountain, California, September-December 1997
Series title:
Journal of Geophysical Research B: Solid Earth
DOI:
10.1029/2000JB900009
Volume
105
Issue:
B4
Year Published:
2000
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Cascades Volcano Observatory
Description:
10 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth
First page:
8447
Last page:
8456
Time Range Start:
1997-09-01
Time Range End:
1997-12-31
Country:
United States
State:
California
Other Geospatial:
Horseshoe Lake;Mammoth Mountain