Evidence for crustal degassing of CF4 and SF6 in Mojave Desert groundwaters
Geochimica et Cosmochimica Acta
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Abstract
Dissolved tetrafluoromethane (CF4) and sulfur hexafluoride (SF6) concentrations were measured in groundwater samples from the Eastern Morongo Basin (EMB) and Mojave River Basin (MRB) located in the southern Mojave Desert, California. Both CF4 and SF6 are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the Mojave Desert. These observations provide the first in situ evidence for a flux of CF4 from the lithosphere. A gradual basin-wide enhancement in dissolved CF4 and SF6 concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium. Dissolved CF4 and SF6 concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the EMB and MRB through the underlying basement. The crustal flux of CF4, but not of SF6, is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity. When fluxes of CF4 and SF6 into Mojave Desert groundwaters are extrapolated to the global scale they are consistent, within large uncertainties, with the fluxes required to sustain the preindustrial atmospheric abundances of CF4 and SF6. ?? 2007 Elsevier Ltd. All rights reserved.
Suggested Citation
Deeds, D., Vollmer, M., Kulongoski, J., Miller, B., Muhle, J., Harth, C., Izbicki, J., Hilton, D.R., Weiss, R., 2008, Evidence for crustal degassing of CF4 and SF6 in Mojave Desert groundwaters: Geochimica et Cosmochimica Acta, v. 72, no. 4, p. 999-1013, https://doi.org/10.1016/j.gca.2007.11.027.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Evidence for crustal degassing of CF4 and SF6 in Mojave Desert groundwaters |
| Series title | Geochimica et Cosmochimica Acta |
| DOI | 10.1016/j.gca.2007.11.027 |
| Volume | 72 |
| Issue | 4 |
| Year Published | 2008 |
| Language | English |
| Contributing office(s) | California Water Science Center |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Geochimica et Cosmochimica Acta |
| First page | 999 |
| Last page | 1013 |